Dikai Liu is a distinguished professor in the Department of Mechanical and Mechatronic Engineering and Co-Director of the Centre for Autonomous Systems (CAS) at the University of Technology Sydney, Australia. His research interest is robotics, an interdisciplinary branch of engineering and science, with the focus on perception, motion planning, physical human-robot interaction, multi-robot systems, bio-inspired robotics, design methodology and robot systems.
He initiated and developed the research themes of infrastructure robotics, robot teams and physical human-robot interaction in CAS. Besides conducting fundamental robotics research, he has been also leading the development of autonomous and assistive robots that can be deployed in real applications, including autonomous robots for steel bridge maintenance, bio-inspired climbing robots for inspection of complex steel structures, intelligent robotic co-worker for human-robot collaborative abrasive blasting, smart hoist for patient transfer, and autonomous underwater robots for underwater structure maintenance. Dikai is a recipient of many patents include USA and Australia patents.
Since 2006, Dikai’s research has received three best paper awards from international conferences, 14 research/engineering excellence awards and one High Commendation, including the 2019 UTS Medal for Research Impact, the 2019 ASME DED Leonardo da Vinci Award (USA), the 2019 BHERT Award for Outstanding Collaboration in Research & Development, the 2016 Australian Engineering Excellence Award (AEEA – category: Engineering Innovation Excellence Award), the 2015 Asia Pacific ICT Alliance (APICTA) Award (category: Industry Application), and the 2015 SafeWork NSW Award for the best solution to an identified workplace health and safety issue. He was a finalist in four international and local awards, including one of the three finalists in the 2013 Australian Museum Eureka Prize for Innovative Use of Technology, one of three finalists of the 2013 IEEE/International Federation of Robotics (IFR) Invention & Entrepreneurship in Robotics and Automation (IERA) Award, and a finalist of the 2013 AEEA award.
Two of Dikai’s research projects were nominated for the inaugural ARC (Australian Research Council) Engagement and Impact Assessment (EIA) in 2018: the autonomous abrasive-blasting robot project nominated for the 09-Engineering discipline, and the project of multi-robot systems for automated container handling nominated for the 08-IT discipline. The two projects received four ratings of ‘High’ for the EIA across Engineering and Information & Computing Sciences.
Dikai has successfully won eight ARC grants, 11 contract research projects, two IRT foundation grants, one Enterprise Connect grant and two UTS Partnership grants. The external research funding he received, as the first named Chief Investigator, is $10.5 million
Dikai’s research has been reported by newspapers, TV news and media reports, including BBC News, ABC News, SBS News, TVBS (Taiwan), Sydney Morning Herald, The Robot Report, etc.
Senior Member, Institution of Electrical and Electronic Engineers (IEEE);
Member, The American Society of Mechanical Engineers (ASME);
Member, Engineers Australia;
Can supervise: YES
Current research topics (Scholarships availabe for potential PHD students):
- Infrastructure Robotics: exploration, localisation, high-level planning and collision avoidance for climbing robots and robot manipulators in complex 3D environments such as truss structures;
- physical Human-Robot Collaboration (pHRC): human models, trust modelling, safety in pHRC, interaction dynamics, role change and brain-robot interaction;
- Bio-inspired robotics: climbing gait and locomotion of humans and animals, design methodology, and compliant/soft grippers,
- Underwater Robotics: body-arm coordination and control under large disturbance;
Undergraduate: Dynamics and Control; Advanced Manufacturing; Introduction to Mechanical and Mechatronic Engineering;
Postgraduate: Design Optimisation for Manufacturing;
Dai, P, Lu, W, Le, K & Liu, D 2020, 'Sliding Mode Impedance Control for contact intervention of an I-AUV: Simulation and experimental validation', Ocean Engineering, vol. 196.
Lu, W & Liu, D 2020, 'A2: Extracting cyclic switchings from DOB-nets for rejecting excessive disturbances: A2: Extracting cyclic switchings from DOB-nets for rejecting excessive disturbances', Neurocomputing, vol. 400, pp. 161-172.View/Download from: Publisher's site
© 2020 Reinforcement Learning (RL) is limited in practice by its poor explainability, which is responsible for insufficient trustiness from users, unsatisfied interpretation for human intervention, inadequate analysis for future improvement, etc. This paper seeks to partially characterize the interplay between dynamical environments and a previously-proposed Disturbance OBserver net (DOB-net). The DOB-net is trained via RL and offers optimal control for a set of Partially Observable Markovian Decision Processes (POMDPs). The transition function of each POMDP is largely determined by the environments (excessive external disturbances). This paper proposes an Attention-based Abstraction (A2) approach to extract a finite-state automaton, referred to as a Key Moore Machine Network (KMMN), to capture the switching mechanisms exhibited by the DOB-net in dealing with multiple such POMDPs. A2 first quantizes the controlled platform by learning continuous-discrete interfaces. Then it extracts the KMMN by finding the key hidden states and transitions that attract sufficient attention from the DOB-net. Within the resultant KMMN, three patterns of cyclic switchings (between key hidden states) are found, and saturated controls are shown synchronized with unknown disturbances. Interestingly, the found switchings have previously appeared in the control design for often-saturated systems. They are interpreted via an analogy to the discrete-event subsystem of hybrid control.
Yu, H, Lu, W, Han, Y, Liu, D & Zhang, M 2020, 'Heterogeneous Dimensionality Reduction for Efficient Motion Planning in High-Dimensional Spaces', IEEE Access, vol. 8, pp. 42619-42632.View/Download from: Publisher's site
© 2013 IEEE. Increasing the dimensionality of the configuration space quickly makes trajectory planning computationally intractable. This paper presents an efficient motion planning approach that exploits the heterogeneous low-dimensional structures of a given planning problem. These heterogeneous structures are obtained via a Dirichlet process (DP) mixture model and together cover the entire configuration space, resulting in more dimensionality reduction than single-structure approaches from the existing literature. Then, a unified low-dimensional trajectory optimization problem is formulated based on the obtained heterogeneous structures and a proposed transversality condition which is further solved via SQP in our implementation. The positive results demonstrate the feasibility and efficiency of our trajectory planning approach on an autonomous underwater vehicle (AUV) and a high-dimensional intervention autonomous underwater vehicle (I-AUV) in cluttered 3D environments.
Woolfrey, J, Lu, W, Vidal-Calleja, T & Liu, D 2019, 'Clarifying clairvoyance: Analysis of forecasting models for near-sinusoidal periodic motion as applied to AUVs in shallow bathymetry', Ocean Engineering, vol. 190.View/Download from: Publisher's site
© 2019 Elsevier Ltd This paper shows that Gaussian Process Regression (GPR) with a periodic kernel has better mean prediction accuracy and uncertainty bounds than time series or Fourier series when forecasting motion data of underwater vehicles subject to wave excitation. Many robotic systems, such as autonomous underwater vehicles (AUVs), are required to operate in environments with disturbances and relative motion that make task performance difficult. This motion often exhibits periodic, near-sinusoidal behaviour. By predicting this motion, control strategies can be developed to improve accuracy. Moreover, factoring in uncertainty can aid the robustness of these predictive control methods. Time series and Fourier series have been applied to several predictive control problems in a variety of fields. However, there are contradictory results in performance based on parameters, assessment criteria, and application. This paper seeks to clarify these discrepancies using AUV motion as a case study. GPR is also introduced as a third candidate for prediction based on previous applications to time series forecasting in other fields of science. In addition to assessing mean prediction accuracy, the ability of each model to adequately bound prediction error is also considered as a key performance indicator.
Bykerk, L, Quin, P & Liu, D 2019, 'A Method for Selecting the Next Best Angle-of-Approach for Touch-Based Identification of Beam Members in Truss Structures', IEEE Sensors Journal, vol. 19, no. 10, pp. 3939-3949.View/Download from: Publisher's site
© 2001-2012 IEEE. A robot designed to climb truss structures such as power transmission towers is expected to have an adequate tactile sensing in the grippers to identify a structural beam member and its properties. Depending on how a gripper grasps a structural member, defined as the Angle-of-Approach (AoA), the extracted tactile data can result in erroneous identifications due to the similarities in beam cross-sectional shapes and sizes. In these cases, further grasps at favorable Angles-of-Approach (AoAs) are required to correctly identify the beam member and its properties. This paper presents an information-based method which uses tactile data to determine the next best AoA for the identification of beam members in truss structures. The method is used in conjunction with a state estimate of beam shape, dimension, and AoA calculated by a Random Forest classifier. The method is verified through simulation by using the data collected using a soft gripper retrofitted with simple tactile sensors. The results show that this method can correctly identify a structural beam member and its properties with a small number of grasps (typically fewer than 4). This method can be applied to other adaptive robotic gripper designs fitted with suitable tactile sensors, regardless of the number of sensors used and their layout.
Hassan, M, Liu, D & Xu, D 2019, 'A Two-Stage Approach to Collaborative Fiber Placement through Coordination of Multiple Autonomous Industrial Robots', Journal of Intelligent and Robotic Systems: theory and applications, vol. 95, pp. 915-933.View/Download from: Publisher's site
Nguyen, K-D & Liu, D 2019, 'Gibbon-inspired Robust Asymmetric Brachiation along an Upward Slope', INTERNATIONAL JOURNAL OF CONTROL AUTOMATION AND SYSTEMS, vol. 17, no. 10, pp. 2647-2654.View/Download from: Publisher's site
Woolfrey, J, Lu, W & Liu, D 2019, 'A Control Method for Joint Torque Minimization of Redundant Manipulators Handling Large External Forces', Journal of Intelligent and Robotic Systems: theory and applications, vol. 96, pp. 3-16.View/Download from: Publisher's site
© 2019, The Author(s). In this paper, a control method is developed for minimizing joint torque on a redundant manipulator where an external force acts on the end-effector. Using null space control, the redundant task is designed to minimize the torque required to oppose the external force, and reduce the dynamic torque. Furthermore, the joint motion can be weighted to factor in physical constraints such as joint limits, collision avoidance, etc. Conventional methods for joint torque minimization only consider the internal dynamics of the manipulator. If external forces acting on the end-effector are inadvertently implemented in to these control methods this could lead to joint configurations that amplify the resulting joint torque. The proposed control method is verified through two different case studies. The first case study involves simulation of high-pressure blasting. The second is a simulation of a manipulator lifting and moving a heavy object. The results show that the proposed control method reduces overall joint torque compared to conventional methods. Furthermore, the joint torque is minimized such that there is potential for a manipulator to execute certain tasks beyond its nominal payload capacity.
Yu, H, Lu, W, Liu, D, Han, Y & Wu, Q 2019, 'Speeding up Gaussian Belief Space Planning for Underwater Robots Through a Covariance Upper Bound', IEEE ACCESS, vol. 7, pp. 121961-121974.View/Download from: Publisher's site
hassan, M, liu, D & Paul, G 2018, 'Collaboration of Multiple Autonomous Industrial Robots through Optimal Base Placements', Journal of Intelligent and Robotic Systems, vol. 90, no. 1-2, pp. 113-132.View/Download from: Publisher's site
Multiple autonomous industrial robots can be of great use in manufacturing applications, particularly if the environment is unstructured and custom manufacturing is required. Autonomous robots that are equipped with manipulators can collaborate to carry out manufacturing tasks such as surface preparation by means of grit-blasting, surface coating or spray painting, all of which require complete surface coverage. However, as part of the collaboration process, appropriate base placements relative to the environment and the target object need to be determined by the robots. The problem of finding appropriate base placements is further complicated when the object under consideration is large and has a complex geometric shape, and thus the robots need to operate from a number of base placements in order to obtain complete coverage of the entire object. To address this problem, an approach for Optimization of Multiple Base Placements (OMBP) for each robot is proposed in this paper. The approach aims to optimize base placements for multi-robot collaboration by taking into account task-specific objectives such as makespan, fair workload division amongst the robots, and coverage percentage; and manipulator-related objectives such as torque and manipulability measure. In addition, the constraint of robots maintaining an appropriate distance between each other and relative to the environment is taken into account. Simulated and real-world experiments are carried out to demonstrate the effectiveness of the approach and to verify that the simulated results are accurate and reliable.
To, W, paul, G & liu, D 2018, 'A comprehensive approach to real-time fault diagnosis during automatic grit-blasting operation by autonomous industrial robots', Robotics and Computer Integrated Manufacturing, vol. 49, pp. 13-23.View/Download from: Publisher's site
This paper presents a comprehensive approach to diagnose for faults that may occur during a robotic grit-blasting operation. The approach proposes the use of information collected from multiple sensors (RGB-D camera, audio and pressure transducers) to detect for 1) the real-time position of the grit-blasting spot and 2) the real-time state within the lasting line (i.e. compressed air only). The outcome of this approach will enable a grit-blasting robot to autonomous diagnose for faults and take corrective actions during the blasting operation. Experiments are conducted in a laboratory and in a grit-blasting chamber during real grit-blasting to demonstrate the proposed approach. Accuracy of 95% and above has been achieved in the experiments.
Hassan, M & Liu, D 2017, 'Simultaneous area partitioning and allocation for complete coverage by multiple autonomous industrial robots', Autonomous Robots, vol. 41, no. 8, pp. 1609-1628.View/Download from: Publisher's site
© 2017, Springer Science+Business Media New York. For tasks that require complete coverage of surfaces by multiple autonomous industrial robots, it is important that the robots collaborate to appropriately partition and allocate the surface areas amongst themselves such that the robot team's objectives are optimized. An approach to this problem is presented, which takes into account unstructured and complex 3D environments, and robots with different capabilities. The proposed area partitioning and allocation approach utilizes Voronoi partitioning to partition objects' surfaces, and multi-objective optimization to allocate the partitioned areas to the robots whilst optimizing robot team's objectives. In addition to minimizing the overall completion time and achieving complete coverage, which are objectives particularly useful for applications such as surface cleaning, manipulability measure and joint's torque are also optimized so as to help autonomous industrial robots to operate better in applications such as spray painting and grit-blasting. The approach is validated using six case studies that consist of comparative studies, complex simulated scenarios as well as real scenarios using data obtained from real objects and applications.
Pagano, D & Liu, D 2017, 'An approach for real-time motion planning of an inchworm robot in complex steel bridge environments', Robotica, vol. 35, no. 6, pp. 1280-1309.View/Download from: Publisher's site
Copyright © Cambridge University Press 2016 Path planning can be difficult and time consuming for inchworm robots especially when operating in complex 3D environments such as steel bridges. Confined areas may prevent a robot from extensively searching the environment by limiting its mobility. An approach for real-time path planning is presented. This approach first uses the concept of line-of-sight (LoS) to find waypoints from the start pose to the end node. It then plans smooth, collision-free motion for a robot to move between waypoints using a 3D-F2 algorithm. Extensive simulations and experiments are conducted in 2D and 3D scenarios to verify the approach.
Carmichael, MG, Liu, D & Waldron, KJ 2017, 'A framework for singularity-robust manipulator control during physical human-robot interaction', INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH, vol. 36, no. 5-7, pp. 861-876.View/Download from: Publisher's site
Quin, P, Paul, G & Liu, D 2017, 'Experimental Evaluation of Nearest Neighbour Exploration Approach in Field Environments', IEEE Transactions on Automation Science and Engineering, vol. 14, no. 2, pp. 869-880.View/Download from: Publisher's site
Inspecting surface conditions in 3-D environments such as steel bridges is a complex, time-consuming, and often hazardous undertaking that is an essential part of tasks such as bridge maintenance. Developing an autonomous exploration strategy for a mobile climbing robot would allow for such tasks to be completed more quickly and more safely than is possible with human inspectors. The exploration strategy tested in this paper, called the nearest neighbors exploration approach (NNEA), aims to reduce the overall exploration time by reducing the number of sensor position evaluations that need to be performed. NNEA achieves this by first considering at each time step only a small set of poses near to the current robot as candidates for the next best view. This approach is compared with another exploration strategy for similar robots performing the same task. The improvements between the new and previous strategy are demonstrated through trials on a test rig, and also in field trials on a ferromagnetic bridge structure.
To, W, Paul, G & Liu, D 2016, 'An approach for identifying classifiable regions of an image captured by autonomous robots in structural environments', Robotics and Computer Integrated Manufacturing, vol. 37, pp. 90-102.View/Download from: Publisher's site
When an autonomous robot is deployed in a structural environment to visually inspect surfaces, the capture conditions of images (e.g. camera's viewing distance and angle to surfaces) may vary due to un-ideal robot poses selected to position the camera in a collision-free manner. Given that surface inspection is conducted by using a classifier trained with surface samples captured with limited changes to the viewing distance and angle, the inspection performance can be affected if the capture conditions are changed. This paper presents an approach to calculate a value that represents the likelihood of a pixel being classifiable by a classifier trained with a limited dataset. The likelihood value is calculated for each pixel in an image to form a likelihood map that can be used to identify classifiable regions of the image. The information necessary for calculating the likelihood values is obtained by collecting additional depth data that maps to each pixel in an image (collectively referred to as a RGB-D image). Experiments to test the approach are conducted in a laboratory environment using a RGB-D sensor package mounted onto the end-effector of a robot manipulator. A naive Bayes classifier trained with texture features extracted from Gray Level Co-occurrence Matrices is used to demonstrate the effect of image capture conditions on surface classification accuracy. Experimental results show that the classifiable regions identified using a likelihood map are up to 99.0% accurate, and the identified region has up to 19.9% higher classification accuracy when compared against the overall accuracy of the same image.
This paper proposes an approach to improve surface-type classification of images containing inconsistently illuminated surfaces. When a mobile inspection robot is visually inspecting surface-types in a dark environment and a directional light source is used to illuminate the surfaces, the images captured may exhibit illumination variance that can be caused by the orientation and distance of the light source relative to the surfaces. In order to accurately classify the surface-types in these images, either the training image dataset needs to completely incorporate the illumination variance or a way to extract color features that can provide high classification accuracy needs to be identified. In this paper diffused reflectance values are extracted as new color features to classifying surface-types. In this approach, Red, Green, Blue-Depth (RGB-D) data is collected from the environment, and a reflectance model is used to calculate a diffused reflectance value for a pixel in each Red, Green, Blue (RGB) color channel. The diffused reflectance values can be used to train a multiclass support vector machine classifier to classify surface-types. Experiments are conducted in a mock bridge maintenance environment using a portable RGB-Depth sensor package with an attached light source to collect surface-type data. The performance of a classifier trained with diffused reflectance values is compared against classifiers trained with other color features including RGB and L*a*b* color spaces. Results show that the classifier trained with the diffused reflectance values can achieve consistently higher classification accuracy than the classifiers trained with RGB and L*a*b* features. For test images containing a single surface plane, diffused reflectance values consistently provide greater than 90% classification accuracy; and for test images containing a complex scene with multiple surface-types and surface planes, diffused reflectance values are shown to provide an increase in...
Cai, B, Huang, S, Liu, D & Dissanayake, G 2014, 'Rescheduling policies for large-scale task allocation of autonomous straddle carriers under uncertainty at automated container terminals', Robotics And Autonomous Systems, vol. 62, pp. 506-514.View/Download from: Publisher's site
This paper investigates replanning strategies for container transportation task allocation of autonomous Straddle Carriers (SC) at automated container terminals. The strategies address the problem of large-scale scheduling in the context of uncertainty (especially uncertainty associated with unexpected events such as the arrival of a new task). Two rescheduling policies Rescheduling New arrival Jobs (RNJ) policy and Rescheduling Combination of new and unexecuted Jobs (RCJ) policy are presented and compared for long-term Autonomous SC Scheduling (ASCS) under the uncertainty of new job arrival. The long-term performance of the two rescheduling policies is evaluated using a multi-objective cost function (i.e., the sum of the costs of SC travelling, SC waiting, and delay of finishing high-priority jobs). This evaluation is conducted based on two different ASCS solving algorithms an exact algorithm (i.e., branch-and-bound with column generation (BBCG) algorithm) and an approximate algorithm (i.e., auction algorithm) to get the schedule of each short-term planning for the policy. Based on the map of an actual fully-automated container terminal, simulation and comparative results demonstrate the quality advantage of the RCJ policy compared with the RNJ policy for task allocation of autonomous straddle carriers under uncertainty. Long-term testing results also show that although the auction algorithm is much more efficient than the BBCG algorithm for practical applications, it is not effective enough, even when employed by the superior RCJ policy, to achieve high-quality scheduling of autonomous SCs at the container terminals.
Skinner, B, Yuan, S, Huang, S & Liu, D 2013, 'A new crossover approach for solving the multiple travelling salesmen problem using genetic algorithms', European Journal Of Operational Research, vol. 228, no. 1, pp. 72-82.View/Download from: Publisher's site
This paper proposes a new crossover operator called two-part chromosome crossover (TCX) for solving the multiple travelling salesmen problem (MTSP) using a genetic algorithm (GA) for near-optimal solutions. We adopt the two-part chromosome representation technique which has been proven to minimise the size of the problem search space. Nevertheless, the existing crossover method for the two-part chromosome representation has two limitations. Firstly, it has extremely limited diversity in the second part of the chromosome, which greatly restricts the search ability of the GA. Secondly, the existing crossover approach tends to break useful building blocks in the first part of the chromosome, which reduces the GAâs effectiveness and solution quality. Therefore, in order to improve the GA search performance with the two-part chromosome representation, we propose TCX to overcome these two limitations and improve solution quality. Moreover, we evaluate and compare the proposed TCX with three different crossover methods for two MTSP objective functions, namely, minimising total travel distance and minimising longest tour. The experimental results show that TCX can improve the solution quality of the GA compared to three existing crossover approaches.
To allow intuitive communication in human-robot cooperation through tactile information, this paper presents a method to recognize human intended direction in 2-D using a handlebar equipped with uniaxial tactile arrays. The method first extracts various features from the tactile images aiming to reduce computation complexity and increase recognition robustness. A support vector machines classifier was implemented for classifying the intended direction of humans using the extracted features. The algorithm efficiency of using different combinations of features has been investigated and compared through human user studies. In total, five human users in the project team were involved in this research. Experimental results show that the proposed method can achieve 91.7% recognition accuracy if both the training data and validation data contain tactile images from all the users. The method could still achieve 77.5% recognition accuracy when the training and validation data share no common user.
Carmichael, MG & Liu, D 2013, 'Estimating Physical Assistance Need Using a Musculoskeletal Model', IEEE Transactions On Biomedical Engineering, vol. 60, no. 7, pp. 1912-1919.View/Download from: Publisher's site
Technologies that provide physical assistance during tasks are often required to provide assistance specific to the task and person performing it. An example is robotic rehabilitation in which the assistance-as-needed (AAN) paradigm aims to provide operators with the minimum assistance required to perform the task. Current approaches use empirical performance-based methods which require repeated observation of the specific task before an estimate of the needed assistance can be determined. In this paper, we present a new approach utilizing a musculoskeletal model (MM) of the upper limb to estimate the operator's assistance needs with respect to physical tasks. With capabilities of the operator defined at the muscular level of the MM, an optimization model is used to estimate the operator's strength capability. Strength required to perform a task is calculated using a task model. The difference or gap between the operator's strength capability and the strength required to execute a task forms the basis for the new AAN paradigm. We show how this approach estimates the effects of limb pose, load direction, and muscle impairments on a person's ability to perform tasks.
Paul, G, Kwok, NM & Liu, D 2013, 'A novel surface segmentation approach for robotic manipulator-based maintenance operation planning', Automation In Construction, vol. 29, pp. 136-147.View/Download from: Publisher's site
This paper presents a novel approach to segmenting a three-dimensional surface map by considering the task requirements and the movements of an industrial robot manipulator. Maintenance operations, such as abrasive blasting, that are performed by a field robot manipulator can be made more efficient by exploiting surface segmentation. The approach in this paper utilises an aggregate of multiple connectivity graphs, with graph edges defined by task constraints, and graph vertices that correspond to small, maintenance-specific target surfaces, known as Scale-Like Discs (SLDs). The task constraints for maintenance operations are based on the characteristics of neighbouring SLDs. The combined connectivity graphs are analysed to find clusters of vertices, thus segmenting the surface map into groups of related SLDs. Experiments conducted in three typical bridge maintenance environments have shown that the approach can reduce garnet usage by 10%â40% and reduce the manipulator joint movements by up to 35%.
Cai, B, Huang, S, Liu, D, Yuan, S, Dissanayake, G, Lau, H & Pagac, D 2013, 'Multi-objective optimization for autonomous straddle carrier scheduling at automated container terminals', IEEE Transactions on Automation Science and Engineering, vol. 10, no. 3, pp. 711-725.View/Download from: Publisher's site
A multiobjective optimization model is presented in this paper for the Autonomous Straddle Carriers Scheduling (ASCS) problem in automated container terminals, which is more practical than the single objective model. The model considers three objectives [i.e., Straddle Carriers (SCs) traveling time, SC waiting time and finishing time of high-priority container-transferring jobs], and their weighted sum is investigated as the representative example. The presented model is formulated as a pickup and delivery problem with time windows in the form of binary integer programming. An exact algorithm based on Branch-and-Bound with Column Generation (BBCG) is employed for solving the multiobjective ASCS problem. Based on the map of an actual fully automated container terminal, simulation results are compared with the single-objective scheduling to demonstrate the effectiveness and flexibility of the presented multiobjective model, as well as the efficacy of the BBCG algorithm for autonomous SC scheduling.
Khushaba, RN, Kodagoda, S, Liu, D & Dissanayake, G 2013, 'Muscle Computer Interfaces for Driver Distraction Reduction', Computer Methods and Programs in Biomedicine, vol. 110, no. 2, pp. 137-149.View/Download from: Publisher's site
Driver distraction is regarded as a significant contributor to motor-vehicle crashes. One of the important factors contributing to driver distraction was reported to be the handling and reaching of in-car electronic equipment and controls that usually requires taking the drivers' hands off the wheel and eyes off the road. To minimize the amount of such distraction, we present a new control scheme that senses and decodes the human muscles signals, denoted as Electromyogram (EMG), associated with different fingers postures/pressures, and map that to different commands to control external equipment, without taking hands off the wheel. To facilitate such a scheme, the most significant step is the extraction of a set of highly discriminative feature set that can well separate between the different EMG-based actions and to do so in a computationally efficient manner. In this paper, an accurate and efficient method based on Fuzzy Neighborhood Discriminant Analysis (FNDA), is proposed for discriminant feature extraction and then extended to the channel selection problem. Unlike existing methods, the objective of the proposed FNDA is to preserve the local geometrical and discriminant structures, while taking into account the contribution of the samples to the different classes. The method also aims to efficiently overcome the singularity problems of classical LDA by employing the QR-decomposition. Practical real-time experiments with eight EMG sensors attached on the human forearm of eight subjects indicated that up to fourteen classes of fingers postures/pressures can be classified with <7% error on average, proving the significance of the proposed method.
Skinner, B, Yuan, S, Huang, S, Liu, D, Cai, B, Dissanayake, G, Lau, H, Bott, A & Pagac, D 2013, 'Optimisation for job scheduling at automated container terminals using genetic algorithm', Computers and Industrial Engineering, vol. 64, no. 1, pp. 511-523.View/Download from: Publisher's site
This paper presents a genetic algorithm (GA)-based optimisation approach to improve container handling operations at the Patrick AutoStrad container terminal located in Brisbane Australia. In this paper we focus on scheduling for container transfers and encode the problem using a two-part chromosome approach which is then solved using a modified genetic algorithm. In simulation experiments, the performance of the GA-based approach and a sequential job scheduling method are evaluated and compared with different scheduling scenarios. The experimental results show that the GA-based approach can find better solutions which improve the overall performance. The GA-based approach has been implemented in the terminal scheduling system and the live testing results show that the GA-based approach can reduce the overall time-related cost of container transfers at the automated container terminal
Chotiprayanakul, P, Liu, D & Dissanayake, G 2012, 'Human-robot-environment Interaction Interface For Robotic Grit-blasting Of Complex Steel Bridges', Automation In Construction, vol. 27, pp. 11-23.View/Download from: Publisher's site
This paper presents a human-robot-environment interaction (HREI) interface using haptic feedback for a grit-blasting robot operating in close proximity to a complex steel bridge structure. The productivity requirements dictate the need for efficient algorithms for mapping, exploration, and collision-free motion planning. While a large portion of the grit-blasting operation can be automated, a tele-operation is essential to deal with some difficult to access sections such as edges, complex corners, and surfaces which can only be approached through hole. A 3-dimensional virtual force field (3D-VF 2 ) method is developed for capturing the relationship between the robot and its environment. A novel haptic force generation method and a workspace mapping algorithm allow intuitive interaction between the operator and the robot through haptic feedback. The strategies presented are verified in extensive simulations and experiments conducted on a steel bridge with a prototype grit-blasting robot
Meng, X, Wang, S, Qiu, J, Zhang, Q, Zhu, JG, Guo, Y & Liu, D 2011, 'Robust Multilevel Optimization of PMSM Using Design for Six Sigma', IEEE Transactions On Magnetics, vol. 47, no. 10, pp. 3248-3251.View/Download from: Publisher's site
In this paper, a robust optimization method based on design for six sigma (DFSS) is combined to the optimization of a surface mounted permanent synchronous machine (PMSM) by using multilevel genetic algorithm (MLGA). First, MLGA and DFSS are introduced in the robust optimization. Second, by taking into account the tolerances of the motor products, important input parameters could be varied with six sigma distribution and Monte Carlo simulation (MCS) method is used to reduce the calculation cost. Third, to verify the new algorithm, the presented algorithm is applied to the optimization of a PMSM. The results compared with those of traditional GA and MLGA and the discussion of the robust optimization combined with MLGA are presented.
Paul, G, Webb, SS, Liu, D & Dissanayake, G 2011, 'Autonomous Robot Manipulator-Based Exploration And Mapping System For Bridge Maintenance', Robotics And Autonomous Systems, vol. 59, no. 7-8, pp. 543-554.View/Download from: Publisher's site
This paper presents a system for Autonomous eXploration to Build A Map (AXBAM) of an unknown, 3D complex steel bridge structure using a 6 degree-of-freedom anthropomorphic robot manipulator instrumented with a laser range scanner. The proposed algorithm considers the trade-off between the predicted environment information gain available from a sensing viewpoint and the manipulator joint angle changes required to position a sensor at that viewpoint, and then obtains collision-free paths through safe, previously explored regions. Information gathered from multiple viewpoints is fused to achieve a detailed 3D map. Experimental results show that the AXBAM system explores and builds quality maps of complex unknown regions in a consistent and timely manner.
Yuan, S, Skinner, B, Huang, S, Liu, D, Dissanayake, G, Lau, H & Pagac, D 2011, 'A job grouping approach for planning container transfers at automated seaport container terminals', Advanced Engineering Informatics, vol. 25, no. 3, pp. 413-426.View/Download from: Publisher's site
This paper proposes a practical job grouping approach, which aims to enhance the time related performance metrics of container transfers in the Patrick AutoStrad container terminal, located in Brisbane, Australia. It first formulates a mathematical model of the automated container transfers in a relatively complex environment. Apart from the consideration on collision avoidance of a fleet of large vehicles in a confined area, it also deals with many other difficult practical challenges such as the presence of multiple levels of container stacking and sequencing, variable container orientations, and vehicular dynamics that require finite acceleration and deceleration times. The proposed job grouping approach aims to improve the makespan of the schedule for yard jobs, while reducing straddle carrier waiting time by grouping jobs using a guiding function. The performance of the current sequential job allocation method and the proposed job grouping approach are evaluated and compared statistically using a pooled t-test for 30 randomly generated yard configurations. The experimental results show that the job grouping approach can effectively improve the schedule makespan and reduce the total straddle carrier waiting time.
Cheong, C, Tan, KC, Liu, D & Lin, C 2010, 'Multi-objective and prioritized berth allocation in container ports', Annals Of Operations Research, vol. 180, no. 1, pp. 63-103.View/Download from: Publisher's site
This paper considers a berth allocation problem (BAP) which requires the determination of exact berthing times and positions of incoming ships in a container port. The problem is solved by optimizing the berth schedule so as to minimize concurrently the three objectives of makespan, waiting time, and degree of deviation from a predetermined priority schedule. These objectives represent the interests of both port and ship operators. Unlike most existing approaches in the literature which are single-objective-based, a multi-objective evolutionary algorithm (MOEA) that incorporates the concept of Pareto optimality is proposed for solving the multi-objective BAP. The MOEA is equipped with three primary features which are specifically designed to target the optimization of the three objectives. The features include a local search heuristic, a hybrid solution decoding scheme, and an optimal berth insertion procedure. The effects that each of these features has on the quality of berth schedules are studied
Wang, SH, Meng, XJ, Qiu, J, Zhu, J, Wang, Y, Guo, Y, Liu, D & Xu, W 2010, 'Dynamic Multilevel Optimization of Machine Design and Control Parameters for PMSM Drive System Based on Correlation Analysis', IEEE Transactions On Magnetics, vol. 46, no. 8, pp. 2779-2782.View/Download from: Publisher's site
In this paper, a multilevel optimization method is proposed for a motor drive system including a surface-mounted permanent magnet synchronous machine (SPMSM), the converter/inverter, and the control schemes. First, the multilevel optimization is described by using the problem matrix which may be used to allocate the design variables on different levels. The parameters in the problem matrix are deduced by using correlation analysis. Second, the architecture and implementation of multilevel genetic algorithm (MLGA) are carried out. As one of the advantages of MLGA, the dynamic adjustment strategy of GA operators is utilized to improve the optimal performance. The algorithm is then applied to a three-level optimization problem in which the optimization of SPMSM design and the control parameters of drive are considered in different levels. Finally, some results and discussions about the application of the proposed algorithm are presented.
Lindsay, E, Murray, SJ, Liu, D, Lowe, DB & Bright, C 2009, 'Establishment reality vs. maintenance reality: how real is real enough?', European Journal of Engineering Education, vol. 34, no. 3, pp. 229-234.View/Download from: Publisher's site
Remote and virtual laboratories are increasingly prevalent alternatives to the face-to-face laboratory experience; however, the question of their learning outcomes is yet to be fully investigated. There are many presumptions regarding the effectiveness of these approaches; foremost amongst these assumptions is that the experience must be 'real' to be effective. Embedding reality into a remote or virtual laboratory can be an expensive and time-consuming task. Significant efforts have been expended to create 3D VRML models of laboratory equipment, allowing students to pan, zoom and tilt their perspective as they see fit. Multiple camera angles have been embedded into remote interfaces to provide an increased sense of 'realness'. This paper draws upon the literature in the field to show that the necessary threshold for reality varies depending upon how the students are interacting with the equipment. There is one threshold for when they first interact - the establishment reality - which allows the students to familiarise themselves with the laboratory equipment, and to build their mental model of the experience. There is, however, a second, lower, threshold - the maintenance reality - that is necessary for the students' ongoing operation of the equipment. Students' usage patterns rely upon a limited subset of the available functionality, focusing upon only some aspects of the reality that has been originally established. The two threshold model presented in this paper provides a new insight for the development of virtual laboratories in the future.
Lowe, DB, Murray, SJ, Lindsay, E & Liu, D 2009, 'Evolving Remote Laboratory Architectures to Leverage Emerging Internet Technologies', IEEE Transactions on Learning Technologies, vol. 2, no. 4, pp. 289-294.View/Download from: Publisher's site
There is growing research into, and development of, the use of the internet to support remote access by students to physical laboratory infrastructure. These remote laboratories can, under appropriate circumstances, support or even replace traditional (proximal) laboratories, provide additional or improved access at reduced cost, and encourage inter-institutional sharing of expensive resources. Effective design of remote laboratories requires attention to the design of both the pedagogy and the technical infrastructure, as well as how these elements interact. In this paper we consider the architectures of remote laboratories, the shortcomings of existing implementations, and we argue that emerging internet technologies can assist in overcoming these shortcomings. We also consider the opportunities which these technologies provide in moving beyond both existing remote laboratories and existing proximal laboratories, to create opportunities which were not previously possible.
Wang, S, Meng, X, Guo, N, Li, H, Qiu, J, Zhu, J, Guo, Y, Liu, D, Wang, Y & Xu, W 2009, 'Multilevel Optimisation for Surface Mounted PM Machine Incorporating with FEM', IEEE Transactions On Magnetics, vol. 45, no. 10, pp. 4700-4703.View/Download from: Publisher's site
In this paper, multilevel genetic algorithm (MLGA) is presented to solve the optimization of surface mounted permanent magnet synchronous machine (SPMSM), which has features of mixed continuous and discrete design variables, multi-modal objective functions, etc. Firstly, the multilevel optimization problem is described by using the problem matrix. The values in the problem matrix are deduced by correlation analysis. Secondly, the architecture and implementation of MLGA are carried out. Thirdly, the new algorithm is applied to a bilevel optimization of SPMSM to verify this multilevel optimization. The results compared with those of traditional genetic algorithm (GA) and discussions of the multilevel optimization are presented.
Kwok, N, Ha, QP, Liu, D & Fang, G 2009, 'Contrast Enhancement and Intensity Preservation for Gray-Level Images using Multi-objective Particle Swarm Optimisation', IEEE Transactions on Automation Science and Eng..., vol. 6, no. 1, pp. 145-155.View/Download from: Publisher's site
The contrast enhancement of gray-level digital images is considered in this paper. In particular, the mean image intensity is preserved while the contrast is enhanced. This provides better viewing consistence and effectiveness. The contrast enhancement is achieved by maximizing the information content carried in the image via a continuous intensity transform function. The preservation of image intensity is obtained by applying gamma-correction on the images. Since there is always a trade-off between the requirements for the enhancement of contrast and preservation of intensity, an improved multiobjective particle swarm optimization procedure is proposed to resolve this contradiction, making use of its flexible algorithmic structure. The effectiveness of the proposed approach is illustrated by a number of images including the benchmarks and an image sequence captured from a mobile robot in an indoor environment.
To, AW, Paul, G, Kwok, N & Liu, D 2009, 'An efficient trajectory planning approach for autonomous robots in complex bridge environments', International Journal of Computer Aided Engineeri..., vol. 1, no. 2, pp. 185-208.
This paper presents an efficient trajectory planning approach for a 6DOF robotic manipulator conducting grit-blasting in complex bridge structural environments. The proposed approach extends upon robotic grit-blasting planning and incorporates joint movement minimisation in addition to path length minimisation. A genetic algorithm is implemented to optimise initial path plans based on a heuristic pattern for the coverage of surface areas to be blasted. A customised gradient based method is applied for the generation of collision-free joint configurations for grit-blasting based on the identified path plan. A grit-blasting coverage model is developed for discrete non-planar 3D coverage determination to verify the performance of the plan. Extensive simulation and experimental results are also presented in this paper.
This paper presents a system for surface classification using a laser range finder. It is shown that the return intensities and range errors provide sufficient information to distinguish a wide range of surfaces commonly found in a number of environments. A supervised learning scheme (using curves representing the return intensity and range error as a function of angle of incidence) is used to classify the surface type of planar patches. Extensive experimental evidence is presented to demonstrate the potential of the proposed technique. The surface type classification, which uses a typical laser range finder, is targeted for use with autonomous robotic systems in which significantly different interaction is required for each of the various materials present. Results from an on-site experiment demonstrate that the information from the laser range finder is sufficient to identify the different materials (via their surface properties) present in a scene where a bridge structure is being prepared for grit blasting.
Paul, G, Liu, D, Kirchner, NG & Dissanayake, G 2009, 'An Effective Exploration Approach to Simultaneous Mapping and Surface Material-Type Identification of Complex Three-Dimensional Environments', Journal of Field Robotics, vol. 26, no. 11-12, pp. 915-933.View/Download from: Publisher's site
This paper presents an integrated exploration approach for geometric mapping and surface material-type identification of complex three-dimensional (3D) environments using a six-degree-of-freedom industrial robot manipulator. Maps of the surface geometry with the surface material type identified are required for an autonomous robotic system to perform operations in steel bridge maintenance. The proposed approach utilizes information theory to enable multiobjective exploration while new 3D geometric and surface-type data are fused via probabilistic updates. It is verified that the integrated approach enables the robotic system to perform exploration and surface inspection in real-world environments.
Kirchner, NG, Hordern, DL, Liu, D & Dissanayake, G 2008, 'Capacitive sensor for object ranging and material type identification', Sensors And Actuators A-Physical, vol. 148, no. 1, pp. 96-104.View/Download from: Publisher's site
This paper presents a system for object ranging and material type identification using a multifrequency approach for a capacitive sensor. it is shown through an experimental study that the deviation in the readings taken at different sensor drive frequen
Kirchner, NG, Paul, G & Liu, D 2006, 'Bridge Maintenance Robotic Arm: Mechanical Technique to reduce the nozzle Force of a Sandblasting Rig', Journal of Wuhan University of Technology, vol. 28, no. 164, pp. 12-18.
Kwok, N, Liu, D & Dissanayake, G 2006, 'Evolutionary Computing Based Mobile Robot Localization', Engineering Applications of Artificial Intelligence, vol. 19, no. 8, pp. 857-868.View/Download from: Publisher's site
Evolutionary computing techniques, including genetic algorithms (GA), particle swarm optimization (PSO) and ants system (AS) are applied to the localization problem of a mobile robot. Salient features of robot localization are that the system is partially dynamic and information for fitness evaluation is incomplete and corrupted by noise. In this research, variations to the above three evolutionary computing techniques are proposed to tackle the specific dynamic and noisy system. Their performances are compared based on simulation and experiment results and the feasibility of the proposed approach to mobile robot localization is demonstrated.
Tan, K, Chen, YJ, Wang, L & Liu, D 2005, 'Intelligent sensor fusion and learning for autonomous robot navigation', Applied Artificial Intelligence, vol. 19, no. 5, pp. 433-456.View/Download from: Publisher's site
This paper presents the design and implementation of an autonomous robot navigation system for intelligent target collection in dynamic environments. A feature-based multi-stage fuzzy logic (MSFL) sensor fusion system is developed for target recognition, which is capable of mapping noisy sensor inputs into reliable decisions. The robot exploration and path planning are based on a grid map oriented reinforcement path learning system (GMRPL), which allows for long-term predictions and path adaptation via dynamic interactions with physical environments. In our implementation, the MSFL and GMRPL are integrated into subsumption architecture for intelligent target-collecting applications. The subsumption architecture is a layered reactive agent structure that enables the robot to implement higher-layer functions including path learning and target recognition regardless of lower-layer functions such as obstacle detection and avoidance. The real-world application using a Khepera robot shows the robustness and flexibility of the developed system in dealing with robotic behaviors such as target collecting in the ever-changing physical environment.
Tan, YG, Liu, DK, Liu, F & Zhou, ZD 2005, 'Digital robust preview control of path tracking', PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART I-JOURNAL OF SYSTEMS AND CONTROL ENGINEERING, vol. 219, no. I1, pp. 111-117.View/Download from: Publisher's site
Grinding is one of the most versatile methods of removing material from machine parts to provide precise geometry. Dynamic analysis of the grinding process is necessary to reduce the surface waviness and roughness induced by vibrations, and to offer a ma
Crowther, AR, Zhang, N, Liu, D & Jeyakumaran, JM 2004, 'Analysis and simulation of clutch engagement judder and stick-slip in automotive powertrain systems', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 218, no. 12, pp. 1427-1446.View/Download from: Publisher's site
Clutch engagement judder and stick-slip are investigated analytically and numerically to examine the influencing factors on these phenomena. Models are developed for a four degree-of-freedom (4DOF) torsional system with slipping clutch and for a powertrain with automatic transmission system. Stability analysis is performed to demonstrate that clutch judder is dependent on the slope of the friction coefficient and the analysis is verified with numerical simulations. An algorithm for modelling stick-slip is developed and is used in numerical simulations which show that the likelihood of stick-slip is increased by clutch pressure fluctuations, judder approaching engagement, and external torque fluctuations. Numerical simulations for second to thin gear up shifts demonstrate that the likelihood of stick-slip to occur from clutch engagement is increased by clutch applied pressure fluctuations, judder approaching engagement, and external torque fluctuations and that the likelihood of stick-slip occurring is decreased dramatically by applied pressure ramps proximus to the engagement point.
Li, QS, Liu, D, Tang, J, Zhang, N & Tam, CM 2004, 'Combinatorial optimal design of number and positions of actuators in actively controlled structures using genetic algorithms', Journal Of Sound And Vibration, vol. 270, no. 4-5, pp. 611-624.View/Download from: Publisher's site
In this paper, the optimal design of the numbers and positions of actuators in actively controlled structures is formulated as a three-level optimal design problem. Features of this design problem such as discreteness, multi-modality and hierarchical structure are discussed. A two-level genetic algorithm (TLGA) is proposed for solving this problem. The concept, principle and solution process of the TLGA are described. A case study is presented, in which a building is subjected to earthquake excitation and controlled by active tendon actuators. The results of this study show that: (1) the design problem for optimizing number and configuration of actuators simultaneously in actively controlled structures has the features of non-linearity, mixed-discreteness and multi-modality; (2) a three-level design model can give a reasonable description for this kind of design problem; (3) TLGA is an effective algorithm for solving the combinatorial optimization problem.
Liu, D, Yang, YL & Li, QS 2003, 'Optimum Positioning of Actuators In Tall Buildings Using Genetic Algorithm', Computers and Structures, vol. 81, no. 32, pp. 2823-2827.View/Download from: Publisher's site
Zhang, N, Crowther, AR, Liu, D & Jeyakumaran, JM 2003, 'A finite element method for the dynamic analysis of automatic transmission gear shifting with a four-degree-of-freedom planetary gearset element', Proceedings Of The Institution Of Mechanical Engineers Part D-journal Of Automobile Engineering, vol. 217, no. D6, pp. 461-473.View/Download from: Publisher's site
Tam, CM, Leung, A & Liu, D 2002, 'Non-linear models for predicting hoisting times of tower cranes', Journal of computing in civil engineering, vol. 16, no. 1, pp. 76-81.View/Download from: Publisher's site
Li, QS, Liu, D, Leung, AY, Zhang, N & Luo, QZ 2002, 'A multilevel genetic algorithm for the optimum design of structural control systems', International Journal for Numerical Methods in Engineering, vol. 55, no. 7, pp. 817-834.View/Download from: Publisher's site
A multilevel genetic algorithm (MLGA) is proposed in this paper for solving the kind of optimization problems which are multilevel structures in nature and have features of mixed-discrete design variables, multi-modal and non-continuous objective functions, etc. Firstly, the formulation of the mixed-discrete multilevel optimization problems is presented. Secondly, the architecture and implementation of MLGA are described. Thirdly, the algorithm is applied to two multilevel optimization problems. The first one is a three-level optimization problem in which the optimization of the number of actuators, the positions of actuators and the control parameters are considered in different levels. An actively controlled tall building subjected to strong wind action is considered to investigate the effectiveness of the proposed algorithm. The second application considers a combinatorial optimization problem in which the number and configuration of actuators are optimized simultaneously, an actively controlled building under earthquake excitations is adopted for this case study. Finally, some results and discussions about the application of the proposed algorithm are presented.
Zhang, N, Liu, DK, Jeyakumaran, JM & Villanueva, L 2002, 'Modelling of dynamic characteristics of an automatic transmission during shift changes', PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART I-JOURNAL OF SYSTEMS AND CONTROL ENGINEERING, vol. 216, no. I4, pp. 331-341.View/Download from: Publisher's site
Leung, A, Tam, CM & Liu, D 2001, 'Comparative study of artificial neural networks and multiple regression analysis for predicting hoisting times of tower cranes', Building and Environment, vol. 36, no. 4, pp. 457-467.
Li, QS, Fang, JQ, Jeary, AP & Liu, D 2001, 'Decoupling control law for structural control implementation', International Journal of Solids and Structures, vol. 38, no. 34-35, pp. 6147-6162.View/Download from: Publisher's site
Li, QS, Yang, LF, Qu, X, Li, GQ & Liu, D 2001, 'The quintic finite element and finite strip with generalized degrees of freedom in structural analysis', International Journal of Solids and Structures, vol. 38, no. 30-31, pp. 5355-5372.View/Download from: Publisher's site
Luo, QZ, Li, S, Liu, DK & Yang, LF 2001, 'A modified finite segment method for thin-walled single-cell box girders with shear lag', Proceedings of the Institution of Civil Engineers: Structures and Buildings, vol. 146, no. 1, pp. 41-46.View/Download from: Publisher's site
This paper presents a modified finite segment method for shear-lag analysis of thin-walled box girders. The method is based on the hypothesis that the warping displacement of a flange plate is governed by a third-order parabolic curve. Based on the principle of minimum potential energy, the governing differential equations with two unknown displacement functions are derived. The homogeneous solutions of the differential equations are used to represent the displacement functions of the finite element. By mean of the variational principle, the element stiffness equation is developed and the normal longitudinal stresses taking into account the shear lag are obtained. To verify the accuracy of the proposed method, three experiments are conducted so that the present results are compared with those obtained by the model tests and other methods.
Fang, JQ, Li, QS, Liu, D, Jeary, AP & Wong, CK 2000, 'Wind effects on a very tall building and wavelet analysis', Institution of Civil Engineers. Proceedings. Structures and Buildings, vol. 140, no. 2, pp. 151-159.View/Download from: Publisher's site
Li, QS, Fang, JQ & Liu, D 2000, 'Exact solutions for free vibration of single-degree-of-freedom systems with non-periodically varying parameters', Journal of Vibration and Control, vol. 6, no. 3, pp. 449-462.View/Download from: Publisher's site
Li, QS, Fang, JQ, Jeary, AP, Wong, CK & Liu, DK 2000, 'Evaluation of wind effects on a supertall building based on full-scale measurements', Earthquake Engineering and Structural Dynamics, vol. 29, no. 12, pp. 1845-1862.View/Download from: 3.0.CO;2-Q">Publisher's site
This paper describes the results obtained from the full-scale measurements of wind effects on a 70-storey building in Hong Kong. The building which has a height of approximately 370 m is the second tallest structure in Hong Kong. The field data such as wind speed, wind direction and wind-induced acceleration responses have been measured since 1995 including the close passage of two typhoons; typhoon Sally and typhoon Kent. Detailed analysis of the field data is conducted. The full-scale measurements are compared with the wind tunnel results obtained in the Boundary Layer Wind Tunnel Laboratory at Western Ontario University. The amplitude-dependent characteristics of damping and natural frequency that were obtained by using the random decrement technique are investigated. Copyright (C) 2000 John Wiley and Sons, Ltd.
Li, QS, Li, GQ & Liu, D 2000, 'Exact solution for longitudinal vibration of rods coupled by translational springs', International Journal of Mechanical Science, vol. 42, no. 6, pp. 1135-1152.View/Download from: Publisher's site
Li, QS, Liu, D, Fang, JQ & Tam, CM 2000, 'Multi-level optimal design of buildings with active control under winds using genetic algorithms', Journal Of Wind Engineering And Industrial Aerodynamics, vol. 86, no. 1, pp. 65-86.View/Download from: Publisher's site
Li, QS, Liu, D, Fang, JQ, Jeary, AP & Wong, CK 2000, 'Damping in buildings: its neural network model and AR model', Engineering Structures, vol. 22, no. 9, pp. 1216-1223.View/Download from: Publisher's site
Li, QS, Liu, DK, Leung, AY, Zhang, N, Tam, CM & Yang, LF 2000, 'Modelling of structural response and optimization of structural control system using neural network and genetic algorithm', The Structural Design of Tall and Special Buildings, vol. 9, no. 4, pp. 279-293.
In recognition of the increasing importance of accurate seismic vulnerability assessment, this paper deals with procedures and the application of inelastic acceleration and displacement spectra in the seismic assessment of buildings. An identification procedure is outlined, whereby an equivalent single degree of freedom (SDOF) system is devised to represent the building. The SDOF system characteristics (stiffness, strength, post-peak force response and ductility) are readily evaluated from observation of the seismic response of buildings and simple mechanics. The characteristics are then tuned using measurements from instrumented buildings. Based on the earthquake scenario and structural response characteristics, appropriate inelastic acceleration and displacement spectra are selected and used to predict the response. Comparison between the measured and predicted responses for the five buildings studied in the paper confirm the feasibility of the procedure and the realism of the results
Fang, JQ, Li, QS & Liu, DK 1999, 'Non-spillover control design of tall buildings in modal space', Wind and Structures, An International Journal, vol. 2, no. 3, pp. 189-200.View/Download from: Publisher's site
In this paper, a new algorithm for active control design of structures is proposed and investigated. The algorithm preserves the decoupling property of the modal vibration equation and eliminates the spillover problem, which is the main shortcoming in the independent modal space control (IMSC) algorithm. With linear quadratic regulator(LQR) control law, the analytical solution of algebraic Riccati equation and the optimal actuator control force are obtained, and the control design procedure is significantly simplified. A numerical example for the control design of a tall building subjected to wind loads demonstrates the effectiveness of the proposed algorithm in reducing the acceleration and displacement responses of tall buildings under wind actions.
Fang, JQ, Li, QS, Jeary, AP & Liu, DK 1999, 'Damping of tall buildings: Its evaluation and probabilistic characteristics', STRUCTURAL DESIGN OF TALL BUILDINGS, vol. 8, no. 2, pp. 145-153.
Fang, JQ, Li, QS, Jeary, AP, Liu, DK & Wong, CK 1999, 'Probabilistic characteristics of damping in buildings', Wind and Structures, An International Journal, vol. 2, no. 2, pp. 127-131.View/Download from: Publisher's site
This paper describes probabilistic characteristics of damping in a tall building based on the results of full-scale measurement. It is found, through statistical analysis of the damping data, that the probability density function(PDF) of damping at the high amplitude plateau can be well represented by Normal distribution (Gaussian distribution). A stochastic damping model is proposed to estimate amplitude-dependent damping for practical application.
Li, Q, Cao, H, Li, G, Li, S & Liu, D 1999, 'Optimal design of wind-induced vibration control of tall buildings and high-rise structures', Wind and Structures, An International Journal, vol. 2, no. 1, pp. 69-83.View/Download from: Publisher's site
The most common used control device on tall buildings and high-rise structures is active and passive tuned mass damper (ATMD and TMD). The major advantages of ATMD and TMD are discussed. The existing installations of various passive/active control devices on real structures are listed. A set of parameter optimization methods is proposed to determine optimal parameters of passive tuned mass dampers under wind excitation. Simplified formulas for determining the optimal parameters are proposed so that the design of a TMD can be carried out easily. Optimal design of wind-induced vibration control of frame structures is investigated. A thirty-story tall building is used as an example to demonstrate the procedure and to verify the efficiency of ATMD and TMD with the optimal parameters.
Li, QS, Fang, JQ & Liu, DK 1999, 'Evaluation of structural dynamic responses by stochastic finite element method', STRUCTURAL ENGINEERING AND MECHANICS, vol. 8, no. 5, pp. 477-490.View/Download from: Publisher's site
Li, QS, Liu, DK & Fang, JQ 1999, 'Optimum design of actively controlled structures using genetic algorithms', Advances in Structural Engineering, vol. 2, no. 2, pp. 109-118.View/Download from: Publisher's site
Optimal placement of actuators in actively controlled structures is a mixed-discrete optimization problem; it has the characteristics of nonlinear, non-continuous, and so on. For this type of optimization problem, traditional optimization methods based on mathematical programming may not be effective. In this paper, the complexity, discreteness and non-linearity of the optimal design problems of actuator placement are investigated. An optimal control algorithm and active tendon controllers are applied to control the response of a 16-storey building under earthquake loads. A mathematical model of optimal actuator configuration is established. Based on the special optimization problem of actuator configuration in an actively controlled structure, a modified genetic algorithm is presented and applied to solve the problems. A design procedure/method is presented for this kind of optimization problem, and the suitability of this method for the optimization problem is investigated. The numerical calculation and analysis are carried out for the building controlled by active tendon control mechanisms, and the results are discussed and analyzed in detail.
Li, QS, Liu, DK, Fang, JQ, Jeary, AP & Wong, CK 1999, 'Using neural networks to model and predict amplitude dependent damping in buildings', Wind and Structures, An International Journal, vol. 2, no. 1, pp. 25-40.View/Download from: Publisher's site
In this paper, artificial neural networks, a new kind of intelligent method, are employed to model and predict amplitude dependent damping in buildings based on our full-scale measurements of buildings. The modelling method and procedure using neural networks to model the damping are studied. Comparative analysis of different neural network models of damping, which includes multi-layer perception network (MLP), recurrent neural network, and general regression neural network (GRNN), is performed and discussed in detail. The performances of the models are evaluated and discussed by tests and predictions including self-test, `one-lag' prediction and `multi-lag' prediction of the damping values at high amplitude levels. The established models of damping are used to predict the damping in the following three ways: (1) the model is established by part of the data measured from one building and is used to predict the another part of damping values which are always difficult to obtain from field measurements: the values at the high amplitude level. (2) The model is established by the damping data measured from one building and is used to predict the variation curve of damping for another building. And (3) the model is established by the data measured from more than one buildings and is used to predict the variation curve of damping for another building. The prediction results are discussed.
Li, QS, Fang, JQ, Liu, DK & Jeary, AP 1998, 'Vibration analysis of tall buildings with narrow rectangular plane configuration', STRUCTURAL DESIGN OF TALL BUILDINGS, vol. 7, no. 4, pp. 307-322.View/Download from: 3.0.CO;2-#">Publisher's site
Li, QS, Fang, JQ, Liu, DK & Jeary, AP 1998, 'Vibration analysis of tall buildings with narrow rectangular plane configuration', Structural Design of Tall Buildings, vol. 7, no. 4, pp. 307-322.View/Download from: 3.0.co;2-%23">Publisher's site
In this paper, tall buildings of narrow rectangular plane configuration are treated as one-step or multi-step cantilever flexural-shear plates for the analysis of their free vibrations. The governing differential equations for the vibration of flexural-shear plates considering the effects of both flexural and shear deformation are established. The general solutions for one-step flexural-shear plates are derived and used to obtain the eigenvalue equation for multi-step cantilever flexural-shear plates. A new exact approach is presented which combines the transfer matrix method and a closed-form solution for a uniform flexural-shear plate. A numerical example demonstrates that the calculated natural frequencies and mode shapes of a tall building are in good agreement with the experimentally measured data. It is also shown that the effect of shear deformation on the fundamental natural frequency can be ignored, but its effect on the higher natural frequencies should be considered. © 1998 John Wiley & Sons, Ltd.
Webster, C, Jusufi, A & Liu, D 2019, 'A Comparative Survey of Climbing Robots and Arboreal Animals in Scaling Complex Environments' in Robotics and Mechatronics, Springer, Switzerland, pp. 31-45.View/Download from: Publisher's site
The inchworm style climbing robots in current literature will only take us so far in regard to the robotic maintenance of transmission towers. To continue to push towards developing robots that can perform work in reticular structures we must consider a broader spectrum of animals for inspiration. The abilities of Primates in climbing have long been a benchmark in climbing standards, but due to the mechanical and control complexity associated with their development, they are seldom developed. Birds on the other hand offer an alternate solution, utilising less degrees-of-freedom whilst maintaining stability and manoeuvrability. These ancient arboreal specialists may hold they keys to unlocking the next stage in the development of climbing robotics. This work presents lessons learned from a review on primates as well as some preliminary observations on the climbing capabilities of parrots.
Waldron, K, Ward, P, Liu, DK & Waldron, KJ 2013, 'Optimal Design of a Magnetic Adhesion System for Climbing Robots' in Waldron, KJ & Tokhi, MO (eds), Nature-Inspired Mobile Robotics, World Scientific Publishing, Singapore, pp. 375-382.
Wang, D, Kwok, N, Liu, D & Ha, QP 2009, 'Ranked pareto particle swarm optimization for mobile robot motion planning' in Liu, D, Wang, L & Tan, KC (eds), Design and Control of Intelligent Robotic Systems, Springer, Springer-Verlag Berlin Heidelberg, pp. 97-118.View/Download from: Publisher's site
The Force Field (F 2) method is a novel approach for multi-robot motion planning and coordination. The setting of parameters in the (F 2) method, noticeably, can affect its performance. In this research, we present the Ranked Pareto Particle Swarm Optimization (RPPSO) approach as an extension of the basic idea of Particle Swarm Optimization (PSO), which makes it capable of solving multiobjective optimization problems efficiently. In the RPPSO, particles are initiated randomly in the search space; these particles are then evaluated for their qualities with regard to all objectives. Those particles with highly-ranked qualities have preferences to enter the set of Global Best vectors, which stores many currently best solutions found by particles. Thus, particles in RPPSO will search towards many possible directions and the diversity among solutions is well preserved. Ideally, a set of optimal solutions will be found when the termination criterion is met. The effectiveness of the proposed RPPSO is verified in simulation studies. Satisfactory results are obtained for multiobjective optimization problems of multi-robot motion planning in challenging environments with obstacles.
Kulatunga, AK, Skinner, B, Liu, D & Nguyen, HT 2007, 'Distributed simultaneous task allocation and motion coordination of autonomous vehicles using a parallel computing cluster' in Tarn, TJ, Chen, SB & Zhou, C (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 409-420.View/Download from: Publisher's site
Task allocation and motion coordination are the main factors that should be consi-dered in the coordination of multiple autonomous vehicles in material handling systems. Presently, these factors are handled in different stages, leading to a reduction in optimality and efficiency of the overall coordination. However, if these issues are solved simultaneously we can gain near optimal results. But, the simultaneous approach contains additional algorithmic complexities which increase computation time in the simulation environment. This work aims to reduce the computation time by adopting a parallel and distributed computation strategy for Simultaneous Task Allocation and Motion Coordination (STAMC). In the simulation experiments, each cluster node executes the motion coordination algorithm for each autonomous vehicle. This arrangement enables parallel computation of the expensive STAMC algorithm. Parallel and distributed computation is performed directly within the interpretive MATLAB environment. Results show the parallel and distributed approach provides sub-linear speedup compared to a single centralised computing node.
Liu, D & Kulatunga, AK 2007, 'Simultaneous Planning and Scheduling for Multi-Autonomous Vehicles' in Dahal, KP, Tan, KC & Cowling, PI (eds), Evolutionary Scheduling, Springer, Heidelberg, pp. 437-464.View/Download from: Publisher's site
XU, J, Liu, D & Fang, G 2007, 'An efficient method for collision detection and distance queries in a robotic bridge maintenance system' in Tarn, TJ, Chen, SB & Zhou, C (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 71-82.View/Download from: Publisher's site
When applying autonomous industrial robotic systems in an unknown/partially known or cluttered environment, mapping and representation of the environment as well as collision detection becomes crucial. Existing techniques in these areas are generally complex and computationally expensive to implement. In this paper an efficient sphere representation method is introduced for environment representation, collision detection and distance queries. In particular, this method is designed for the application in an autonomous bridge maintenance system. Simulation results show that this method is effective in environment representation and collision detection. Furthermore, the proposed method is also computationally efficient for real-time implementation.
Paul, G, Liu, D & Kirchner, NG 2007, 'An algorithm for surface growing from laser scan generated point clouts' in Tarn, TJ, Chen, SB & Zhou, C (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 481-491.View/Download from: Publisher's site
n robot applications requiring interaction with a partially/unknown environment, mapping is of paramount importance. This paper presents an effective surface growing algorithm for map building based on laser scan generated point clouds. The algorithm directly converts a point cloud into a surface and normals form which sees a significant reduction in data size and is in a desirable format for planning the interaction with surfaces. It can be used in applications such as robotic cleaning, painting and welding.
Singh, AK, Aldini, S, Leong, D, Wang, YK, Carmichael, MG, Liu, D & Lin, CT 2020, 'Prediction Error Negativity in Physical Human-Robot Collaboration', 8th International Winter Conference on Brain-Computer Interface, BCI 2020.View/Download from: Publisher's site
© 2020 IEEE. Cognitive conflict is a fundamental phenomenon of human cognition, particularly during interaction with the real world. Understanding and detecting cognitive conflict can help to improve interactions in a variety of applications, such as in human-robot collaboration (HRC), which involves continuously guiding the semi-autonomous robot to perform a task in given settings. There have been several works to detect cognitive conflict in HRC but without physical control settings. In this work, we have conducted the first study to explore cognitive conflict using prediction error negativity (PEN) in physical human-robot collaboration (pHRC). Our results show that there was a statistically significant (p =. 047) higher PEN for conflict condition compared to normal conditions, as well as a statistically significant difference between different levels of PEN (p =. 020). These results indicate that cognitive conflict can be detected in pHRC settings and, consequently, provide a window of opportunities to improve the interaction in pHRC.
Carmichael, MG, Aldini, S, Khonasty, R, Tran, A, Reeks, C, Liu, D, Waldron, KJ & Dissanayake, G 2019, 'The ANBOT: An Intelligent Robotic Co-worker for Industrial Abrasive Blasting', IEEE International Conference on Intelligent Robots and Systems, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, Macau, China, pp. 8026-8033.View/Download from: Publisher's site
© 2019 IEEE. We present the ANBOT, an intelligent robotic coworker for physical human-robot collaboration. The ANBOT system assists workers performing industrial abrasive blasting, shielding them from the large forces experienced during this physically demanding task. The co-operative robotic system combines the strength and endurance of robots with the decision making of skilled workers. The inherent challenges in human-robot collaboration, combined with the difficult blasting environment required novel design decisions to be made and new solutions to be developed. These include an approach for handling kinematic singularities in a manner suitable for human-robot co-operation, estimating worker pose under poor visibility conditions, and an intuitive control scheme that adapts the robotic assistance based on the estimated strength of the worker. In this work we summarise the ANBOT system and present findings from preliminary site trials. The trials included several real industrial blasting tasks under the control of a skilled abrasive blasting worker who had no experience working alongside a robot. Results demonstrate the suitability of the ANBOT for practical industrial applications.
Hassan, M & Liu, D 2018, 'A Deformable Spiral Based Algorithm to Smooth Coverage Path Planning for Marine Growth Removal', 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), International Conference on Intelligent Robots and Systems, IEEE, Madrid, Spain, pp. 1913-1918.View/Download from: Publisher's site
Marine growths that flourish on the surfaces of underwater structures, such as bridge pylons, make the inspection and maintenance of these structures challenging. A robotic solution, using an Intervention Autonomous Underwater Vehicle (I-AUV), is developed for removing marine growth. This paper presents a Deformable Spiral Coverage Path Planning (DSCPP) algorithm for marine growth removal. DSCPP generates smooth paths to prevent damage to the surfaces of the structures and to avoid frequent or aggressive decelerations and accelerations due to sharp turns. DSCPP generates a spiral path within a circle and analytically maps the path to a minimum bounding rectangle which encompasses an area of a surface with marine growth. It aims to achieve a spiral path with minimal length while preventing missed areas of coverage. Several case studies are presented to validate the algorithm. Comparison results show that DSCPP outperforms the popular boustrophedon-based coverage approach when considering the requirements for the application under consideration.
Lu, W & Liu, D 2018, 'A Frequency-Limited Adaptive Controller for Underwater Vehicle-Manipulator Systems Under Large Wave Disturbances', 13th World Congress on Intelligent Control and Automation (WCICA), World Congress on Intelligent Control and Automation, IEEE, Changsha, China.View/Download from: Publisher's site
Yu, H, Lu, W & Liu, D 2019, 'A Unified Closed-Loop Motion Planning Approach For An I-AUV In Cluttered Environment With Localization Uncertainty', 2019 International Conference on Robotics and Automation (ICRA), International Conference on Robotics and Automation, IEEE, Montreal, CA.View/Download from: Publisher's site
This paper presents a unified motion planning approach for an Intervention Autonomous Underwater Vehicle (I-AUV) in a cluttered environment with localization uncertainty. With the uncertainty being propagated by an information filter, a trajectory optimization problem closed by a Linear-Quadratic-Gaussian controller is formulated for a coupled design of optimal trajectory, localization, and control. Due to the presence of obstacles or complexity of the cluttered environment, a set of feasible initial I-AUV trajectories covering multiple homotopy classes are required by optimization solvers. Parameterized through polynomials, the initial base trajectories are from solving quasi-quadratic optimization problems that are linearly constrained by waypoints from RRTconnect, while the initial trajectories of the manipulator are generated by a null space saturation controller. Simulations on an I-AUV with a 3 DOF manipulator in cluttered underwater environments demonstrated that initial trajectories are generated efficiently and that optimal and collision-free I-AUV trajectories with low state uncertainty are obtained
Aldini, S, Carmichael, MG & Liu, D 2019, 'A Risk Reduction Framework for Design of Physical Human-Robot Collaboration', https://ssl.linklings.net/conferences/acra/acra2019_proceedings/views/b…, Australasian Conference on Robotics and Automation, Adelaide.
As robots designed to physically interact with humans become common in various application areas, shared workspaces and force exchange between human and robot lead to new challenges in terms of safety.
Often, a variety of safety techniques is necessary, and deciding what methods to include in a comprehensive safety framework is not an easy task. This paper is concerned with the design of robotic co-wokers that involve physical Human-Robot Collaboration (pHRC), with humans and robots in continuous direct physical contact and exchanging forces.
A hierarchical risk reduction framework is presented for guiding the design of robotic co-workers to reduce the risk associated with hazards commonly found in pHRC tasks. A case study is presented to demonstrate the use of the framework in designing an Assistance-as-Needed roBOT (ANBOT) which has been extensively tested in practical industry applications.
Hyun, JS, Carmichael, MG, Tran, A, Zhang, S & Liu, D 2019, 'Evaluation of fast, high-detail projected light 3D sensing for robots in construction', Proceedings of the 14th IEEE Conference on Industrial Electronics and Applications, ICIEA 2019, IEEE Conference on Industrial Electronics and Applications, IEEE, Xi'an, China, pp. 1262-1267.View/Download from: Publisher's site
© 2019 IEEE. Robots used on-site in construction need to perceive the surrounding environment to operate autonomously. This is challenging as the construction environment is often less than ideal due to changing lighting conditions, turbid air, and the need to detect fine details. In this work we evaluate a custom made projected light 3D sensor system for suitability and practicality in enabling autonomous robotics for construction. A series of tests are performed to evaluate the sensor based on ability to capture environmental details, operate robustly in challenging lighting conditions, and make accurate geometric measurements. Analysis shows that high fidelity measurements with accuracy in the order of millimeters can be obtained, making the technology a promising solution for robots operating in construction environments.
Aldini, S, Akella, A, Singh, A, Wang, Y-K, Carmichael, M, Liu, D & Lin, C-T 2019, 'Effect of Mechanical Resistance on Cognitive Conﬂict in Physical Human-Robot Collaboration', https://ieeexplore.ieee.org/xpl/conhome/8780387/proceeding, International Conference on Robotics and Automation, IEEE, Canada, pp. 6137-6143.View/Download from: Publisher's site
Physical Human-Robot Collaboration (pHRC) is about the interaction between one or more human operator(s) and one or more robot(s) in direct contact and voluntarily exchanging forces to accomplish a common task. In any pHRC, the intuitiveness of the interaction has always been a priority, so that the operator can comfortably and safely interact with the robot. So far, the intuitiveness has always been described in a qualitative way. In this paper, we suggest an objective way to evaluate intuitiveness, known as prediction error negativity (PEN) using electroencephalogram (EEG). PEN is defined as a negative deflection in event related potential (ERP) due to cognitive conflict, as a consequence of a mismatch between perception and reality. Experimental results showed that the forces exchanged between robot and human during pHRC modulate the amplitude of PEN, representing different levels of cognitive conflict. We also found that PEN amplitude significantly decreases (p <; 0.05) when a mechanical resistance is being applied smoothly and more time in advance before an invisible obstacle, when compared to a scenario in which the resistance is applied abruptly before the obstacle. These results indicate that an earlier and smoother resistance reduces the conflict level. Consequently, this suggests that smoother changes in resistance make the interaction more intuitive.
Bykerk, L & Liu, D 2018, 'Experimental verification of a completely soft gripper for grasping and classifying beam members in truss structures', IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM, IEEE/ASME International Conference on Advanced Intelligent Mechatronics, IEEE, Auckland, New Zealand, pp. 756-761.View/Download from: Publisher's site
© 2018 IEEE. Robotic object exploration and identification methods to date have attempted to mimic human Exploratory Procedures (EPs) using complex, rigid robotic hands with multifaceted sensory suites. For applications where the target objects may have different or unknown cross-sectional shapes and sizes (e.g. beam members in truss structures), rigid grippers are not a good option as they are unable to adapt to the target objects. This may make it very difficult to recognise the shape and size of a beam member and the approaching angles which would result in a secure grasp. To best meet the requirements of adaptability and compliancy, a soft robotic gripper with simple exteroceptive force sensors has been designed. This paper experimentally verifies the gripper design by assessing its performance in grasping and adapting to a variety of target beam members in a truss structure. The sensor arrangement is also assessed by verifying that sufficient data is extracted during a grasp to recognise the approaching angle of the gripper. Firstly, the gripper is used to grasp each beam member from various angles of approach and readings from the force sensors are collected. Secondly, the collected sensor data is used to train and then test a range of commonly used classifiers for classification of the angle of approach. Thirdly, the classification results are analysed. Through this process, it is found that the gripper is proficient in grasping the variety of target beam members. Despite the uncertainty in the gripper pose, the sensor data collected from the soft gripper during a grasp is sufficient for classification of the angles of approach.
Hassan, M & Liu, D 2018, 'Performance Evaluation of an Evolutionary Multiobjective Optimization Based Area Partitioning and Allocation Approach', IEEE/ASME International Conference on Advanced Intelligent Mechatronics, IEEE, Auckland, New Zealand, pp. 527-532.View/Download from: Publisher's site
An Area Partitioning and Allocation (APA) approach was presented in . The approach focused on optimizing the coverage performance of Autonomous Industrial Robots (AIRs) using multiple conflicting objectives and Voronoi partitioning. However, questions related to the optimality, convergence, and consistency of the Pareto solutions were not studied in details. In this paper, Inverted Generational Distance (IGD) metric is used to verify the convergence of the Pareto front towards Pareto optimal front (PF*). The consistency in obtaining similar Pareto fronts for independent optimization runs is studied. The computational complexity of the approach with respect to the size of the coverage area and the number of AIRs is also discussed. Two application scenarios are used in this research.
Wang, T, Lu, W & Liu, D 2018, 'A Case Study: Modeling of A Passive Flexible Link on A Floating Platform for Intervention Tasks', 2018 13th World Congress on Intelligent Control and Automation, IEEE, Changsha, China.
This paper focuses on modeling of a robotic system consisting of a floating platform and a passive flexible-link, which is subjected to three-dimensional large bending deformation during intervention tasks. It investigates the feasibility and efficacy of the quasi-Lagrangian approach and the Euler-Bernoulli beam assumption in modeling this system. Simulations and experiments were conducted to evaluate the model. Then the contact force was calculated with given external input force along with the pose and velocities of the robot, which is validated by the measurements obtained from force-torque sensors. It also found that the accelerations calculated from the model have some deviation from the results obtained from a tracking system.
Wang, T, Lu, W & Liu, D 2018, 'Excessive Disturbance Rejection Control of Autonomous Underwater Vehicleusing Reinforcement Learning', 2018 Australasian Conference on Robotics and Automation, Lincoln, New Zealand.
Small Autonomous Underwater Vehicles (AUV) in shallow water might not be stabilized well by feedback or model predictive control. This is because wave and current disturbances may frequently exceed AUV thrust capabilities and disturbance estimation and prediction models available are not sufficiently accurate. In contrast to classical model-free Reinforcement Learning (RL), this paper presents an improved RL for Excessive disturbance rejection Control (REC) that is able to learn and utilize disturbance behaviour, through formulating the disturbed AUV dynamics as a multi-order Markov chain. The unobserved disturbance behaviour is then encoded in the AUV state-action history of fixed length, its embeddings are learned within the policy optimization. The proposed REC is further enhanced by a base controller that is pre-trained on iterative Linear Quadratic Regulator (iLQR) solutions for a reduced AUV dynamic model, resulting in hybrid-REC. Numerical simulations on pose regulation tasks have demonstrated that REC significantly outperforms a canonical controller and classical RL, and that the hybrid-REC leads to more efficient and safer sampling and motion than REC.
Tran, A, Liu, D, Ranasinghe, R & Carmichael, M 2018, 'Identifying Human Hand Orientation around a Cylindrical Handlebar for physical Human-Robot Interaction', International Symposium on Robotics, Munich, pp. 427-434.
Tran, A, Liu, D, Ranasinghe, R & Carmichael, M 2018, 'Method for Quantifying a Robot's Confidence in its Human Co-worker in Human-Robot Cooperative Grit-Blasting', International Symposium on Robotics, Munich, pp. 474-481.
Katuwandeniya, K, Ranasinghe, R, Dantanarayana, L, Dissanayake, G & Liu, D 2018, 'Calibration of a Rotating Laser Range Finder using Intensity Features', 2018 15th International Conference on Control, Automation, Robotics and Vision, ICARCV 2018, International Conference on Control, Automation, Robotics and Vision, IEEE, Singapore, Singapore, pp. 228-234.View/Download from: Publisher's site
© 2018 IEEE. This paper presents an algorithm for calibrating a '3D range sensor' constructed using a two-dimensional laser range finder (LRF), that is rotated about an axis using a motor to obtain a three-dimensional point cloud. The sensor assembly is modelled as a two degree of freedom open kinematic chain, with one joint corresponding to the axis of the internal mirror in the LRF and the other joint set along the axis of the motor used to rotate the body of the LRF. In the application described in this paper, the sensor unit is mounted on a robot arm used for infrastructure inspection. The objective of the calibration process is to obtain the coordinate transform required to compute the locations of the 3D points with respect to the robot coordinate frame. Proposed strategy uses observations of a set of markers arbitrarily placed in the environment. Distances between these markers are measured and a metric multidimensional scaling is used to obtain the coordinates of the markers with respect to a local coordinate frame. Intensity associated with each beam point of a laser scan is used to locate the reflective markers in the 3D point cloud and a least squares problem is formulated to compute the relationship between the robot coordinate frame, LRF coordinate frame and the marker coordinate frame. Results from experiments using the robot, LRF combination to map a cavity inside a steel bridge structure are presented to demonstrate the effectiveness of the calibration process.
Ranasinghe, R, Dissanayake, G & Liu, D 2018, 'Sensing for Autonomous Navigation Inside Steel Bridges', Proceedings of IEEE Sensors, IEEE SENSORS, IEEE, New Delhi, India, pp. 1-4.View/Download from: Publisher's site
© 2018 IEEE. The main contribution of this paper is a strategy to build a map of a bridge structure and estimate the precise location of a robot within it. In particular, the focus is on the autonomous navigation of a robot inside the steel arches that support the Sydney Harbour Bridge. A two dimensional laser range finder sensor, rotated about an axis perpendicular to its spin axis is used to capture the geometry of the environment in the form of a set of three-dimensional points; a point cloud. First, the approximate robot location is estimated by exploiting the fact that the environment predominantly consists of planes. Using this location estimate as an initial guess, the iterative closest point (ICP) algorithm is used to align point clouds obtained from nearby locations. Results from the ICP, together with a simultaneous localisation and mapping algorithm is then used to obtain accurate estimates of the locations of all the poses from where information is gathered, as well as a complete map of the environment. Results from experiments are used to demonstrate the effectiveness of proposed techniques.
Liu, D & Nguyen, KD 2017, 'Robust Control of a Brachiating Robot', 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), International Conference on Intelligent Robots and Systems, IEEE, Vancouver Canada.View/Download from: Publisher's site
This paper investigates the robust control of an underactuated brachiating robot. Inspired by the pendulumlike movements in gibbons' arboreal locomotion, the controllers are designed to synchronize the brachiator with a virtual oscillator. Two schemes are proposed: a model-dependent feedback linearization scheme and a sliding-mode scheme that is independent of the system model. The simulation results illustrate that the proposed schemes are robust to the arbitrary initial configurations of the brachiator and the limitation in the motor torque at the elbow joint. Furthermore, both controllers enable the underactuated robot to brachiate along a structural member with an upward slope.
Lu, W & Liu, D 2017, 'Active Task Design in Adaptive Control of Redundant Robotic Systems', Australasian Conference on Robotics and Automation 2017, Australasian Conference on Robotics and Automation, ARAA, Sydney Australia, pp. 1-6.
This paper seeks for possibilities of using robots' kinematic redundancy to excite the system persistently, through actively designing a secondary task in the null space of a primary task. Resulted parameter convergence in adaptive control leads to better system stability and performance.
A measure in Grassmannian, referred to as Subspace Discrepancy Measure (SDM), is proposed for evaluating the additional benefit from the secondary task in converging unknown parameters to their true values. This measure evaluates the angles among subspaces that the parameter estimations are converging to, given different secondary tasks. The subspaces are obtained from Principal Component Analysis (PCA) on a small amount of samples of parameter estimations. The SDM is used to determine the choice of the secondary task online through a trial-and-evaluation procedure actively. Numerical simulations demonstrated that the secondary task chosen by SDM enhances the parameter convergence.
Carmichael, MG, Aldini, S & Liu, D 2017, 'Human user impressions of damping methods for singularity handling in human-robot collaboration', Australasian Conference on Robotics and Automation, ACRA, Australasian Conference on Robotics and Automation, ARAA, Australia, pp. 107-113.
Kinematic singularity is a fundamental and well understood problem of robot manipulators, with many methods having been developed to ensure safe and robust operation in proximity to singularity. However little attention has been given to the scenario where the robot and human are working in physical contact to collaboratively perform a task. In such a scenario the feelings and impressions of the human operator should be considered when developing solutions for handling singularity. This work presents an experimental study comparing three modes of handling kinematic singularities with respect to the impressions of the human operator. Two of the modes are based on traditional Damped-Least-Squares. The third method uses an asymmetric damping behavior proposed as being well suited for applications involving physical human-robot interaction. The three modes are tested and compared by subjects performing a mock industrial task, and feedback from the subjects analyzed to identify the preferred mode. Results indicate that the choice of method used affects the user's impressions of the interaction, and the asymmetrical damping behavior can produce a preferred interaction experience with human operators during tasks.
Khonasty, R, Carmichael, MG, Liu, D & Aldini, S 2017, 'Effect of External Force and Bimanual Operation on Upper Limb Pose during Human-Robot Collaboration', Australasian Conference on Robotics and Automation 2017, Australasian Conference on Robotics and Automation, ARAA, Sydney Australia, pp. 1-9.
During physical Human-Robot Interaction
(pHRI) in industrial applications such as
human-robot collaborative abrasive blasting,
the operator often interacts with the robot using
two hands, exchanging forces through handle
bars. For the robot to provide appropriate
assistance to the operator and for safe interaction,
it would be beneficial for the robot
to know the pose of the user. This problem
is often challenging due to environmental factors,
limited sensing capability in the environment
and the robot, and redundancy of the human
upper-limb. This paper presents experimental
study on how two-hand interaction and
force exchange affect the operators upper-limb
pose, which can be characterized by swivel angle.
The poses of ten subjects were recorded as
they interacted with a collaborative robot. Differences
in the adopted upper limb pose were
analyzed with respect to factors such as unimanual
versus bimanual operation, and the amplitude
of interaction force between an operator
and the robot. The results discovered that the
the effect of bimanual operation on the upper
limb pose differs between individuals and the
magnitude of the force had a varying effect on
the pose. The requirement of applying a force
forward produced an overall lower swivel angle
Khonasty, R, Carmichael, MG, Liu, D & Waldron, K 2017, 'Upper Body Pose Estimation Utilizing Kinematic Constraints from Physical Human-Robot Interaction', Australasian Conference on Robotics and Automation 2017, Australasian Conference on Robotics and Automation, ARAA, Sydney Australia, pp. 1-10.
In physical Human-Robot Interaction (pHRI),
knowing the pose of the operator is beneficial
and may allow the robot to better accommodate
the human operator. Due to a
large redundancy in the human body, determining
the pose of the human operator is difficult
to achieve in unstructured environments
especially in human-robot collaborative operations
where the robot often occludes the human
from vision-based sensors. This work presents
an upper body pose estimation method based
on exploiting known positions of the human operator's
hands while performing a task with the
robot. Upper body pose is estimated using upper
limb kinematic models alongside sensor information
and model approximations to produce
solutions that are biomechanically feasible.
The pose estimation method was compared
to upper body poses obtained using a motion
capture system. It was shown to be able to
perform robustly with varying amounts of available
information. This approach is well suited
in applications where robots are controlled using
well-defined interfaces such as handlebars,
operating in unstructured environments.
Bykerk, L, Liu, D & Waldron, K 2016, 'A Topology Optimisation Based Design of a Compliant Gripper for Grasping Objects with Irregular Shapes', 2016 IEEE International Conference on Advanced Intelligent Mechatronics (AIM), IEEE/ASME International Conference on Advanced Intelligent Mechatronics, IEEE, Banff, Canada.View/Download from: Publisher's site
Complex steel structures such as power transmis-
sion towers require regular inspection and maintenance during
their lifetime. This work is currently completed by teams of
human workers who climb the live structures. The exposure
of these workers to the risks of climbing and completing
work on towers provides motivation for developing a robotic
substitute. There are many complex elements of climbing power
transmission towers, such as the variation in beam shapes,
sizes and orientations. To the best of our knowledge, there
is no existing robotic grasping solution that can be directly
used in this complex environment. This paper presents a
topology optimisation based design of a compliant gripper
for grasping objects with irregular shapes such as the beam
members found in power transmission towers. The structure of
the gripper is obtained through the use of a modified topology
optimisation model where stiffness constraints are implemented
in the optimisation to increase the strength of the gripper in
desired areas. The stiffness constrained topology optimisation
produces a novel gripper design which is validated through both
simulations and physical testing of the manufactured gripper
on a variety of physical objects.
Zhang, T, Huang, S, Liu, D, Shi, L, Zhou, C & Xiong, R 2016, 'A Method of State Estimation for Underwater Vehicle Navigation Around A Cylindrical Structure', 2016 IEEE 11th Conference on Industrial Electronics and Applications (ICIEA), IEEE Conference on Industrial Electronics and Applications, IEEE, Hefei, China, pp. 101-106.View/Download from: Publisher's site
Recently, increasing efforts have been focused on the development and adoption of autonomous underwater vehicles (AUVs) for various applications. However, the GPS signals are usually unavailable, the vehicle dynamics is very uncertain, and the complicated vision based localization algorithms may not work well in the underwater environments. Hence, accurate and timely state estimation using low-cost sensors remains a challenge for the control and navigation of AUVs. This paper considers the state estimation problem for underwater vehicle navigation around a cylindrical structure. The vehicle is assumed to be equipped with only low-cost sensors: an inertia measurement unit (IMU), a pressure sensor and a monocular camera. By exploiting the prior knowledge on the size and shape of the structure, an efficient algorithm for estimating the state of the AUV is developed without using any dynamic model. Firstly, a state observer is proposed under the condition that the localization result (rotational and translational position) is available. Next, we present a method for localization based on the IMU readings, pressure sensor readings and the image of the cylindrical structure, which uses the geometry of the structure and only requires simple image processing (line extraction). Then we prove that the proposed observer is globally stable. Preliminary experimental results and simulation results are reasonable and promising, which implies the proposed method has potential to be used in the real AUV navigation applications.
Reeks, C, Carmichael, M, Liu, D & Waldron, K 2016, 'Angled sensor configuration capable of measuring tri-axial forces for pHRI', Proceedings - IEEE International Conference on Robotics and Automation, IEEE International Conference on Robotics and Automation, IEEE, Stockholm, Sweden, pp. 3089-3094.View/Download from: Publisher's site
This paper presents a new configuration for single axis tactile sensor arrays molded in rubber to enable tri-axial force measurement. The configuration requires the sensing axis of each sensor in the array to be rotated out of alignment with respect to external forces. This angled sensor array measures shear forces along axes in a way that is different to a planar sensor array. Three sensors using the angled configuration (22.5°, 45° and 67.5°) and a fourth sensor using the planar configuration (0°) have been fabricated for experimental comparison. Artificial neural networks were trained to interpret the external force applied along each axis (X, Y and Z) from raw pressure sensor values. The results show that the angled sensor configuration is capable of measuring tri-axial external forces with a root mean squared error of 1.79N, less error in comparison to the equivalent sensor utilizing the planar configuration (4.52N). The sensors are then implemented to control a robotic arm. Preliminary findings show angled sensor arrays to be a viable alternative to planar sensor arrays for shear force measurement; this has wide applications in physical Human Robot Interaction (pHRI).
Woolfrey, JK, Liu, DK & Carmichael, M 2016, 'Kinematic Control of an Autonomous Underwater Vehicle-Manipulator System Using Autoregressive Prediction of Vehicle Motion and Model Predictive Control', Proceedings - IEEE International Conference on Robotics and Automation, IEEE International Conference on Robotics and Automation, IEEE, Stockholm, Sweden.View/Download from: Publisher's site
Hassan, M, Liu, DL & Paul, GP 2016, 'Modeling and Stochastic Optimization of Complete Coverage under Uncertainties in Multi-Robot Base Placements', Intelligent Robots and Systems (IROS), 2016 IEEE/RSJ International Conference on, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE (Institute of Electrical and Electronics Engineers), Daejeon, Korea, pp. 2978-2984.View/Download from: Publisher's site
Uncertainties in base placements of mobile, autonomous industrial robots can cause incomplete coverage in tasks such as grit-blasting and spray painting. Sensing and localization errors can cause such uncertainties in robot base placements. This paper addresses the problem of collaborative complete coverage under uncertainties through appropriate base placements of multiple mobile and autonomous industrial robots while aiming to optimize the performance of the robot team. A mathematical model for complete coverage under uncertainties is proposed and then solved using a stochastic multi-objective optimization algorithm. The approach aims to concurrently find an optimal number and sequence of base placements for each robot such that the robot team's objectives are optimized whilst uncertainties are accounted for. Several case studies based on a real-world application using a real-world object and a complex simulated object are provided to demonstrate the effectiveness of the approach for different conditions and scenarios, e.g. various levels of uncertainties, different numbers of robots, and robots with different capabilities.
Paul, G, Liu, L & Liu, D 2016, 'A Novel Approach to Steel Rivet Detection in Poorly Illuminated Steel Structural Environments', Control, Automation, Robotics and Vision (ICARCV), 2016 14th International Conference on, International Conference on Control, Automation, Robotics and Vision, IEEE, Phuket, Thailand.View/Download from: Publisher's site
It is becoming increasingly achievable for steel
bridge structures, which are normally both inaccessible and
hazardous for humans, to be inspected and maintained by
autonomous robots. Steel bridges have been traditionally constructed
by securing plate members together with rivets. However,
rivets present a challenge for robots both in terms of cleaning and
surface traversal. This paper presents a novel approach to RGBD
image and point cloud analysis that enables rivets to be rapidly
and robustly located using low cost, non-contact sensing devices
that can be easily affixed to a robot. The approach performs
classification based on: (a) high-intensity blobs in color images,
(b) the non-linear perturbations in depth images, and (c) surface
normal clusters in 3D point clouds. The predicted rivet locations
from the three classifiers are combined using a probabilistic
occupancy mapping technique. Experiments are conducted in
several different lab and real-world steel bridge environments,
where there is no external lighting infrastructure, and the sensors
are attached to a mobile platform, i.e. a climbing inspection robot.
The location of rivets within 2m of the robot can be robustly
located within 10mm of their correct location. The state of voxels
can be predicted with above 95% accuracy, in approximately 1
second per frame.
Quin, PD, Paul, G, Alempijevic, A & Liu, D 2016, 'Exploring in 3D with a Climbing Robot: Selecting the Next Best Base Position on Arbitrarily-Oriented Surfaces', Intelligent Robots and Systems (IROS), 2016 IEEE/RSJ International Conference on, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, Daejeon, Korea, pp. 5770-5775.View/Download from: Publisher's site
This paper presents an approach for selecting the next best base position for a climbing robot so as to observe the highest information gain about the environment. The robot is capable of adhering to and moving along and transitioning to surfaces with arbitrary orientations. This approach samples known surfaces, and takes into account the robot kinematics, to generate a graph of valid attachment points from which the robot can either move to other positions or make observations of the environment. The information value of nodes in this graph are estimated and a variant of A* is used to traverse the graph and discover the most worthwhile node that is reachable by the robot. This approach is demonstrated in simulation and shown to allow a 7 degree-of-freedom inchworm-inspired climbing robot to move to positions in the environment from which new information can be gathered about the environment.
Yang, C, Paul, G, Ward, P & Liu, D 2016, 'A Path Planning Approach Via Task-Objective Pose Selection with Application to an Inchworm-Inspired Climbing Robot', IEEE/ASME International Conference on Advanced Intelligent Mechatronics, AIM, IEEE/ASME International Conference on Advanced Intelligent Mechatronics, IEEE, Banff, Canada, pp. 401-406.View/Download from: Publisher's site
This paper presents a stepping path planning
approach for a climbing robot inspired kinematically from
an inchworm caterpillar's looping locomotion. This approach
generates an optimised multi-step path to traverse through
space and to land a specific footpad onto a selected point on
a surface with a specific footpad orientation. The candidate
landing joint configuration for each step is generated by a pose
selection process, using an optimisation technique with task-
objective functions based on the constraints of the robot. Then
another technique is used to obtain a new set of poses satisfying
strict constraints of the landing motion. The set of candidate
landing poses is used to compute the subsequent steps. A valid
motion trajectory, which avoids all obstacles, can be generated
by a point-to-point planner for each of the landing poses from
the current pose. This single step planning technique is then
expanded to multi-step path planning by building a search
tree, where a combination of steps is evaluated and optimised
by a cost function, which includes objectives related to robot
movement. This approach is implemented and validated on
the climbing robot in real-world steel bridge environments.
The planner successfully finds multi-step paths in these field
trials enabling the robot to traverse through several complex
structures inside the bridge steel box girders.
Tran, A, Liu, D, Ranasinghe, R, Carmichael, M & Liu, C 2015, 'Analysis of Human grip strength in physical Human Robot Interaction', Proceedings - Analysis of Human grip strength in physical Human Robot Interaction, Conference on Applied Human Factors and Ergonomics, ELSEVIER SCIENCE BV, Las Vegas.View/Download from: Publisher's site
The purpose of this paper is to explore how an operator's grip plays a role in physical Human Robot Interaction (pHRI). By considering how the operator reacts to or initiates changes in control, it is possible to study the operator's grip pattern. By analyzing the grip pattern, it is possible to incorporate their natural response in order to create safer and more intuitive interfaces. An experiment where an exoskeleton and human collaborate in order to complete a path following task has been chosen to observe the forces applied by the user at the handle to determine the interaction between the operator and robot. A ThruMode Matrix Array sensor has been wrapped around the robot's handle to measure the applied pressure. By introducing the sensor it not only enables the measurement of the applied forces and how they are applied but also a measure of how tight the user is gripping the handle. Previous studies show that the natural response of a human to an unexpected event is to tighten their grip, indicating that how an operator grasps the handle can be related to the operator's intention. In order to investigate how the operator's grip of the handle changes, the experiments presented in this paper examine two different scenarios which might occur during an interaction, the first where the robot attempts to deviate from the path and the second where the operator wishes to deviate to a new path. The results of the experiments show that whether the operator or the robot initiates the transition, a measurable change in how the operator grasps the handle. The information in this paper can lead to new applications in pHRI by exploring the possible uses of an operator's grasping strength.
Carmichael, MG & Liu, D 2013, 'Human Biomechanical Model Based Optimal Design of Assistive Shoulder Exoskeleton', Field and Service Robotics, International Conference on Field and Service Robotics, Springer, Brisbane, QLD, Australia, pp. 245-258.View/Download from: Publisher's site
Carmichael, MG & Liu, D 2015, 'Upper Limb Strength Estimation of Physically Impaired Persons using a Musculoskeletal Model: A Sensitivity Analysis', Proceedings of the 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE, Milan, Italy, pp. 2438-2441.View/Download from: Publisher's site
Sensitivity of upper limb strength calculated from a musculoskeletal model was analyzed, with focus on how the sensitivity is affected when the model is adapted to represent a person with physical impairment. Sensitivity was calculated with respect to four muscle-tendon parameters: muscle peak isometric force, muscle optimal length, muscle pennation, and tendon slack length. Results obtained from a musculoskeletal model of average strength showed highest sensitivity to tendon slack length, followed by muscle optimal length and peak isometric force, which is consistent with existing studies. Muscle pennation angle was relatively insensitive. The analysis was repeated after adapting the musculoskeletal model to represent persons with varying severities of physical impairment. Results showed that utilizing the weakened model significantly increased the sensitivity of the calculated strength at the hand, with parameters previously insensitive becoming highly sensitive. This increased sensitivity presents a significant challenge in applications utilizing musculoskeletal models to represent impaired individuals.
Carmichael, MG, Khonasty, R & Liu, D 2015, 'A Multi-stage Design Framework for the Development of Task-specific Robotic Exoskeletons', Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE, Milan, Italy.View/Download from: Publisher's site
Hassan, M, Liu, D, Paul, G & Huang, S 2015, 'An Approach to Base Placement for Effective Collaboration of Multiple Autonomous Industrial Robots', Proceedings - IEEE International Conference on Robotics and Automation, IEEE International Conference on Robotics and Automation, Institute of Electrical and Electronics Engineers (IEEE), Washington State Convention Center in Seattle, Washington, USA, pp. 3286-3291.View/Download from: Publisher's site
There are many benefits for the deployment of multiple autonomous industrial robots to carry out a task, particularly if the robots act in a highly collaborative manner. Collaboration can be possible when each robot is able to autonomously explore the environment, localize itself, create a map of the environment and communicate with other robots. This paper presents an approach to the modeling of the collaboration problem of multiple robots determining optimal base positions and orientations in an environment by considering the team objectives and the information shared amongst the robots. It is assumed that the robots can communicate so as to share information on the environment, their operation status and their capabilities. The approach has been applied to a team of robots that are required to perform complete surface coverage tasks such as grit-blasting and spray painting in unstructured environments. Case studies of such applications are presented to demonstrate the effectiveness of the approach.
Paul, G, Quin, P, To, A & Liu, D 2015, 'A Sliding Window Approach to Exploration for 3D Map Building Using a Biologically Inspired Bridge Inspection Robot', Proceedings of the IEEE International Conference on CYBER Technology in Automation, Control, and Intelligent Systems, IEEE International Conference on CYBER Technology in Automation, Control, and Intelligent Systems, IEEE, Shenyang, China, pp. 1097-1102.View/Download from: Publisher's site
This paper presents a Sliding Window approach to viewpoint selection when exploring an environment using a RGB-D sensor mounted to the end-effector of an inchworm climbing robot for inspecting areas inside steel bridge archways which cannot be easily accessed by workers. The proposed exploration approach uses a kinematic chain robot model and information theory-based next best view calculations to predict poses which are safe and are able to reduce the information remaining in an environment. At each exploration step, a viewpoint is selected by analysing the Pareto efficiency of the predicted information gain and the required movement for a set of candidate poses. In contrast to previous approaches, a sliding window is used to determine candidate poses so as to avoid the costly operation of assessing the set of candidates in its entirety. Experimental results in simulation and on a prototype climbing robot platform show the approach requires fewer gain calculations and less robot movement, and therefore is more efficient than other approaches when exploring a complex 3D steel bridge structure.
Paul, G, Quin, P, Yang, C & Liu, D 2015, 'Key Feature-Based Approach for Efficient Exploration of Structured Environments', Proceedings of the 2015 IEEE International Conference on Robotics and Biomimetics (ROBIO), IEEE International Conference on Robotics and Biomimetics, IEEE, Zhuhai, China, pp. 90-95.View/Download from: Publisher's site
This paper presents an exploration approach for robots to determine sensing actions that facilitate the building of surface maps of structured partially-known environments. This approach uses prior knowledge about key environmental features to rapidly generate an estimate of the rest of the environment. Specifically, in order to quickly detect key features, partial surface patches are used in combination with pose optimisation to select a pose from a set of nearest neighbourhood candidates, from which to make an observation of the surroundings. This paper enables the robot to greedily search through a sequence of nearest neighbour poses in configuration space, then converge upon poses from which key features can best be observed. The approach is experimentally evaluated and found to result in significantly fewer exploration steps compared to alternative approaches.
Zhang, T, Huang, S & Liu, D 2014, 'Comparison of Two Strategies of Path Planning for Underwater Robot Navigation Under Uncertainty', 2014 13th International Conference on Control Automation Robotics and Vision, ICARCV 2014, International Conference on Control, Automation, Robotics and Vision, IEEE, Singapore, pp. 1-6.View/Download from: Publisher's site
This paper considers path planning for underwater robot in navigation tasks. The main challenge is how to deal with uncertainties in the underwater environment such as motion model error and sensing error. To overcome this challenge, two high level control methods have been presented and compared, which are based on the Model Predictive Control (MPC) strategy and the Partially Observable Markov Decision Process (POMDP) model, respectively. Navigation time, collision frequency, energy consumption and accuracy in localization are used as the assessment criteria for the two methods. It is shown that the MPC-based method is more efficient for our application scenarios while the POMDP-based method can provide more robust solutions.
Zhang, T, Huang, S & Liu, D 2014, 'Comparison of Two Strategies of Path Planning for Underwater Robot Navigation Under Uncertainty', 2014 13TH INTERNATIONAL CONFERENCE ON CONTROL AUTOMATION ROBOTICS & VISION (ICARCV), 13th International Conference on Control Automation Robotics & Vision (ICARCV), IEEE, Singapore, SINGAPORE, pp. 901-906.
Carmichael, MG, Moutrie, B & Liu, D 2014, 'A Framework for Task-Based Evaluation of Robotic Coworkers', 2014 13th International Conference on Control Automation Robotics and Vision, ICARCV 2014, International Conference on Control, Automation, Robotics and Vision, IEEE, Singapore, pp. 1362-1367.View/Download from: Publisher's site
Compared to a robotic system that performs a task alone, a robot coworker performing tasks in collaboration with a human operator is subject to additional constraints which can limit the ability of the system to perform the task as required. This work presents a framework for analyzing the ability of a robotic coworker to perform specific tasks in collaboration with a human. The framework allows systematic evaluation of robotic systems based on traditional robot performance measures such as reachable workspace and payload capacity, as well as considering additional factors which arise due to the task being performed collaboratively with a human; such as the reach and strength of the human, human-robot collision, and satisfying desired assistance paradigms. Application of the framework is demonstrated in a case study analyzing a robot designed to assist a human during a materials handling task.
Quin, PD, Alempijevic, A, Paul, G & Liu, D 2014, 'Expanding Wavefront Frontier Detection: An Approach for Efficiently Detecting Frontier Cells', https://ssl.linklings.net/conferences/acra/acra2014_proceedings/views/b…, Australasian Conference on Robotics and Automation, Australasian Robotics and Automation Association, Melbourne, pp. 1-10.
Frontier detection is a key step in many robot exploration algorithms. The more quickly frontiers can be detected, the more efficiently and rapidly exploration can be completed. This paper proposes a new frontier detection algorithm called Expanding Wavefront Frontier Detection (EWFD), which uses the frontier cells from the previous timestep as a starting point for detecting the frontiers in the current timestep. As an alternative to simply comparing against the naive frontier detection approach of evaluating all cells in a map, a new benchmark algorithm for frontier detection is also presented, called Naive Active Area frontier detection, which operates in bounded constant time. EWFD and NaiveAA are evaluated in simulations and the results compared against existing state-of-the-art frontier detection algorithms, such as Wavefront Frontier Detection and Incremental-Wavefront Frontier Detection.
Dantanarayana, L, Ranasinghe, R, Tran, A, Liu, D & Dissanayake, G 2014, 'A novel collaboratively designed robot to assist carers', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), International Conference on Social Robotics (ICSR), SPRINGER-VERLAG BERLIN, Sydney, Australia, pp. 105-114.View/Download from: Publisher's site
© Springer International Publishing Switzerland 2014. This paper presents a co-design process and an assisted navigation strategy that enables a novel assistive robot, Smart Hoist, to aid carers transferring non-ambulatory residents. Smart Hoist was codesigned with residents and carers at IRT Woonona residential care facility to ensure that the device can coexist in the facility, while providing assistance to carers with the primary aim of reducing lower back injuries, and improving the safety of carers and patients during transfers. The Smart Hoist is equipped with simple interfaces to capture user intention in order to provide assisted manoeuvring. Using the RGB-D sensor attached to the device, we propose a method of generating a repulsive force that can be combined with the motion controller's output to allow for intuitive manoeuvring of the Smart Hoist, while negotiating with the environment. Extensive user trials were conducted on the premises of IRTWoonona residential care facility and feedback from end users confirm its intended purpose of intuitive behaviour, improved performance and ease of use.
Hassan, M, Liu, D, Huang, S & Dissanayake, G 2014, 'Task Oriented Area Partitioning and Allocation for Optimal Operation of Multiple Industrial Robots in Unstructured Environments', 2014 13th International Conference on Control Automation Robotics and Vision, ICARCV 2014, International Conference on Control, Automation, Robotics and Vision, IEEE, Marina Bay Sands, Singapore, pp. 1184-1189.View/Download from: Publisher's site
When multiple industrial robots are deployed in field applications such as grit blasting and spray painting of steel bridges, the environments are unstructured for robot operation and the robot positions may not be arranged accurately. Coordination of these multiple robots to maximize productivity through area partitioning and allocation is crucial. This paper presents a novel approach to area partitioning and allocation by utilizing multiobjective optimization and voronoi partitioning. Multiobjective optimization is used to minimize: (1) completion time, (2) proximity of the allocated area to the robot, and (3) the torque experienced by each joint of the robot during task execution. Seed points of the voronoi graph for voronoi partitioning are designed to be the design variables of the multiobjective optimization algorithm. Results of three different simulation scenarios are presented to demonstrate the effectiveness of the proposed approach and the advantage of incorporating robots' torque capacity.
Liu, DK, Dissanayake, G, Valls Miro, J & Waldron, KJ 2014, 'Infrastructure robotics: Research challenges and opportunities', 31st International Symposium on Automation and Robotics in Construction and Mining, ISARC 2014 - Proceedings, International Symposium on Automation and Robotics in Construction, ISARC, Sydney, Australia, pp. 43-49.View/Download from: Publisher's site
Infrastructure robotics is about research on and development of methodologies that enable robotic systems to be used in civil infrastructure inspection, maintenance and rehabilitation. This paper briefly discusses the current research challenges and opportunities in infrastructure robotics, and presents a review of the research activities and projects in this field at the Centre for Autonomous Systems, University of Technology Sydney.
To, AW, Paul, G, Rushton-Smith, D, Liu, D & Dissanayake, G 2012, 'Automated and Frequent Calibration of a Robot Manipulator-mounted IR Range camera for Steel Bridge Maintenance', Field and Service Robotics Vol 92 - Results of the 8th International Conference on Field and Service Robotics, International Conference on Field and Service Robotics, Springer-Verlag, Matsushima, Miyagi, Japan, pp. 205-218.View/Download from: Publisher's site
This paper presents an automated and cost-effective approach to frequent hand-eye calibration of an IR range camera mounted to the end-effector of a robot manipulator for use in a field environment. A set of three reflector discs arranged in a structured pattern attached to the robot platform is used to provide high contrast image features with corresponding range readings for accurate calculation of the camera-to-robot base transform. Using this approach the hand-eye transform between the IR range camera and robot end-effector can be determined by considering the robot manipulator model. Experimental results show that a structured lightingbased IR range camera can be reliably hand-eye calibrated to a 6DOF robot manipulator using the presented automated approach. Once calibrated, the IR range camera can be positioned with the manipulator so as to generate a high resolution geometric map of the surrounding environment suitable for performing the grit-blasting task.
Ward, PK, Manamperi, P, Brooks, P, Mann, P, Kaluarachchi, W, Matkovic, L, Paul, G, Yang, C, Quin, P, Pagano, D, Liu, D, Waldron, K & Dissanayake, G 2014, 'Climbing Robot for Steel Bridge Inspection: Design Challenges', Proceedings for the Austroads Publications Online, Austroads Bridge Conference, ARRB Group, New South Wales, pp. 1-13.
Inspection of bridges often requires high risk operations such as working at heights, in confined spaces, in hazardous environments; or sites inaccessible by humans. There is significant motivation for robotic solutions which can carry out these inspection tasks. When inspection robots are deployed in real world inspection scenarios, it is inevitable that unforeseen challenges will be encountered.
Since 2011, the New South Wales Roads & Maritime Services and the Centre of Excellence for Autonomous Systems at the University of Technology, Sydney, have been working together to develop an innovative climbing robot to inspect high risk locations on the Sydney Harbour Bridge. Many engineering challenges have been faced throughout the development of several prototype climbing robots, and through field trials in the archways of the Sydney Harbour Bridge. This paper will highlight some of the key challenges faced in designing a climbing robot for inspection, and then present an inchworm inspired robot which addresses many of these challenges.
Carmichael, MG & Liu, D 2013, 'Admittance Control Scheme for Implementing Model-based Assistance-As-Needed on a Robot', 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE, Osaka, Japan, pp. 870-873.View/Download from: Publisher's site
A model-based assistance-as-needed paradigm has been developed to govern the assistance provided by an assistive robot to its operator. This paradigm has advantages over existing methods of providing assistance-as-needed for applications such as robotic rehabilitation. However, implementation of the model-based paradigm requires a control scheme to be developed which controls the robot so as to provide the assistance calculated by the model-based paradigm to its operator. In this paper an admittance control scheme for providing model-based assistance-as-needed is presented. It is developed considering its suitability for human-robot interaction, and its role within the model-based assistance-as-needed framework. Results from the control implemented on an example robot showed it is capable of providing the operator with the desired level of assistance as governed by the model-based paradigm. This is an essential requirement for the paradigm to be capable of providing efficacious assistance-as-needed in applications such as robotic rehabilitation.
Carmichael, MG & Liu, D 2013, 'Experimental Evaluation of a Model-based Assistance-As-Needed Paradigm using an Assistive Robot', 35th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE, Osaka, Japan, pp. 866-869.View/Download from: Publisher's site
In robotic rehabilitation a promising paradigm is assistance-as-needed. This is because it promotes patient active participation which is essential for neuro-rehabilitation. A model-based assistance-as-needed paradigm has been developed which utilizes a musculoskeletal model representing the subject to calculate their assistance needs. In this paper we experimentally evaluate this model-based paradigm to control an assistive robot and provide a subject with assistance-as-needed at the muscular level. A subject with impairments defined in specific muscle groups performs a number of upper limb tasks, whilst receiving assistance from a robotic exoskeleton. The paradigm is evaluated on its ability to provide assistance only as the subject needs, depending on the tasks being performed and the impairments defined. Results show that the model-based assistance-as-needed paradigm was relatively successful in providing assistance when it was needed.
Quin, PD, Paul, G, Liu, D & Alempijevic, A 2013, 'Nearest Neighbour Exploration with Backtracking for Robotic Exploration of Complex 3D Environments', Proceedings of Australasian Conference on Robotics and Automation, Australasian Conference on Robotics and Automation, Australian Robotics & Automation Association, Sydney, Australia, pp. 1-8.
Australasian Conference on Robotics and Automation
Rushton-Smith, D, To, AW, Paul, G & Liu, D 2013, 'An Accurate and Reliable Approach to Calibration of a Robot Manipulator-Mounted IR Range Camera for Field Applications', International Symposium on Robotics and Mechatronics, International Symposium on Robotics and Mechatronics, Research Publishing, Singapore, pp. 335-344.
Sehestedt, SA, Paul, G, Rushton-Smith, D & Liu, D 2013, 'Prior-knowledge Assisted Fast 3D Map Building of Structured Environments for Steel Bridge Maintenance', IEEE International Conference on Automation Science and Engineering, IEEE Conference on Automation Science and Engineering, IEEE, Madison, WI, USA, pp. 1040-1046.View/Download from: Publisher's site
Practical application of a robot in a structured, yet unknown environment, such as in bridge maintenance, requires the robot to quickly generate an accurate map of the surfaces in the environment. A consistent and complete map is fundamental to achieving reliable and robust operation. In a real-world and field application, sensor noise and insufficient exploration oftentimes result in an incomplete map. This paper presents a robust environment mapping approach using prior knowledge in combination with a single depth camera mounted on the end-effector of a robotic manipulator. The approach has been successfully implemented in an industrial setting for the purpose of steel bridge maintenance. A prototype robot, which includes the presented map building approach in its software package, has recently been delivered to industry.
Quin, PD, Paul, G, Alempijevic, A, Liu, D & Dissanayake, G 2013, 'Efficient Neighbourhood-Based Information Gain Approach for Exploration of Complex 3D Environments', 2013 IEEE International Conference on Robotics and Automation (ICRA), IEEE International Conference on Robotics and Automation, IEEE, Karlsruhe, Germany, pp. 1343-1348.View/Download from: Publisher's site
This paper presents an approach for exploring a complex 3D environment with a sensor mounted on the end effector of a robot manipulator. In contrast to many current approaches which plan as far ahead as possible using as much environment information as is available, our approach considers only a small set of poses (vector of joint angles) neighbouring the robot's current pose in configuration space. Our approach is compared to an existing exploration strategy for a similar robot. Our results demonstrate a significant decrease in the number of information gain estimation calculations that need to be performed, while still gathering an equivalent or increased amount of information about the environment.
Lie, S, Liu, D & Bongers, B 2012, 'A cooperative approach to the design of an Operator Control Unit for a semi-autonomous grit-blasting robot', Australasian Conference on Robotics and Automation (ACRA) 2012, Australasian Conference on Robotics and Automation, Australian Robotics and Automation Association (ARAA), Wellington, New Zealand, pp. 1-7.
Due to the diverse range of applications that robots cover today, Human Robot Interaction interface design has become an equally diverse area. This diverse area is characterised by the different types of end users that make use of the robots. For robots to be useful to end users their needs have to be well understoodby the robotics development teams. One approach that facilitates understanding the end users needs is Cooperative Design. This paper presents the results of a study that took a Cooperative Design approach to the design and development of a robotic Operator Control Unit. The results presented here demonstrate that end users involved in the cooperative design approach thought it added important value to the design outcome, that they enjoyed the process and that it helped build interpersonal relationships within the development team.
Lozano, A, Peters, G, Liu, D & Waldron, K 2011, 'Study of Ant Locomotion in Surface Transitions for Climbing Robot Design', Field robotics : proceedings of the 14th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, International Conference on Climbing and Walking Robots (CLAWAR), World Scientific, Paris, France, pp. 173-180.View/Download from: Publisher's site
Many climbing robots designed based on simple representations of the arthropod body have proven to be able to move on relatively flat surfaces and simple environments. However these robots are not able to navigate in complex environments such as steel bridges. This paper presents experimental studies on ant locomotion, particularly focusing on ant leg gait and posture when traversing a variety of complex surfaces, with the aim of providing climbing robot designers a better understanding of biological ant locomotion through a complex terrain.
Pagano, D, Liu, D & Waldron, K 2012, 'A Method for Optimal Design of an Inchworm Climbing Robot', Proceedings of the 2012 IEEE International Conference on Robotics and Biomimetics, IEEE International Conference on Robotics and Biomimetics, IEEE, Guangzhou, China, pp. 1293-1298.View/Download from: Publisher's site
Many ferromagnetic structures require regular inspection and maintenance to ensure their longevity, structural integrity and aesthetics. These operations are often very hazardous to workers, as they are normally performed at height or in confined spaces, and can expose workers to hazardous materials such as lead based paints and vehicle fumes. An inchworm climbing robot has been proposed as a solution that would improve the quality of the inspection procedure and the occupational health and safety for the maintenance personnel while reducing setup times and costs. However, a number of challenges in designing such an inchworm robot arise from the environmental, mobility and safety factors. This paper describes these challenges for given design applications and presents a method to optimise the design to address the challenges. Analyses of the results attest to the feasibility of the solution.
Tang, R & Liu, D 2012, 'An enhanced dynamic model for McKibben pneumatic muscle actuators', Australasian Conference on Robotics and Automation, ACRA.
An enhanced dynamic force model of a type of small and soft McKibben-type pneumatic muscle (PM) actuator has been developed. This model takes the factor of external loads and a more sophisticated form of friction into account, and is presented as a polynomial function of pressure, contraction length, contraction velocity and external load. The coefficients in this model are determined from a series of experiments with constant loads and step pressure inputs. Comparison study with other models is conducted assuming the Coulomb friction as a constant force. The results demonstrate a solid enhancement of the presented model.
Ward, PK & Liu, D 2012, 'Design of a high capacity Electro Permanent Magnetic adhesion for climbing robots', 2012 IEEE International Conference on Robotics and Biomimetics (ROBIO), IEEE International Conference on Robotics and Biomimetics, IEEE, Guangzhou, China, pp. 217-222.View/Download from: Publisher's site
The interest for robotic solutions to perform inspection and maintenance of steel structures is realised with reduced costs, improved safety and improved efficiency. However current robotic solutions are limited by the required adhesion to support the robot and payload device. The design of an Electro Permanent Magnetic device is studied to yield a high capacity adhesion method for use with industrial climbing robots. The adhesion device must provide a lightweight, low power and a failsafe solution for ferromagnetic surfaces. The design process to achieve maximum holding force for Electro Permanent Magnets is presented.
Carmichael, MG & Liu, D 2012, 'A Task Description Model for Robotic Rehabilitation', 34th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, International Conference of the IEEE Engineering in Medicine and Biology Society, The Printing House, San Diego, CA, pp. 3086-3089.View/Download from: Publisher's site
The desire to produce robots to aid in physical neurorehabilitation has led to the control paradigm Assistance- As-Needed. This paradigm aims to assist patients in performing physical rehabilitation tasks whilst providing the least amount of assistance required, maximizing the patients effort which is essential for recovery. Ideally the provided assistance equals the gap between the capability required to perform the task and the patients available capability. Current implementations derive a measure of this gap by critiquing task performance based on some criteria. This paper presents a task description model for tasks performed by a patients limb, allowing physical requirements to be calculated. Applied to two upper limb tasks typical of rehabilitation and daily activities, the effect of task variations on the tasks physical requirements are observed. It is proposed that using the task description model to compensate for changing task requirements will allow better support by providing assistance closer to the true needs of the patient
Chotiprayanakul, P, Liu, D & Paul, G 2011, 'Effect of view distance and movement scale on haptic-based teleoperation of industrial robots in complex environments', Proceedings of the 28th International Symposium on Automation and Robotics in Construction, ISARC 2011, Automation and Robotics International Symposium, Curran Associates, Inc., Seoul, Korea, pp. 1019-1024.View/Download from: Publisher's site
This paper presents the study on the effect of view distance and movement scale on performance of haptic based teleoperation of a sandblasting robot in complex steel bridge maintenance environments. The operational performance, measured by the Index of Performance (IP), is defined based on the speed and the control accuracy of the manipulator. View distance (i.e. the distance between a display space and an object movement space) and movement scale between hand movement and manipulator movement, which are normally selected empirically, have significant effect the performance. In this paper, an experimental approach is used for determining view distance and movement scale. The sandblasting robotic system is used as an example industrial application in the experiments. Results of the experiments show a range of the view distance and the movement scale that can improve the performance of haptic-based teleoperation of industrial robots in complex environments.
Lozano, A, Peters, G & Liu, D 2011, 'Analysis of an Arthropodal System for Design of a Climbing Robot', 28th International Symposium on Automation and Robotics in Construction (ISARC 2011), ISARC2011 conference organiser, Seoul, Korea, pp. 832-838.
This paper will discuss research on ant locomotion, especially in climbing adaptability and transversing steel bridge configurations, for the design of a climbing robot for inspection and condition assessment of complex steel bridge structures. Experiments in ant locomotion were performed and captured using high-speed video equipment capable of recording at 1000fps. Analysis of the data found that certain body postures in ants are adopted before proceeding with their intended direction, such as when climbing a vertical obstacle. Information on ant body posture, compliance and movement in climbing will also be presented. Furthermore, the working volumes of ant leg pairs are determined through computer aided analysis, which provides essential data for determining possible ant foot positions for locomotion. Discussions on how the findings can be used in designing a climbing robot is also presented.
Carmichael, MG & Liu, D 2011, 'Towards using Musculoskeletal Models for Intelligent Control of Physically Assistive Robots', International Conference of the IEEE Engineering in Medicine and Biology Society, International Conference of the IEEE Engineering in Medicine and Biology Society, The Printing House, Boston, MA, pp. 8162-8165.View/Download from: Publisher's site
With the increasing number of robots being developed to physically assist humans in tasks such as rehabilitation and assistive living, more intelligent and personalized control systems are desired. In this paper we propose the use of a musculoskeletal model to estimate the strength of the user, from which information can be utilized to improve control schemes in which robots physically assist humans. An optimization model is developed utilizing a musculoskeletal model to estimate human strength in a specified dynamic state. Results of this optimization as well as methods of using it to observe muscle-based weaknesses in task space are presented. Lastly potential methods and problems in incorporating this model into a robot control system are discussed.
Cai, B, Huang, S, Liu, D, Yuan, S, Dissanayake, G, Lau, H & Pagac, D 2011, 'Optimisation model and exact algorithm for Autonomous Straddle Carrier Scheduling at automated container terminals', Proceedings of 2011 IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, San Francisco, California, USA, pp. 3686-3693.View/Download from: Publisher's site
In this paper, an optimisation model based on Pickup and Delivery Problem with Time Windows (PDPTW), and an exact algorithm based on Branch-and-Bound with Column Generation (BBCG), are presented for Autonomous Straddle Carriers Scheduling (ASCS) problem at automated container terminals. The ASCS problem is firstly modeled into a PDPTW, which is formulated as a Binary Integer Programming (BIP) and then solved by Column Generation (CG) in the Branch-and-Bound (BB) framework. The BBCG algorithm is also compared to another two exact algorithms [i.e., Binary integer Programming with Dynamic Programming (BPDP) and Exhaustive Search with Permutation and Combination (ESPC)] for the ASCS problem solving. Based on the map of an actual automated container terminal, simulation results and discussions are presented to demonstrate the effectiveness and efficiency of the presented model and algorithm for autonomous vehicle scheduling.
Chotiprayanakul, P, Liu, D & Dissanayake, G 2011, 'An Extended Hand Movement Model for Haptic-based Remote Operation of a Steel Bridge Maintenance Robot', 28th International Symposium on Automation and Robotics in Construction (ISARC 2011), ISARC2011 conference organiser, Seoul, Korea, pp. 1196-1202.
Khushaba, RN, Kodagoda, S, Liu, D & Dissanayake, G 2011, 'Electromyogram (EMG) based Fingers Movement Recognition Using Neighborhood Preserving Analysis with QR-Decomposition', Intelligent Sensor, Sensor Network, and Information Processing (ISSNIP2011), International Conference on Intelligent Sensors, Sensor Networks and Information Processing, IEEE, Adelaide - Australia, pp. 1-6.View/Download from: Publisher's site
Surface Electromyogram (EMG) signals recorded from an amputee's residual muscles have been investigated as a source of control for prosthetic devices for many years. Despite the extensive research focus on the EMG control of arm and gross hand movements, more dexterous individual and combined prosthetic finger control has not received the same amount of attention. To facilitate such a control scheme, the first and the most significant step is the extraction of a set of highly discriminative feature set that can well separate between the different fingers movements and to do so in a computationally efïcient manner. In this paper, an accurate and efïcient feature projection method based on Fuzzy Neighborhood Preserving Analysis (FNPA) with QR-decomposition, is proposed and denoted as FNPA. Unlike existing attempts in fuzzy linear discriminant analysis, the objective of the proposed FNPA is to minimize the distance between samples that belong to the same class and maximize the distance between the centers of different classes, while taking into account the contribution of the samples to the different classes. The method also aims to efïciently overcome the singularity problems of classical LDA and Fuzzy LDA. The proposed FNPA is validated on EMG datasets collected from nine subjects performing 10 classes of individual and combined fingers movements. Practical results indicate the significance of FNPA in comparison to many other feature projection methods with an average accuracy of 91%, using only two EMG electrodes.
Khushaba, RN, Kodagoda, S, Liu, D & Dissanayake, G 2011, 'Electromyogram (EMG) based fingers movement recognition using neighborhood preserving analysis with QR-decomposition', 2011 Seventh International Conference on Intelligent Sensors, Sensor Networks and Information Processing, 2011 Seventh International Conference on Intelligent Sensors, Sensor Networks and Information Processing (ISSNIP), IEEE.View/Download from: Publisher's site
Manamperi, P, Brooks, PA, Kaluarachchi, W, Peters, G, Ho, A, Lie, S, To, AW, Paul, G, Rushton-Smith, D, Webb, SS, Liu, D & Dissanayake, G 2011, 'Robotic Grit-blasting: Engineering Challenges', Austroads 8th Bridge Conference: Sustainable Bridges: The Thread of Society, Austroads Bridge Conference, 2011 Austroads Bridge Conference (ABC 2011), Sydney, Australia, pp. 321-330.
Infrastructure shortage and aging are worldwide issues. Australia, in particular, faces unique challenges in maintaining infrastructures such as roadways and bridges. Corrosion is the primary cause of failure in steel bridges, and is minimised by painting the steel structure. Stripping of rust and deteriorated paint by grit-blasting is an effective and practical method. However, grit-blasting operation is extremely labour intensive and hazardous. It is one of the biggest expenditure items in bridge maintenance operations. Robotics technologies can provide effective solutions to assist bridge maintenance workers in grit blasting. Since 2005, the NSW Roads & Traffic Authority (RTA) and the Centre of Excellence for Autonomous Systems at the University of Technology, Sydney have been working together in developing a robotic system for assisting bridge maintenance workers, with the ultimate objective of preventing human exposure to hazardous and dangerous dust containing rust, paint particles and lead, relieving human workers from labor intensive tasks, and reducing costs associated with bridge maintenance. A prototype robotic system has been developed and tested in both lab setup and on-site. Many engineering issues have been identified for deploying such a system in the field. This paper will present these issues and discuss the solutions.
Peters, G, Pagano, D, Liu, D & Waldron, K 2010, 'A prototype climbing robot for inspection of complex ferrous structures', Proceedings of the 13th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR'2010), International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, World Scientific, Nagoya, Japan, pp. 150-156.
Currently many hazardous maintenance and inspection tasks, such as paint inspection and corrosion condition monitoring of steel structures, are being performed manually by workers, which causes serious health and safety problems. This paper presents a concept climbing robot, with the aim of exploring highly complex ferrous structures such as steel bridges, for the purpose of inspection duties. To demonstrate this concept, a quadruped prototype is developed. A modular architecture that simplifies the development process and improves reusability has been implemented. Permanent magnet compliant pads on each foot provide a simple method of adhesion on the highly complex and unsmooth surface of a bridge. A simple detachment mechanism has been employed. Experiments have been conducted to prove the concept and test the design of the prototype.
Carmichael, MG, Liu, D & Waldron, K 2010, 'Investigation of Reducing Fatigue and Musculoskeletal Disorder with Passive Actuators', Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, Taipei, Taiwan, pp. 2481-2486.View/Download from: Publisher's site
Robotic systems such as exoskeletons can be effectively used in the reduction of fatigue and musculoskeletal disorders (MSD) associated with physical tasks, but robots which work in physical contact with humans pose problems with user safety. A novel approach to developing intrinsically safe robots is to use passive actuators which have the advantage of being safer, ensuring stability, high force/weight ratios and lower power consumption. It is however not clear how effective an exoskeleton utilizing passive actuators would be in reducing fatigue and the risk of MSD. This paper analyzes the benefit of using such a system with results from dynamic simulations and an experiment using a specially designed mechanism used for evaluation. Results indicate that fatigue and effort could be reduced if robot impedance is minimized. Experiments also highlighted issues of implementing such a system into practice.
To, AW, Paul, G & Liu, D 2010, 'Image Segmentation for Surface Material-type Classification using 3D Geometry Information', Proceedings of the 2010 IEEE International Conference on Information and Automation (ICIA2010), IEEE International Conference on Information and Automation, IEEE, Harbin, China, pp. 1717-1722.View/Download from: Publisher's site
This paper describes a novel approach for the segmentation of complex images to determine candidates for accurate material-type classification. The proposed approach identifies classification candidates based on image quality calculated from viewing distance and angle information. The required viewing distance and angle information is extracted from 3D fused images constructed from laser range data and image data. This approach sees application in material-type classification of images captured with varying degrees of image quality attributed to geometric uncertainty of the environment typical for autonomous robotic exploration. The proposed segmentation approach is demonstrated on an autonomous bridge maintenance system and validated using gray level cooccurrence matrix (GLCM) features combined with a naive Bayes classifier. Experimental results demonstrate the effects of viewing distance and angle on classification accuracy and the benefits of segmenting images using 3D geometry information to identify candidates for accurate material-type classification.
Paul, G, Webb, SS, Liu, D & Dissanayake, G 2010, 'A Robotic System for Steel Bridge Maintenance: Field Testing', Proceedings of the Australasian Conference on Robotics and Automation 2010 (ACRA 2010), Proceedings of the Australasian Conference on Robotics and Automation, Australasian Conference on Robotics and Automation, Brisbane, Queensland, Australia, pp. 1-8.
This paper presents the field testing results of an autonomous manipulator-based robotic system that strips the paint and rust from steel bridges [Liu et al., 2008]. The key components of this system are sensing and planning, which have been presented in other research papers. The grit-blasting field trial presented in this paper spanned 6 weeks, and included 20 hours over 4.5 days of actual grit-blasting operation. The field testing has verified the algorithms developed for exploration, mapping, surface segmentation, robot motion planning and collision avoidance. It has also proved that the robotic system is able to perform bridge maintenance operations (grit-blasting), reduce human workers' exposure to hazardous and dangerous debris (containing rust, lead-based paint particles), and relieve workers from labour-intensive tasks. The system has been shown to position a grit-blast nozzle so as to remove the paint and rust at the same rate that is expected of a worker with equivalent equipment: small grit-blasting pot and medium-sized hose nozzle. Testing in the field has also highlighted important issues that need to be addressed.
Yuan, S, Skinner, B, Huang, S, Liu, D, Dissanayake, G, Lau, H, Pagac, D & Pratley, T 2010, 'Mathematical Modelling of Container Transfers for a Fleet of Autonomous Straddle Carriers', Proceedings of the 2010 IEEE International Conferences on Robotics and Automation, IEEE International Conference on Robotics and Automation, IEEE, Anchorage, Alaska, USA, pp. 1261-1266.View/Download from: Publisher's site
The main contribution of this paper is a mathematical model describing performance metrics for coordinating multiple mobile robots in a seaport container terminal. The scenario described here requires dealing with many difficult practical challenges such as the presence of multiple levels of container stacking and sequencing, variable container orientations, and vehicular dynamics that require finite acceleration and deceleration times. Furthermore, in contrast to the automatically guided vehicle planning problem in a manufacturing environment, the container carriers described here are free ranging. Although, the port structure imposes a set of âvirtualâ roadways along which the vehicles are allowed to travel, path planning is essential in preventing contention and collisions. A performance metric which minimises total yard-vehicle usage, while producing robust traffic plans by encouraging both early starting and finishing of jobs is presented for different vehicle fleet sizes and job allocation scenarios.
Cheong, C, Tan, KC & Liu, D 2009, 'Solving the berth allocation problem with service priority via multi-objective optimization', Proceedings of the 2009 IEEE Symposium on Computational Intelligence in Scheduling (CISched 2009), IEEE Symposium on Computational Intelligence in Scheduling, IEEE, Sheraton Music City Hotel, Nashville, TN, USA, pp. 95-102.
This paper studies a multi-objective instance of the berth allocation problem (BAP). The BAP involves the determination of exact berthing times and positions of incoming ships in a container port so as to minimize concurrently the three objectives of makespan of the port, total waiting time of the ships, and degree of deviation from a predetermined service priority schedule. These objectives represent the interests of both port and ship operators. Unlike most existing approaches in the literature which are singleobjective- based, a multi-objective evolutionary algorithm (MOEA) that incorporates the concept of Pareto optimality is proposed for solving the multi-object BAP. The multi-objective approach reveals several interesting characteristics of the BAP.
Chotiprayanakul, P & Liu, D 2009, 'Workspace mapping and force control for small haptic device based robot tele-operation', Proceedings of the 2009 IEEE International Conference on Information and Automation (ICIA2009), IEEE International Conference on Information and Automation, IEEE, Zhuhai/Macau, China, pp. 1613-1618.View/Download from: Publisher's site
When a large robot manipulator is remotely controlled by means of a small haptic device, there are two issues which should be addressed: mapping of robot arm workspace and haptic device workspace, and accurate and safe control of the movement of the robot arm. This paper presents a haptic device workspace spanning control method for haptic-based teleoperation. The spanning control method includes haptic-space scaling control, drift control and edge motion control. A force control algorithm is also presented to control the robot armï½s motion in complex 3D environments. Experimental results demonstrate that the mapping method and the force control algorithm can remotely control a robot arm to rapidly reach target positions, minimize the oscillation of the haptic device handle, achieve accurate positioning and provide the operator with efficient touch sensing.
Yuan, S, Lau, H, Liu, DK, Huang, SD, Dissanayake, G, Pagac, D & Pratley, T 2009, 'Simultaneous Dynamic Scheduling and Collision-Free Path Planning for Multiple Autonomous Vehicles', ICIA: 2009 INTERNATIONAL CONFERENCE ON INFORMATION AND AUTOMATION, VOLS 1-3, IEEE International Conference on Information and Automation (ICIA 2009), IEEE, Zhuhai, PEOPLES R CHINA, pp. 507-+.
Bright, C, Lindsay, E, Lowe, DB, Murray, SJ & Liu, D 2008, 'Factors That Impact Learning Outcomes in Both Simulation and Remote Laboratories', Ed-Media 2008: World Conference on Educational Multimedia, Hypermedia and Telecommunications, Educational Multimedia, Hypermedia & Telecommunications, AACE, Vienna, Austria, pp. 6251-6258.
Chotiprayanakul, P, Wang, D, Kwok, N & Liu, D 2008, 'A Haptic Base Human Robot Interaction Approach for Robotic Grit Blasting', ISARC 2008 - Proceedings from the 25th International Symposium on Automation and Robotics in Construction, 25th International Symposium on Automation and Robotics in Construction, International Association for Automation and Robotics in Construction (IAARC).View/Download from: Publisher's site
Chotiprayanakul, P, Wang, D, Kwok, N & Liu, D 2008, 'A haptic-based human robot interaction approach for robotic grit blasting', Selected Papers of the 25th International Symposium on Automation and Robotics in Construction, International Symposium on Automation and Robotics in Construction, IAARC, Vilnius, Lithuania, pp. 148-154.
Lau, H, Pratley, T, Liu, D, Huang, S & Pagac, D 2008, 'An implementation of prioritized path planning for a large fleet of autonomous straddle carriers', International Federation of Operational Research Societies (IFORS), Sandton, South Africa.
Lindsay, E, Murray, SJ, Liu, D, Lowe, DB & Bright, C 2008, 'Establishment reality vs maintenance reality: how real is real enough?', SEFI 2008: 36th Annual Conference of the European Society for Engineering Education, Annual Conference of European Society for Engineering Education, European Society for Engineering Education, Aarlborg, Denmark, pp. 1-4.
Lowe, DB, Murray, SJ, Lindsay, E, Liu, D & Bright, C 2008, 'Reflecting Professional Reality in Remote Laboratory Experiences', REV 2008: Remote Engineering and Virtual Instrumentation, Remote Engineering and Virtual Instrumentation, International Association of Online Engineering, Dusseldorf, Germany, pp. 1-5.
Murray, S, Lowe, D, Lindsay, E, Lasky, V & Liu, D 2008, 'Experiences with a Hybrid Architecture for Remote Laboratories', FIE: 2008 IEEE FRONTIERS IN EDUCATION CONFERENCE, VOLS 1-3, IEEE Frontiers in Education Conference 2008, IEEE, Saratoga Springs, NY, pp. 502-+.
Ren, T, Kwok, N, Liu, D & Huang, S 2008, 'Path Planning for a Robotic Arm Sand-blasting System', Proceedings of the IEEE International Conference on Information and Automation, IEEE International Conference on Information and Automation, IEEE, Zhangjiajie City, Hunan, China, pp. 1067-1072.View/Download from: Publisher's site
Steel bridges are vulnerable to corrosion and their surfaces have to be de-rusted and repainted regularly. Since the process is complicated, expensive and the removed paints are harmful to human workerspsila health; the use of an automatic robotic system would be an attractive alternative. This paper presents an approach for planning paths for a robotic arm used in the sand-blasting operation. A hexagonal topology-based coverage pattern is adopted to reduce the amount of un-blasted areas and an editing process is included to confine the blasted areas within desirable boundaries. Furthermore, a genetic algorithm is employed to obtain an effective path with minimum arm travel distances and magnitude of turns. Collisions to obstacles are alleviated by making use of the force-field strategy. The effectiveness of the proposed methods is verified by simulations based on an industrial robot arm model and a complex bridge environment.
Wang, D, Liu, D, Kwok, N & Waldron, K 2008, 'A subgoal-guided force field method for robot navigation', Proceedings of the IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications, American Society of Mechanical Engineering, IEEE, Beijing China, pp. 488-493.View/Download from: Publisher's site
Motion planning and collision avoidance functionality are crucial attributes to the successful deployment of mobile robots. This research analyzes some shortcomings of the canonical F2 method and then presents subgoal-guided force-field (SGF2) method to mitigate these drawbacks. In the proposed approach, a robot identifies openings in an environment in front of itself on the basis of sensor data. The midpoints of these openings are determined and selected as subgoal candidates. A cost function is then utilized to evaluate their suitability. One subgoal is then chosen and used by the F2 method to generate a steering force which will drive the robot to the subgoal. The subgoal is continuously updated from realtime sensor data until the global goal is reached. Simulations are carried out to demonstrate the effectiveness of the proposed approach.
Clifton, M, Paul, G, Kwok, N & Liu, D 2008, 'Evaluating performance of multiple RRTs', Proceedings of the IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications, American Society of Mechanical Engineering, IEEE, Beijing, China, pp. 564-569.View/Download from: Publisher's site
This paper presents experimental results evaluating the performance of a new multiple Rapidly exploring Random Tree (RRT) algorithm. RRTs are randomised planners especially adept at solving difficult, high dimensional path planning problems. However, environments with low-connectivity due to the presence of obstacles can severely affect convergence. Multiple RRTs have been proposed as a means of addressing this issue, however, this approach can adversely affect computational efficiency. This paper introduces a new and simple method which takes advantage of the benefits path of multiple trees, whilst ensuring the computational burden of maintaining them is minimised. Results indicate that multiple RRTs are able to reduce the logarithmic complexity of the search, most notably in environments with high obstacle densities.
Liu, D, Dissanayake, G, Manamperi, P, Fang, G, Paul, G, Kirchner, NG & Chotiprayanakul, P 2008, 'A robotic system for steel bridge maintenance: research challenges and system design', Proceedings of the Australasian Conference on Robotics and Automation, Australasian Conference on Robotics and Automation, Australian Robotics and Automation Association, Australia National University, Canberra, Australia, pp. 1-7.
Cheong, C, Lin, C, Tan, KC & Liu, D 2007, 'A Multi-Objective Evolutionary Algorithm for Berth Allocation in a Container Port', Proceedings of the IEEE Congress on Evolutionary Computation, IEEE Congress on Evolutionary Computation, IEEE, Singapore, pp. 927-934.View/Download from: Publisher's site
This paper considers a berth allocation problem (BAP) which requires the determination of exact berthing times and positions of incoming ships in a container port. The problem is solved by optimizing the berth schedule so as to minimize concurrently the three objectives of make span, number of crossings, and waiting time. These objectives represent the interests of both port and ship operators. A multi-objective evolutionary algorithm (MOEA) that incorporates the concept of Pareto optimality is proposed for solving the multi-objective BAP. The MOEA is equipped with a novel solution decoding scheme which is specifically designed to optimize the use of berth space. The MOEA is also able to function in a dynamic context which is of more relevance to a real-world situation.
Lindsay, E, Liu, D, Murray, SJ & Lowe, DB 2007, 'Remote Laboratories in Engineering Education: Trends in Students' Perceptions', Proceedings of the 18th Conference of the Australasian Association of Engineering Education, Annual Conference of Australasian Association for Engineering Education, Australasian Association for Engineering Education, University of Melbourne, Australia, pp. 1-6.
Skinner, B, Nguyen, HT & Liu, D 2007, 'Classification of EEG signals using a genetic-based machine learning classifier', Proceedings of the 29th International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE Engineering in Medicine and Biology Society Annual Conference, IEEE, Lyon, France, pp. 3120-3123.View/Download from: Publisher's site
This paper investigates the efficacy of the geneticbased learning classifier system XCS, for the classification of noisy, artefact-inclusive human electroencephalogram (EEG) signals represented using large condition strings (108bits). EEG signals from three participants were recorded while they performed four mental tasks designed to elicit hemispheric responses. Autoregressive (AR) models and Fast Fourier Transform (FFT) methods were used to form feature vectors with which mental tasks can be discriminated. XCS achieved a maximum classification accuracy of 99.3% and a best average of 88.9%. The relative classification performance of XCS was then compared against four non-evolutionary classifier systems originating from different learning techniques. The experimental results will be used as part of our larger research effort investigating the feasibility of using EEG signals as an interface to allow paralysed persons to control a powered wheelchair or other devices.
Skinner, B, Nguyen, HT & Liu, D 2007, 'Distributed classifier migration in XCS for classification of electroencephalographic signals', Proceedings of the IEEE Congress on Evolutionary Computation, IEEE Congress on Evolutionary Computation, IEEE, Singapore, pp. 2829-2836.View/Download from: Publisher's site
This paper presents an investigation into combining migration strategies inspired by multi-deme parallel genetic algorithms with the XCS learning classifier system to provide parallel and distributed classifier migration. Migrations occur between distributed XCS classifier sub-populations using classifiers ranked according to numerosity, fitness or randomly selected. The influence of the degree-of-connectivity introduced by fully-connected, bi-directional ring and uni-directional ring topologies is examined. Results indicate that classifier migration is an effective method for improving classification accuracy, improving learning speed and reducing final classifier population size, in the single-step classification of noisy, artefact- inclusive human electroencephalographic signals. The experimental results will be used as part of our larger research effort investigating the feasibility of using EEG signals as an interface to allow paralysed persons to control a powered wheelchair or other devices.
Skinner, B, Nguyen, HT & Liu, D 2007, 'Hybrid optimisation method using PGA and SQP algorithm', Proceedings of the IEEE Symposium on Foundations of Computational Intelligence, Symposium on Foundations of Computational Intelligence, IEEE, Honolulu, Hawaii, USA, pp. 73-80.
This paper investigates the hybridisation of two very different optimisation methods, namely the Parallel Genetic Algorithm (PGA) and Sequential Quadratic Programming (SQP) algorithm. The different characteristics of genetic-based and traditional quadratic programming-based methods are discussed and to what extent the hybrid method can benefit the solving of optimisation problems with nonlinear complex objective and constraint functions. Experiments show the hybrid method effectively combines the robust and global search property of Parallel Genetic Algorithms with the high convergence velocity of the Sequential Quadratic Programming Algorithm, thereby reducing computation time, maintaining robustness and increasing solution quality.
Tan, KC, Goh, CK, Teoh, EJ & Liu, D 2007, 'A hybrid evolutionary approach for heterogeneous multiprocessor scheduling', Proceedings of the 8th International Conference on Intelligent Technologies (InTech), International Conference on Intelligent Technologies, University of Technology, Sdyney, Sydney, Australia, pp. 261-268.
Guo, Y, Zhu, J, Liu, D, Lu, H & Wang, S 2007, 'Application of multi-level mult-domain modelling in the design and analysis of a PM transverse flux motor with SMC core', the 7th International Conference on Power Electronics and Drive Systems (PEDS07), International Conference on Power Electronics and Drive Systems, IEEE, Bangkok, Thailand, pp. 27-31.View/Download from: Publisher's site
This paper presents the design and analysis of a permanent magnet (PM) transverse flux motor with soft magnetic composite (SMC) core by applying multi-level multi-domain modeling. The design is conducted in two levels. The upper level is composed of a group of equations which describe the electrical and mechanical characteristics of the motor. The lower level consists of two domains: electromagnetic analysis and thermal calculation. The initial design, including structure, materials and major dimensions, is determined according to existing experience and empirical formulae. Then, optimization is carried out at the system level (the upper level) for the best motor performance by optimizing the structural dimensions. To successfully deal with such a multi-level multi-domain optimization problem, an effective modeling with both high computational accuracy and speed is required. For accurately computing the key motor parameters, such as back electromotive force, winding inductance and core loss, magnetic field finite element analysis is performed. The core loss in each element is stored for effective thermal calculation, and the winding inductance and back EMF are stored as a look-up table for effective analysis of the motor's dynamic performance. The presented approach is effective with good accuracy and reasonable computational speed.
Guo, Y, Zhu, J, Liu, D, Lu, H & Wang, S 2007, 'Application of multi-level multi-domain modeling in the design and analysis of a PM transverse flux motor with SMC core', 2007 INTERNATIONAL CONFERENCE ON POWER ELECTRONICS AND DRIVE SYSTEMS, VOLS 1-4, 7th International Conference on Power Electronics and Drive Systems (PEDS 2007), IEEE, Bangkok, THAILAND, pp. 275-+.
Kwok, N, Fang, G, Ha, QP & Liu, D 2007, 'An enhanced particle swarm optimization algorithm for multi-modal functions', Proceedings of the 2007 IEEE International Conference on Mechatronics and Automation (IEEE ICMA), IEEE International Conference on Mechatronics and Automation, IEEE, Harbin, Heilongjiang, China, pp. 457-462.View/Download from: Publisher's site
The particle swarm optimization algorithm has been frequently employed to solve various optimization problems. Although the algorithm is performing satisfactorily while tackling unit-modal optimizations, enhancements in dealing with multi-modal functions are indeed desirable. Convergence of particles to the optimum solution is a primary and traditional requirement, however, this is achieved only after all the solutions space has been covered and evaluated. In this work, the focus is directed towards maintaining sufficient divergence of particles in multi-modal problems, by developing an alternative social interaction scheme among the swarm members. Particularly, a multiple-leaders strategy is employed in the new PSO algorithm to prevent pre-mature convergence. Results from benchmark problems are included to illustrate the effectiveness of the proposed method.
Kwok, N, Ha, QP, Liu, D, Fang, G & Tan, KC 2007, 'Efficient particle swarm optimization: a termination condition based on the decision-making approach', Proceedings of the IEEE Congress on Evolutionary Computation, 2007, IEEE Congress on Evolutionary Computation, IEEE, Singapore, pp. 3353-3360.View/Download from: Publisher's site
Evolutionary computation algorithms, such as the particle swarm optimization (PSO), have been widely applied in numerical optimizations and real-world product design, not only for their satisfactory performances but also in their relaxing the need for detailed mathematical modelling of complex systems. However, as iterative heuristic searching methods, they often suffer from difficulties in obtaining high quality solutions in an efficient manner. Since unnecessary resources used in computation iterations should be avoided, the determination of a proper termination condition for the algorithms is desirable. In this work, termination is cast as a decision-making process to end the algorithm. Specifically, the non-parametric sign- test is incorporated as a hypothetical test method such that a quantifiable termination in regard to specifiable decision-errors can be assured. Benchmark optimization problems are tackled using the PSO as an illustrative optimizer to demonstrate the effectiveness of the proposed termination condition.
Kirchner, NG, Liu, D, Taha, T & Paul, G 2007, 'Capacitive Object Ranging and Material Type Classifying Sensor', Proceedings of the 8th International Conference on Intelligent Technologies (InTech), International Conference on Intelligent Technologies, University of Technology, Sydney, Sydney, Australia, pp. 130-135.
Kirchner, NG, Taha, T, Liu, D & Paul, G 2007, 'Simultaneous Material Type Classification And Mapping Data Acquisition Using A Laser Range Finder', Proceedings of the 8th International Conference on Intelligent Technologies (InTech), International Conference on Intelligent Technologies, University of Technology, Sydney, Sydney, Australia, pp. 124-129.
This paper presents a method for single sensor simultaneous derivation of three-dimensional mapping data and material type data for use in an autonomous sandblasting system. A Hokuyo laser range finders firmware has been modified so that it returns intensity data. A range error and return intensity analyzing algorithm allows the material type of the sensed object to be determined from a set of known materials. Empirical results have demonstrated the systems ability to classify material type (under alignment and orientation constraints) from a set of known materials common to sandblasting environments (wood, concrete, metals with different finishes and cloth/fabric) and to successfully classify objects both when static and when fitted to an in-motion 6-DOF anthropomorphic robotic arm.
Paul, G, Liu, D, Kirchner, NG & Webb, SS 2007, 'Safe and efficient autonomous exploration technique for 3D mapping of a complex bridge maintenance environment', Proceedings of the 24th International Symposium on Automation and Robotics in Construction (ISARC 2007), International Symposium on Automation and Robotics in Construction, Indian Institute of Technology Madras, Kochi, Kerala, India, pp. 99-104.
Chotiprayanakul, P, Liu, D, Wang, D & Dissanayake, G 2007, 'A 3-dimensional force field method for robot collision avoidance in complex environments', Proceedings of the 24th International Symposium on Automation and Robotics in Construction (ISARC 2007), International Symposium on Automation and Robotics in Construction, Indian Institute of Technology Madras, Kochi, Kerala, India, pp. 139-145.
Chotiprayanakul, P, Liu, D, Wang, D & Dissanayake, G 2007, 'Collision-Free Trajectory Planning for Manipulator Using Virtual Force based Approach', Proceedings of the International Conference on Engineering, Applied Sciences, and Technology (ICEAST 2007), International Conference on Engineering, Applied Sciences, and Technology, KMITL, Bangkok, Thailand, pp. 351-354.
Valls Miro, J, Taha, T, Wang, D, Dissanayake, G & Liu, D 2007, 'An efficient strategy for robot navigation in cluttered environments in the presence of dynamic obstacles', Proceedings of the 8th International Conference on Intelligent Technologies (InTech), International Conference on Intelligent Technologies, University of Technology, Sydney, Sydney, Australia, pp. 74-81.
Wang, D, Kwok, NM, Liu, DK, Lau, H & Dissanayake, G 2007, 'PSO-Tuned F-2 method for multi-robot navigation', 2007 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-9, IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, San Diego, CA, pp. 3771-3776.
Cheong, C, Tan, K, Liu, D & Xu, J 2006, 'A Multiobjective Evolutionary Algorithm for Solving Vehicle Routing Problem with Stochastic Demand', Proceedings of 2006 IEEE Congress on Evolutionary Computation, IEEE Congress on Evolutionary Computation, IEEE, Vancouver, Canada, pp. 5519-5526.View/Download from: Publisher's site
This paper considers the routing of vehicles with limited capacity from a central depot to a set of geographically dispersed customers where actual demand is revealed only when the vehicle arrives at the customer. The solution to this vehicle routing problem with stochastic demand (VRPSD) involves the optimization of complete routing schedules with minimum travel distance, driver remuneration, and number of vehicles, subject to a number of constraints such as vehicle time window and capacity. To solve such a multiobjective combinatorial optimization problem, this paper presents a multiobjective evolutionary algorithm that incorporates two VRPSD-specific heuristics for local exploitation and a route simulation method to evaluate the fitness of solutions. A novel way of assessing the quality of solutions to the VRPSD on top of comparing their expected costs is also proposed. It is shown that the algorithm is capable of finding useful tradeoff solutions which are robust to the stochastic nature of the problem.
Cheong, CY, Tan, KC, Liu, DK & Xu, JX 2006, 'A multiobjective evolutionary algorithm for solving vehicle routing problem with stochastic demand', 2006 IEEE CONGRESS ON EVOLUTIONARY COMPUTATION, VOLS 1-6, IEEE Congress on Evolutionary Computation, IEEE, Vancouver, CANADA, pp. 1355-+.
McIntyre, DG, Liu, DK, Lasky, VL & Murray, SJ 2006, 'A remote water-level rig laboratory for e-learning', 2006 7TH INTERNATIONAL CONFERENCE ON INFORMATION TECHNOLOGY BASED HIGHER EDUCATION AND TRAINING, VOLS 1 AND 2, 7th International Conference on Information Technology Based Higher Education and Training, IEEE, Sydney, AUSTRALIA, pp. 77-81.View/Download from: Publisher's site
Taha, T, Miro, JV & Liu, D 2006, 'An efficient path planner for large mobile platforms in cluttered environments', 2006 IEEE CONFERENCE ON ROBOTICS, AUTOMATION AND MECHATRONICS, VOLS 1 AND 2, IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Bangkok, THAILAND, pp. 671-+.
Kwok, N, Ha, QP, Liu, D & Fang, G 2006, 'Intensity-Preserving Contrast Enhancement for Gray Level Images Using Multi-Objective Particle Swarm Optimisation', Proceedings of the 2006 IEEE Conference on Automation Science and Engineering, IEEE Conference on Automation Science and Engineering, IEEE, Shanghai, China, pp. 19-24.View/Download from: Publisher's site
This paper addresses the enhancement of the contrast of gray-level digital images while preserving the mean image intensity, thus, providing better viewing consistency and effectiveness. The contrast enhancement is achieved by maximizing the information content carried in the image with a continuous intensity transform function and the mean image intensity is preserved, by using the gamma-correction approach. Since the contrast enhancement and intensity preservation are contradicting, a multi-objective particle swarm optimization (MPSO) algorithm is developed to resolve this trade-off. Benchmark images, street senses and skyline images are included to illustrate the effectiveness of the proposed approach
Kwok, N, Liu, D, Tan, K & Ha, QP 2006, 'An Empirical Study on the Settings of Control Coefficients in Particle Swarm Optimization', Proceedings of the 2006 IEEE Congress on Evolutionary Computation, IEEE Congress on Evolutionary Computation, IEEE, Vancouver BC, Canada, pp. 3165-3172.View/Download from: Publisher's site
The effects of randomness of control coefficients in particle swarm optimization (PSO) are investigated through empirical studies. The PSO is viewed as a method to solve a coverage problem in the solution space when the global-best particle is reported as the solution. Randomness of the control coefficients, therefore, plays a crucial role in providing an efficient and effective algorithm. Comparisons of performances are made between the uniform and Gaussian distributed random coefficients in adjusting particle velocities. Alternative strategies are also tested, they include: i) pre-assigned randomness through the iterations, ii) selective hybrid random adjustment based on the fitness of the particles. Furthermore, the effect of velocity momentum factor is compared between a constant and random momentum. Numerical results show that performances of the proposed variations are comparable to the conventional implementation for simple test functions. However, enhanced performances using the selective and hybrid strategy are observed for complicate functions.
Kwok, NM, Liu, DK, Tan, KC & Ha, QP 2006, 'An empirical study on the settings of control coefficients in particle swarm optimization', 2006 IEEE Congress on Evolutionary Computation, CEC 2006, pp. 823-830.
The effects of randomness of control coefficients in Particle Swarm Optimization (PSO) are investigated through empirical studies. The PSO is viewed as a method to solve a coverage problem in the solution space when the global-best particle is reported as the solution. Randomness of the control coefficients, therefore, plays a crucial role in providing an efficient and effective algorithm. Comparisons of performances are made between the uniform and Gaussian distributed random coefficients in adjusting particle velocities. Alternative strategies are also tested, they include: i) pre-assigned randomness through the iterations, ii) selective hybrid random adjustment based on the fitness of the particles. Furthermore, the effect of velocity momentum factor is compared between a constant and random momentum. Numerical results show that performances of the proposed variations are comparable to the conventional implementation for simple test functions. However, enhanced performances using the selective and hybrid strategy are observed for complicate functions. ©2006 IEEE.
Paul, G & Liu, D 2006, 'Replanning of Multiple Autonomous Vehicles in Material Handling', 2006 IEEE Conference on Robotics, Automation and Mechatronics, IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Bangkok, Thailand, pp. 1-6.View/Download from: Publisher's site
The fully automated docks in Australia present opportunities for applications of autonomous vehicles and engineering innovation. When planning tasks to be done by multi-autonomous vehicles in an enclosed area with a known dynamic map (i.e. bi-directional path network), there are many issues that have not yet been comprehensively solved. The real world presents more complexity than the initial algorithms addressed. There are problems that occur due to interaction with the real-world. This means autonomous vehicles can stop, are affected, or face problems, and hence tasks and vehicles' paths and motion need to be replanned. In order to replan, a greater understanding of the state of vehicles, the state of the map, and importantly the importance of tasks and vehicles is definitely needed. This paper explores the improvements made to replanning by gaining a thorough understanding of the map and then utilising map information to make the best, most efficient replanning decision. Five replanning methods are investigated and four options which combine the methods in different ways are tested in this research. A map analysis method is also presented. Simulation studies show that map information based replanning is the most efficient method out of those tested
Kirchner, NG, Liu, D & Dissanayake, G 2006, 'Bridge Maintenance Robotic Arm: Capacitive Sensor for Obstacle Ranging in Particle Laden Air', Proceedings of the 23rd International Symposium on Automation and Robotics in Construction, International Symposium of Automation and Robotics in Construction, Japan Robot Association, Tokyo, Japan, pp. 596-601.
Kulatunga, AK, Liu, D, Dissanayake, G & Siyambalapitiya, SB 2006, 'Ant Colony Optimization based Simultaneous Task Allocation and Path Planning of Autonomous Vehicles', Proceedings of the IEEE Conference on Cybernetics and Intelligent Systems, IEEE International Conference on Cybernetics and Intelligent Systems, IEEE, Bangkok, Thailand, pp. 823-828.View/Download from: Publisher's site
This paper applies a meta-heuristic based ant colony optimization (ACO) technique for simultaneous task allocation and path planning of automated guided vehicles (AGV) in material handling. ACO algorithm allocates tasks to AGVs based on collision free path obtained by a proposed path and motion planning algorithm. The validity of this approach is investigated by applying it to different task and AGV combinations which have different initial settings. For small combinations, i.e. small number of tasks and vehicles, the quality of the ACO solution is compared against the optimal results obtained from exhaustive search mechanism. This approach has shown near optimal results. For larger combinations, ACO solutions are compared with simulated annealing algorithm which is another commonly used meta-heuristic approach. The results show that ACO solutions have slightly better performance than that of simulated annealing algorithm
Liu, DK, Wang, D & Dissanayake, G 2006, 'A force field method based multi-robot collaboration', 2006 IEEE CONFERENCE ON ROBOTICS, AUTOMATION AND MECHATRONICS, VOLS 1 AND 2, IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Bangkok, THAILAND, pp. 511-+.
Liu, DK, Wu, X, Kulatunga, AK & Dissanayake, G 2006, 'Motion coordination of multiple autonomous vehicles in dynamic and strictly constrained environments', 2006 IEEE CONFERENCE ON CYBERNETICS AND INTELLIGENT SYSTEMS, VOLS 1 AND 2, IEEE Conference on Cybernetics and Intelligent Systems, IEEE, Bangkok, THAILAND, pp. 683-+.
Wang, D, Liu, D & Dissanayake, G 2006, 'A Variable Speed Force Field Method for Multi-Robot Collaboration', Proceedings of the IEEE/RSJ International Conference on Robots and Intelligent Systems, 2006, IEEE/RSJ International Conference on Robots and Intelligent Systems, IEEE, Beijing, China, pp. 2697-2702.
Lasky, V, Liu, D, Murray, SJ & Choy, KK 2005, 'A Remote PLC System for e-Learning', Proc of the 4th ASEE/AAEE Global Colloquium on Engineering Education, ASEE Global Colloquium of Engineering Education, AAEE, Sydney, Australia, pp. 1-10.
McLachlan, S, Arblaster, JI, Liu, D, Valls Miro, J & Chenoweth, L 2005, 'A multi-stage shared control method for an intelligent mobility assistant', 2005 IEEE 9th International Conference On Rehabilitation Robotics, IEEE International Conference on Rehabilitation Robotics, IEEE, Chicago, USA, pp. 426-429.
This paper presents a multi-stage shared control method (MSSC) which can be used to control the movement of a robotic mobility assistant designed to facilitate safe mobilization for people with unstable gait. The multi-stage control module consists of user intent, obstacle avoidance and fuzzy logic components. The user intent represents the persons commands. The obstacle avoidance component reads datarepresenting any obstacles in the vicinity of the assistant and uses the Vector Field Histogram (VFH) algorithm to select a suitable path to avoid any obstacles in the path of travel. The fuzzy logic component is responsible for merging the user intent and obstacle avoidance information such that the users request is satisfied to the highest extent possible. When an unsafe situation presents itself the users request(s) will be partially or wholly overridden so the assistant can return to a safe state. The system has been designed to be dynamically configurable so as to suit different users in terms of gait stability and strength, preferred speed of travel and level of control over the system. It has been tested both in a simulated environment and real-world operating conditions and has been shown to effectively avoid obstacles with minimal disruption to the user and their intent.
Wang, D, Liu, D, Wu, X & Tan, K 2005, 'A Force Field Method for Robot Navigation', Proceedings of the 3rd International Conference on Computational Intelligence, Robotics and Autonomous Systems, International Conference on Computational Intelligence, Robotics and Autonomous Systems, CIRAS & FIRA Organising Committee 2005, Singapore, pp. 1-6.
Li, R, Chen, W, Yu, M & Liu, D 2004, 'Fuzzy Intelligent Control of Automotive Vibration Via Magneto-Rheological Damper', Proceedings of the 2004 IEEE Conference on Cybernetics and Intelligent Systems (CIS2004), IEEE International Conference on Cybernetics and Intelligent Systems, IEEE, Singapore, pp. 503-507.View/Download from: Publisher's site
Based on analyses of characteristics of magneto-rheological (MR) damper, a hierarchical fuzzy intelligent controller is proposed for vibration control of an automotive vehicle with MR dampers. This controller consists of control level and coordination level. In the control level, a semiactive fuzzy logic controller is designed for each MR suspension system based on a hybrid control strategy of sky-hook control and ground-hook control. In the coordination level, a coordination controller is designed to coordinate the four independent semiactive fuzzy logic controllers by adjusting their output parameters according to the system feedback. To validate the results of hierarchical fuzzy intelligent control, a MR semiactive suspension control and test system is set up and is implemented on a mini bus, which is equipped with four controllable MR dampers. Test results indicate that the hierarchical fuzzy intelligent controller can effectively reduce the vertical vibration and improve the ride comfort and handle stability of automobile.
Skinner, B, Nguyen, HT & Liu, D 2004, 'Performance Study of a Multi-Deme Parallel Genetic Algorithm with Adaptive Mutation', Proceedings of the 2nd International Conference on Autonomous Robots and Agents (ICARA'04), International Conference on Autonomous Robots and Agents, Massey University, Palmerston North, New Zealand, pp. 88-94.
Zheng, T, Liu, D & Wang, P 2004, 'Priority Based Dynamic Multiple Robot Path Planning', Proceedings of the 2nd International Conference on Autonomous Robots and Agents (ICARA'04), International Conference on Autonomous Robots and Agents, Massey University, New Zealand, Palmerston North, New Zealand, pp. 373-378.
Kulatunga, AK, Liu, D & Dissanayake, G 2004, 'Simulated Annealing Algorithm Based Multi-Robot Coordination', Preprints of the 3rd IFAC Symposium on Mechatronic Systems, The 3rd IFAC Symposium on Mechatronic Systems, International Federation of Automatic Control (IFAC), Sydney, Australia, pp. 411-415.
Kwok, N, Liu, D, Fang, G & Dissanayake, G 2004, 'Path Planning for Bearing-Only Simultaneous Localisation and Mapping', Proceedings of the 2004 IEEE Conference on Robotics, Automation and Mechatronics (RAM), IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Singapore, pp. 828-833.
Simultaneous localisation and mapping (SLAM) is the process of estimating the pose of a mobile robot and the locations of landmarks by using sensors. When SLAM is cast as an information extraction procedure, its quality can be defined as the amount of uncertainty contained in the resultant estimation. Due to the characteristic of the bearing-only sensor and the geometry of the environment, the estimation uncertainty relies critically on the amount of information obtained from measurements and the efficiency of information extraction by the estimator. These quantities are dependent on the relative position between the robot and the landmarks, i.e., the path of the robot motion. Therefore, a well planned path of motion for the robot can significantly improve the SLAM quality. A genetic algorithm is adopted in this research to design a near-optimal one-step-ahead robot path subject to a multiple of planning objectives. The use of genetic algorithm together with a Pareto set, is proved to be efficient in reducing the estimation uncertainty and improving the quality of SLAM by simulation results.
Liu, D, Lau, H & Dissanayake, G 2003, 'A Hierachical Approach and A Multilevel Genetic Algorithm For Vehicle Path Plan', Proceedings of International Conference on Computational Intelligence, Robotics and Autonomous Systems, International Conference on Computational Intelligence, Robotics and Autonomous Systems, Centre for Intelligent Control, National University of Singapore, Singapore, pp. 1-6.
Crowther, AR, Zhang, N, Liu, D & Jeyakumaran, JM 2002, 'A finite element method for dynamic analysis of automatic transmission gear shifting', Proc. of the 6th International Conference on Motion and Vibration Control, International Conference on Motion and Vibration Control, JSME, Saitama, Japan, pp. 514-519.
Kirpitchenko, I, Zhang, N, Tchernykh, S & Liu, D 2002, 'Dynamics and control of grinding machines', Proceedings of The 6th International Conference on Motion and Vibration Control, The Japan Society of Mechanical Engineers, Saitama, Japan, pp. 1039-1044.
Liu, D, Zhang, N, Jeyakumaran, JM & Villanueva, L 2002, 'Transient characteristics of an automatic transmission during shift changes', Applied Mechanics: Progress and Applications, The Third Australasian Congress on Applied mechanics, World Scientific, Sydney, Australia, pp. 683-688.
Liu, D, Zhang, N, Brown, TA & Tam, C 2002, 'A Multilevel Hybrid Genetic Algorithm For Structural Control System Optimization', Proc. of the 6th Int. Conference on Motion and Vibration Control, International Conference on Motion and Vibration Control, JSME, Saitama, Japan, pp. 154-159.
Liu, D, Zhang, N, Jeyakumaran, JM & Villanueva, L 2000, 'Dynamics and Shift Control of Automatic Transmissions', Proc. of the Fifth International Conference on Motion and Vibration Control, International Conference on Motion and Vibration Control, UTS, Sydney, australia, pp. 597-602.