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Professor Dikai Liu

Biography

Professor Dikai Liu received his PhD degree in 1997 and joined UTS in 2000. His main research interests include robotics (exploration, localisation, motion planning and collision avoidance), robot teams and physical human-robot interaction. Professor Liu has been developing novel methods and algorithms that enable robots to operate in unstructured, dynamic and/or complex 3D environments autonomously or collaboratively with human users and other robots. He has also been developing robotic systems that can be practically deployed in real applications, including autonomous grit-blasting robots for steel bridge maintenance, assistive robots for human strength augmentation in industrial applications, bio-inspired climbing robots for steel structure inspection and condition assessment, and autonomous underwater robots for cleaning and inspection of underwater structures, and smart robotic hoist for patient transfer.

Professor Liu is Co-Director of the UTS Centre for Autonomous Systems.

Awards/Award Finalists:

(1) 2015 Asia Pacific ICT Alliance (APICTA) Award;

(2) 2015 SafeWork NSW Awards for the best solution to an identified workplace health and safety issue, “Bridge inspection robot”, Australia;

(3) 2015 iAwards National Merit Award, Australia;

(4) 2015 iAwards New South Wales Merit Award, Australia;

(5) Finalist of the 2013 Australian Engineering Excellence Awards (AEEA);

(6) Engineering Excellence Award Sydney (EEAS) (Category: Research and Development), 2013;

(7) Engineering Excellence Award Sydney (EEAS) (Category: Control Systems and Communications), 2013;

(8) Finalist of the 2013 Australian Museum Eureka Prize for Innovative Use of Technology, 2013

(9) Finalist of the 2013 IEEE/IFR Invention & Entrepreneurship in Robotics and Automation (IERA) Award.

(10) UTS Vice-Chancellor’s Award for Research Excellence through Partnership, 2012

(11) Best Paper for the Biomedical Sensing and Sensors Symposium, ISSNIP 2011

(12) Best student paper award, ISARC’2007, Kochi, India

(13) Best paper award, ISARC’2006, Tokyo, Japan

(14) Carrick Australian Awards for University Teaching_Citation for Outstanding Contributions to Student Learning, Australia, 2006.

Patents:

(1) P. Ward, D.K.Liu, “Adhesion system for a climbing vehicle”, Australian Patent application number: 2013902595, filing date: 12 July 2013. International (PCT) Patent application WO 2015/003221

(2) M. Carmichael, D.K.Liu, “Robotic exoskeleton apparatus”, Australian Patent application number: 2013904101, filing date: 24 Oct 2013; International (PCT) Patent application No. PCT/AU2014/001010

(3) N. Kirchner, D.K. Liu, G. Dissanayake, “An algorithmic extension to laser based range finders that introduces the novel function of non-contact material type identification”, Provisional Patent Number: 2007904898;

Professional Services:

Editorial Board Member of the Int. J. of Biomechatronics and Biomedical Robotics, and the Int. J. of Intelligent Computing and Cybernetics; Program Co-Chair of the 2016 IEEE AIM conference, Local Organising Committee Chair of the 2013 CLAWAR; Publicity Chair of 2010 ACM/IEEE HRI; PC member of over 50 conferences, and paper reviewer of over 20 international journals.

Professional

Senior Member, Institution of Electrical and Electronic Engineers (IEEE);

Member, The American Society of Mechanical Engineers (ASME);

Observer, The IFToMM Robotics and Mechatronics committee;

Member, Institution of Engineers, Australia;

Image of Dikai Liu
Director, Research, School of Mechanical and Mechatronic Engineering
Director, CAS - Centre for Autonomous Systems
Core Member, CAS - Centre for Autonomous Systems
BE (WHUT), ME (WHUT), PhD (WHUT)
Member, Institution of Engineers, Australia
Member, Institution of Electrical and Electronic Engineers
 
Phone
+61 2 9514 2587

Research Interests

  • Robotics: exploration, localisation, motion planning and collision avoidance for mobile robot and robot manipulators in complex 3D environments; multi-robot coordination and control; robotic systems for infrastructure maintenance; bio-inspired robotics;
  • Human-Robot Interaction: interaction modelling; physical human-robot interaction; design methodology;
  • Assisted Care and Health: intelligent robots for assisted care; robotic systems for rehabilitation; novel actuators;

Industrial Transformation of Research Outcomes in Robotics Research:

• Autonomous grit-blasting robots deployed in the Sydney Harbour Bridge for steel bridge maintenance (News and reports: SMH, BBC, ABC, ABC News Radio, The Robot Report, TVBS(Taiwan)). An Australian start-up company, SABRE Autonomous Solutions, was formed in 2013 to commercialise this technology;

• Biologically inspired autonomous climbing robot for confined space inspection of the Sydney Harbour Bridge (News and reports: ABC News, SMH, CIO, Youtube);

• Robotic hoist for patient transfer in hospitals and nursing homes;

• Multi-robot coordination systems for automated material handling;

Can supervise: Yes

Category 1: All supervisory roles

Undergraduate: Dynamics and Control; Advanced Manufacturing; Introduction to Mechanical and Mechatronic Engineering;
Postgraduate: Design Optimisation for Manufacturing;

Chapters

Ward, P.K., Liu, D., Waldron, K. & Hassan, M. 2013, 'Optimal Design of a Magnetic Adhesion for Climbing Robots' in Waldron, K.J., Tokhi, M.O. & Virk, G.S. (eds), Nature-Inspired Mobile Robotics, World Scientific Publishing, Singapore, pp. 375-382.
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Designing a magnetic adhesion system for climbing robots requires careful selection of design parameters to achieve a feasible solution. There are many considerations which must be taken into account, such as, size constraints for the intended environment and robot configuration, the maximum load that can be supported by the climbing robot, and the expected air gaps during operation. With consideration of the design challenges, an optimal design for a magnetic adhesion system is presented. Based on the optimal design a prototype footpad has been constructed for use on an inchworm climbing robot and experimental results are presented.
Wang, D., Kwok, N., Liu, D. & Ha, Q.P. 2009, 'Ranked pareto particle swarm optimization for mobile robot motion planning' in Liu, D., Wang, L. & Tan, K.C. (eds), Design and Control of Intelligent Robotic Systems, Springer, Springer-Verlag Berlin Heidelberg, pp. 97-118.
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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.
XU, J., Liu, D. & Fang, G. 2007, 'An efficient method for collision detection and distance queries in a robotic bridge maintenance system' in Tarn, T.J., Chen, S.B. & Zhou, C. (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 71-82.
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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, N.G. 2007, 'An algorithm for surface growing from laser scan generated point clouts' in Tarn, T.J., Chen, S.B. & Zhou, C. (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 481-491.
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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.
Kulatunga, A.K., Skinner, B., Liu, D. & Nguyen, H.T. 2007, 'Distributed simultaneous task allocation and motion coordination of autonomous vehicles using a parallel computing cluster' in Tarn, T.J., Chen, S.B. & Zhou, C. (eds), Robotic Welding, Intelligence and Automation, Springer, Heidelberg, pp. 409-420.
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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, A.K. 2007, 'Simultaneous Planning and Scheduling for Multi-Autonomous Vehicles' in Dahal, K.P., Tan, K.C. & Cowling, P.I. (eds), Evolutionary Scheduling, Springer, Heidelberg, pp. 437-464.
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Conferences

Reeks, C., Carmichael, M., Liu, D. & Waldron, K. 2016, 'Angled sensor configuration capable of measuring tri-axial forces for pHRI', IEEE International Conference on Robotics and Automation (ICRA), IEEE, Stockholm, Sweden, pp. 3089-3094.
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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, J.K., Liu, D.K. & Carmichael, M. 2016, 'Kinematic Control of an Autonomous Underwater Vehicle-Manipulator System Using Autoregressive Prediction of Vehicle Motion and Model Predictive Control', IEEE International Conference on Robotics and Automation 2016, Stockholm, Sweden.
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 International Conference on Advanced Intelligent Mechatronics (AIM), IEEE, Banff, Canada, pp. 401-406.
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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.
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 International Conference on Advanced Intelligent Mechatronics (AIM), IEEE, Banff, Canada.
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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 (ICIEA), IEEE, Hefei, China, pp. 101-106.
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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.
Hassan, M., Liu, D.L. & Paul, G.P. 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, International Conference on Intelligent Robots and Systems (IROS), IEEE (Institute of Electrical and Electronics Engineers), Daejeon, Korea, pp. 2978-2984.
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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 (ICARCV), IEEE, Phuket, Thailand.
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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, P.D., 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.
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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.
Carmichael, M.G. & Liu, D. 2013, 'Human Biomechanical Model Based Optimal Design of Assistive Shoulder Exoskeleton', Field and Service Robotics, Springer, Brisbane, pp. 245-258.
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Hassan, M., Liu, D., Paul, G. & Huang, S. 2015, 'An Approach to Base Placement for Effective Collaboration of Multiple Autonomous Industrial Robots', International Conference on Robotics and Automation (ICRA), Institute of Electrical and Electronics Engineers (IEEE), Washington State Convention Center in Seattle, Washington, USA, pp. 3286-3291.
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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.
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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.
Tran, A., Liu, D., Ranasinghe, R., Carmichael, M. & Liu, C. 2015, 'Analysis of Human grip strength in physical Human Robot Interaction', Applied Human Factors and Ergonomics, Las Vegas.
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, M.G. & 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, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE, Milan, Italy, pp. 2438-2441.
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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, M.G., Khonasty, R. & Liu, D. 2015, 'A Multi-stage Design Framework for the Development of Task-specific Robotic Exoskeletons', 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Milan, Italy.
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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 (ROBIO), IEEE, Zhuhai, China, pp. 90-95.
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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.
To, A.W., 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.
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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.
Quin, P.D., 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/by..., Australasian Conference on Robotics and Automation, Australasian Robotics and Automation Association, Melbourne, pp. 1-10.
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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', SOCIAL ROBOTICS, pp. 105-114.
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Liu, D.K., Dissanayake, G., Valls Miro, J. & Waldron, K.J. 2014, 'Infrastructure robotics: Research challenges and opportunities', 31st International Symposium on Automation and Robotics in Construction and Mining, ISARC 2014 - Proceedings, pp. 43-49.
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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.
Carmichael, M.G., Moutrie, B. & Liu, D. 2014, 'A Framework for Task-Based Evaluation of Robotic Coworkers', The 13th International Conference on Control, Automation, Robotics and Vision (ICARCV2014), IEEE, Singapore, pp. 1362-1367.
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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.
Zhang, Huang & Liu 2014, 'Comparison of Two Strategies of Path Planning for Underwater Robot Navigation Under Uncertainty', the 13th International Conference on Control, Automation, Robotics and Vision (ICARCV 2014), IEEE, Singapore.
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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.
Hassan, M., Liu, Huang & Dissanayake 2014, 'Task Oriented Area Partitioning and Allocation for Optimal Operation of Multiple Industrial Robots in Unstructured Environments', International Conference on Control, Automation, Robotics and Vision, ICARCV, IEEE Xplore, Marina Bay Sands, Singapore, pp. 1184-1189.
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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.
Ward, P.K., Quin, P., Pagano, D., Yang, C., Liu, D., Waldron, K., Dissanayake, D., Paul, G., Brooks, P., Mann, P., Kaluarachchi, W., Manamperi, P. & Matkovic, L. 2014, 'Climbing Robot for Steel Bridge Inspection: Design Challenges', Austroads Publications Online, 9th Austroads Bridge Conference, ARRB Group, New South Wales.
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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.
Quin, P.D., 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 (ICRA), IEEE, Karlsruhe, Germany, pp. 1343-1348.
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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.
Sehestedt, S.A., 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 International Conference on Automation Science and Engineering, IEEE, Madison, WI, USA, pp. 1040-1046.
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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.
Rushton-Smith, D., To, A.W., 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.
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Carmichael, M.G. & 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), EMBC 2013, IEEE, Osaka, Japan, pp. 870-873.
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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, M.G. & 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), IEEE, Osaka, Japan, pp. 866-869.
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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, P.D., 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.
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Australasian Conference on Robotics and Automation
Lozano, A., Peters, G., Liu, D. & Waldron, K. 2011, 'Study of Ant Locomotion in Surface Transitions for Climbing Robot Design', 14th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR2011), 14th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines (CLAWAR2011), World Scientific, Paris, France, pp. 173-180.
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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.
Ward, P.K. & Liu, D. 2012, 'Design of High Capacity Electro Permanent Magnetic Adhesion for Climbing Robots', Proceedings of the 2012 IEEE International Conference on Robotics and Biomimetrics, 2012 IEEE Conference on Robotics and Biomimetics, IEEE, Guangzhou, China, pp. 217-222.
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The interest for robotic solutions to perform inspection and maintenance of steel structures is realised with reduced costs, improved safety and improved ef¬ciency. 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 fail safe solution for ferromagnetic surfaces. The design process to achieve maximum holding force for Electro Permanent Magnets is presented.
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 2012, Australian Robotics and Automation Association (ARAA), Wellington, New Zealand, pp. 1-7.
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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.
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, 2012 IEEE International Conference on Robotics and Biomimetics (ROBIO), IEEE, Guangzhou, China, pp. 1293-1298.
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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.
Carmichael, M.G. & Liu, D. 2012, 'A Task Description Model for Robotic Rehabilitation', 34th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, IEEE EMBS 2012, The Printing House, San Diego, pp. 3086-3089.
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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
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.
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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.
Khushaba, R.N., 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), IEEE, Adelaide - Australia, pp. 1-6.
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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 efcient manner. In this paper, an accurate and efcient 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 efciently 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.
Manamperi, P., Brooks, P.A., Kaluarachchi, W., Peters, G., Ho, A., Lie, S., To, A.W., Paul, G., Rushton-Smith, D., Webb, S.S., Liu, D. & Dissanayake, G. 2011, 'Robotic Grit-blasting: Engineering Challenges', Sustainable Bridges: The Thread of Society, Sustainable Bridges: The Thread of Society, 2011 Austroads Bridge Conference (ABC 2011), Sydney, Australia, pp. 321-330.
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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.
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.
Chotiprayanakul, P., Liu, D. & Paul, G. 2011, 'Effect of View Distance and Movement Scale on Haptic-based Teleoperation of a Sand-blasting Robotic System for Complex Steel Bridge Maintenance', Proceedings of the 28th International Symposium on Automation and Robotics in Construction (ISARC 2011), ISARC2011 conference organiser, Seoul, Korea, pp. 1019-1024.
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.
Carmichael, M.G. & 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.
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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.
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, pp. 1019-1024.
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.
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.
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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.
To, A.W., 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.
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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.
Carmichael, M.G., 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.
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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.
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.
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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.
Paul, G., Webb, S.S., 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.
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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., Lau, H., Liu, D., Huang, S., Dissanayake, G., Pagac, D. & Pratley, T. 2009, 'Simultaneous dynamic scheduling and collision-free path planning for multiple autonomous vehicles', Proceedings of the 2009 IEEE International Conference on Information and Automation (ICIA-2009), IEEE International Conference on Information and Automation, IEEE, Zhuhai/Macau, China, pp. 522-527.
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When autonomous vehicles are deployed to perform transportation tasks within a confined space and strict time constraint, the problem of optimizing the assignment of tasks to vehicles is complicated by the need to ensure safety (they do not collide with or impede each other) and maximize the efficiency and productivity. With the increasing number of autonomous vehicles in practical settings, the ability to schedule tasks in a manner that inherently considers the effects of task allocations on space contention (which in turn compromises efficiency) is important to performance improvement. The main contribution of this paper is an approach to simultaneously conduct dynamic task allocation and collision-free path planning in an environment where multiple autonomous vehicles operate on a network of paths and where each path segment can only be occupied by one vehicle at a given instant. In particular, a generic algorithm for effective task allocation is investigated and applied in conjunction with an application-specific objective function. The proposed approach is able to solve the dynamic scheduling, planning and collision avoidance problem in an integrated way such that the overall productivity of the transportation system is improved. Simulation results based on a real-world industrial material handling environment demonstrate the feasibility and effectiveness of the proposed method.
Cheong, C., Tan, K.C. & 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.
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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.
Brooks, P.A., Manamperi, P., Liu, D. & Dissanayake, G. 2009, 'A robotic grit-blasting system for steel bridge maintenance', The 2009 Australasian Corrosion Association (ACA) conference, 15-18 November 2009,, Coffs Harbour, NSW, Australia.
Corrosion is the primary cause of failure in steel bridges. Stripping of rust and deteriorated paint and then repainting the steel are the procedures in steel bridge maintenance, and is one of the biggest expenditure items in bridge maintenance activities. Grit-blasting, which is an effective and efficient method of paint stripping, is extremely labour intensive and hazardous. Workers have to not only spend long periods of time handling forces of 100N and above, but also need to take precautions to avoid exposure to the dust containing hazardous materials and chemicals. Thus supplementing manual labour in grit-blasting with robotic aids has a significant health, safety and economic impact.
Manamperi, P., Brooks, P.A., Liu, D. & Dissanayake, G. 2009, 'Advanced robotic technologies for steel bridge maintenance', The 7th Austroads Bridge Conference website, The 7th Austroads Bridge Conference, Austroads, Auckland, New Zealand, pp. 1-8.
Bridges are essential in transport infrastructure worldwide. Corrosion is the primary cause of failure in steel bridges, and is minimized by painting the steel structure. Steel bridge coating maintenance consists of two procedures: the stripping of rust and deteriorated paint and then repainting the steel; and is one of the biggest expenditure items in bridge maintenance activities. An effective and efficient method of paint stripping is grit blasting, and herein lies the critical problem. Grit blasting is extremely labour intensive and hazardous. Workers have to not only spend long periods of time handling forces of 100N and above, but also need to take precautions to avoid exposure to the dust containing hazardous materials and chemicals. Thus supplementing manual labour in grit blasting with robotic aids will have a significant health, safety and economic impact.
Yuan, S., Huang, S., Liu, D., Lau, H., Pagac, D. & Pratley, T. 2009, 'Problem formulation of simultaneously dynamic scheduling and collision-free path planning for multiple autonomous vehicles in automated container terminals', International Symposium for Maritime Logistics and Supply Chain Systems, Singapore.
This work is motivated by an actual application of dispatching and path planing for a fleet of autonomous straddle carriers operated by Patrick Stevedores at the fully automated container terminal located in Brisbane, Australia. In this application, the straddle carriers can localize themselves and navigate autonomously within in the seaport. They can also pick up, transport, and drop down the containers without any human interference. The container transportation tasks performed by the fully autonomous straddle carriers include moving containers from quay crane area to yard, from yard to quay crane area, from yard to yard, from truck area to yard and from yard to truck area.
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.
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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 arm½s 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.
To, A.W., Paul, G., Kwok, N. & Liu, D. 2008, 'An integrated approach to planning for autonomous grit-blasting robot in complex bridge environments', Proceedings of 2008 Fourth I*PROMS Virtual Conference International Conference on Innovative Production Machines and Systems, International Conference on Innovative Production Machines and Systems, Whittles Publishing, Cardiff University, Wales, UK, pp. 313-318.
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This paper describes an integrated approach to robot manipulator path and motion planning in complex bridge environments. It incorporates grit-blasting specific considerations including blasting effect, coverage, path length and robot arm joint movement. A genetic algorithm is implemented for path planning with the use of environment data to increase planning efficiency. A customized gradient based method is applied in selecting collision free joint configurations for the identified path. A grit-blast coverage model is also developed for discrete non-planar 3D coverage determination to verify the performance of the planned path and motion.
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.
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Lowe, D.B., Murray, S.J., 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.
Bright, C., Lindsay, E., Lowe, D.B., Murray, S.J. & 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.
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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.
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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.
Murray, S.J., Lowe, D.B., Lindsay, E., Lasky, V. & Liu, D. 2008, 'Experiences with a Hybrid Architecture for Remote Laboratories', FiE 2008: The 38th Annual Frontiers in Education Conference, ASEE/IEEE Frontiers in Education Conference, IEEE, Saratgoa Springs, USA, pp. 15-19.
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There is growing interest in the use of remote laboratories to access physical laboratory infrastructure. These laboratories can support additional practical components in courses, provide improved access at reduced cost, and encourage sharing of expensive resources. Effective design of remote laboratories requires attention to both the pedagogic design and the technical support, as well as how these elements interact. We discuss our experiences with a remote laboratory implementation based on a hybrid architecture. This architecture utilises a Web front-end allowing student access to an arbitration system, which permits students to select one of a number of experiments, before being allocated to a particular experimental station. The interaction with the equipment then occurs through a separate stand-alone application which runs on its own virtualized server which the user accesses via a remote desktop client. This hybrid architecture has many benefits, as well as some limitations. For example, it allows rich control and monitoring interfaces to be developed, but also requires students to understand a slightly more complex process for establishing the control. We discuss the reactions to this architecture by different cohorts of students as well as the extent to which the architecture facilitates evolution and expansion of the laboratories.
Liu, D., Dissanayake, G., Manamperi, P., Fang, G., Paul, G., Kirchner, N.G. & 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.
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Lindsay, E., Murray, S.J., Liu, D., Lowe, D.B. & 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.
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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.
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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.
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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.
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.
Murray, S., Lowe, D., Lindsay, E., Lasky, V., Liu, D. & IEEE 2008, 'Experiences with a Hybrid Architecture for Remote Laboratories', FIE: 2008 IEEE FRONTIERS IN EDUCATION CONFERENCE, VOLS 1-3, pp. 502-506.
Paul, G., Liu, D., Kirchner, N.G. & Webb, S.S. 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.
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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.
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Kwok, N., Ha, Q.P., Liu, D., Fang, G. & Tan, K.C. 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.
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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.
Skinner, B., Nguyen, H.T. & 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.
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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.
Kwok, N., Fang, G., Ha, Q.P. & 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.
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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.
Skinner, B., Nguyen, H.T. & 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.
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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.
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.
Cheong, C., Lin, C., Tan, K.C. & 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.
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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.
Tan, K.C., Goh, C.K., Teoh, E.J. & 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.
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Kirchner, N.G., 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.
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Kirchner, N.G., 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.
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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.
Lindsay, E., Liu, D., Murray, S.J. & Lowe, D.B. 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.
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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.
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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.
Skinner, B., Nguyen, H.T. & 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.
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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.
Wang, D., Kwok, N., Liu, D., Lau, H. & Dissanayake, G. 2007, 'PSO-tuned F2 method for multi-robot navigation', 2007 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE/RSJ International Conference on Intelligent Robots and Systems, IEEE, San Diego, California, USA, pp. 3765-3770.
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The F (Force Field) method is a novel approach for multi-robot motion planning and collision avoidance. The setting of parameters is however vital to its performance. This paper presents an approach using Particle Swarm Optimization (PSO) to properly determine the control parameters for the F2 method. The goal of the optimization is to minimize the resultant path lengths. The approach presented in this paper can be used as a tool to obtain optimal parameters for various tasks before their execution. Simulations are carried out in various environments to show the feasibility of this approac
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.
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Kwok, N., Ha, Q.P., 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.
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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, Q.P. 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.
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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.
Kulatunga, A.K., Liu, D., Dissanayake, G. & Siyambalapitiya, S.B. 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.
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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
McIntyre, D.G., Liu, D., Lasky, V. & Murray, S.J. 2006, 'A Remote Water-Level Rig Laboratory for e-Learning', Proceedings of the 7th International Conference on Information Technology base Higher Education and Training, International Confernce on Information Technology Base Higher Education and Training, IEEE, Sydney, Australia, pp. 1-5.
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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.
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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
Liu, D., Wang, D. & Dissanayake, G. 2006, 'A Force field Method Based Multi Robot Collaboration', Proceedings of IEEE Conference on Robotics, Automation and Mechatronics, 2006, IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Bangkok, Thailand, pp. 662-667.
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A force field (F2) based multi-robot collaboration method is presented in this paper. In this method, a virtual force field is generated for every moving robot and continuously changing based on the robot status including its traveling speed, dimension, priority, location and environment, etc. The interactions among robots' force fields and obstacles provide a natural way for collision avoidance and collaboration while robots are on their way to goals. In this paper, the definition of reaction force direction is modified to reduce robot orientation oscillations which occur when a robot approaches obstacles or other robots. Then the influence of task priority on motion planning and the problem of deadlock in multi-robot cases are discussed. Simulations in a real indoor environment were carried out and demonstrated the feasibility and effectiveness of this method
Liu, D., Wu, X., Kulatunga, A.K. & Dissanayake, G. 2006, 'Motion Coordination of Multiple Autonomous Vehicles in Dynamic and Strictly Constrained Environments', Proceedings of the IEEE Conference on Cybernetics and Intelligent Systems, IEEE International Conference on Cybernetics and Intelligent Systems, IEEE, Bangkok, Thailand, pp. 204-209.
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With the increasing applications of fully autonomous vehicles, efficient motion coordination of multi-autonomous vehicles becomes a very important problem as it significantly affects the productivity. This problem is even harder to solve with the increases of the number of autonomous vehicles employed in a dynamic changing environment and constraints to vehicle movement. This paper presents a simultaneous path and motion planning (SiPaMoP) approach to coordinate motions of multi-autonomous vehicles in dynamic and strictly constrained environments. This approach integrates the path planning, collision avoidance and motion planning into a comprehensive model, which has so far not attracted a lot of attention in the academic literature, and optimizes vehicles' path and speed to minimize the completion time of a set of tasks. Simulation results demonstrated that this approach can effectively coordinate the motion of a team of vehicles, and solve the problems of traffic congestion and collision under various traffic conditions
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.
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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.
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.
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Kirchner, N.G., 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.
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Taha, T., Valls Miro, J. & Liu, D. 2007, 'An efficient path planner for large mobile platforms in cluttered enviornments', Proceedings of the 2006 IEEE International Conference on Robotics, Automation Mechatronics (RAM), IEEE Conference on Robotics, Automation and Mechatronics, IEEE, Bangkok, Thailand, pp. 225-230.
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This paper presents a one step smooth and efficient path planning algorithm for navigating a large robotic platform in known cluttered environments. The proposed strategy, based on the generation of a novel search space, relies on non-uniform density sampling of the free areas to direct the computational resources to troubled and difficult regions, such as narrow passages, leaving the larger open spaces sparsely populated. A smoothing penalty is also associated to the nodes to encourage the generation of gentle paths along the middle of the empty spaces. Collision detection is carried out off-line during the creation of the configuration space to speed up the actual search for the path, which is done on-line. Results prove that the proposed approach considerably reduces the search space in a meaningful and practical manner, improving the computational cost of generating a path optimised for fine and smooth motion
Liu, D.K., Wu, X., Kulatunga, A.K., Dissanayake, G. & IEEE 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, pp. 683-688.
Kwok, N.M., Liu, D.K., Tan, K.C. & Ha, Q.P. 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.
McLachlan, S., Arblaster, J.I., 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.
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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.
Lasky, V., Liu, D., Murray, S.J. & Choy, K.K. 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.
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.
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Skinner, B., Nguyen, H.T. & 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.
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Kulatunga, A.K., 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.
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.
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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.
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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.
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.
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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.
Liu, D., Zhang, N., Jeyakumaran, J.M. & 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.
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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.
Crowther, A.R., Zhang, N., Liu, D. & Jeyakumaran, J.M. 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.
Liu, D., Zhang, N., Brown, T.A. & 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., Lu, F. & Q, S.L. 2000, 'Optimal Number and Positions of Actuators in Actively Controlled Structures', Proc. of the 5th International Conference on Motion and Vibration Control, International Conference on Motion and Vibration Control, UTS, Sydney, Australia, pp. 347-352.
Liu, D., Zhang, N., Jeyakumaran, J.M. & 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.

Journal articles

Quin, P., Paul, G. & Liu, D. 2017, 'Experimental Evaluation of Nearest Neighbour Exploration Approach in Field Environments', IEEE Transactions on Automation Science and Engineering.
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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.
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.
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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.
To, W., paul, G. & liu, D. 2017, 'A comprehensive approach to real-time fault diagnosis during automatic grit-blasting operation by autonomous industrial robots', Robotics and Computer-Integrated Manufacturing.
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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, pp. 1-20.
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© 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.
hassan, M., liu, D. & Paul, G. 2017, 'Collaboration of Multiple Autonomous Industrial Robots through Optimal Base Placements', Journal of Intelligent and Robotic Systems.
Carmichael, M.G., Liu, D. & Waldron, K.J. 2017, 'A framework for singularity-robust manipulator control during physical human-robot interaction', The International Journal of Robotics Research, pp. 027836491769874-027836491769874.
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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.
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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.
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.
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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.
To, A.W., Paul, G. & Liu, D. 2014, 'Surface-type classification using RGB-D', IEEE Transactions on Automation Science and Engineering, vol. 11, no. 2, pp. 359-366.
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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...
Paul, G., Kwok, N.M. & Liu, D. 2013, 'A novel surface segmentation approach for robotic manipulator-based maintenance operation planning', Automation In Construction, vol. 29, pp. 136-147.
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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%.
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.
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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
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.
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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.
Carmichael, M.G. & Liu, D. 2013, 'Estimating Physical Assistance Need Using a Musculoskeletal Model', IEEE Transactions On Biomedical Engineering, vol. 60, no. 7, pp. 1912-1919.
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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.
Khushaba, R.N., 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.
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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.
Wu, H., Liu, H. & Liu, D. 2013, 'Two Dimensional Direction Recognition Using Uniaxial Tactile Arrays', IEEE Sensors Journal, vol. 13, no. 2, pp. 4897-4903.
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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.
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.
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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.
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, no. NA, pp. 11-23.
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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 algo
Meng, X., Wang, D.O., not USe, S., Qiu, J., Zhang, Q., Zhu, J., 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.
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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, S.S., 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.
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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.
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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, K.C., 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.
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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, S.H., Meng, X.J., 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.
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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, S.J., Liu, D., Lowe, D.B. & 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.
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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, D.B., Murray, S.J., 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.
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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.
Paul, G., Liu, D., Kirchner, N.G. & 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.
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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, N.G., Liu, D. & Dissanayake, G. 2009, 'Surface Type Classification With a Laser Range Finder', IEEE Sensors Journal, vol. 9, no. 9, pp. 1160-1168.
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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.
To, A.W., 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.
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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.
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.
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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, Q.P., 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.
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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.
Kirchner, N.G., Hordern, D.L., 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.
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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, N.G., 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.
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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.
Liu, D., Wu, X., Paul, G. & Dissanayake, G. 2006, 'Case Studies on an Approach to Multiple Autonomous Vehicle Motion Coordination', Journal of Wuhan University of Technology, vol. 26, no. 164, pp. 26-31.
Tan, K., Chen, Y.J., Wang, L. & Liu, D. 2005, 'Intelligent sensor fusion and learning for autonomous robot navigation', Applied Artificial Intelligence, vol. 19, no. 5, pp. 433-456.
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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.
Zhang, N., Kirpitchenko, I. & Liu, D. 2005, 'Dynamic model of the grinding process', Journal Of Sound And Vibration, vol. 280, no. 1-2, pp. 425-432.
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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
Tan, Y., Liu, D., Liu, F. & Zhou, Z.D. 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. 11, pp. 111-117.
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A robust optimal preview control method is presented in this paper for path tracking control problems to improve robustness and tracking precision of path tracking control systems. The known path information is used as reference input signals. Simulation
Tan, Y.G., Liu, D.K., Liu, F. & Zhou, Z.D. 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. 2, pp. 111-117.
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A robust optimal preview control method is presented in this paper for path tracking control problems to improve robustness and tracking precision of path tracking control systems. The known path information is used as reference input signals. Simulation results show that this method is valid not only for improving the performance of highly accurate trajectory control but also for improving system stabilization. &copy; IMechE 2005.
Crowther, A.R., Zhang, N., Liu, D. & Jeyakumaran, J.M. 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.
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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, Q.S., Liu, D., Tang, J., Zhang, N. & Tam, C.M. 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.
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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.
Zhang, N., Crowther, A.R., Liu, D. & Jeyakumaran, J.M. 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.
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Li, Q.S., Fang, J.Q. & Liu, D. 2003, 'Failure Probability Prediction of Concrete Components', Cement and Concrete Research, vol. 33, pp. 1631-1636.
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Liu, D., Yang, Y.L. & Li, Q.S. 2003, 'Optimum Positioning of Actuators In Tall Buildings Using Genetic Algorithm', Computers and Structures, vol. 81, no. 32, pp. 2823-2827.
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Zhang, N., Liu, D., Jeyakumaran, J.M. & Villanueva, L. 2002, 'Modelling of dynamic characteristics of an automatic transmission during shift changes', Journal of Systems and Control Engineering, vol. 216, no. 4, pp. 331-341.
This paper describes modelling of the transient dynamics of an automatic transmission during gear changes. A brief introduction to the automatic transmission system and the dynamic characteristics of the transmission components during the gear changes are presented. Then, detailed mathematical models of a four-speed automatic transmission manufactured by BTR Automotive, Australia, are developed. A mode description method is used to describe the transient shifting process and a modular structure of the transmission system, which consists of a torque converter module, geartrain module, hydraulic system module and modules of clutches and bands, is presented. As an application, the developed simulation system is applied to investigate the transient performance of the automatic transmission during the 1-2 shift process. The output torque profiles predicted by the model simulation correlate very well with the experimental data measured from vehicle tests.
Li, Q.S., Liu, D., Leung, A.Y., Zhang, N. & Luo, Q.Z. 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.
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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, D., Jeyakumaran, J.M. & Villanueva, L. 2002, 'Modelling of dynamic characteristics of an automatic transmission during shift changes', Proceedings of the Institution of Mechanical Enginee..., vol. 216, no. 4, pp. 331-341.
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This paper describes modelling of the transient dynamics of an automatic transmission during gear changes. A brief introduction to the automatic transmission system and the dynamic characteristics of the transmission components during the gear changes are presented. Then, detailed mathematical models of a four-speed automatic transmission manufactured by BTR Automotive, Australia, are developed. A mode description method is used to describe the transient shifting process and a modular structure of the transmission system, which consists of a torque converter module, geartrain module, hydraulic system module and modules of clutches and bands, is presented. As an application, the developed simulation system is applied to investigate the transient performance of the automatic transmission during the 1-2 shift process. The output torque profiles predicted by the model simulation correlate very well with the experimental data measured from vehicle tests.
Tam, C.M., 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.
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Luo, Q.Z., Li, Q.S., Liu, D. & Yang, L.F. 2001, 'A modified finite segment method for thin-walled box girders with shear lag', Institution of Civil Engineers. Proceedings. Structures and Buildings, vol. 146, no. 1, pp. 41-46.
Li, Q.S., Liu, D., Zhang, N., Tam, C.M. & Yang, L.F. 2001, 'Multi-level design model and genetic algorithm for structural control system optimization', Earthquake Engineering and Structural Dynamics, vol. 30, pp. 927-942.
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The integrated optimum problem of structures subjected to strong earthquakes and wind excitations, optimizing the number of actuators, the conguration of actuators and the control algorithms simultaneously, is studied. Two control algorithms, optimal control and acceleration feedback control, are used as the control algorithms. A multi-level optimization model is proposed with respect to the solution procedure of the optimum problem. The characteristics of the model are analysed, and the formulation of each suboptimization problem at each level is presented. To solve the multi-level optimization problem, a multi-level genetic algorithm (MLGA) is proposed. The proposed model and MLGA are used to solve two multi-level optimization problems in which the optimization of the number of actuators, the positions of actuators and the control algorithm are considered in dierent levels. In problem 1, an example structure is excited by strong wind, and in problem 2, an example structure is subjected to strong earthquake excitation.
Li, Q.S., Fang, J.Q., Jeary, A.P. & Liu, D. 2001, 'Decoupling control law for structural control implementation', International Journal of Solids and Structures, vol. 38, no. 34-35, pp. 6147-6162.
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Li, Q.S., Yang, L.F., Qu, X., Li, G.Q. & 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.
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Leung, A., Tam, C.M. & 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, Q.S., Liu, D.K., Leung, A.Y., Zhang, N., Tam, C.M. & Yang, L.F. 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.
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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
Li, Q.S., Fang, J.Q., Jeary, J.P., Wong, C.K. & Liu, D. 2000, 'Evaluation of wind effects on a super tall building based on full scale measurements', Earthquake Engineering and Structural dynamics, vol. 29, no. 12, pp. 1845-1862.
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Li, Q.S., Liu, D., Leung, A., Zhang, N., Tam, C.M. & Yang, L.F. 2000, 'Modeling of structural response and optimization of structural control system using neural network and genetic algorithm', The Structural Design of Tall Buildings, vol. 9, pp. 279-293.
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Li, Q.S., Liu, D., Fang, J.Q., Jeary, A.P. & Wong, C.K. 2000, 'Damping in buildings: its neural network model and AR model', Engineering Structures, vol. 22, no. 9, pp. 1216-1223.
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Li, Q.S., Liu, D., Fang, J.Q. & Tam, C.M. 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.
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Li, Q.S., Li, G.Q. & 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.
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Fang, J.Q., Li, Q.S., Liu, D., Jeary, A.P. & Wong, C.K. 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.
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Li, Q.S., Fang, J.Q. & 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.
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