Dr Walker is currently employed as a Senior Lecturer on a Discovery Early Career Researcher Awards (DECRA) investigating novel hybrid, electric and conventional vehicle technologies. He was previously employed at UTS as a Chancellors Postdoctoral Research Fellow, focusing research on innovative drivetrain and powertrain technologies. His current research includes dynamics and control of vehicle powertrains and development of novel hybrid and electric vehicle powertrain architectures, including design, integration and transient dynamic analysis.
More Broadly his current research topics includes vibration analysis, powertrain dynamics and control, powertrain hybridization and electrification, vehicle integration, hybrid energy storage systems, electrification and hybridization of two wheelers and ultra-compact vehicles, toroidal continuously variable transmissions, traction drives, and novel hybrid technologies.
Dr Walker is the UTS team lead for the Australian Technology Network of Universities team for the 2019 World Solar Challenge. Current and previous collaborative research projects includes international and local industrial partners, such as Beijing Electric Vehicle Co., AVL/NTC Powertrains, Ultimate Transmissions, AutoCRC and Changzhou New Energy Vehicle Research Academy.
Specialties: automotive transmission systems, vehicle dynamics, Matlab modelling, dSpace, steady state and transient vibration studies, shift and launch dynamics, hybrid and electric vehicles, powertrains.
Dr Walker is currently a member of the Editorial Board for Mechanical Systems and Signal Processing.
He sits on the Faculty Board and the Research Degrees Committee at UTS.
Can supervise: YES
- Vibration analysis
- Vehicle system dynamics
- Powertrain dynamics and control
- Powertrain hybridization and electrification
- Vehicle integration
- Hybrid energy storage systems
- Electrification and hybridization of two wheelers and ultra compact vehicles
- Toroidal continuously variable transmissions
- Traction drives
- Novel hybrid technologies
Dr Walker is a lecturer in:
- Machine Dynamics (48640)
- Mechanical Vibration and Measurement (48601)
Cong, TN, Walker, PD, Zhang, N & Ruan, J 2020, 'Efficiency improvement of a novel dual motor powertrain for plug-in hybrid electric buses', PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART D-JOURNAL OF AUTOMOBILE ENGINEERING, vol. 234, no. 7, pp. 1869-1882.View/Download from: Publisher's site
Nguyen, CT, Walker, PD & Zhang, N 2020, 'Shifting strategy and energy management of a two-motor drive powertrain for extended-range electric buses', Mechanism and Machine Theory, vol. 153.View/Download from: Publisher's site
© 2020 This paper studies the shifting strategy and energy management of a two-motor drive powertrain for extended-range electric buses. To do this, a multibody dynamic model is first established for transient investigation. A novel shift schedule is second proposed by integrating a priority factor for the engaging gear into the equivalent motor efficiency. According to vehicle speed and power, the shift schedule results in two possible cases: single-gear and double-gear change. Optimal shifting strategies are third recommended to eliminate the torque interruption under those possible gear changes. To optimize the torque allocation to two motors and minimize fuel consumption, a model predictive control-based energy management strategy is then developed. Finally, this paper simulates shift quality and energy economy in comparison with a conventional one-motor drive powertrain. The results show that torque interruptions generate large jerks in the one-motor configuration. Conversely, the two-motor configuration achieves great shift quality by eliminating the torque interruptions mostly during single-gear upshift or entirely under double-gear downshift. The two-motor drive powertrain also improves energy economy significantly by 9.1% compared to the conventional configuration.
Tawadros, P, Awadallah, M, Walker, P & Zhang, N 2020, 'Using a low-cost bluetooth torque sensor for vehicle jerk and transient torque measurement', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 234, no. 2-3, pp. 423-437.View/Download from: Publisher's site
© IMechE 2019. This paper presents the use and development of a specific wireless torque measurement system that is used to obtain the transient torque performance of vehicle transmissions. The torque sensor is strain-based, using surface-mounted strain gauges on a prop shaft. The gauges are connected to a compact printed circuit board, which is clamped to the shaft next to the strain gauges using a three-dimensional printed housing. The printed circuit board contains an amplifier, low-pass filter, analog-to-digital converter, microcontroller and bluetooth transceiver. The printed housing is impact resistant carbon-reinforced nylon and securely retains the printed circuit board and the battery powering the device. The transmitted torque data are received by a transceiver, which is interfaced to a PC through an RS-232 connection. NI LabVIEW is used to process, display and save data. The wireless torque sensor was installed to the Unit Under Test at the output shaft of the five-speed manual transmission. The Unit Under Test was installed on a dynamometer for verification purposes and the transient torque was recorded under various operational conditions. The transient output torque of the manual transmission is measured and compared with results obtained from simulations performed under similar operating conditions. The two sets of transient responses show a good correlation with each other and hence demonstrate that the torque sensor meets the major design specifications. The data obtained will be used to enhance the fidelity of the software model.
Tian, Y, Yang, H, Mo, W, Zhou, S, Zhang, N & Walker, PD 2020, 'Optimal coordinating gearshift control of a two-speed transmission for battery electric vehicles', Mechanical Systems and Signal Processing, vol. 136, p. 106521.
Tian, Y, Zhang, N, Zhou, S & Walker, PD 2020, 'Model and gear shifting control of a novel two-speed transmission for battery electric vehicles', MECHANISM AND MACHINE THEORY, vol. 152.View/Download from: Publisher's site
Hossain, MI, Eager, D & Walker, P 2020, 'Greyhound racing ideal trajectory path generation for straight to bend based on jerk rate minimization', Scientific Reports, vol. 10, no. 1.View/Download from: Publisher's site
This paper presents methods for modelling and designing an ideal path trajectory between straight and bend track path segments for racing greyhounds. To do this, we numerically generate clothoid and algebraic curve segments for racing quadrupeds using a sequential vector transformation method as well as using a helper equation for approaching ideal clothoid segments that would respect greyhound kinematic parameters and boundary conditions of the track. Further, we look into the limitations of using a clothoid curve for racing dog track path design and propose a smooth composite curve for track transition design which roughly maintains G3 curvature continuity for smooth jerk to overcome limitations of a clothoid transition. Finally, we show results from race data modelling and past injury data, which provide a strong indication of clothoid curve segments improving the dynamics and safety of racing greyhounds while reducing injuries.
Gao, P, Du, Y & Walker, PD 2019, 'Vibration energy and repeated-root modes of disc rotor for high-frequency brake squeal', Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics, vol. 233, no. 2, pp. 363-378.View/Download from: Publisher's site
Gao, P, Walker, PD, Liu, H, Zhou, S & Xiang, C 2019, 'Application of an adaptive tuned vibration absorber on a dual lay-shaft dual clutch transmission powertrain for vibration reduction', Mechanical Systems and Signal Processing, vol. 121, pp. 725-744.
Gao, P, Xiang, C, Liu, H, Walker, P & Zhou, H 2019, 'Vibration reduction performance parameters matching for adaptive tunable vibration absorber', Journal of Intelligent Material Systems and Structures, vol. 30, no. 2, pp. 198-212.View/Download from: Publisher's site
© The Author(s) 2018. Based on the principle of vibration absorber, an adaptive tunable vibration absorber with the magnetorheological elastomer as the core intelligent component was designed to eliminate variable frequency vibration of the powertrain system. The simulation of the magnetic circuit of the adaptive tunable vibration absorber was carried out to ensure the magnetic field generated by the design with a closed magnetic circuit could meet the requirement. The transient dynamic simulation analysis of the adaptive tunable vibration absorber shows that the natural frequency of the vibration absorber could well follow the external excitation signal. The natural vibration sensitivity analysis of the 4-degree-of-freedom dynamic system of the powertrain system was performed to obtain the key moment of inertia that affects the natural frequencies of each stage and then the installation position of the adaptive tunable vibration absorber corresponding to external excitation near the resonant frequency band could be determined. Subsequently, taking the third natural vibration as an example, an adaptive tunable vibration absorber with corresponding variable-stiffness range was installed on the key moment of inertia affecting the vibration of this order. The transient changes of each natural vibration frequency of the powertrain system with the adaptive tunable vibration absorber were studied and then the best starting and stopping frequencies were determined. According to the optimal frequency tuning scheme, the variation range of the storage modulus required for the magnetorheological elastomer material in the limited magnetic field range was obtained. The relationship between the controllable current and the torsional stiffness of the vibration absorber is established. Aiming at the vibration problem near the third-order natural vibration, the best vibration reduction performance parameters were matched to the adaptive tunable vibration absorber. Finally, a time...
Nguyen, CT, Walker, PD & Zhang, N 2019, 'Beneficial Investigation of Extended-Range Electric Powertrains with Dual Motor Input and Automated Manual Transmission', arXiv preprint arXiv:1912.00584.
Shalby, M, Dorrell, DG & Walker, P 2019, 'Multi–chamber oscillating water column wave energy converters and air turbines: A review', International Journal of Energy Research, vol. 43, no. 2, pp. 681-696.View/Download from: Publisher's site
Shalby, M, Elhanafi, A, Walker, P & Dorrell, DG 2019, 'CFD modelling of a small–scale fixed multi–chamber OWC device', Applied Ocean Research, vol. 88, pp. 37-47.
Tawadros, P, Awadallah, M, Walker, P & Zhang, N 2019, 'Using a low-cost bluetooth torque sensor for vehicle jerk and transient torque measurement', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, p. 0954407019861613.
Gao, P, Ruan, J, Du, Y, Walker, PD & Zhang, N 2019, 'The prediction of braking noise in regenerative braking system using closed-loop coupling disk brake model', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 233, no. 14, pp. 3721-3735.View/Download from: Publisher's site
Liang, J, Walker, PD, Ruan, J, Yang, H, Wu, J & Zhang, N 2019, 'Gearshift and brake distribution control for regenerative braking in electric vehicles with dual clutch transmission', Mechanism and Machine Theory, vol. 133, pp. 1-22.View/Download from: Publisher's site
OAPA An accelerated second order super twisting sliding mode observer with an adaptive gain is proposed for a typical nonlinear system. The key contribution of this algorithm is that the rate of convergence of observation error is accelerated remarkably by introducing "system damping". Chattering issue is attenuated with satisfactory performance compared to conventional sliding mode observer. Furthermore adaptive gain can vary with deviation between the trajectory and sliding mode switching manifold dynamically so that overshoot can be reduced. The novel observer is proven mathematically to be convergent in a finite time. Finally, an example of nonlinear system is given to verify the performance.
Lin, C, Sun, S, Yi, J, Walker, P & Zhang, N 2019, 'Accelerated adaptive super twisting sliding mode observer-based drive shaft torque estimation for electric vehicle with automated manual transmission', IET Intelligent Transport Systems, vol. 13, no. 1, pp. 160-167.View/Download from: Publisher's site
Wu, H, Walker, P, Wu, J, Liang, J, Ruan, J & Zhang, N 2019, 'Energy management and shifting stability control for a novel dual input clutchless transmission system', Mechanism and Machine Theory, vol. 135, pp. 298-321.
Wu, J, Ruan, J, Zhang, N & Walker, PD 2019, 'An Optimized Real-Time Energy Management Strategy for the Power-Split Hybrid Electric Vehicles', IEEE Transactions on Control Systems Technology, vol. 27, no. 3, pp. 1194-1202.View/Download from: Publisher's site
IEEE This paper proposes a new real-time energy management strategy (R-EMS) to improve the fuel economy performance of the power-split hybrid electric vehicles (HEVs). Being different from most conventional optimization-based EMS, the R-EMS does not need priori information of the driving cycle and is used to the online control of HEV. The forward dynamic model of power-split powertrain is built based on the Prius MY10. At each instant, the proposed R-EMS tries to minimize the equivalent consumed power of the HEV, which is the weighted summation of gasoline power and battery output power. The equivalence factor of battery output power has a clear physical meaning that is the efficiency of gasoline energy transferred to battery energy. Another two coefficients are introduced to control the state of charge (SOC) of battery. By considering the engine torque and engine speed as two independent or dependent design variables, respectively, the 2-D R-EMS and 1-D R-EMS are formed. Several typical driving cycles are used to simulate the performance of the R-EMS, and the results show that the proposed R-EMS not only maintains the battery SOC but also saves the fuel consumption compared with the rule-based EMS.
Yang, H, Zhang, Y, Liang, J, Liu, J, Zhang, N & Walker, PD 2019, 'Robust Deadbeat Predictive Power Control with a Discrete-Time Disturbance Observer for PWM Rectifiers under Unbalanced Grid Conditions', IEEE Transactions on Power Electronics, vol. 34, no. 1, pp. 287-300.View/Download from: Publisher's site
This paper presents a robust deadbeat predictive power control (DPPC) for pulsewidth modulation (PWM) rectifiers with the consideration of parameter mismatches under unbalanced grid conditions. First, conventional DPPC is modified to extend its application to both ideal and unbalanced grid conditions. Second, a tracking error of the modified DPPC with inaccurate grid-side impedance is analyzed. Third, a discrete-time power disturbance observer (DPDO) is designed to achieve accurate power control with mismatched parameters. The designed DPDO can predict complex power at the next sampling instant and estimate system disturbance simultaneously. Therefore, the DPDO can contribute to eliminate the steady-state tracking error resulting from disturbances caused by inaccurate parameters and compensate one-step delay in digital implementation. Although satisfactory steady-state performance can be obtained with modified DPPC and DPDO, transient performance still deteriorates significantly with an inaccurate value of the grid-side inductance. Thus, an online adaptive method to estimate mismatched inductance is finally developed based on the proposed DPDO. Both DPPC and DPDO are implemented in the stationary reference frame without coordinate transformation. Theoretical analysis confirms that the proposed DPDO can track disturbance without phase lag or magnitude error. Experimental tests and comparative studies with a prior DPPC on a two-level PWM rectifier validate the effectiveness of the proposed scheme.
Hayati, H, Eager, D & Walker, P 2019, 'The effects of surface compliance on greyhound galloping dynamics', Proceedings of the Institution of Mechanical Engineers Part K: Journal of Multi-Body Dynamics, vol. 233, no. 4, pp. 1033-1043.
Li, H, Luo, Z, Gao, L & Walker, P 2018, 'Topology optimization for functionally graded cellular composites with metamaterials by level sets', Computer Methods in Applied Mechanics and Engineering, vol. 328, pp. 340-364.View/Download from: Publisher's site
The application of auxetic composites in practice often relies on a compromise between properties as auxetics are mostly too porous (not dense enough or not stiff enough) to bear structural loads. Hence, the focus of this paper is topological design optimization of new functionally graded cellular composites with auxetics using a level set method. Firstly, a new hierarchical multi-scale formulation is developed to account for both the auxetic behavior of the microstructure and the stiffness of the macrostructure. The composite, comprising multiple layers of periodic microstructures, is tailored to have functionally graded properties for stiffness and auxetic behaviors, subject to volumetric gradient constraints. Secondly, the microstructures underpinning composite layers are topologically designed under the consideration of boundary and loading conditions of the macrostructure. Finally, a level set method is applied to evolve the shape and topology of the microstructure for each layer, with the numerical homogenization method to evaluate the effective properties of the microstructures. Several numerical examples are used to demonstrate the effectiveness of the proposed method. It can be seen that such composites systematically gear together the features of the functionally graded materials, cellular composites, and metamaterials towards a new kind of man-made composites.
Fan, X, Walker, PD & Wang, Q 2018, 'Modeling and simulation of longitudinal dynamics coupled with clutch engagement dynamics for ground vehicles', Multibody System Dynamics, vol. 43, no. 2, pp. 153-174.View/Download from: Publisher's site
© 2017, The Author(s). During the engagement of the dry clutch in automotive transmissions, clutch judder may occur. Vehicle suspension and engine mounts couple the torsional and longitudinal models, leading to oscillations of the vehicle body that are perceived by the driver as poor driving quality. This paper presents an effective formulation for the modeling and simulation of longitudinal dynamics and powertrain torsional dynamics of the vehicle based on non-smooth dynamics of multibody systems. In doing so friction forces between wheels and the road surface are modeled along with friction torque in the clutch using Coulomb's friction law. First, bilateral constraint equations of the system are derived in Cartesian coordinates and the dynamical equations of the system are developed using the Lagrange multiplier technique. Complementary formulations are proposed to determine the state transitions from stick to slip between wheels and road surface and from the clutch. An event-driven scheme is used to represent state transition problem, which is solved as a linear complementarity problem (LCP), with Baumgarte's stabilization method applied to reduce constraint drift. Finally, the numerical results demonstrate that the modeling technique is effective in simulating the vehicle dynamics. Using this method stick-slip transitions between driving wheel and the road surface and from the clutch, as a form of clutch judder, are demonstrated to occur periodically for certain values of the parameters of input torque from engine, and static and dynamic friction characteristics of tire/ground contact patch and clutch discs.
Copyright © 2018 Inderscience Enterprises Ltd. This paper provides a new and easy way that a diagram-model with vehicle speed – vehicle torque (VS-VT) coordinates, as a basis to test the efficiency of Electric Machine (EM) in a multi-speed powertrain. A 2-speed dual clutch transmission (DCT) is used as the investigation object. To validate the new method, a Simulink model and a testing rig in the laboratory are involved. Results demonstrate that the new method is simpler than the Simulink model and testing rig to make the characteristics of the electric motor more visible, which provides more space for further investigation. Based on the new diagram model, another new method for the optimisation of gear ratios is introduced, which is based on the cycle tracks density (CTD) on the new diagram-model. Thanks to the new process, the performance of the electrified drivetrain will be improved and researching and developing investment can be saved through an easy and visible process.
Awadallah, M, tawadros, P, Walker, P & zhang, N 2018, 'Comparative fuel economy, cost and emissions analysis of a novel mild hybrid and conventional vehicles', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering.View/Download from: Publisher's site
Mild hybrid vehicles have been explored as a potential pathway to reduce vehicle emissions cost-effectively. The use of manual transmissions to develop novel hybrid vehicles provides an alternate route to producing low cost electrified powertrains. In this paper, a comparative analysis examining a conventional vehicle and a mild hybrid electric vehicle is presented. The analysis considers fuel economy, capital and ongoing costs and environmental emissions, and includes developmental analysis and simulation using mathematical models. Vehicle emissions (nitrogen oxides, carbon monoxide and hydrocarbons) and fuel economy are computed, analysed and compared using a number of alternative driving cycles and their weighted combination. Different driver styles are also evaluated. Studying the relationship between the fuel economy and driveability, where driveability is addressed using fuel-economical gear shift strategies. Our simulation suggests the hybrid concept presented can deliver fuel economy gains of between 5 and 10%, as compared to the conventional powertrain.
Liang, J, Yang, H, Wu, J, Zhang, N & Walker, PD 2018, 'Power-on shifting in dual input clutchless power-shifting transmission for electric vehicles', MECHANISM AND MACHINE THEORY, vol. 121, pp. 487-501.View/Download from: Publisher's site
Liang, J, Yang, H, Wu, J, Zhang, N & Walker, PD 2018, 'Shifting and power sharing control of a novel dual input clutchless transmission for electric vehicles', MECHANICAL SYSTEMS AND SIGNAL PROCESSING, vol. 104, pp. 725-743.View/Download from: Publisher's site
Mo, W, Walker, PD, Fang, Y, Wu, J, Ruan, J & Zhang, N 2018, 'A novel shift control concept for multi-speed electric vehicles', Mechanical Systems and Signal Processing, vol. 112, pp. 171-193.View/Download from: Publisher's site
© 2018 Elsevier Ltd This paper proposes a novel synchronizer 'Harpoon-Shift' aiming at improving the comfort and efficiency of gearbox, meanwhile, simplifying the shifting control strategy for multi-speed electric vehicles. It will overcome one of the biggest shortcomings of traditional synchronizer system with frictional cone clutch. Experiment is established to investigate the torque and speed responses during the engagement of gears pairs. Then, based on previous testing results, the relationship of the peak torque and minimum speed difference to implement gear shifting with various spring coefficients is investigated. In addition, a mathematical model of the Harpoon-Shift system is developed to simulate the engagement process. The simulation results of system transient responses are validated against the data measured on testing rig. The model is then improved to study the impact of the rotating inertia, speed and speed difference on the torsional vibration and required time of engagement. Both of the simulation and experimental results show the significant improvement of proposed synchronizer to conventional cone clutch synchronizer.
Ruan, J, Walker, PD, Wu, J, Zhang, N & Zhang, B 2018, 'Development of continuously variable transmission and multi-speed dual-clutch transmission for pure electric vehicle', ADVANCES IN MECHANICAL ENGINEERING, vol. 10, no. 2.View/Download from: Publisher's site
Sun, L, Walker, P, Feng, K & Zhang, N 2018, 'Multi-objective component sizing for a battery-supercapacitor power supply considering the use of a power converter', Energy, vol. 142, pp. 436-446.View/Download from: Publisher's site
© 2017 Elsevier Ltd Owing to a lack of power density of conventional batteries, the onboard energy storage systems of an electric vehicle has to be oversized to compensate worst-case load condition, which is sub-optimal as it induces a heavy penalty on overall system weight and cost. One solution to overcome this limitation is to hybridize it with supercapacitors in order to boost its power performance via a power converter. This paper presents a multi-objective optimization problem over the parameters of such hybrid energy storage systems, with the aims to solve two conflicting objectives – cost and total stored energy in the hybrid energy storage system, under a set of pre-defined design constraints. An algorithm is first developed to find all feasible solutions to the problem. Two popular design examples are then tested differentiating Lithium Iron Phosphate based batteries from Lithium Manganese Oxide/Nickel-Cobalt-Manganese based batteries. A Pareto frontier is recreated for each example and an ξ-constraint method is finally adopted to choose the best member for comparison. This is so far, according to the authors' knowledge, the first reported multi-objective optimal sizing method for an active hybrid energy storage system considering the effect of the power converter to gain a clearer understanding of its impact over various design choices.
Tian, Y, Ruan, J, Zhang, N, Wu, J & Walker, P 2018, 'Modelling and control of a novel two-speed transmission for electric vehicles', MECHANISM AND MACHINE THEORY, vol. 127, pp. 13-32.View/Download from: Publisher's site
Wu, J, Liang, J, Ruan, J, Zhang, N & Walker, P 2018, 'A robust energy management strategy for EVs with dual input power-split transmission', Mechanical Systems and Signal Processing, vol. 111, pp. 442-455.View/Download from: Publisher's site
© 2018 Elsevier Ltd A novel power-split powertrain is proposed for the electric vehicles (EVs), which consists of dual propelling motor and one planetary gear set. The original motor is replaced by two downsize motor without changing the total power. The power distribution between the two downsize motors is determined by the parameters specifications of planetary gear set, which ensures the dual input powertrain has at least the same drivability performance as conventional single input powertrain. The planetary gear set is used to realize the power-split function by adjusting the gear ratio continuously to improve overall motor efficiency. The multibody dynamic model of the planetary gear set is built, considering the effect of inertia of all components. Based on the efficiency maps of the two motors, an energy management optimization model is built to minimize the consumed power of motors and transmission at each instant. The acceleration of sun gear and mechanical power of planetary gear set are constrained to avoid the large impact of transmission. A penalty factor is introduced in the objective function to realize the robust control of motor speed. Three driving cycles are used to demonstrate the improvement of energy efficiency compared to the traditional EVs with single-speed transmission.
Wu, J, Liang, J, Ruan, J, Zhang, N & Walker, PD 2018, 'Efficiency comparison of electric vehicles powertrains with dual motor and single motor input', Mechanism and Machine Theory, vol. 128, pp. 569-585.View/Download from: Publisher's site
© 2018 Elsevier Ltd Two novel dual motor input powertrains are proposed to improve the energy efficiency of electric vehicles (EVs). The first powertrain is based on a dual motor with planetary gear transmission (DMPGT), which connects two motors to the sun gear and ring gear respectively, and the carrier is engaged with output shaft. Two band brakes equipped on the sun gear and ring gear can realize three driving modes. The second powertrain is based on a dual motor with parallel axle transmission (DMPAT). It also provides three driving modes through switching on and off the two motors. To evaluate the two proposed powertrains, they will be compared with the widely adopted single motor with 1-speed and with 2-speed powertrains. The gear ratios of the powertrains are selected aiming at the vehicle dynamic performance, while the gear or mode shifting is designed to maximize the efficiency of EVs through an instantaneous optimization algorithm. The simulation results of the two proposed powertrains in three typical driving cycles demonstrate that the EVs equipped with both DMPGT and DMPAT have a higher overall efficiency than the EVs equipped with single motor input powertrain.
Yang, H, Zhang, Y, Liang, J, Gao, J, Walker, PD & Zhang, N 2018, 'Sliding-Mode Observer Based Voltage-Sensorless Model Predictive Power Control of PWM Rectifier under Unbalanced Grid Conditions', IEEE Transactions on Industrial Electronics, vol. 65, no. 7, pp. 5550-5560.View/Download from: Publisher's site
© 1982-2012 IEEE. A sliding-mode grid voltage observer (SMGVO) is proposed and experimentally verified in this paper for voltage-sensorless operation under an unbalanced network. The fundamental positive sequence component (FPSC) and fundamental negative sequence component (FNSC) are inherently separated in the observer without employing any additional filters. Due to embedded filtering effect, high frequency chattering and harmonic ripples can be well suppressed. Additionally, dc components can be completely rejected. As a result, dc offset would not cause fundamental frequency oscillations in magnitude and frequency of the estimated FPSC and FNSC. Owing to the predictive ability of SMGVO, one-step delay can be directly compensated using state variables in the observer. By combining estimation and prediction into one stage, the designed SMGVO turns out to be a compact solution for finite-control-set model predictive power control without voltage sensors. Theoretical proof is derived to verify that FPSC and FNSC can be accurately estimated and separated. Experimental results obtained from a two-level PWM rectifier confirm the effectiveness of the whole control system.
Yang, H, Zhang, Y, Liang, J, Xia, B, Walker, PD & Zhang, N 2018, 'Deadbeat control based on a multipurpose disturbance observer for permanent magnet synchronous motors', IET ELECTRIC POWER APPLICATIONS, vol. 12, no. 5, pp. 708-716.View/Download from: Publisher's site
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2017, 'Dynamic modelling and simulation of a manual transmission based mild hybrid vehicle', Mechanism and Machine Theory, vol. 112, pp. 218-239.View/Download from: Publisher's site
© 2017 Elsevier LtdThis paper investigates the development of a mild hybrid powertrain system through the integration of a conventional manual transmission equipped powertrain and a secondary power source in the form of an electric motor driving the transmission output shaft. The primary goal of this paper is to study the performance of partial power-on gear shifts through the implementation of torque hole filling by the electric motor during gear changes. To achieve this goal, mathematical models of both conventional and mild hybrid powertrain are developed and used to compare the system dynamic performance of the two systems. This mathematical modelling is used to run different simulations for gear-shift control algorithm design during system development, allowing us to evaluate the achievable performance and its dependency on system properties. The impact of motor power on the degree of torque hole compensation is also investigated, keeping in mind the practical limits to motor specification. This investigation uses both the output torque, vehicle speed as well as vibration dose value to evaluate the quality of gearshifts at different motor sizes. Results demonstrate that the torque hole may be eliminated using a motor power of 50 kW. However, the minimum vibration dose value during gear change is achieved using a peak power of 16–20 kW.
Driven by stricter mandatory regulations on fuel economy improvement and emissions reduction, market penetration of electrified vehicles will increase in the next ten years. Within this growth, mild hybrid vehicles will become a leading sector. The high cost of hybrid electric vehicles (HEV) has somewhat limited their widespread adoption, especially in developing countries. Conversely, it is these countries that would benefit most from the environmental benefits of HEV technology. Compared to a full hybrid, plug‐in hybrid, or electric vehicle, a mild hybrid system stands out due to its maximum benefit/cost ratio. As part of our ongoing project to develop a mild hybrid system for developing markets, we have previously investigated improvements in drive performance and efficiency using optimal gearshift strategies, as well as the incorporation of high power density supercapacitors. In this paper, the fuel and emissions of a baseline conventional vehicle and mild hybrid electric vehicle (MHEV) are compared. The objective of this analysis is to compare the fuel economy and Greenhouse Gas (GHG) emissions of the baseline and MHEV models, using low and high-density traffic patterns chosen for their similarity to traffic density profiles of our target markets. Results demonstrate the benefits of a lower ongoing cost for the HEV architecture. These advantages include torque-hole filling between gear changes, increased fuel efficiency and performance.
Lin, C, Sun, S, Walker, P & Zhang, N 2017, 'Off-line optimization based active control of torsional oscillation for electric vehicle drivetrain', Applied Sciences, vol. 7, no. 12, pp. 1-18.View/Download from: Publisher's site
© 2017 by the authors. As there is no clutch or hydraulic torque converter in electric vehicles to buffer and absorb torsional vibrations. Oscillation will occur in electric vehicle drivetrains when drivers tip in/out or are shifting. In order to improve vehicle response to transients, reduce vehicle jerk and reduce wear of drivetrain parts, torque step changes should be avoided. This article mainly focuses on drivetrain oscillations caused by torque interruption for shifting in a Motor-Transmission Integrated System. It takes advantage of the motor responsiveness, an optimal active control method is presented to reduce oscillations by adjusting motor torque output dynamically. A rear-wheel-drive electric vehicle with a two gear automated manual transmission is con sidered to set up dynamic differential equations based on Newton's law of motion. By linearization of the affine system, a joint genetic algorithm and linear quadratic regulator method is applied to calculate the real optimal motor torque. In order to improve immediacy of the control system, time consuming optimization process of parameters is completed off-line. The active control system is tested in AMEsim® and limitation of motor external characteristics are considered. The results demonstrate that, compared with the open-loop system, the proposed algorithm can reduce motion oscillation to a satisfied extent when unloading torque for shifting.
Walker, PD, Fang, Y & Zhang, N 2017, 'Dynamics and control of clutchless automated manual transmissions for electric vehicles', Journal of Vibration and Acoustics, Transactions of the ASME, vol. 139, no. 6.View/Download from: Publisher's site
© 2017 by ASME. This paper presents a study of the dynamics and control of clutchless automated manual transmissions (CLAMT) for the purpose of investigating the system behavior during up and down shifts. To achieve this, a multibody dynamic model of the proposed powertrain is implemented to simulate the transient behavior of the system, including a direct current (DC) equivalent model of the electric machine (EM) and a synchronizer mechanism model. Closed-loop control of motor speed and torque is used in conjunction with synchronizer mechanism actuation to functionally achieve gear shifting without the need for a primary friction clutch. This includes nested torque-speed closed-loops to implement alternative motor control functionalities at different stages of gear change. To evaluate the performance of shift control, shift metrics including longitudinal jerk, vibration dose value (VDV), and shifting duration are evaluated from simulation results. These results demonstrate the most significant impact on the transient response of the powertrain results from the reduction and reinstatement of motor torque during shift control. Speed control of the motor during the shift transient directly impacts on the duration of shifting, but not the transient response of the powertrain.
Walker, PD, Zhu, B & Zhang, N 2017, 'Powertrain dynamics and control of a two speed dual clutch transmission for electric vehicles', Mechanical Systems and Signal Processing, vol. 85, pp. 1-15.View/Download from: Publisher's site
The purpose of this paper is to demonstrate the application of torque based powertrain control for multi-speed power shifting capable electric vehicles. To do so simulation and experimental studies of the shift transient behaviour of dual clutch transmission equipped electric vehicle powertrains is undertaken. To that end a series of power-on and power-off shift control strategies are then developed for both up and down gear shifts, taking note of the friction load requirements to maintain positive driving load for power-on shifting. A mathematical model of an electric vehicle powertrain is developed including a DC equivalent circuit model for the electric machine and multi-body dynamic model of the powertrain system is then developed and integrated with a hydraulic clutch control system model. Integral control of the powertrain is then performed through simulations on the develop powertrain system model for each of the four shift cases. These simulation results are then replicated on a full scale powertrain test rig. To evaluate the performance of results shift duration and vehicle jerk are used as metrics to demonstrate that the presented strategies are effective for shift control in electric vehicles. Qualitative comparison of both theoretical and experimental results demonstrates reasonable agreement between simulated and experimental outcomes.
Wu, J, Luo, Z, Zhang, N & Walker, P 2017, 'Uncertain dynamic analysis for rigid-flexible mechanisms with random geometry and material properties', Mechanical Systems and Signal Processing, vol. 85, no. 15, pp. 487-511.View/Download from: Publisher's site
This paper proposes an uncertain modelling and computational method to analyze dynamic responses of rigid-flexible multibody systems (or mechanisms) with random geometry and material properties. Firstly, the deterministic model for the rigid-flexible multibody system is built with the absolute node coordinate formula (ANCF), in which the flexible parts are modeled by using ANCF elements, while the rigid parts are described by ANCF reference nodes (ANCF-RNs). Secondly, uncertainty for the geometry of rigid parts is expressed as uniform random variables, while the uncertainty for the material properties of flexible parts is modeled as a continuous random field, which is further discretized to Gaussian random variables using a series expansion method. Finally, a non-intrusive numerical method is developed to solve the dynamic equations of systems involving both types of random variables, which systematically integrates the deterministic generalized-α solver with Latin Hypercube sampling (LHS) and Polynomial Chaos (PC) expansion. The benchmark slider-crank mechanism is used as a numerical example to demonstrate the characteristics of the proposed method.
Wu, J, Walker, PD, Ruan, J & Zhang, N 2017, 'Target torque estimation for gearshift in dual clutch transmission with uncertain parameters', Applied Mathematical Modelling, vol. 51, pp. 1-20.View/Download from: Publisher's site
© 2017 Elsevier Inc. The target torque of engaging clutches during gearshift is a key factor that affects the dynamic response of powertrains equipped with the dual clutch transmissions (DCT). This paper investigates a method to estimate the target torque of engaging clutches under conditions where engine torque and measurement signals contain white noise and some vehicle parameters (the radius of wheel and rolling friction coefficient) are uncertain. To compute the target torque accurately, the state of system should be estimated when the uncertain parameters exist. The vehicle powertrain is modeled as the 3DOF system when one clutch is closed and the 4DOF system when two clutches are open, while the measured signals include speeds of the engine, transmission, and vehicle (rotational speed of wheels). In addition to traditional extended Kalman filter (EKF), both the joint extended Kalman filter (JEKF) and dual extended Kalman filter (DEKF) are used to estimate the target torque. The simulation results show that DEKF and JEKF provide much higher accuracy in the estimation of target torque than EKF when some parameters of the model are uncertain, so as to produce a better ride performance of the transmission during gearshift, i.e. reduction of power interruption and compressed shifting time. Furthermore, the DEKF provides higher accuracy than the JEKF in estimating uncertain parameters.
Yang, H, Zhang, Y, Walker, PD, Liang, J, Zhang, N & Xia, B 2017, 'Speed sensorless model predictive current control with ability to start a free running induction motor', IET Electric Power Applications, vol. 11, no. 5, pp. 893-901.View/Download from: Publisher's site
© The Institution of Engineering and Technology. In this study, a speed-sensorless finite control set-model predictive current control method is proposed based on an adaptive full order observer. The control system features simplicity and low cost because of no requirement for speed measurement, modulator and tuning of weighting factors. In most sensorless based schemes, the motor is assumed to be started from standstill. There is limited research considering starting a free running motor with unknown rotational direction and speed. To start a free-running induction motor (IM), the feedback gain matrix is designed to guarantee the convergence of estimated speed to actual speed even with incorrect initial value. To improve the efficiency, amplitude of flux is adjusted along with load condition. The presented results show that the proposed method is able to smoothly start an IM with unknown initial speed and work well over a wide speed range. The effectiveness of the proposed method is verified by both simulation and experimental tests on a two-level inverter fed IM drive platform.
Yang, H, Zhang, Y, Walker, PD, Zhang, N & Xia, B 2017, 'A Method to Start Rotating Induction Motor Based on Speed Sensorless Model-Predictive Control', IEEE Transactions on Energy Conversion, vol. 32, no. 1, pp. 359-368.View/Download from: Publisher's site
© 2016 IEEE.In some cases, such as restarting after power interruption or starting a motor rotated by external load, the motor may be rotating before being powered by the inverter. For speed-sensorless operation, as both the initial rotational direction and speed is unknown, it would be difficult to achieve smooth and fast resumption of normal operation if the starting scheme is not deliberately designed. In this paper, a method based on adaptive full order observer (AFO) is proposed to address this problem. For AFO without a properly designed feedback gain matrix, the estimated speed cannot converge to the actual speed if initial estimated speed is significantly lower than the actual speed. Through analyzing the transfer function of stator current error, the convergence condition of speed estimation is deduced. A feedback gain matrix and the condition for shifting to normal operation are subsequently proposed to improve restarting performance. The detailed design and implementation of the proposed method combined with finite control set model-predictive flux control is illustrated. Simulation and experimental results validate the effectiveness of the developed schemes.
Yang, H, Zhang, Y, Yuan, G, Walker, PD & Zhang, N 2017, 'Hybrid Synchronized PWM Schemes for Closed-Loop Current Control of High-Power Motor Drives', IEEE Transactions on Industrial Electronics, vol. 64, no. 9, pp. 6920-6929.View/Download from: Publisher's site
© 1982-2012 IEEE. For high-power drives, switching frequency is usually restricted to several hundred hertz to minimize the switching losses. To maintain the current distortions and torque ripples at a reasonable level, synchronized pulse patterns with half-wave and quarter-wave symmetries are employed. The analytic compensation is derived by Fourier analysis to ensure the proportionality between the voltage reference and the output voltage of an inverter for pulse width modulation (PWM) with low pulse ratio. A simple yet very effective method with varying sampling rate is proposed to maintain synchronization even for fast dynamic processes. The fast and smooth transition between different PWM patterns is achieved by compensating phase angle of the voltage reference through the analysis of stator flux trajectories. The effectiveness of the proposed method is validated on a down-scaled 2.2-kW induction motor drives.
Ruan, J, Walker, P & Zhang, N 2016, 'A comparative study energy consumption and costs of battery electric vehicle transmissions', APPLIED ENERGY, vol. 165, pp. 119-134.View/Download from: Publisher's site
Ruan, J, Walker, P, Zhang, N & Xu, G 2016, 'The Safety and Dynamic Performance of Blended Brake System on a Two-Speed DCT Based Battery Electric Vehicle', SAE INTERNATIONAL JOURNAL OF PASSENGER CARS-MECHANICAL SYSTEMS, vol. 9, no. 1, pp. 143-153.View/Download from: Publisher's site
Zhou, X, Walker, PD & Zhang, N 2016, 'A numerical study of the impact of wet clutch drag torque on the performance of two-speed electric vehicles', vol. 2, no. 2, pp. 178-204.View/Download from: Publisher's site
© 2016 Inderscience Enterprises Ltd. In order to study the economy performance of a two-speed electric vehicle (EV) equipped with a wet dual clutch transmission (DCT), this paper presents a theoretical analysis of drag torque in wet clutches, and investigates the relationship between drag torque, transmission gear ratios, and their optimisation. As such, the application of drag torque effects in gear ratio optimisation is conducted. Through this paper mathematic models for a two-speed EV is presented and a procedure to obtain the reasonable optimal gear ratio pairs and corresponding shift schedule for a two-speed EV is described in detail, with consideration of wet clutch drag torque. Through simulation and parametric analysis using different test driving cycles, including constant speed, NEDC and UDDS, the effects of drag torque is studied in gear ratio selection and EV efficiency and economy, with result demonstrating a significant influence on overall vehicle performance, and degradation of drivetrain efficiency.
Ruan, J, Walker, PD, Watterson, PA & Zhang, N 2016, 'The dynamic performance and economic benefit of a blended braking system in a multi-speed battery electric vehicle', APPLIED ENERGY, vol. 183, pp. 1240-1258.View/Download from: Publisher's site
Walker, PD & Roser, HM 2015, 'Energy consumption and cost analysis of hybrid electric powertrain configurations for two wheelers', APPLIED ENERGY, vol. 146, pp. 279-287.View/Download from: Publisher's site
Salisa, AR, Walker, PD, Zhang, N & Zhu, JG 2015, 'Comparative cost-based analysis of a novel plug-in hybrid electric vehicle with conventional and hybrid electric vehicles', International Journal of Automotive and Mechanical Engineering, vol. 11, no. 1, pp. 2262-2271.View/Download from: Publisher's site
© 2015 Universiti Malaysia Pahang. Hybrid electric vehicles provide higher fuel efficiency and lower emissions through the combination of the conventional internal combustion engine with electric machines. This paper analyzes and compares two types of hybrid electric powertrain with a conventional vehicle powertrain to study the lifetime costs of these vehicles. The novelty of the University of Technology Sydney plug-in hybrid electric vehicle (UTS PHEV) arises through a special power-splitting device and energy management strategy. The UTS PHEV and comparative powertrains are studied through numerical simulations to determine fuel consumption for the proposed low and high congestion drive cycles. Satisfactory results are achieved in terms of fuel economy, the all-electric range and electrical energy consumption for the UTS PHEV powertrain, providing significant improvement over the alternative powertrains. The analysis of these vehicles is extended to include a cost-based analysis of each powertrain in order to estimate the total lifetime costs at different fuel prices. The results obtained from this analysis demonstrate that whilst the conventional powertrain is cheaper in terms of purchase and maintenance costs, both alternative configurations are more cost-effective overall as the average price of fuel increases.
Walker, PD & Zhang, N 2015, 'Numerical investigations into shift transients of dual clutch transmission equipped powertrains with multiple nonlinearities', Journal of Vibration and Control, vol. 21, no. 8, pp. 1473-1486.View/Download from: Publisher's site
Walker, PD, Salisa, AR, Zhu, B & Zhang, N 2015, 'Modelling and optimisation of pure electric vehicle powertrains: a comparison of single and two speed transmissions', International Journal of Vehicle Performance, vol. 2, no. 1, pp. 85-102.View/Download from: Publisher's site
The purpose of this paper is to investigate the integrated design and
selection of transmission and electric machine for the development of multispeed electric vehicle (EV) powertrains. Multi-variable optimisation, in the form of genetic algorithms, is applied to the systems design of single and two speed EVs powertrains. Simulation-in-the-loop-based optimisation for the determination of primary motor, transmission and driveline design variables is conducted through the application of alternative driving cycle scenarios. The results for two speed optimisation demonstrate the capability to meet vehicle performance demands at a reduced motor size without increasing losses in the motor. Whilst, comparison of result for both single and two speed powertrains has demonstrated that the two speed provides a more consistent average cycle loss across alternative driving cycles, and improved low speed acceleration. Additionally, the impact of driving cycle selection is demonstrated to strongly influence outcomes of the optimisation procedure.
Zhu, B, Zhang, N, Walker, P, Zhou, X, Zhan, W, Wei, Y & Ke, N 2015, 'Gear shift schedule design for multi-speed pure electric vehicles', Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 229, no. 1, pp. 1-13.View/Download from: Publisher's site
As pure electric vehicles are considered to be a major growth trend in the automotive industry, research into and development of efficient electric powertrain systems and related control technologies have become popular research topics. The growing importance and use of multi-speed transmissions in these vehicles make shift schedule design and research a crucial aspect of the powertrain systems design of pure electric vehicles. This paper provides a gear shift schedule calculation method for pure electric vehicles, which includes a dynamic shift schedule and an economic shift schedule calculation method, demonstrating how to optimize the shift points and to produce the upshift and downshift lines based on the motor efficiency map. Through the establishment of a pure electric vehicle model, simulation results show that a properly designed shift schedule can improve the working region of the motor and can refine the dynamic performance and the economic performance of the vehicle. Finally, rig testing results are demonstrated to be comparable with simulations and indicate the correctness of the method.
Walker, PD & Zhang, N 2014, 'Active damping of transient vibration in dual clutch transmission equipped powertrains: A comparison of conventional and hybrid electric vehicles', Mechanism and Machine Theory, vol. 77, pp. 1-12.View/Download from: Publisher's site
The purpose of this paper is to investigate the active damping of automotive powertrains for the suppression of gear shift related transient vibrations. Conventionally, powertrain vibration is usually suppressed passively through the application of torsional dampers in dual clutch transmissions (DCT) and torque converters in planetary automatic transmissions (AT). This paper presents an approach for active suppression of transient responses utilising only the current sensors available in the powertrain. An active control strategy for manipulating engine or electric machine output torque post gear change via a proportional-integral-derivative (PID) controller is developed and implemented. Whilst conventional internal combustion engine (ICE) powertrains require manipulation of the engine throttle, for HEV powertrains the electric machine (EM) output torque is controlled to rapidly suppress powertrain transients. Simulations for both conventional internal combustion engine and parallel hybrid vehicles are performed to evaluate the proposed strategy. Results show that while both the conventional and hybrid powertrains are both capable of successfully suppressing undesirable transients, the EM is more successful in achieving vibration suppression.
Walker, PD & Zhang, N 2014, 'Transmission of Engine Harmonics to Synchronizer Mechanisms in Dual Clutch Transmissions', Journal of Vibration and Acoustics, vol. 136, no. 5.View/Download from: Publisher's site
Synchronizer mechanisms play an important role in the selection and engagement of gears in manual, automated manual, and dual clutch transmissions (DCTs). These mechanisms rely heavily on the balancing of torque loads in cone clutches, dog gears, and from losses in the gearbox to ensure repeatable and reliable actuation, with excessive wear on friction and contact surfaces, leading to degradation of actuation and potential mechanism failure. DCTs, in particular, provide a unique operating environment for synchronizers, most notably is its actuation with the engine still driving the wheels during normal driving conditions. Thus, the consideration of increased transmitted vibrations through the powertrain must be evaluated to study the impact of these vibrations on the synchronizer. To conduct this investigation, this paper develops a detailed multibody dynamic model of a typical automotive powertrain equipped with a DCT. This includes engine models with torque harmonics that capture the instantaneous torque variations from piston firing in the engine. As the main consideration of this paper is the influence of engine harmonics, the semi-definite powertrain model is simplified to a fixed-free system and the response of the synchronizer mechanism to harmonic torque inputs is analyzed. Parametric analysis of the system is conducted to analyze the influence of variables—including gear ratio, torsional damper, system damping, and engine configuration—on the dynamic response of the mechanism. Results demonstrate the influence of each of these variables on synchronizer dynamics in the steady state, with stiffness of torsional damper having the strongest influence on forced vibration. Additionally, results vary significantly between single and dual lay-shaft transmissions.
Walker, PD, Zhu, B & Zhang, N 2014, 'Nonlinear Modeling and Analysis of Direct Acting Solenoid Valves for Clutch Control', Journal of Dynamic Systems, Measurement, and Control, vol. 136, no. 5, pp. 051023-1-051023-9.View/Download from: Publisher's site
The purpose of this paper is to develop a comprehensive nonlinear model of a typical direct acting solenoid valves utilized for clutch control in wet dual clutch transmissions. To do so, mathematical models of the integrated electrohydraulic solenoid valve and wet clutch piston assembly are developed in the Simulink environment of Matlab. Through simulation the operating characteristics of the control valve are analyzed, demonstrating that the valve achieves dual functionalities of high flow and accurate pressure control depending on demands. This is realized through the designed force balancing of the valve spool. The dependency of the system to system variables on input pressure and the influence of air content on dynamic response of the valve are investigated. The resilience of output pressure is demonstrated to these variables, indicating strong system reliability. Finally, the model is then validated using in situ experimental testing on a powertrain test rig. The comparison of experimental and simulated results for steady state pressure as well as step and ramp input responses demonstrate good agreement.
Zhou, X, Walker, P, Zhang, N, Zhu, B & Ruan, J 2014, 'Numerical and experimental investigation of drag torque in a two-speed dual clutch transmission', Mechanism and Machine Theory, vol. 79, pp. 46-63.View/Download from: Publisher's site
The theoretical analysis of drag torques within a two-speed dual clutch transmission is presented in this article. The numerical models are developed to study the different sources of drag torques in dual clutch transmission. Simulations are performed in Matlab/Simulink platform to investigate the variation of drag torques under different operating conditions. Then an experimental investigation is conducted to evaluate the proposed model using an electric vehicle powertrain test rig. Outcomes of experimentation confirm that simulation results agree well with test data. Therefore the proposed model performs well in the prediction of drag torque for the transmission, and can be applied to assess the efficiency of the transmission. Results demonstrate that the entire drag torque is dominated by the viscous shear in the wet clutch pack and gear churning losses. This lays a theoretical foundation to future research on reducing drag torque and applications of drag torque in powertrain system efficiency optimization.
Walker, PD & Zhang, N 2013, 'Modelling of dual clutch transmission equipped powertrains for shift transient simulations', Mechanism and Machine Theory, vol. 60, pp. 47-59.View/Download from: Publisher's site
Popular methods for simulation of shift control in dual clutch transmissions rely on two assumptions, (1) the application of minimal degrees of freedom for the powertrain model, and (2) the use of mean torque engine models to describe engine torque. Such assumptions will impact on both the observed powertrain response and control of lightly damped powertrains. In this paper these two assumptions are tested through a comparative numerical study of shift transient control through the application of alternate powertrain and engine models.
To study the influence of engine torque harmonics, model degrees of freedom, and dual mass flywheels on the transient response of a vehicle powertrain equipped with a dual clutch transmission two powertrain models are presented. Four degree of freedom and 15 degree of freedom models are compared using free vibration analysis and shift transient simulations. Models are then extended to include an engine model with torque harmonics resulting from piston-by-piston firing of the engine with and without the addition of a dual mass flywheel to study the impact on powertrain response. Results indicate that degrees of freedom, engine model, and flywheel model all contribute significantly to variance in powertrain response under each configuration.
► Alternate modelling strategies for powertrains equipped with dual clutch transmissions ► Shift transient simulations with different powertrain models to study response ► Demonstration of harmonic engine torque models for control ► Simulation of the use of dual mass flywheels for vibration isolation
Walker, PD, Abdul Rahman, S, Zhu, B & Zhang, N 2013, 'Modelling, Simulations, and Optimisation of Electric Vehicles for Analysis of Transmission Ratio Selection', Advances in Mechanical Engineering, vol. 5, pp. 1-13.View/Download from: Publisher's site
Pure electric vehicles (PEVs) provide a unique problem in powertrain design through the meeting of performance specifications whilst maximising driving range. The consideration of single speed and multispeed transmissions for electric vehicles provides two strategies for achieving desired range and performance specifications. Through the implementation of system level vehicle models, design analysis, and optimisation, this paper analyses the application of both single speed and two-speed transmission applications to electric vehicles. Initially, transmission ratios are designed based on grade and top speed requirements, and impact on vehicle traction curve is evaluated. Then performance studies are conducted for different transmission ratios using both single speed and two-speed powertrain configurations to provide a comparative assessment of the vehicles. Finally, multivariable optimisation in the form of genetic algorithms is employed to determine an optimal gear ratio selection for single speed and two-speed PEVs. Results demonstrate that the two-speed transmission is capable of achieving better results for performance requirements over a single speed transmission, including vehicle acceleration and grade climbing. However, the lower powertrain efficiency reduces the simulated range results.
Walker, PD, Zhang, N, Zhan, W & Zhu, B 2013, 'Modelling And Simulation Of Gear Synchronisation And Shifting In Dual-clutch Transmission Equipped Powertrains', Proc. of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, vol. 227, no. C2, pp. 276-287.View/Download from: Publisher's site
Dual-clutch transmissions have increased in prevalence through the combination of high efficiency and shift quality. This is achieved through the automation of conventional manual transmission synchronisers for gear selection with automated clutch-to-clutch shift control, minimising loss of traction to the road. This article derives a suitably detailed model of a dual-clutch transmission equipped powertrain for the transient simulation and analysis of combined synchroniser engagement and gear shifts. Models are derived for a powertrain equipped with a wet dual-clutch transmission with particular focus on a detailed synchroniser mechanism model, including speed synchronisation, ring unblocking and indexing stages of engagement. To demonstrate the combination of synchroniser engagement with clutch-to-clutch shifting, several simulations are conducted to study the variation of chamfer alignment, vehicle speed and synchroniser engagement timing on powertrain response. Results indicate that vehicle speed and chamfer alignment have only limited impact on the quality of shifting. Synchroniser timing can have a more significant influence on shift quality, stressing the need for independence of these processes.
Zhu, B, Zhang, N, Walker, P, Zhan, W, Zhou, X & Ruan, J 2013, 'Two-Speed DCT Electric Powertrain Shifting Control and Rig Testing', Advances in Mechanical Engineering, vol. 2013, pp. 1-10.View/Download from: Publisher's site
Dual clutch transmissions (DCTs) are recognized as being suitable for electric drive applications as they can drive with high
efficiency and achieve good shifting comfort. A two-speed DCT electric drivetrain is described in this paper, comprised of only two
gear pairs and a final drive gear in the two-speed gearbox. The fundamental shifting control algorithm is provided. On the testing
rig of University of Technology, Sydney (UTS) powertrain lab, shifting controls and some driving cycle controls were realized.The
results demonstrated that the control algorithm functioned well both in transient shifting control process and in the driving cycle
Walker, PD & Zhang, N 2012, 'Engagement and control of synchroniser mechanisms in dual clutch transmissions', Mechanical Systems and Signal Processing, vol. 26, no. 1, pp. 320-332.View/Download from: Publisher's site
The study of synchroniser engagements in dual clutch transmissions is undertaken in this paper, identifying limitations to the repeatability of actuation, demonstrating one popular solution for positive synchroniser control and offering an alternate engagement tool. Principally, high wet clutch drag and the synchroniser design have lead to detrimental alignments conditions, where indexing chamfers on sleeve and target gear delay engagement of the mechanism and lead to potential sleeve block out. This paper focuses on the investigation of different control methods for overcoming these detrimental alignment conditions. The application of a closed loop control method to overcome block out related engagements is studied, and, for comparison, a novel engagement tool for overriding all chamfer alignment conditions is introduced and evaluated. Results have demonstrated that both techniques have some limitations, with the novel tool being capable of providing direct control of all chamfer engagements with limited extension of the duration of synchroniser engagements; however, some tuning of mechanism parameters is required for different engagement conditions.
Walker, PD & Zhang, N 2012, 'Investigation of synchroniser engagement in dual clutch transmission equipped powertrains', Journal Of Sound And Vibration, vol. 331, no. 6, pp. 1398-1412.View/Download from: Publisher's site
Transient response of a dual clutch transmission (DCT) powertrain to synchroniser mechanism engagements is investigated using a lumped inertia model of the powertrain. Original research integrates lumped inertia powertrain models for the DCT with a detailed synchroniser mechanism model and two separate engine models, comprising of a mean torque model and a harmonic torque model, using torque derived from piston firing. Simulations are used to investigate the synchroniser mechanism engagement process in a previously unscrutinised operating environment. Simulations are performed using both engine torque models, with the mean torque model demonstrates the highly nonlinear nature of synchroniser mechanism engagement, and the powertrain response to the engagement process. Through the introduction of harmonic engine torques, additional excitation is present in the mechanism during engagement, and increased vibration of the synchroniser sleeve results. The impact of vibrations is particularly important to the increased wear of indexing chamfer contact surfaces.
Walker, PD & Zhang, N 2011, 'Parameter study of synchroniser mechanisms applied to Dual Clutch Transmissions', International Journal of Powertrains, vol. 1, no. 2, pp. 198-220.View/Download from: Publisher's site
The modelling, simulation and analysis of a synchroniser mechanism as a component of wet Dual Clutch Transmissions (DCT) is presented in this paper. Mechanism engagement is demonstrated using rigid body models with a detailed drag torque model, to establish its variation over the process. Dimensionless equivalent cone and chamfer torques are used to study the impact of drag torque from a design perspective, and parameter studies performed to verify this method. Outcomes suggest the high dependency of speed synchronisation on both cone angle and friction coefficient, while the chamfer torque are highly dependent on chamfer angle, but not friction coefficient.
Walker, PD, Zhang, N & Tamba, RT 2011, 'Control Of Gear Shifts In Dual Clutch Transmission Powertrains', Mechanical Systems and Signal Processing, vol. 25, no. 6, pp. 1923-1936.View/Download from: Publisher's site
To achieve the best possible responses during shifting in dual clutch transmissions it is commonplace to integrate clutch and engine control, while the clutch is used to match speeds between the engine and wheels via reduction gears, poor engine control
Walker, PD, Zhang, N, Tamba, RT & Fitzgerald, SP 2011, 'Simulations of drag torque affecting synchronisers in a dual clutch transmission', Japan Journal of Industrial and Applied Mathematics, vol. 28, no. 1, pp. 119-140.View/Download from: Publisher's site
Drag torque contributes significantly to the engagement of synchronisers in vehicle transmissions. Little is understood of how drag torque varies during transient engagement. Considerable analysis, however, has shown it affects engagement and can cause the mechanism to fail. To demonstrate the significance of the role that drag torque plays during synchroniser engagement in a wet clutch dual clutch transmission numerical models of the mechanism and drag torque are developed. This includes torsional resistances from bearings, gear windage and friction, viscous shear in the concentrically aligned shafts and thewet clutch pack. Simulations are performed in MatlabÂ® to evaluate the drag torques acting on the mechanism. The results of simulations using this model demonstrate that the drag torque is dominated by the viscous drag in the wet clutch. Furthermore simulations demonstrate the nonlinear nature of this torque, and the peak drag torque is identified as being significantly larger that typical estimations.
Walker, P, Zhanga, N, Jeyakamurana, J, Tambab, R & Fitzgeraldb, S 2008, 'Recent advancements in Dual Clutch Transmission Modelling and Simulation', INTER-NOISE and NOISE-CON Congress and Conference Proceedings, vol. 2008, pp. 5879-5888.
Lidfors Lindqvist, A & Walker, PD 2020, 'Handling Dynamics of a Lightweight Solar-Electric Vehicle with Direct Yaw Moment Control' in Advances in Dynamics of Vehicles on Roads and Tracks, Springer, Singapore, pp. 1169-1177.View/Download from: Publisher's site
© 2020, Springer Nature Switzerland AG. Electric vehicles are commercially becoming more popular due to their high efficiency and low emission capabilities. The electrification of the powertrain allows for more efficient layouts compared to conventional vehicles, such as the use of in-wheel motors. These motors present new opportunities when it comes to vehicle stability control as they can be driven and controlled individually. This paper investigates the vehicle handling dynamics of a lightweight solar-electric vehicle in comparison to a standard sized commercial vehicle with direct yaw moment control. The research is based on the Australian Technology Networks' Bridgestone World Solar Challenge vehicle that will participate in the 2019 competition. The vehicle is rear wheel drive, with room for a driver and one passenger. To allow for space for the solar arrays the vehicle is considerably large compared to its weight. Conventional yaw controls commonly use yaw and/or sideslip as a control variable, this paper employs dynamic curvature as a control variable. The main goal to improve the yaw rate and sideslip as a result of improving the dynamic curvature variable was achieved. The dynamic properties and control response of the two vehicles are studied via co-simulation of Simcenter Amesim™ and MATLAB Simulink.
Halkon, B, Cheong, I, Visser, G, Walker, P & Oberst, S 2020, 'An experimental assessment of torsional and package vibration in an industrial engine-compressor system', Vibrations in Rotating Machinery 12, Liverpool.
Shalby, M, Dorrell, DG, Walker, P & Elhanafi, A 2019, 'An Experimental Investigation into the Wave Power Extraction of a Small-Scale Fixed Multi-Chamber OWC Device', 2019 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE), 11th Annual IEEE Energy Conversion Congress and Exposition (ECCE), IEEE, Baltimore, MD, pp. 4982-4987.
Nguyen, CT, Zhang, N, Walker, P & Ruan, J 2019, 'Power-split strategy of a novel dual-input series-parallel hybrid electric vehicle', 2019 IEEE International Conference on Industrial Technology, IEEE International Conference on Industrial Technology, IEEE, Melbourne, Australia.View/Download from: Publisher's site
This paper proposes a novel dual-input powertrain for series-parallel hybrid electric vehicle (HEV) which includes one engine, two motors/generators (MGs), and a dual-input automated manual transmission (AMT). Although hybrid powertrain with multi-power sources have been recognized that has great potential to improve fuel economy, the challenge here is how to manage the operation of the powertrain elements. To do this, firstly, the powertrain configuration is analysed in detail, all operating modes, such as in accelerating and decelerating condition, are presented. Secondly, the simulation model of the powertrain system is built. Thirdly, a power-split strategy is proposed to manage the power flow aiming at minimize total energy consumption. Finally, the simulation result is compared between vehicle adopted proposed series-parallel configuration and a traditional parallel type. The results demonstrate that the proposed series-parallel powertrain and power-split strategy have the ability to keep engine and MGs working in high efficiency regions. Furthermore, the coordination of the powertrain elements makes the series-parallel HEV achieve better performances without any compromising in energy efficiency compared to the equivalent parallel HEV.
Walker, PD, Ruan, J, Zhou, S & Zhang, N 2019, 'Clutch-to-clutch gearshift control for multi-speed electric vehicles during regenerative braking events', Proceedings of the IEEE International Conference on Industrial Technology, IEEE International Conference on Industrial Technology, IEEE, Melbourne, Australia, pp. 1593-1598.View/Download from: Publisher's site
© 2019 IEEE. Electric vehicles with stepped automatic transmissions provide benefits for improve drive performance and lower energy consumption. To deliver the desired operational functionality of power-on shifting for all driving states, this paper presents a novel methodology for the achievement of power-on gear shifts during regenerative braking events in electric vehicles equipped with multi-speed transmissions. Separate algorithms are developed for upshift and downshift events, where the control of clutches is considered for both torque and inertia phases of these events. Consideration is given primarily to the delivery of negative friction torque through the clutches during the inertia phase of gear change. A multi-body dynamic model of a dual clutch transmission equipped powertrain is then developed, including a DC equivalent motor model and piecewise clutch models, to evaluate the performance of these clutch control algorithms. Results of these simulations demonstrate the effectiveness of these shift control strategies and the capacity to maintain brake torque to the road during shift events.
Hayati, H, Eager, D & Walker, P 2019, 'An impact attenuation surfacing test to analyse the dynamic behaviour of greyhound racetrack sand surface', WEC2019: World Engineers Convention 2019, World Engineers Conventio, Engineers Australia, Melbourne, Australia, pp. 391-401.
The underfoot surface affects the dynamics of legged locomotion of any kind from a legged robot to a racing greyhound. In racing greyhounds, the surface is one of the leading risk factors contributing to life-threatening injuries. The current standard type of material used in greyhound racing tracks is sand. Two variables affect the sand functional behaviour, namely: the moisture content; and rate of compaction. This paper analyses the effect of altering the moisture content and density on the dynamic behaviour of the sand surface. This paper also presents a method to obtain the mechanical coefficients of the surface via an standard impact test which was applied as an input in the legged locomotion simulation over compliant terrains. The results show that a sand sample with the 20% moisture content and density of 1.35 g/cm3 has the most favourable behaviour with regards to injury prevention.
Hossain, MI, Eager, D & Walker, P 2019, 'Simulation of Racing Greyhound Kinematics', Proceedings of the 9th International Conference on Simulation and Modeling Methodologies, Technologies and Applications, International Conference on Simulation and Modeling Methodologies, Technologies and Applications, SCITEPRESS-Science and Technology Publications, Lda, Prague, Czech Republic, pp. 47-56.View/Download from: Publisher's site
This paper outlines greyhound dynamics results for yaw rate, speed, and the congestion pattern during a race derived through numerical modelling. The simulation results presented are also correlated to actual race data to validate modelling performance and reliability. The tasks carried out include the development of a numerical model for greyhound veering and race related supporting models, creating track 3D models replicated from actual survey data of the track, establishing a simulation environment that emulates an actual greyhound race, and the processing of both simulation and actual race data. The results show that greyhounds are susceptible to experience varying high acceleration in first five seconds into the race, during which a minimum average forward acceleration of 3.9 m/s2 was calculated, a peak yaw rate magnitude of 0.4 rad/s before the bend while transitioning into the track, and congestion during a race is affected by lure driving performance.
Shalby, M, Walker, P, Dorrell, D & Elhanafi, A 2018, 'Validation of a Numerical Model for a Small Scale Fixed Multi-Chamber OWC Device', Proceedings of the Thirteenth (2018) Pacific-Asia Offshore Mechanics Symposium, Pacific-Asia Offshore Mechanics Symposium, International Society of Offshore and Polar Engineers, Jeju Island, Korea, pp. 332-337.
Wave Energy Converters (WECs) have excellent potential as a source of renewable energy that is yet to be commercially realised. Recent attention has been focused on the installation of Oscillating Water Column (OWC) devices as part of breakwaters or harbour walls to provide advantages of cost-sharing structures and proximity of power generation facilities to existing infrastructure. In this paper, a time domain numerical model of a fixed Multi-Chamber Oscillating Water Column (MC-OWC) is developed in MATLAB. This model is validated against a scale model experiments performed in a wave flume and good agreement is found. The validated model is used to investigate the effect of the power take-off damping on device performance parameters for a given environmental condition.
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2018, 'Hardware-in-the-Loop Simulation for the Design and Testing of Motor in Advanced Powertrain Applications', IEEE International Symposium on Industrial Electronics, International Symposium on Industrial Electronics, IEEE, Cairns, QLD, Australia, pp. 817-824.View/Download from: Publisher's site
© 2018 IEEE. In this work, a validation procedure is presented, for an electric propulsion system used in a mild hybrid electric vehicle powertrain. The vehicle is configured based upon a brushless DC (permanent magnet synchronous) motor installed as electric propulsion system in a mild hybrid electric vehicle. Hardware-in-the-loop (HIL) techniques are used to enable rapid prototyping, as well as validate the specified characteristics of the motor unit, which was purchased as an off-the-shelf item. The validation results of the work in summary indicate that whilst the motor unit does not meet quoted specifications, it nevertheless functions acceptably for the purpose of the hybrid electric vehicle application.
Ruan, J, Walker, PD, Wu, J, Tian, Y & Zhang, N 2018, 'A novel dual-motor two-speed direct drive battery electric vehicle drivetrain', 31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018.
Copyright © 2018 Society of Automotive Engineers of Japan, Inc. All rights reserved This study proposes a parallel shaft based dual-motor BEV powertrain to boost motor efficiency, ultimately, saving limited battery energy and cost. The proposed powertrain adopts two motors with permanent engaged gears to maximize the motor efficiency. Economic shifting strategy and smooth motor torque transfer control are designed and tested in a Simscape® based dynamic model. Simulation results show energy efficiency improvement can be achieved. Thanks to the torque transfer control strategy, low vehicle jerk is recorded during the shifting. Results demonstrate that the proposed dual-motor powertrain superior to the traditional single motor counterpart in terms of economiy, drivability and cost.
Walker, PD, Tian, Y, Ruan, J & Zhang, N 2018, 'A novel two speed planetary transmission for electric vehicicle applications', 31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018.
Copyright © 2018 Society of Automotive Engineers of Japan, Inc. All rights reserved Multispeed transmissions are becoming more appealing in heavy and light electric vehicles as they offer increased functionality of the designed platform and the ability to reduce the size of motor and battery alike. This paper presents the dynamic modelling and control of a two speed automatic transmission integrated with Ravigneaux planetary gearset for the development of a novel electric vehicle platform. The system is characterised by requiring only one active actuator for gear shift control, relying on the application of brake bands and one way clutches for gear shift, minimising viscous friction and maximising transmission efficiency. Then the control process for up and down gear shifts is designed and implemented using Matlab, demonstrating quality gear shifts without the need of two positively controlled clutches. Experimental evaluation of shift transients on a scaled test rig is performed to demonstrate successful control of the transmission.
Yang, H, Zhang, Y, Liang, J, Zhang, N & Walker, P 2018, 'Robust Digital Current Control Based on Adaptive Disturbance Estimation for PMSM Drives with Low Pulse Ratio', ICEMS 2018 - 2018 21st International Conference on Electrical Machines and Systems, International Conference on Electrical Machines and Systems, IEEE, Jeju, South Korea, pp. 1252-1257.View/Download from: Publisher's site
© 2018 KIEE EMECS (KIEE Electrical Machinery and Energy Conversion Systems). For high-power or high-speed motor drives, the low switching frequency to fundamental frequency ratio leads to poor bandwidth or even instability of the current control loop if the controller is not properly designed. In this paper, a digital predictive current controller is constructed based on an exactly discretized model to overcome this issue. Then, a method of online disturbance adaptation is proposed to compensate for the side impact of motor parameter mismatches on the tracking performance. Additionally, online inductance adaptation is further incorporated to improve transient performance. Compared with the prior complex-vector proportional-integral controller, the proposed current controller presents faster dynamic responses and better parameter robustness. Simulation and experimental tests on a permanent magnet synchronous motor drive confirm the effectiveness of the proposed control schemes.
Hayati, H, Walker, P, Mahdavi, F, Stephenson, R, Brown, T & Eager, D 2018, 'A Comparative Study of Rapid Quadrupedal Sprinting and Turning Dynamics on Different Terrains and Conditions: Racing Greyhounds Galloping Dynamics', Volume 4A: Dynamics, Vibration, and Control, ASME 2018 International Mechanical Engineering Congress and Exposition, ASME, Pittsburgh, Pennsylvania, USA, pp. 1-7.View/Download from: Publisher's site
Identifying optimum athletic race track surfacing for greyhounds to reduce risk of injuries is a challenging practice as there are several single and coupled variables that should be considered as risk factors. To study the impact of bend and straight sections, surface type and camber, on biomechanics of galloping quadrupeds, an inertial measurement unit (IMU).
has been used to measure the associated galloping accelerations. The IMU was sewn into a pocket located on the back of the greyhounds racing jacket positioned between the two forelegs. Simultaneous kinematics were performed using high frame rate (HFR) videos for calibrating IMU data. The results showed that there were lower G-forces on galloping on grass than wet sand which is consistent with the mechanical behavior of grass (grass is softer than wet sand). Moreover, galloping around the bend had higher G-forces than galloping along the straight section suggesting an excessive force is applied on the greyhound's limbs due to centrifugal force. A cambered bend assisted the greyhounds in having a smoother gait and lower G-forces when compared to a flat bend. The results reported in this paper will not only be beneficial for the welfare of racing greyhounds, but will also contribute in the simulation of legged locomotion for bio-inspired engineering and robotics.
Wang, H, Wu, H, Liang, J, Zhang, N, Walker, PD & Ji, J 2018, 'Power sharing and shifting stability control for a dual input electric vehicle transmission system', 31st International Electric Vehicle Symposium and Exhibition, EVS 2018 and International Electric Vehicle Technology Conference 2018, EVTeC 2018.
Copyright © 2018 Society of Automotive Engineers of Japan, Inc. All rights reserved This paper presents a real-time power sharing strategy to maximize the overall efficiency by distributing the power demand between the motors properly. As both motors are powered by the onboard battery, an enumeration based searching approach is designed to improve the efficiency and reduce the computational cost. Like many energy management strategies, the proposed approach also suffers from the drawback of frequent gear-shifting. To make the transmission system more stable, a cost function is designed and added to the system. To verify the effectiveness of the proposed method, a mathematical model is built and the results demonstrate the achieved improvements.
Hayati, H, Walker, P, Brown, T, Kennedy, P & Eager, D 2018, 'A simple spring-loaded inverted pendulum (SLIP) model of a bio-inspired quadrupedal robot over compliant terrains', Proceedings of the ASME 2018 International Mechanical Engineering Congress and Exposition IMECE2018, International Mechanical Engineering Congress and Exposition, ASME, USA.View/Download from: Publisher's site
Copyright © 2018 ASME. To study the impact of compliant terrains on the biomechanics of rapid legged movements, a well-known spring loaded inverted pendulum (SLIP) model is deployed. The model is a three-degrees-of-freedom system (3 DOF), inspired by galloping greyhounds competing in a racing condition. A single support phase of hind-leg stance in a galloping gait is taken into consideration due to its primary function in powering the greyhounds locomotion and higher rate of musculoskeletal injuries. To obtain and solve the nonlinear second-order differential equation of motions, the Lagrangian method and MATLABb R2017b (ode45 solver), which is based on the Runge-Kutta method, has been used, respectively. To get the viscoelastic behavior of compliant terrains, a Clegg hammer test was developed and performed five times on each sample. The effective spring and damping coefficients of each sample were then determined from the hysteresis curves. The results showed that galloping on the synthetic rubber requires more muscle force compared with wet sand. However, according to the Clegg hammer test, wet sand had a higher impact force than synthetic rubber which can be a risk factor for bone fracture, particularly hock fracture, in greyhounds. The results reported in this paper are not only useful for identifying optimum terrain properties and injury thresholds of an athletic track, but also can be used to design control methods and shock impedances for legged robots performing on compliant terrains
Shalby, M, Walker, P & Dorrell, D 2017, 'Modelling of the multi-chamber oscillating water column in regular waves at model scale', Energy Procedia, International Conference on Energy and Environment Research, Elsevier, Porto, Portugal, pp. 323-329.View/Download from: Publisher's site
This paper studies the reliability of numerical models used for estimating multi-chamber oscillating water column (MC-OWC) response in the time-domain. The model for the internal water surface level and instantaneous pressure inside the chamber at regular waves conditions using a hybrid system of hydrodynamic and thermodynamic rigid piston models without power take-off. Reliability is assessed using experimental data obtained from a wave tank used in the model concept validation. The results show the method could be extended to describe the hydrodynamics of the MC-OWC in regular and irregular wave conditions.
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2017, 'A Low-Cost and Novel Approach in Gearshift Control for a Mild-Hybrid Powertrain', IEEE Transportation Electrification Conference and Expo (ITEC), 2017 IEEE, IEEE, Chicago, Illinois, USA, pp. 754-760.View/Download from: Publisher's site
A novel, the low-cost mild hybrid powertrain is described. It relies on a manual, or robotized manual transmission together with a BLDC motor coupled at the output for filling the torque hole between gear changes. In order to keep manufacturing cost low and improve commercial attractiveness, it incorporates gearshift strategies that deliver high-quality gear shifts. A deliberate downsizing of componentry is implemented as far as possible to reduce cost, and control strategies are employed to exploit the maximum potential of the architecture using methods including torque-fill, ICE-assist, and ICE start-stop. The architecture is developed in simulation using an existing conventional platform to investigate system properties and their effect on performance. In particular, we discuss the gear-shift control algorithm design. Until the cost of full hybrids and fuel cell vehicles is significantly reduced, such a mild hybrid may have the potential to provide the right cost-benefit balance to achieve strong market penetration.
Awadallah, M, Tawadros, P, Walker, P, Zhang, N & Tawadros, J 2017, 'A Comparative Fuel Analysis of a novel HEV with conventional vehicle', Proceedings of the 2017 IEEE 85th Vehicular Technology Conference (VTC Spring), Vehicular Technology Conference, IEEE, Sydney, Australia, pp. 1-6.View/Download from: Publisher's site
Improvements in fuel economy have always been a dominating driver of vehicle engineering. With some exceptions, benefits attained from hybrid powertrains to transient power delivery has not been the emphasis of research and development efforts. Developing cities around the world would realise significant benefits from improvements to fuel economy, which is outlined in this research by assessing the benefits of a novel HEV architecture. These benefits are compared to a conventional ICEpowered vehicle equivalent, which has an advantage in terms lower upfront costs. The commercial success of HEV implementation, therefore, is determined by its price comparison to conventional vehicles and payback over a number of years of use. This becomes especially important in regions of low-middle income, where the market is much more price-sensitive. The fuel economy of a conventional vehicle and mild hybrid electric vehicle are compared in this paper. This analysis includes vehicle modelling and simulation. Fuel economy is assessed and referenced with standard drive cycles provided by the U.S Environmental Protection Agency. Results demonstrate the benefits of a lower ongoing cost for the HEV architecture.
Awadallah, M, Tawadros, P, Walker, P, Zhang, N & Tawadros, J 2017, 'A System Analysis and Modeling of a HEV based on Ultracapacitor Battery', IEEE Transportation Electrification Conference and Expo (ITEC), 2017 IEEE, IEEE, Chicago, Illinois, USA, pp. 792-798.View/Download from: Publisher's site
There is a clear shift toward the implementation of electrified vehicles in the market, influenced by the introduction of stricter mandatory regulations on fuel economy improvement and emissions reduction. Of these vehicles, the penetration of hybrid vehicles in the market has much potential for growth in the next few years. The adoption of these vehicles has been limited by the high cost of HEV's, which have less uptake in developing regions. Considering this point, developing countries would see the greatest benefit in adopting HEV technology. A mild hybrid system has an observable advantage in these markets due to its maximum benefit/cost ratio when compared to a full hybrid, plug‐in hybrid or electric vehicles.
This paper discusses the development of a mild hybrid system for such markets with a focus on improving drive performance and efficiency. To achieve this, high power density ultracapacitors are used based on their fast charging and discharging characteristics, together with intelligent drivetrain control taking advantage of the ultracapacitors' characteristics to deliver smooth torque delivery during gear change (torquefilling). A comparison and analysis is undertaken, of both conventional powertrain and an otherwise identical powertrain but for the incorporation of components required for the mild hybrid system. Software models simulated the powertrains in specific driving conditions, with observations made of the advantages of MHEV over conventional drivetrains. The model demonstrated increased fuel efficiency and performance.
Fang, Y, Ruan, J, Walker, P & Zhang, N 2017, 'Comparison of effect on motor among 2-, 3-and 4-speed transmission in electric vehicle', 2017 IEEE INTERNATIONAL CONFERENCE ON MECHATRONICS (ICM), IEEE International Conference on Mechatronics (IEEE-ICM), IEEE, Federat Univ Australia, Gippsland Campus, Gippsland, AUSTRALIA, pp. 455-459.
Sun, L, Zhang, N, Awadallah, M & Walker, P 2017, 'An innovative control strategy for a hybrid energy storage system (HESS)', Proceedings of the IEEE International Conference on Mechatronics, IEEE International Conference on Mechatronics, IEEE, Gippsland, Victoria, Australia, pp. 434-439.View/Download from: Publisher's site
Electric Vehicles (EVs) adopting both batteries and supercapacitors have attracted a significant amount of attention in research communities due to its unique power sharing capabilities. A Hybrid Energy Storage System (HESS) can effectively reduce power stress that would otherwise be applied to batteries alone, and whose weight and size is still a common concern when competing against conventional ICE-powered cars. In this paper, a high-level control strategy is developed to adaptively split the load between two sources for an electric vehicle adopting HESS under real-life load fluctuations. A converter — Supercapacitor Pack (SP) coupled HESS upon which such an algorithm is deployed on, is proposed to divert excess power into the SP via a smart Power Converter (PC) which is located in between in order to regulate both behaviors. Such a power split strategy (PSS) is designed in such a way to track real-time load profiles and determines one important variable — the cut-off frequency. A simplified HESS model is first developed. The power split algorithm is coded in Matlab and then applied to this HESS model. Finally, the overall system is tested comprehensively over 4 EPA driving cycles. Simulation results prove its effectiveness in coping with even the harshest driving scenarios in real life.
Shalby, M, Walker, P & Dorrell, D 2016, 'The Characteristics of the Small Segment Multi-Chamber Oscillating Water Column', Proceedings of the 3rd Asian Wave & Tidal Energy Conference (AWTEC 2016), Asian Wave and Tidal Energy Conference, #02-11, Blk 12, Lorong Bakar Batu, 348745 SINGAPORE, Singapore, pp. 795-800.
Shalby, MM, Walker, P & Dorrell, D 2016, 'The investigation of a segment multi-chamber oscillating water column in physical scale model', Proceedings of the 2016 IEEE International Conference on Renewable Energy Research and Applications (ICRERA), International Conference on Renewable Energy Research and Applications (ICRERA), IEEE, UK, pp. 183-188.View/Download from: Publisher's site
Renewable energy has gained much attention and there is a substantial body of both theoretical and experimental research . A wide variety of technologies have been proposed, studied and a few tested in real condition at full size . Of the new technologies, wind and wave have reached a degree of mature technology. Ocean wave energy is regarded as one of the major renewable energy resources with great potential for development over the course of the next few years but it is still virtually untapped. It has the advantages of a high energy density and continual availability  .
The oscillating water column (OWC) is one type of wave energy converter (WEC). It is designed to extract energy from ocean waves by using water to move trapped air and thus drive an air turbine.
The OWC device is considered as the oldest and the most widely researched type of the wave energy device. It has been successfully constructed and tested at several sites. There are several reasons for using this device; the low operational cost, and the only moving part of the energy conversion mechanism are the rotors of a turbine. Hence it has less negative environmental impact . Many devices operate in real ocean waves ; the most powerful wave energy devices constructed were the Osprey in the UK in 1995, and the the greenWave device in Australia in 2014. Both were rated 1 MW and near-shore plants. Both were severely storm damaged. Recently the successful deployment of a OWC at Jeju Island, South Korea, worked at rated power of 500 kW. These successful devices show that the obstacles can be overcome with further research . Table 1 summarizes most of the OWC devices that have been installed in various countries with the real or expected capacity and the turbine type that was used to extract the power.
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2016, 'Comparative System Dynamic Modeling of a Conventional and Hybrid Electric Powertrain', Power Engineering, The International conference on Power Transmissions (ICPT), J B Tratsart Ltd, Chongqing, China, pp. 231-238.View/Download from: Publisher's site
Hybrid Electric Vehicles (HEVs) provide many known benefits over conventional vehicles, including reduced emissions, increased fuel economy, and performance. The high cost of HEVs has somewhat limited their widespread adoption, especially in developing countries. Conversely, it is these countries that would benefit most from the environmental benefits of HEV technology. As part of our ongoing project to develop a cost-effective and viable mild HEV for these markets, dynamic simulations are required to ensure that the proposed designs are to achieve their desired targets. In this paper, mathematical models of the powertrain are used to analyze and compare the dynamics of both a conventional power train and one with the addition of components required for the Mild Hybrid system. Using Matlab and Simulink, simulations of both powertrains under particular driving conditions are performed to observe the advantages of the MHEV over conventional drivetrains. These benefits include torque-hole filling between gear changes, increased fuel efficiency and performance.
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2016, 'Eliminating the Torque Hole: Using a Mild Hybrid EV Architecture to Deliver Better Driveability', 2016 IEEE Transportation Electrification Conference and Expo, Asia-Pacific, ITEC Asia-Pacific 2016, IEEE Transportation Electrification Conference and Expo (ITEC Asia-Pacific), IEEE, Busan, South Korea, pp. 173-179.View/Download from: Publisher's site
Hybrid vehicle engineering has traditionally and dominantly focused on fuel economy benefits and emissions reductions. Although the transient power delivery benefits of hybrid powertrains are well-understood, these are not a primary focus of the majority of research and development efforts, with some exceptions. Our approach to this problem is to deliver a low-cost, low-tech mild-hybrid powertrain, with unique power delivery features designed to appeal to price-sensitive, but aspirational consumers. The powertrain is a simple post transmission parallel hybrid configuration. It utilizes a low powered four-cylinder engine coupled to a four-speed manual transmission through a robotically-actuated clutch. A low-voltage BLDC motor is directly connected to the transmission output shaft, before the final drive. Our research focuses on bringing the benefits of HEV architecture to the world's developing cities, where, it can be confidently argued, local emissions reductions are needed the most. Crucial to the success of this research is the understanding that compared to an equivalent ICE-powered vehicle, an HEV competes at a price disadvantage, no matter how cost-effective the solution is. This disadvantage is amplified in regions of low-middle income, where price sensitivity is greatest. It must, therefore, present better value than an equivalent conventional vehicle if it is to be commercially successful in these particularly price-sensitive markets. We discuss the extent to which control can be used to deliver transient power delivery gains in such a setup, and offer an example powertrain for simulation. To validate the concept, simulation of this research is performed in MATLAB and Simulink. The prototype is based on a generic engine and a BLDC motor. The results mainly focus on the electric drive and comparison of the transient response of drivetrains.
Awadallah, M, Tawadros, P, Walker, P & Zhang, N 2016, 'Selection and characterisation of PMSM motor for mild HEV applications', EVS 2016 - 29th International Electric Vehicle Symposium, Electric Vehicle Symposium, Electric Drive Transportation Association, Montréal, Québec, Canada.
This paper presents a theoretical background and real-time validation procedure for an electric propulsion system for a mild-hybrid vehicle configuration, based on a permanent magnet synchronous motor (PMSM) on the output shaft of a manual transmission. The validation technique uses the rapid prototyping technique of hardware-in-the-loop (HIL) in order to validate the characteristics of an off-the-shelf PMSM and controller by implementing them in a HIL model of the mild hybrid vehicle. The results obtained suggest that whilst the motor did not meet the manufacturer-rated specifications, it would nevertheless function acceptably for the purposes of the proposed mild hybrid vehicle architecture.
Walker, PD, Durack, J & Durack, M 2015, 'Accepting slip as an ally in CVT design and control', 4th International CTI Symposium China, Shanghai.
Ruan, J, Zhang, N & Walker, P 2015, 'Comparing of single reduction and CVT based transmissions on battery electric vehicle', 2015 IFToMM World Congress Proceedings, IFToMM 2015, IFToMM World Congress, Taipei, Taiwan.View/Download from: Publisher's site
With the deterioration of the air pollution, growing public concerns over the exhaustion of global fossil energy and the explosive growth of passenger vehicles, the improvement and popularity of electric vehicles (EVs) have increased in market share. The primary goal of EV powertrain design is achieving the same performance, e.g. launching and driving range, as that of Internal Combustion Engine vehicles. To realize this target, a novel propulsion system is proposed in this paper. A comparison of driving performance and energy saving are completed among single reduction, continuously variable transmission (CVT) and proposed system on EVs. The simulation results show that the optimized motor propulsion system has a significant improvement on battery energy saving, range extension and vehicle cost.
Walker, PD, Fang, Y, Roser, H & Zhang, N 2015, 'Dynamics and Control of Clutchless AMTs', Proceedings of the 16th Asia Pacific Vibration Conference, Asia-Pacific Vibration Conference, Bach Khoa Publishing House, Hanoi Vietnam, pp. 368-373.
Walker, PD, Roser, H, Zhang, N & Fang, Y 2015, 'Comparison of Powertrain System Configurations for Electric Passenger Vehicles', Proceedings of the SAE Technical Papers, Asia Pacific Automotive Engineering Conference, Society of Automotive Engineers, Melbourne; Australia.View/Download from: Publisher's site
Electric vehicles (EV) are considered a practical alternative to conventional and hybrid electric passenger vehicles, with higher overall powertrain efficiencies by omitting the internal combustion engine. As a consequence of lower energy density in the battery energy storage as compared to fossil fuels powered vehicles, EVs have limited driving range, leading to a range phobia and limited consumer acceptance. Particularly for larger luxury EVs, electric motors with a single reduction gear typically do not achieve the diverse range of function needs that are present in multi-speed conventional vehicles, most notably acceleration performance and top speed requirements. Subsequently, multi-speed EV powertrains have been suggested for these applications. Through the utilization of multiple gear ratios a more diverse range of functional needs can be realized without increasing the practical size of the electric motor. The major limitation of multi-speed EV powertrains is that the increased transmission complexity introduces additional losses to the vehicle. Through a number of simulations this paper studies the integration of multispeed transmission with EV platforms. Particularly, it investigates the performance improvements of both B and E class vehicle platforms realized through utilization of two and three speed transmissions. Also the potential application of hybrid energy storage systems (i.e. batteries combined with super-capacitors) is studied. Results demonstrate that there can be significant benefits attained for both small and large passenger vehicles through the application of multi-speed transmissions. However, optimization of these ratios must be considered in the analysis.
Friedrich, C, Roser, HM, Hubbertz, H & Walker, PD 2014, 'Towards Automated Design of Fastening Systems for Accelerated Product Development', ASME 2014 International Mechanical Engineering Congress and Exposition, International Mechanical Engineering Congress & Exposition, ASME Publishing, Montreal, Canada, pp. 1-9.View/Download from: Publisher's site
Although considered a well-established machine element, screw fastening systems are required to fulfill ever increasing demands for performance, reliability, economy, and sustainability. Yet there are limitations to the capabilities of existing design procedures which often neglect a comprehensive analysis of both soft and hard design parameters over the entire system life cycle.
This paper presents a holistic approach towards automated design of screw joints, going beyond established methods by incorporating soft (intangible) design parameters additionally. Based on the vectorial design method developed by Friedrich, a multi-objective optimization process is used to tradeoff various, often conflicting design parameters from the vectorial design approach (such as screw diameter, assembly method, preload loss, material strength, etc.) to derive an optimum solution with a high level of confidence.
For this, a complex network of strategy parameters and safety factors is used (optimization parameters). It is referred to geometry, material, contact, assembly and production for boundary conditions. A definite solution for the model of the fastening system must incorporate analytical functions, numerical relationships and correlation with technical and nontechnical aspects (including cost and environmental impact).
This multi-objective approach entails inherent flexibility enabling designers to set application specific design priorities as a key part prior to defining an optimized solution. Overall, this gives the capability for an automated design process, which
can be performed with computational engineering. A major benefit from this is saving product development time and therefore cost as well as evaluating influence-intensity of design parameters (rating of influencing values).
An example of a wheel bolt connection is provided to demonstrate this approach referring to a well-known application. From this it is outlined that conflicting safety factors lead to an opti...
Roser, HM & Walker, PD 2014, 'Managing the Conceptualisation Process in Innovative Engineering Design, Demonstrated on a Hybrid Two-Wheeler Design Case Study', 2014 Proceedings of the ASME 12th Biennial Conference on Engineering Systems Design and Analysis, ASME Biennial Conference on Engineering Systems Design and Analysis (ESDA), American Society of Mechanical Engineers, Copenhagen, Denmark.View/Download from: Publisher's site
The process of conceptualizing innovative designs is multifaceted and inherently difficult to perform successfully. It is largely characterized by the designers capability to find solutions to design problems beyond existing norms. General agreement suggests this process should entail a holistic approach for conceiving new ideas, which are expanded, assessed, developed, refined, and implemented as part of an iterative problem solving cycle. Suitable design procedures and skills are therefore vital as most of the final cost of a product or system is committed within the early conceptualization stage. This paper builds on engineering design techniques previously developed by the author, namely the Design Process Framework in conjunction with the Concept Assessment Taxonomy (CAT) at the heart of concept development . The main emphasis of the work presented herein is the application of said framework to a new design challenge in order to further test and demonstrate its practicality in a real world context: the conceptual development of an innovative, modular, hybridelectric powertrain for two-wheelers.
Ruan, J & Walker, P 2014, 'An Optimal Regenerative Braking Energy Recovery System for Two-Speed Dual Clutch Transmission-Based Electric Vehicles', Technical Papers from the SAE 2014 World Congress & Exhibition, SAE World Congress, SAE International, Detroit, USA, pp. 1-8.View/Download from: Publisher's site
Regenerative braking energy recovery bears significance in extending the driving mileage of electric vehicles (EVs) while fulfilling real-time braking demands. Braking energy strategy plays a significant role in improving the regenerative braking performance and ensuring braking safety. This paper presents a regenerative braking energy recovery strategy for an example EV with a two-speed Dual Clutch Transmission (DCT). The two-speed DCT, with simple structure, can effectively extend the active vehicle speed-range for regenerative braking . Meanwhile, a shifting strategy is proposed for the DCT, working with the presented braking energy recovery strategy, to optimize the brake force distribution between front and rear wheels, motor and friction brake force. The EVs' model with the proposed regenerative braking strategy and the optimal shifting schedule was established and implemented in Matlab/Simulink. A testing rig based on an example EV was then set up in our laboratory to experimentally validate the proposed strategy. The simulation and experimental results show significant agreement. It verified that the proposed regenerative braking control strategy could not only exhibit excellent performance, but also make it possible to recover more braking energy though adding the two-speed DCT.
Ruan, J, Walker, P & Zhu, B 2014, 'Experimental Verification of regenerative braking energy recovery system based on electric vehicle equipped with 2-speed DCT', Proceedings of the 7th IET international conference on Power Electronics, Machines and Drives, IET International Conference on Power Electronics, Machines and Drives, IEEE, Manchester, Uk, pp. 1-8.View/Download from: Publisher's site
Electric vehicles (EVs), as the most promising long term trend in environment friendly transportation, worldwide attracts significant amount of research. However the consumer acceptance of EVs is still restricted by the limited range in comparison to its counterpart-internal combustion engine vehicles. Energy recovery through regenerative braking, as an inherent advantage of EVs, is a feasible option to contribute to the alleviation of this problem by recuperating braking energy during braking. The motor recovers electric energy instead of dissipating heat when driver decelerates vehicle. There have also been many attempts at integrating various transmissions with EVs to extend the mileage and improve the performance of electric vehicle, but few have noticed that Dual Clutch Transmission (DCT) as a higher efficiency transmission system may be more suitable for EVs than other transmissions, especially with a simpler structure when only two speed ratios are utilised. In this paper, a regenerative braking system for Two-Speed Dual Clutch Transmission-based electric vehicles is proposed. Results from simulation and experiment validate that the proposed braking energy recovery system works efficiently on a Two-speed DCT based EV.
Walker, P, Durack, M & Durack, J 2014, 'LABORATORY TESTING OF A NEW FORM OF TOROIDAL CVT', FISITA World Congress and Exposition, Maastricht, The Netherlands.
De Novellis et al. 2012 (1) reported on an EHL tribological model and used this to compare the performance of three fundamentally different toroidal CVT's. These were a full and a half toroid CVT and a new "Double Roller Full Toroidal Variator CVT" (DFTV) as developed by Ultimate Transmissions (UT). The DFTV geometry achieves zero spin at 1:1 ratio and low spin elsewhere. The model predicted exceptional efficiencies and power densities for the new CVT. Ultimate Transmissions has manufactured a test transmission embodying both the double roller variator and a new UT developed mechanical steering system with a 9.6:1 ratio spread referred to as Direct Roller Steering (DRS). Based on a proposed 150 Nm small car transmission the test transmission has been modified from its original design to facilitate independent control of all parameters and measurement of relevant system characteristics. The University of Technology Sydney has undertaken an extensive range of tests of the test transmission using its motoring dynamometer test bed allowing both steady state analysis and data collection during continuous ratio sweeps. Test sequences were established to allow separate identification of efficiency losses associated with thrust bearings and those that are inherent to the CVT traction contact regions. Results demonstrate the dynamic stability of the DRS steering system at varying speeds across its full ratio spread and for varying forward and reverse output torque. With measured thrust bearing losses removed, the central CVT demonstrates efficiencies up to 96% at 1:1 transmission ratio for a traction coefficient of 0.07, compared to 98% efficiency as predicted using a UT design tool calibrated against the work of De Novellis (1). At high and low transmission ratios the decreases in efficiency due to increasing contact spin are generally in line with these same predictions. The results of this experimental investigation demonstrate that the DFTV has excellent efficiency ch...
Walker, PD & Roser, HM 2014, 'Configuration Design and Energy Balancing of Compact-Hybrid Powertrains', 2014 Proceedings of the ASME 12th Biennial Conference on Engineering Systems Design and Analysis, ASME Biennial Conference on Engineering Systems Design and Analysis (ESDA), American Society of Mechanical Engineers, Copenhagen, Denmark.View/Download from: Publisher's site
The development of compact and efficient hybrid electric vehicle powertrains for low initial and on-going costs requires consideration of numerous, often competing factors. Appropriately designing and sizing these powertrains requires the consideration of requirements for vehicle range and performance, considered directly through the sizing of motors and engines, and indirectly through minimization of vehicle mass whilst being constrained by total stored energy in the vehicle, against the impact on vehicle emissions and on purchase and ongoing operational costs. In addition to these considerations the actual driver use will strongly influence the energy consumed and vehicle emissions. It therefore becomes beneficial to provide flexibility in hybrid vehicle configuration design to enable the minimization of vehicle emissions and ongoing vehicle costs. The purpose of this paper is to study the various alternative vehicle powertrain configurations for application to small scale hybridization demands, such as scooters or motorcycles. Powertrain configurations studied in this paper include plug-in hybrid electric (PHEV), battery hybrid electric (BHEV), and a pure electric vehicle (PEV). To design and size each of the configurations a statistical approach is taken, power and load demands are studied and utilized to size powertrain components. Results are extended to size vehicle energy storage for electric only range of 25, 50 and 100 km, and total vehicle range of 100 km for the BHEV and 200 km for the PHEV. Based on the results developed from the analysis mathematical models of each of the powertrain configurations are then developed in Matlab/Simulink and numerical studies of vehicle energy consumption in comparison to range are conducted. Outcomes of these simulations are compared to an operating cost based analysis of the suggested powertrains; the benefits and limitations of each design are considered in detail.
Ruan, J, Zhang, N & Walker, P 2014, 'Comparing Of the Effects of CVT and DCT on the EVs Including Braking Energy Recovery', 8th Australasian Congress on Applied Mechanics 2014 (ACAM 8), Australasian Congress on Applied Mechanics, Engineers Australia, Australia.View/Download from: Publisher's site
Walker, PD, Roser, HM & Zhang, N 2013, 'Performance Evaluation of Two-Speed Electric Vehicles', SUSTAINABLE AUTOMOTIVE TECHNOLOGIES 2013, 5th International Conference on Sustainable Automotive Technologies (ICSAT), SPRINGER INTERNATIONAL PUBLISHING AG, Ingolstadt, GERMANY, pp. 263-268.View/Download from: Publisher's site
Walker, PD, Zhang, N & Fang, Y 2014, 'Experimental investigation of efficiency losses in a two speed electric vehicle', 8th Australasian Congress on Applied Mechanics, ACAM 2014, as Part of Engineers Australia Convention 2014, Australasian Congress on Applied Mechanics, Informit, Melbourne, Australia, pp. 23-32.
Electric vehicles (EV) are considered a practical alternative to conventional and hybrid electric passenger vehicles, with higher overall powertrain efficiencies by omitting the internal combustion engine. As a consequence of lower energy density in the battery energy storage as compared to fossil fuels powered vehicles, EV powertrains have limited driving range, leading to a range phobia and limited consumer acceptance. Particularly for larger luxury PEVs, electric motors with a single reduction gear typically do not achieve the diverse range of function needs that are present in multi-speed conventional vehicles, most notably acceleration performance and top speed requirements. Subsequently, multi-speed EV powertrains have been suggested for these applications. Through the utilisation of multiple gear ratios a more diverse range of functional needs can be realised without increasing the practical size of the electric motor. This paper builds on previous research to conduct an experimental investigation of the losses present in a multi-speed EV powertrain. The major limitation of multi-speed EV powertrains is that the increased transmission complexity introduces additional losses to the vehicle. Utilising the UTS Powertrain test rig the instantaneous losses of a multispeed and comparative single speed powertrain are investigated under the NEDC driving cycle, combining urban and highway style driving modes. This includes the power throughput evaluation of motor/controller and transmission, and the parasitic losses associated with control of clutch solenoids and the electric hydraulic fluid pump. The results demonstrate that while the single speed EV has improved overall efficiency by comparison to the multispeed equivalent powertrain, the comparative efficiencies are unlikely to significantly degrade the vehicle driving range.
Zhou, X, Walker, P, Zhang, N, Zhu, B & Ruan, J 2014, 'Study of Power Losses in a Two-Speed Dual Clutch Transmission', Papers from the SAE World Congress, SAE World Congress, SAE International, Detroit, USA, pp. 1-6.View/Download from: Publisher's site
This paper mainly studies the power losses in a refined two-speed dual clutch transmission which is equipped in a electric vehicle test rig. Both numerical and experimental investigations are carried out. After theoretical analysis of the power losses original sources, the developed model is implemented into simulation code to predict the power losses . In order to validate the effectiveness of the proposed model, results from experimental test are used to compare the difference the simulation and test. The simulation and test result agree well with each other. Results show that the power losses in the two-speed are mainly generated by multi-plate wet clutch drag torque and gear churning loss
Zhou 1, X, Walker, P, Zhang, N, Zhu, B & Ruan, J 2013, 'Simulation of Thermal behavior of a Two-speed Dual Clutch Transmssion', 5th Asia Pacific Congress On Computational Mechanics (APCOM V) & 4th International Symposium On Computational Mechanics (ISCM VI), Asian-Pacific Conference on Computational Mechanics, Singapore, Singapore.
Roser, H, Walker, PD & Zhang, N 2013, 'Robustness Analysis of Two-Speed Electric Vehicles', ASME 2013 International Mechanical Engineering Congress and Exposition, International Mechanical Engineering Congress & Exposition, AMER SOC MECHANICAL ENGINEERS, American Society of Mechanical Engineers, pp. V013T14A018-V013T14A018.View/Download from: Publisher's site
Walker, PD & Zhang, N 2013, 'Influence of Engine Harmonics on Synchroniser Mechanism Dynamics', Volume 4A: Dynamics, Vibration and Control - ASME 2013 International Mechanical Engineeing Congress and Exposition, International Mechanical Engineering Congress & Exposition, American Society of Mechanical Engineers, San Siego, USA, pp. 1-9.View/Download from: Publisher's site
Synchronizer mechanisms play an important role in the selection and engagement of gears in manual, automated manual and dual clutch transmissions (DCT). These mechanisms rely heavily on the balancing of torque loads in cone clutches, dog gears and from losses in the gearbox to ensure repeatable and reliable actuation, with excessive wear on friction and contact surfaces leading to degradation of actuation and potential mechanism failure. Dual clutch transmissions, in particular, provide a unique operating environment for synchronizers, most notably is its actuation with the engine still driving the wheels during normal driving conditions. Thus, the consideration of increased transmitted vibrations through the powertrain must be evaluated to study the impact of these vibrations on the synchronizer. To conduct this investigation this paper develops a detailed multi-body dynamic model of a typical automotive powertrain equipped with a dual clutch transmission. This includes engine models with torque harmonics that capture the instantaneous torque variations from piston firing in the engine. As the main consideration of this paper is the influence of engine harmonics, the semi-definite powertrain model is simplified to a fixed-free system and the response of the synchronizer mechanism to harmonic torque inputs is analyzed. Parametric analysis of the system is conducted to analyze the influence of variables including gear ratio, torsional damper, system damping, and engine configuration on the dynamic response of the mechanism. Results demonstrate the influence of each of these variables on synchronizer dynamics in the steady state, with stiffness of torsional damper having the strongest influence on forced vibration. Additionally, results vary significantly between single and dual lay-shaft transmissions.
Walker, PD, Roser, HM & Zhang, N 2013, 'Performance Evaluation of Two-Speed Electric Vehicles', Sustainable Automotive Technologies 2013, International Conference of Sustainable Automotive Technologies, Springer, Ingolstadt, Germany, pp. 263-268.View/Download from: Publisher's site
This paper presents the findings of a theoretical analysis of a two-speed Dual-Clutch Transmission (DCT) for electric vehicle applications. Electric drives incorporating DCTs can offer improved driving economy, range, acceleration and climbing gradeability, with potentially smaller electric motors (EMs). Through simulation, this paper studies the influence of road grade on EV performance and how motor downsizing impacts on vehicle range and acceleration performance. Particular attention focused on how such vehicles perform using a variety of different drive cycles. Results show that as expected range is heavily influenced by driving cycle. However, for a reduction in motor peak power there is minimal variation in vehicle range. Vehicle performance is also demonstrated to be reasonable through significant reduction in motor size.
Zhou, X, Walker, PD, Zhang, N & Zhu, B 2013, 'Performance improvement of a two speed EV through combined gear ratio and shift schedule optimization', SAE Technical Papers presented at SAE 2013 World Congress & Exhibition, SAE World Congress, SAE, Detroit, Michigan, pp. 1-9.View/Download from: Publisher's site
This paper proposes an approach to optimize the economy performance of a two-speed electric vehicle (EV) by combining gear shifting schedule design and gear ratios selection. Mathematic models for the two-speed EV subsystems are developed, including thos
Zhu, B, Zhang, N, Walker, P, Zhan, W, Yueyuan, W, Ke, N & Zhou, X 2013, 'Two Motor Two Speed Power-Train System Research of Pure Electric Vehicle', SAE Technical Paper, SAE Technical Paper, SAE, Society of Automotive Engineers.View/Download from: Publisher's site
Abdul Rahman, S, Walker, PD, Zhang, N, Zhu, J & Du, H 2012, 'A Comparative study of vehicle drive performance and energy efficiency', Proceedings of the 4th International Conference on Sustainable Automotive Technologies, International Conference on Sustainable Automotive Technologies, Springer, Melbourne, Victoria, Australia, pp. 319-324.
In this paper, two typres of increasingly more efficient and greener vehicles are analyzed and compared. These vehicles are: a proposed conceptual series-parrallel powertrain, the University of Technology, Sydney plug-in hybrid electric vehicle (UTS PHEV); and, a conventional series-parrallel hybrid electric vehicle with an internal combustion engine. The UTS PHEV requires only a single electric machine to function as an electric motor or generator in different time intervals controlled by a special energy management strategy. The UTS PHEV uses two energy storage device, the battery and the untracapacitor, which can work together effectively to maintain the state of charge at a high level in order to improve the vehicle drive performance and energy efficiency. With the assistance of a novel automatic transmission, the UTS PHEV can operate under multiple modes to suit the needs of various driving cycles including those in an emergency. A special power and energy management strategy was developed to control the power flows within the vehicle according to the desired operating mode.
Walker, PD, Abdul Rahman, S, Zhang, N, Zhan, W, Lin, Y & Zhu, B 2012, 'Modelling and simulation of a two speed electric vehicle', Proceedings of the 4th International Conference on Sustainable Automotive Technologies, International Conference on Sustainable Automotive Technologies, Springer, Melbourne, Victorial, Australia, pp. 193-198.
Electric vehicles offer an alternative to hybrid and conventional vehicles through the use of electcric drive without fossil fuel consumption. This shifts green house gas production from the vehicle to power stations, but if power is supplied from renewable sources, such as wind power, zero emissions are generated. Practical vehicle design requires the consieration of competing demands of vehicle acceleration and performance against range and vehicle efficiency. Thus, considering requirements such as grade climbing and acceleration against vehicle range and power consumption, a two speed transmission is suggested for this vehicle study to increase motor operation at high torque and efficiency regions. To evaluate the application of such a transmission, a two speed electric vehicle powertrain is developed in SimulinkÂ®. Simulations are conducted to demonstrate the performance of the two speed electric vehicle. Results reveal the capability of the two speed vehicle to meet various performance criteria and provide an indication of effective range under different drive cycles.
Walker, PD, Zhang, N, Zhu, B & Abdul Rahman, S 2012, 'Dynamics and control of gear shifts in a two speed electric vehicle', Proceedings: the 7th Australasian Congress on Applied Mechanics (ACAM 7), 9-12 December 2012, the University of Adelaide, North Terrace Campus/National Committee on Applied Mechanics of Engineers Australia, Australasian Congress on Applied Mechanics, Engineers Australia, Adelaide, Australia, pp. 698-698.
Zhou, XX, Walker, PD, Zhang, N, Zhu, B & Ding, F 2012, 'The influence of transmission ratios selection on electric vehicle motor performance', ASME 2012 International Mechanical Engineering Congress and Exposition, American Society of Mechanical Engineers, pp. 289-296.
Walker, PD & Zhang, N 2011, 'Clonk induced response from synchronizer engagements in dual clutch transmissions', Dynamics for Sustainable Engineering, Asia-Pacific Vibration Conference, Hong Kong Polytechnic University, Hong Kong, pp. 1322-1332.
The dual clutch transmission (DCT) is capable of providing mechanical efficiencies comparable to manual transmissions with clutch-to-clutch shifting capabilities of planetary automatic transmissions. Vehicle powertrain equipped with DCTs are considered to be lightly damped dynamic systems, with damping sourced from torsional vibration absorbers and parasitic losses in clutches, transmission and differential considerably less that the damping provided by torque converters in planetary automatics. Consequently, DCTs are exposed to increased response under transient conditions, typically requiring more stringent control strategies for performing clutch-to-clutch shifts, for example. Synchronizer actuation, however, is not given the same detailed level of control to ensure minimization of observable transient response, nevertheless, the high degree of nonlinearity in the mechanismsâ actuation presents potential for initiation of undesirable transients. This paper is tasked with investigating the nonlinear engagement of synchronizers contribution to the introduction of noise, vibration, and harshness (NVH). Of particular interest is the initiation of clonk response in the powertrain, considered to be high frequency (300-5000Hz) elasto-acoustic response in powertrains, typically induced through the nonlinear response, such as synchronizer engagement, interacting with frequencies in long hollow shafts. A multi degree of freedom model of a dual clutch transmission equipped powertrain is presented using lumped inertia-stiffness elements, structured to provide the capabilities for synchronizer engagement using mean engine torque and nonlinear synchronizer models. Synchronizer engagements are undertaken for a variety of input pressures in conditions associated with clonk response. Time and frequency domain results for shaft and sleeve responses post-synchronization are used to evaluate the introduction of frequencies consistent with clonk response. The influence of...
Zhou, X, Zhang, N & Walker, PD 2011, 'Launch Control of a Dual Clutch Transmission Using a Detailed Hydraulic Component Model', Dynamics for Sustainable Engineering, Asia-Pacific Vibration Conference, The Hong Kong Polytechnic University, Hong Kong, pp. 2001-2006.
Dual clutch transmissions (DCTs) have emerged as a viable alternative to conventional planetary automatics and continuously variable transmissions (CVTs) with the development of precise control strategies. Although technology advancement greatly improves the transmission performance in recent years, undesirable vibration and noise is still the draw backs to DCT application. The hydraulic sub-component is a particular source of nonlinear response that influences launch performance. Clutch engagement judder, as part of vehicle noise, vibration and harshness (NVH), is an important vehicle attribute in the design of DCT which combines the advantages of manual transmission (MT) and conventional automatic transmission (AT). This paper studies the vehicle vibration during launch. In this paper, a system analytical model including detailed hydraulic control module will be presented for clutch engagement control during launch for vehicles having a DCT. And the control method mainly includes determining the engine throttle position and clutch pressure of the transmission to make the vehicle accelerate smoothly. In particularly, the attributes between launching with two clutches or one clutch are compared and evaluated, which are validated through simulation in MATLAB/Simulink.
Walker, PD, Zhang, N, Tamba, RT & Fitzgerald, SP 2010, 'Dynamics and simulations of shifting in a dual clutch transmission', Proceedings of the 6th Australiasian Congress on Applied Mechanics, Australasian Congress on Applied Mechanics, Engineers Australia, Perth, Western Australia, pp. 1-10.
In this paper a finite element model of a dual clutch transmission (DCT) equipped rear wheel drive powertrain is developed for the study of transient dynamics during clutch-to-clutch shifting. Damped free vibration analysis is performed to identify natural frequencies and damping ratios. These results indicate that damping in the DCT is significantly lower than in comparable automatic transmissions. Clutch pressure signals are employed from a constant torque shift control algorithm with engine throttle angle control for transient simulations. These simulations demonstrate inadequacy of the sole use of torque control for providing high quality gear shifts in DCTs. To rectify this issue the torque phase of shifting was restricted by applying a ramp increase in clutch torque to reduce pressure overshoot during simulations. Results demonstrate a reduction in post lockup transients; however it is suggested that inclusion of time delay in shift control must be considered to achieve best possible performance.
Walker, PD, Zhang, N, Tamba, RT & Fitzgerald, SP 2009, 'Synchroniser modeling with application specific to the dual clutch transmission', Proceedings of the 13th Asia-Pacific Vibration Conference (APVC 09), Asia Pacific Vibration Conference, University of Canterbury, Christchurch, New Zealand, Christchurch, New Zealand, pp. 1-10.
The synchromesh type synchroniser has been introduced to dual clutch transmission applications for gear selection prior to shifting. Historical research into this type of mechanism has targeted the application to manual transmission systems only. Such work targets the phenomena associated with driver feel such as shift effort and âdouble bumpâ. Now automated, the control of the synchroniser is less concerned with such aspects of the actuation, focus not trends towards repeatability of the process as well as speed of engagement. The actuation of this type of mechanism relies on the balancing of torques derived from engagement chamfers, the cone clutch and losses experienced in the transmission. These torques affect the displacement of sleeve, asynchronisation of the target gear, as well as the unblocking of synchroniser ring and indexing of the gear to the locked position. Thus a simplified model of the synchroniser mechanism and associated gear is developed for the purpose of simulating its operation in a dual clutch transmission. Unlike similar simulations this model targets the actuation of the mechanism using input forces from the controller, rather than using the control of sleeve displacement to determine maximum forces experience by the driver. To assess how operating characteristics have varied the mechanism has been modelled in the MatlabÂ® environment. This paper presents the techniques used to model the mechanism, including the governing principles of synchroniser actuation and drag torque. Simulation results demonstrate that the primary variation in the mechanism is through the indexing chamfers. Additionally the influence of temperature variation is demonstrated for a fifth gear upshift, and the detrimental effects of cold starts demonstrated.
Walker, PD & Hong, G 2007, 'Measurement of micro synthetic jet actuation using intensity of disturbance', Proceedings of the 16th Australasian Fluid Mechanics Conference, Australasian Fluid Mechanics Conference, School of Engineering, The University of Queensland, Crown Plaza, Gold Coast, Australia, pp. 1236-1241.
Walker, PD 2011, 'Synchroniser analysis and shift dynamics of powertrains equipped with dual clutch transmissions'.