T.P. Leung

Concordia University Montreal, Montréal, Quebec, Canada

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Publications (28)11.04 Total impact

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    Conference Proceeding: Fuzzy neural control of systems with unknown dynamic using Q-learning strategies
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    ABSTRACT: In this paper an efficient Q-learning paradigm implemented on a fuzzy CMAC network is proposed. The fuzzy CMAC network topological architecture is described. The continuous states of the system are partitioned into a number of fuzzy boxes. With the proposed fuzzy CMAC the Q-values of agents in the fired fuzzy boxes are evaluated and the control actions with maximum Q-values can be derived. The proposed hybrid adaptive and learning type of Fuzzy Neural control system based on the Q-learning is applied to the control of a pH-neutralization process.
    Fuzzy Systems, 2003. FUZZ '03. The 12th IEEE International Conference on; 06/2003
  • Conference Proceeding: A dynamic weight-fuzzy neural network for nonlinear dynamic system control
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    ABSTRACT: A class of fuzzy neural network with dynamic weights is proposed and its corresponding network topological architecture with suitable supervised learning algorithm is presented. Using the proposed network in control system design, a priori knowledge of the control system is not essential and this includes the order of the control system. The proposed network is applied to the control of a highly nonlinear pH-neutralization process. Simulation shows that the proposed dynamic learning control strategy has better dynamic quality, stronger robustness, adaptability and intelligence while comparing to the conventional control techniques, which demand the explicit and quantitative mathematical model of the system under control.
    Fuzzy Systems, 2001. The 10th IEEE International Conference on; 01/2002
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    Article: Case-based reasoning and adaptation in hydraulic production machine design
    C M Vong, T P Leung, P K Wong
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    ABSTRACT: Case-based reasoning (CBR) can support hydraulic circuit design. Existing expert systems for hydraulic system design use production rules as its source of knowledge. However, this leads to problems of knowledge acquisition and knowledge base maintenance. This paper describes the application of CBR to hydraulic circuit design for production machines, which helps solving problems using past experience. A technique Case-based adaptation (CBA) is implemented in the adaptation stage of CBR so that adaptation becomes much easier. A prototype system has been developed to verify the usefulness of CBR and CBA in hydraulic production machines.
    Engineering Applications of Artificial Intelligence 01/2002; 15:567-585. · 1.66 Impact Factor
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    Article: Robust adaptive control of a class of nonlinear systems with unknown backlash-like hysteresis
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    ABSTRACT: Deals with adaptive control of a class of nonlinear dynamic systems preceded by unknown backlash-like hysteresis nonlinearities, where the hysteresis is modeled by a differential equation. By exploiting solution properties of the differential equation and combining those properties with adaptive control techniques, a robust adaptive control algorithm is developed without constructing a hysteresis inverse. The new control law ensures global stability of the adaptive system and achieves both stabilization and tracking to within a desired precision. Simulations performed on a nonlinear system illustrate and clarify the approach
    IEEE Transactions on Automatic Control 01/2001; · 2.11 Impact Factor
  • Conference Proceeding: A Dynamic Weight-Fuzzy Neural Network With Nonlinear Dynamic System Control.
    01/2001
  • Conference Proceeding: Roundness control in taper turning using FCC techniques
    E.H.K. Fung, S.M. Cheung, T.P. Leung
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    ABSTRACT: In this study, forecasting and compensatory control (FCC) techniques are employed to improve the workpiece roundness accuracy in taper turning on an experimental lathe. This paper describes the methodology to online determine, model and forecast the workpiece roundness error using autoregressive (AR) modelling and the aspects associated with its practical implementation on the turning process. Experimental results have shown that an improvement of around 24% was achieved for the roundness error of workpieces in the taper turning operations
    American Control Conference, 1997. Proceedings of the 1997; 07/1997
  • Conference Proceeding: Approximate linearization of nonlinear systems: a neural network approach
    Hai-Long Pei, Qi-Jie Zhou, T.P. Leung
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    ABSTRACT: Recent researches show that neural networks have the ability to approximate a function as well as its derivatives. This result offers a promising opportunity to introduce neural network theory into nonlinear system control. In this paper a novel method of approximate nonlinear system linearization with neural networks is proposed. The network approximator is designed to integrate the involutive equation of a nonlinear system no matter whether the integrability condition is satisfied or not. Simulation results show that this method is feasible
    Intelligent Control, 1996., Proceedings of the 1996 IEEE International Symposium on; 10/1996
  • Conference Proceeding: Combined inverse system method and neural network for designing nonlinear excitation control law
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    ABSTRACT: In this paper, an inverse system method (ISM), which is a simple exact linearization method for nonlinear system design, has been employed to design a nonlinear excitation control law of synchronous generator, and neural network is proposed for the controller to provide desired controller output. The main motivation is to exploit generalization capabilities of neural networks to interpolate between training data, and thus to deal with system parametric uncertainties caused by a large sudden fault. Simulation results show that transient stability of the perturbed power system can be improved
    Neural Networks, 1995. Proceedings., IEEE International Conference on; 12/1995
  • Conference Proceeding: A two-switching surface variable structure control scheme for a flexible manipulator
    F.C.K. Cheung, E.H.K. Fung, T.P. Leung
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    ABSTRACT: A novel control scheme for the flexible manipulator based on variable structure system theory is proposed and tested. The controller shows the robustness towards the variation of the system parameters. Also the performance of the controller can be tuned easily without complicated calculation for stability. Experimental results are presented and they are compared with those obtained from the hybrid proportional controller which is based on the optimal control scheme
    American Control Conference, 1995. Proceedings of the; 07/1995
  • Conference Proceeding: A design method for vehicle dynamic systems based on fuzzy logic control
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    ABSTRACT: Presents a new approach using a fuzzy logic control method based on reference model tracking to overcome the uncertainties of vehicle dynamic systems. Simulation of the lateral velocity and the yaw rate control show that it is satisfactory to apply this method to vehicle dynamic control resulting in close matching with the reference model
    American Control Conference, 1995. Proceedings of the; 07/1995
  • Conference Proceeding: A brushless DC motor velocity regulator using a variable structure controller with varying switching surfaces
    C.K. Lee, N.M. Kwok, T.P. Leung
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    ABSTRACT: A system using a variable structure controller (VSC) in the sliding mode is robust to disturbances. However, this advantage cannot be obtained in the reaching phase. The remedial approach adopted here is that a small switching surface slope is used at the beginning and then it is increased continuously when the system output approaches the reference setting. This method reduces the duration of the reaching phase and hence the sensitivity to disturbances during the early control period. Simulation of a brushless DC motor velocity regulator system to illustrate the effectiveness of the approach is included in this paper
    Power Electronics and Drive Systems, 1995., Proceedings of 1995 International Conference on; 03/1995
  • Conference Proceeding: Object-oriented CAD for electro-pneumatic sequential circuit design in low cost automation
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    ABSTRACT: This paper describes an object-oriented CAD system for electro-pneumatic sequential circuits. The system is organised in an object-oriented manner for supporting both pneumatic power system and control system design. An algorithm is developed based on the Karnaugh mapping method to generate indexing equations to link appropriate objects to perform sequential control system design. The algorithm developed can handle an ordinary sequence, a sequence with simultaneous paths and a time delay function. A class which encapsulates this algorithm is described in detail. A prototype system (OOCADEP) written in C++ has been developed to demonstrate the concept
    Emerging Technologies and Factory Automation, 1994. ETFA '94., IEEE Symposium on; 12/1994
  • Conference Proceeding: Genetic algorithms for optimal dynamic control of robot arms
    D.P. Kwok, T.P. Leung, Fang Sheng
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    ABSTRACT: This paper describes the use of genetic algorithms (GAs) for optimizing the parameters of PID controllers for a 6-DOF robot arm. An efficient GA is designed to optimal-tune the parameters of the PID controller of each joint for a single step response and for the tracking of other specified trajectories. This GA is required to optimize fitness functions related to the combinations of different performance indices such as ISE, time-optimal and others. The simulations are carried out on a PUMA 560 arm model being controlled by PID controllers with their parameters optimized using the proposed GA. The simulation results obtained are compared with that obtained by traditional optimization techniques, wherever applicable
    Industrial Electronics, Control, and Instrumentation, 1993. Proceedings of the IECON '93., International Conference on; 12/1993
  • Conference Proceeding: A new learning control strategy for robots in constrained manipulation
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    ABSTRACT: In this paper, an iterative learning control strategy is presented for a class of constrained robots. The controller design is based on the reduced form of the robot model. The strategy guarantees the perfect motion tracking of the robot with its end-effector moving on a linear and frictionless constrained surface in the presence of unknown bounded disturbances. The bounded and adjustable force tracking error is obtained
    TENCON '93. Proceedings. Computer, Communication, Control and Power Engineering.1993 IEEE Region 10 Conference on; 11/1993
  • Conference Proceeding: Globally stable adaptive controller of robot manipulators
    Zhou Qijie, Xu Jianmin, T.P. Leung
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    ABSTRACT: This paper addresses an adaptive inverse dynamics robotic control algorithm. Based on Lyapunov stability theory, the theorems on the global stability of robotic system are proven. The proposed algorithm is easy to implement and the robotic system is robust to parameter uncertainty and payload variation. Simulation results show the effectiveness of the scheme
    TENCON '93. Proceedings. Computer, Communication, Control and Power Engineering.1993 IEEE Region 10 Conference on; 11/1993
  • Conference Proceeding: Neural-network-based model reference adaptive control
    Xu Jianmin, Zhou Qijie, T.P. Leung
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    ABSTRACT: This paper presents the learning algorithm of a neural network being applied to identification of affine nonlinear systems, and proposes a neural-network-based model reference adaptive control approach. The theorems on exponential stability of the system are proven. Simulation results show that this method is feasible
    TENCON '93. Proceedings. Computer, Communication, Control and Power Engineering.1993 IEEE Region 10 Conference on; 11/1993
  • Conference Proceeding: Intelligent Self-Tuning Control of Varying Delay Systems
    Xu Jianmin, Zhou Qijie, T.P. Leung
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    ABSTRACT: Not Available
    Aerospace Control Systems, 1993. Proceedings. The First IEEE Regional Conference on; 06/1993
  • Conference Proceeding: Implicit adaptive inverse dynamics control of robot manipulators
    J.-M. Xu, Q.-J. Zhou, T.P. Leung
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    ABSTRACT: An implicit adaptive inverse dynamics control scheme for robot manipulators is presented. Instead of estimating manipulator parameters, the feedback gain is directly updated according to the bounds of uncertainties of the robotic system. Two theorems are proven, and the resulting algorithm can tolerate the variation of physical parameters to some extent. The controller parameters have a certain relation to the desired position and velocity accuracy, such that the choice for them is easy. Simulation results verify the effectiveness of the approach
    Robotics and Automation, 1993. Proceedings., 1993 IEEE International Conference on; 06/1993
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    Article: A sliding mode controller with bound estimation for robot manipulators
    C.-Y. Su, T.-P. Leung
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    ABSTRACT: A sliding-mode control algorithm combined with an adaptive scheme, which is used to estimate the unknown parameter bounds, is developed for the trajectory control of robot manipulators. The major contribution of this methodology lies in the use of a special matrix, called the regressor, which makes it possible to isolate the unknown parameters from the robotic dynamics. Based on the upper bounds of those unknown parameters, which are estimated by a simple adaptive law, the proposed VSS (variable-structure-system) controller guarantees the stability of the closed-loop system. The robustness analysis shows that in the presence of the uncertainties, which are assumed to be unbounded and rapidly varying, the closed-loop system can still be stabilized. Chattering is reduced by using the boundary layer technique. Simulation results show the validity of the proposed algorithm
    IEEE Transactions on Robotics and Automation 05/1993;
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    Article: Real-time implementation of regressor-based sliding mode control algorithm for robotic manipulators
    C.-Y. Su, T.-P. Leung, Y. Stepanenko
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    ABSTRACT: A regressor-based variable-structure control scheme has been developed for the trajectory control of robot manipulators in the presence of disturbances, parameter variations, and unmodeled dynamics. The method is based on the regressor structure given by J.J.E. Slotine and W. Li, without parameter adaptation. This avoids the requirement of persistency of excitation, and the convergence of the overall transient exponential. The method is robust against a class of state-dependent uncertainties, which may result, for example, from unmodeled dynamics. The problem of chattering is solved by the smoothing control law. It is with respect to a set around the origin, which can be made arbitrarily small. To illustrate the feasibility of this controller, it was implemented using a Motorola M68000 microprocessor on a two-link revolute joint manipulator subjected to a variable payload. Experimental results confirm the validity of accurate tracking capability and the robust performance
    IEEE Transactions on Industrial Electronics 03/1993; · 5.16 Impact Factor