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- 검색키워드
- 저자 : Abbas Erfanian (검색결과 2 건)
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Vahab Nekoukar,Abbas Erfanian 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.6
A major challenge to developing neuroprostheses for walking and to widespread acceptance of these walking systems is the design of a robust control strategy that provides satisfactory tracking performance, to be robust against time-varying properties of neuromusculoskeletal dynamics, day-to-day variations, muscle fatigue, and external disturbances, and to be easy to apply without requiring offline identification during different experiment sessions. The lower extremities of human walking are a highly nonlinear, highly time-varying, multi-actuator, multi-segment with highly inter-segment cou-pling, and inherently unstable system. Moreover, there always exist severe structured and unstructured uncertainties such as spasticity, muscle fatigue, external disturbances, and unmodeled dynamics. Ro-bust control design for such nonlinear uncertain multi-input multi-output system still remains as an open problem. In this paper we present a novel robust control strategy that is based on combination of adaptive fuzzy control with a new well-defined sliding-mode control (SMC) with strong reachability for control of walking in paraplegic subjects. Based on the universal approximation theorem, fuzzy logic systems are employed to approximate the neuromusculoskeletal dynamics and an adaptive fuzzy controller is designed by using Lyapunov stability theory to compensate for approximation errors. The proposed control strategy has been evaluated on a planar model of bipedal locomotion as a virtual patient. The results indicate that the proposed strategy provides accurate tracking control with fast convergence during different conditions of operation, and could generate control signals to compensate the effects of muscle fatigue, system parameter variations, and external disturbances. Interesting observation is that the controller generates muscle excitation that mimic those observed during normal walking.
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A Finite-time Adaptive Fuzzy Terminal Sliding Mode Control for Uncertain Nonlinear Systems
Ehsan Rouhani,Abbas Erfanian 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.4
In this study, a new adaptive fuzzy terminal sliding mode (AFTSM) control is presented for control of uncertain nonlinear systems with disturbances. The proposed controller incorporates terminal-based gradient descent (GD) algorithm and fuzzy logic system into a continuous nonsingular terminal sliding mode. The nonlinear dynamics of the system to be controlled are approximated with the fuzzy logic system and an adaptive law based on the terminal-based GD is proposed for online updating the parameters. The most advantage of the proposed terminal-based GD is the finite-time convergence compared to the conventional GD learning algorithm. It is proved that under the proposed terminal sliding mode and updating law, the tracking and approximation errors converge to the neighbourhood of zero in a very short time. Simulation results are given to illustrate the performance of the proposed AFTSM control through the control of a second-order system and a two-link rigid robotic manipulator. The simulation results show that faster and high-precision tracking performance is obtained compared with the conventional continuous terminal sliding mode control methods. Moreover, the proposed terminal sliding mode is applied to control of joint movement generated by functional electrical stimulation. The experiment results verify that accurate control of movement is obtained using the proposed control scheme.
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