A Finite-time Adaptive Fuzzy Terminal Sliding Mode Control for Uncertain Nonlinear Systems

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.