Adaptive second-order dynamic sliding-mode control based on fuzzy disturbance-observer

Abstract

In the sliding-mode control of nonlinear systems with uncertainties and disturbances,we prove that the partial derivative of the Gaussian fuzzy basic function vector with respect to the state vector is bounded under any condition,thus resolving the key problem in combining a second-order dynamic sliding-mode control with the fuzzy identification.In addition,we design a second-order dynamic terminal-sliding-mode control which converges in a finite period of time without chattering.The output of the fuzzy disturbance-observer is employed as the compensation signal for the adaptive robust control.The stability of the system is proved by using Lyapunov theorem.The proposed control scheme is applied to the attitude-angles tracking of a near space vehicle;the increment of the convergence time in this application of higher-order sliding-mode control has been analyzed.Results show that this control scheme effectively suppresses the chattering and is with strong robustness,fast tracking speed,and high precision.Compared with the conventional terminal-sliding-mode control,the second-order dynamic terminal-sliding-mode control causes limited increment of the convergence time,demonstrating the efficacy of this control scheme in engineering application.