Mingyue Cui, Hongzhao Liu, and Wei Liu
Adaptive siding mode control, extended state observer, filteringbackstepping method, nonlinear system with uncertanties
A backstepping adaptive sliding mode control strategy based on extended state observer (ESO) is proposed for uncertain nonlinear system with unknown system functions and unknown external disturbance. The backstepping adaptive sliding mode control and the ESO theory are combined in the developed controller, and thus the restriction of all the states in the nonlinear system should be completely measurable is abolished. Through a simple coordinate transformation, the general nonlinear model is transformed into a strict-parametric-feedback form, which is more suitable for the design of the sliding mode controller by backstepping method. In the presence of unknown states and total uncertainties, the ESO is employed to estimate the unknown states and the total uncertainties. Thereafter, the backstepping sliding mode control law and adaptive law of switch gain are designed to guarantee that the tracking errors can converge to zeros rapidly and stably. And then, the derivatives of the virtual control are computed by using a filter without having to analytically or numerically differentiate it. Therefore, the implementation of the backstepping design method is significantly simplified. Comparative simulation experiment results all show that the proposed controller can improve the chattering problem of the sliding mode control and improve the dynamic performance of the system.
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