Sliding mode control with extended state observer for a class of nonlinear uncertain systems

This paper integrates extended state observer into sliding mode controller for better transient and steady-state performance and robustness against nonlinearity, uncertainty, and time-varying disturbance. The design process of the proposed controller is composed of two main stages. Firstly, all the nonlinearity, uncertainty, and time-varying disturbance of the system are considered as the total disturbance, which is estimated by a designed high-order extended state observer (HESO). Secondly, by integrating the sliding mode control into the HESO, the composite controller is formed. Benefits from HESO's disturbance estimation and online compensation, the problem of chattering is substantially alleviated. Thanks to the sliding mode term, the closed-loop system will converge to the reference even under severe disturbances. The numerical and experimental results for a calibration-free robotic hand-eye coordination system indicate the effectiveness and robustness of the proposed approach.