Robust anti-disturbance control of nonlinear systems by a dual-pole assignment based disturbance observer design

This paper proposes a robust anti-disturbance control scheme for nonlinear systems subject to time-varying load disturbances. Firstly, a nonlinear generalized proportional-integral observer (NGPIO) is designed to estimate the system state, load disturbance and its high-order derivatives in real time. Different from the existing single-pole assignment based GPIO designs, a dual-pole assignment approach is proposed to determine the NGPIO gain, such that the observer gain responsible for estimating the disturbance dynamics could be specifically tuned with only slightly impact on the observer gain associated with the state estimation. By virtue of the estimated system state and load disturbance, a nonlinear anti-disturbance controller is then designed, followed by robust stability analysis of the resulting closed-loop system. Finally, two illustrative examples are presented to verify the effectiveness and advantages of the proposed method.