A Cascade Finite-Time Nonlinear Extended State Observer for Active Disturbance Rejection Control

Zhicheng Gao, Qiang Ding, Xudong Zhao

Abstract: Extended state observer(ESO) is a class of high-gain observers and plays a significant role in output feedback control theory for uncertain nonlinear systems. However, it faces a challenge in industrial applications when the output is corrupted by high-frequency measurement noise, which means the core parameter, referred to as bandwidth, cannot be too large. It faces a trade-off between convergence rate and noise suppression. In this paper, A new cascade finite-time nonlinear ESO(FTNESO) combining cascade structure and finite-time nonlinear observer, which provides extra degree of freedom to design the controller, is proposed to improve the estimation performance in the presence of measurement noise. Based on the proposed cascade FTESO, an active disturbance rejection control scheme(ADRC) is established, and the controller is applied to the nonlinear gas turbine model to show its effectiveness.