On Active Disturbance Rejection Control: Stability Analysis and Applications in Disturbance Decoupling Control

One main contribution of this dissertation is to analyze the stability characteristics of extended state observer (ESO) and active disturbance rejection control (ADRC). In particular, asymptotic stability of the dynamic system that describes the estimation error and the closed-loop system is established where the plant dynamics is completely known. In the face of large dynamic uncertainties, the estimation error, the closed-loop tracking error, and its up to the (n− 1) order derivatives are shown to be bounded. Furthermore, it is demonstrated that the error upper bounds, in general, monotonously decrease with the observer and control loop bandwidths. The second contribution is to develop a dynamic disturbance decoupling control strategy for square multivariable systems based on ADRC. The proposed method has been successfully applied to chemical process problems and micro-electro-mechanical systems gyroscopes. It is shown that a largely unknown square multivariable system can be readily decoupled by actively estimating and rejecting the effects of both the internal plant dynamics and external disturbances. By requiring little information on the plant model, the intention is to make the new decoupling approach practical.