The Study Of Disturbance Rejection For Several Classes Of Nonlinear Systems Based On Disturbance Observer

As we all know,according to the known information of system,distur-bance observer is an important tool to estimate the unknown disturbance,using estimation in feedback control which provides conditions for rejection disturbance or compensation disturbance.Disturbance Observer Based Control(DOBC)is an important disturbance offset method and its basic idea is to design disturbance observer or filter to estimate unknown disturbances in the first place.Then,using the estimation of disturbance constructs feed-forward compensator for the disturbance rejection,combining it with a feedback controller.Finally,it achieves the goal of keeping the composite closed-loop system stable.DOBC strategy has been applied in many nonlinear systems.Considering several nonlinear systems with different structures,the corresponding disturbance rejection schemes based on disturbance observer are proposed.The main contents of this paper are stated as follows:Firstly,the disturbance rejection control based on disturbance observer consists of a class of nonlinear systems as well as unknown disturbance and nonlinear dynamic.The unknown nonlinear function was approached by a fuzzy logic system.Then,the estimation of disturbance is gained by designing T-S model nonlinear disturbance observer.The disturbance observer and feed-forward compensator with adaptive control are integrated to reject the composite disturbances and guarantee asymptotic stability of the closed-loop system.Finally,the simulation example is adopted to test the accuracy and effectiveness of the proposed strategy.Secondly,on the basis of disturbance observer,a disturbance rejection method is proposed for a class of pure-feedback nonlinear systems with mismatched disturbances.The mismatched disturbances are generated by exogenous systems and satisfy partially known information.The disturbance observer is designed to estimate the unknown disturbances.The back-stepping controller based on disturbance observer is constructed to guarantee the asymptotic stability of the closed-loop.The simulation example shows that the proposed strategy is correct and effective.Thirdly,compared with last chapter,the scope of the system and disturbance has been further extended.This chapter proposes an anti-disturbance control scheme basedon disturbance observer.Firstly,a two-step disturbance observer is constructed to estimate the external disturbance.Then,the composite controller based on disturbance observer is constructed to reject the disturbance for the asymptotic stability of the closed-loop.The simulation example is given to demonstrate the correctness and feasibility of the proposed method.