Disturbance Rejection Control Methods Analysis Based On Disturbance Observer

The control performance of modern industrial systems has inevitably suffered from various disturbances,uncertainties and nonlinearities,including the change of external environment,inaccurate model or unmodelled dynamics,the stochastic parameter perturbations and nonlinear couplings of multivariable systems.Therefore,disturbance rejection becomes a key objective in control system design.Disturbance observer based control(DOBC)approach has advantages such as simple structure and easy online tuning,it can well handle with the disturbances in the input channel of control system in practical applications.According to different requirements of system on the control performance,DOBC can combine with different control strategies,thus effectively improve the disturbance rejection and performance of systems.In general,it is an effective disturbance rejection method.In this paper,based on the design method of disturbance observer and combined with other different control strategies,the disturbance rejection control of systems with disturbance in input terms is studied.The main results of this paper are as follows:1)Construct a disturbance observer for a class of discrete-time linear system with two types of disturbances,then estimate the disturbance in the input channel.On the other hand,consider the noise as another kind of disturbance of the system,based on the Lyapunov stability theory and H infinity control theory,some sufficient conditions are given to design a controller,which ensure the resulting closed-loop system stable and satisfy the H_? performance index.2)For a class of discrete-time control system with disturbance,the disturbance rejection problem of the system under the event-triggered control strategy is studied.First,a disturbance observer based on event-triggered control strategy is constructed,then based on Lyapunov stability theory,sufficient conditions are given to guarantee the closed-loop system asymptotically stable.LMIs method is used to solve the inequality criteria.Finally,a disturbance rejection controller under the event-triggered control strategy is designed and the system obtain good performance.3)Propose a method for constructing probabilistic disturbance rejection controller for uncertain systems in which a scenario optimization method is used to deal with the nonlinear and unbounded uncertainties.For disturbance rejection,a disturbance observer is considered and a state-feedback controller is designed based on Lyapunov stability theory and H_? control theory.Sufficient conditions are presented to ensure that the resulting closed-loop system is stable and a prescribed H infinity performance index is satisfied.4)For a class of nonlinear discrete time systems with two types of disturbances,T-S fuzzy model is adopted to describe the nonlinear system according to IF-THEN rules,and a disturbance observer is constructed to estimate the disturbance in the input channel.Based on the Lyapunov stability theory and H infinity control theory,some sufficient conditions are given to guarantee that the closed-loop system asymptotically stable.Finally,a fuzzy based event-triggered disturbance rejection controller is designed and system get a nice performance of control.5)For a class of discrete time systems with saturation nonlinearity,the invariant set theory is used to deal with the saturation characteristics,and a disturbance observer is constructed to estimate the disturbance in the input channel.Controller of the closed-loop system is designed based on the sufficient conditions for stability.To verify the effectiveness of the proposed disturbance rejection methods,numerical simulation is carried out.