Design Of Sliding Mode Controllers For A Class Of Nonlinear Systems With Mismatched Disturbances

With the improvement of control precision of system,the problems of disturbances for nonlinear systems have become more and more important.Sliding mode control has attracted much attention because of superior robustness in dealing with the problems of disturbances.The traditional sliding mode control shows well robustness towards the problems of matched disturbances.However,it is insufficient for the problems of mismatched disturbances.Hence this paper has proposed the design of disturbance observer based sliding mode controllers for T-S fuzzy models of nonlinear system with mismatched disturbances.1?The paper has proposed the method of adaptive sliding mode control based on singular value decomposition and disturbance observer when restrictive condition of the singular value decomposition is satisfied.The approach has combined the information of disturbance estimations and adaptive control theory with the design of sliding mode control.Compared with the traditional sliding mode control,this method has better performance towards the problems of mismatched disturbances;2.In view of constraint problems of the singular value decomposition,the paper has proposed the approach of disturbance observer based adaptive sliding mode control.The new method is designed by the original system and it has a smaller constraint and a larger scope of application;3.This paper has also put forward the adaptive integral sliding mode control method based on disturbance observer.This method can eliminate the reaching mode of the traditional sliding mode control.What's more,it can solve the problems of the suppression of mismatched disturbances to a certain extent,which is more effective than the traditional integral sliding mode method.Compared with the traditional sliding mode control,disturbance observer based adaptive sliding mode control has following two advantages:First of all,the new approach can solve the problems of mismatched disturbances to a certain extent.Secondly,disturbance observer based adaptive sliding mode control shows better performance than traditional sliding mode control towards the problems of chattering.At last,towards problems of mismatched disturbances of nonlinear systems,the article has proved the superiority of above new methods when compared with the traditional sliding mode control by simulations.