Anti-disturbance Controller Design For Nonlinear Systems With Disturbances

Nonlinear feedback control has always been an important task in the area of control.Due to the widespread existence of nonlinearity and uncertainty in the real world,such as measure-ment noise,modeling errors,external disturbances and unmodeled dynamics,these uncertain-ties and disturbances have a severe impacts on the dynamic performance of the closed-loop systems.In real physical systems,it is difficult or even impossible to measure all states.Therefore,it is very important to study this kind of nonlinear systems with uncertainties and disturbances,and to design the corresponding anti-disturbances controller in theory and en-gineering.Within recent decades,robust control of nonlinear systems with uncertainty have attracted extensive attention,and many fruitful research achievements have been produced,such as adaptive feedback linearization,adaptive backstepping,sliding mode control and so on.In this dissertation,for one type of nonholonomic systems with uncertainty,one type of nonholonomic systems with certain growth constraints and a class of nonlinear systems with external disturbances,the anti-disturbances controllers are designed by using backstepping,dynamic gain scaling technique and extended state observer techniques.The research work of this dissertation mainly includes the following three parts:First,for a class of nonholonomic systems with uncertainties,the global output feedback stabilization problem is studied.The external disturbance term is regarded as a general state,and then a high gain extended state observer is constructed to estimate the external disturbance and states of systems at the same time.Dynamic gain scaling transform is used to reconstruct the systems,using backstepping method,the systems converge to the equilibrium point,and all the signals of the closed-loop systems are globally bounded.Two simulation examples are proposed to verify that the control algorithm is effective.Second,the output feedback control problem for one type of nonholonomic systems with certain growing constraints is taken into account.External disturbance is regarded as an extended state,a kind of extended state observer is constructed to estimate the systems states and disturbance.For the sake of reconstructing the original systems,a dynamic gain scaling technology is designed,by making use of the controller of feedback control,the systems can realize asymptotical stability,and all the signals of the closed-loop systems are globally bounded.Two simulations demonstrate the effectiveness of the control algorithm.Third,this part studies the global asymptotic stability regulation problem of a class of nonlinear systems with external disturbances.Firstly,all states and external disturbance of the systems are estimated by means of a high gain extended state observer.Then the dynamic gain scaling technique is used to reconstruct the systems.Furthermore,the output feedback with dynamic high gain is carried out for the systems,and the controller is constructed to achieve global asymptotic stability for this kind of nonlinear systems,and all signals of the closed-loop systems can also achieve global bounded.Two simulation examples are proposed to verify that the control algorithm is effective.