Research On Two Sliding Mode Control Methods And Their Applications

Sliding mode control has been widely applied in practical applications because of its simple physical implementation,fast response and strong robustness since it was proposed.It has become one of the main methods of system controller desig n.In this thesis,two sliding mode control methods,namely,sliding mode control based on reaching law and integral sliding mode control,and their applications are studied.The main contributions of this thesis are listed as follows:1.In order to solve the problems of severe chattering,slow convergence in sliding mode control system,a novel sliding mode reaching law is designed,which combines the advantages of saturation function and power term.The saturation function effectively alleviates the step jump caused by the sign function in the general reaching law,and achieves the purpose of suppressing chattering.The power term is introduced to improve the dynamic quality of the system by changing the coefficient of the power term.The existence and accessibility of the reaching law are proved by Lyapunov theory.By comparing with exponential reaching law and power reaching law,the reaching law designed in this thesis not only has better advantages in reducing chattering,but also in improving the dynamic quality of the system when the states approach the sliding surface.Finally,the new reaching law is applied to the nominal model control system of a two-arm manipulator with disturbance to verify its robustness and superiority.2.Integral sliding mode control has the advantage of simple design.It can not only solve the nonlinear and uncertain problems,but also weaken the chattering and reduce the steady-state error of the system.Therefore,another part of this thesis takes heterogeneous multi-agent systems with disturbances and unmeasured velocity as the research background.A new consistency protocol is designed based on integral sliding mode control theory and finite time stability theory,which can make the system achieve consistency in finite time and make the system achieve good control performance.In this protocol,the integral sliding surface is designed reasonably only according to the position information of the system,so that the trajectory of the system always starts from the sliding surface,eliminates the approaching motion stage in the traditional sliding mode,and improves the robustness of the system.The sufficient conditions for finite-time consensus are obtained by employing finite time stability theory.Finally,simulations are provided to verify the effectiveness of the proposed schemes.