Missile Guidance Law Research Based On Sliding Mode Control Theory

In recent decades,sliding mode control algorithm has become a hot research area for general scholars owing to its high robustness.Sliding mode control algorithm can make the system achieve immunity effect to specific interference,and the accurate control model of the controlled object is not required,indeed,the algorithm is easily applied to practice.Consequently,this control method is especially suitable for the design of missile terminal guidance law.However,the extension of sliding mode variable structure algorithm has been impeded because using the classical sliding mode control algorithm the output of the controller easily generate chattering phenomenon which brings a certain pressure for control system.So it is hard to promote to the missile terminal guidance system.In the meanwhile,this control algorithm cannot guarantee that the control system fast convergence in the limited time,and to some extent,it has a bad influence on the system performance.So sliding mode control algorithm is needed to improvement,and then apply it to the design of air-to-air missile terminal guidance law so can make guidance law improve accuracy.Investigating the sliding mode control system,the basic principle is introduced and described in the aspect of mathematics.Then the robustness of the control system is analyzed and the design methods are presented.Aiming at the chattering problem occurs in sliding mode control system,a detailed analysis is given out and several common solutions are summarized.The composition and working principle of the missile guidance control system is introduced in detail.Several kinds of the currently guidance system are considered.According to different guidance system,their application scenarios and their corresponding advantages and disadvantages are given,and explain some definition of the missile guidance system.Finally,the geometric model of terminal guidance is analyzed and the interception mathematical model is established.Aiming at the problem of the too slowly convergence speed in traditional sliding mode control scheme,a finite time convergent guidance law design approach which considers the property of autopilot is proposed.Firstly,the terminal sliding mode and nonsingular terminal sliding mode control method are introduced,and the mathematical analysis based on different control methods is presented.According to the established mathematical model of missile terminal guidance,a new terminal guidance law design method based on nonsingular terminal sliding mode control scheme is developed,and using the design method of reaching law to ensure the system having good dynamic performance.The chattering problem of the control law is analyzed and an immunosuppressive scheme is discussed.Theoretically,the stability,finite time accessibility and convergence of the designed control law are proved.The superiority of the proposed guidance law is illustrated by the simulation example.To deal with the interception problem of hypersonic target when using present guidance law,inspired by thought of the head pursuit(HP)guidance law,a forward intercept guidance law based on second order sliding mode variable structure is proposed.The HP method is introduced and the forward intercept mathematical model is established.Then the necessary condition of the forward intercept is analyzed,a second order sliding mode control algorithm is developed.Based on the proposed approach,a second order sliding mode HP design method is presented.Finally,the performance of the algorithm is validated by simulation example.From the simulation results,it can be concluded that by using the proposed guidance law the control system has high robustness,and there is no chattering problem in the control input,finally the missile can effectively intercept high supersonic aircraft in the end.