Air-to-Air Missile Terminal Guidance Law Research Of Based On The Variable Structure Control

Because of the simple control and the less quantity that needed to be measured, proportional guidance law in classical guidance law has been widely applied in engineering. With the continuous development of technology, new type missile in order to be able to adapt to a wide range fight, which constantly improve its own overload capacity and increase its mobility. Under this situation, seeking a new method of guidance to improve the guidance precision is imperative. This paper is based on air-to-air missile as the research object. Adopt variable structure control strategy combining with local stability theory and make fully use of the limited information acquired to analyze and study terminal guidance law for the large maneuvering target.Main research and achievements are summarized as follows:Firstly, set up the relative movement mathematical model under two-dimensional plane, combining finite time convergence with local stability theory, design a kind of locally finite time convergence that can solve the problem of global convergence which is usually required in general control system, and do theoretical analysis for the interception area as well. In the design process, regard the target maneuvering acceleration as bounded disturbance. It is proved by Lyapunov function that the system got convergent in the end. Respectively considering sine and square wave signal and simulation results show that the methods are effective.Secondly, considering that the autopilot has an effect on guidance accuracy, so in the process of guidance law designing, here the autopilot is considered as a first-order inertia link, local convergence guidance law with the consideration of the the firstorder autopilot is designed. Because in actual cases, the autopilot has high order dynamic properties, so here the autopilot is also considered as a second-order inertia link, local convergence guidance law with the consideration of the the second-order autopilot is designed. As to the unpredictable situation of target maneuvering acceleration, also set an upper bound for it. Simulation results show that when the autopilot is considered as high order inertial link, it has higher guidance precision.Finally, considering the situation that relative movement mathematical model established under the three dimensional space is more conformed to actual situation. So use the combined method of sliding mode variable structure control and local stability theory to design sliding mode variable structure guidance law. Due to target maneuvering acceleration generally unmeasured, in practice, it is always set an upper bound value according to the engineering experience. Therefore, use adaptive control method to do real-time estimation for target maneuvering acceleration further more. Simulation results show that under the effect of this guidance law, the trajectory get more smooth and miss distance get much less.