Design Of Missile Altitude Control System With Variable Structure Control

Flight height is an important tactics index of evaluating missile performance. The traditional design method of missile altitude control system adopts PID control. PID control has been successfully used in many fields such as aviation, spaceflight, missile and other industry control system. The study object in the thesis is missile that flies hedgehopping over sea at minimum altitude. Many interference problem must be solved when missile flies at minimum altitude, otherwise the missile would be dangerous of bumping into the sea under the circumstances of bad weather and wave. The different kinds of interference factors are contradictions with requirements of control system, which can not be solved by PID control. To overcome disturbance problem of hedgehopping over the sea, variable structure method is proposed. The central content in this paper is the design of missile altitude control system with variable structure. The research has practical meaning.The central contents in this thesis include: Firstly, the reference frame is defined and movement equation and transfer function of the missile body in pitch plane are developed. The altitude model of stabilization loop is formulated. Secondly, the pitch loop and the altitude stabilization loop are designed and simulated by traditional PD control theory and PID control method respectively. And then, we also analyze problems existing in thecontrol loop of missile adopting PID control theory; Thirdly, we design altitude stabilization loop of missile adopting proportional control rule of variable structure control, and derivate design method of proportional control rule in detail. The two simulation results adopting different methods are compared in this thesis. Lastly, performances of restraining interference of two methods and robustness of variable structure to altitude control are also discussed.It is proved from simulation results that this design method has simple structure and excellent robustness. The performance of variable structure control is better than that of PID control method, and that is possible to make missile more digitalized. The conclusions of the thesis have real significance and bright future.