Sliding Mode Variable Structure Ammunition Attitude Control

Going along with the changes of combat missions in the modern warfare, the precision of the missiles have been requested increasingly demanding, so more and more requirements are put forward to the attitude control of missiles. As the deformation of the sliding mode in the sliding mode of variable structure control, sliding mode control in the missile attitude control has strong robustness. But variable structure control has some disadvantages. Actually, there is a certain delay while the missile executes the controlled instructions. This delay makes the sliding mode switch shuttles along the default sliding surface. It is very easy for system to generate terrible twitter. To this problem, this paper combines fuzzy control and the sliding mode of variable structure control, constitute fuzzy variable structure control, which can not only maintain the advantage of the sliding mode of variable structure control, but also decrease in variable control system by fuzzy logic.First of all, this paper describes the content and features of the sliding mode of variable structure control, and then demonstrates the feasibility of the missile attitude control using sliding mode theory, gives the general steps of designing sliding mode. Defined some coordinate frames which are needed to design the system of missile attitude controller, and introduce the switch relations between these coordinates. We analysis the forces and the movement of the missile, build up math models which can describe the missile's dynamics. Some math factors which can descript the uncertainty are put in the models, for there are system perturbation and external disturbance when the missile is controlled. Transformative the missile's dynamics into a nonlinear system model which is desired in the designing of sliding mode controller. According the requirement of the control system and the math mode of the missile, we set up a variable structure control law. Select fuzzy reaching law to calculate system's control law in order to eliminate the twitter, the fuzzy sliding mode controller is designed with the combination of sliding mode and fuzzy logic. We get PWPF (Pulse Width Pulse Frequency) modulators into the system in order to get continuously variable control torque. To facilitate the selection of PWPF modulator parameters, we build up a optimizing function model. By the optimizing function model, genetic algorithm is applied to optimize the PWPF parameters, to make sure the control system to get the best effect.At last this paper researches the designed control system's simulation problem using the Matlab/Simulink, and then presents the result of the simulation. The results show that the twitter is effectively decreased in the fuzzy sliding mode low. at the same time, the switching frequency is reduced under the PWPF modulator.