Fuzzy-Variable Structure Control On Missile's Attitude System

Going along with the rapid development of science and technology, more and more requirements are put forward to the attitude control of missiles. As a synthesis method in control system, the sliding mode of variable structure control is invariable, and which is its most excellent advantage in the missile attitude control system. But variable structure control has some disadvantages. Because in the real system there unavoidably exists inertia in switch equipment, it is very easy for the system to generate terrible twitter when variable structure control switches in variable control logic, which makes variable control become a obstacle in its application. This paper combines fuzzy control and traditional variable structure control, and constitutes fuzzy variable structure control, which can not only maintain the advantages of fuzzy controller, but also decrease the twitter in variable control system.Firstly, this paper describes the background of my paper, and the generation, characteristics, questions of variable structure control and fuzzy control. Then some coordinate frames which are needed in the research are defined and the switch relations between these coordinates are also introduced. We analysis the forces which are acted on the missile, build up models which can describe the missile's nonlinear dynamics and then the math models are predigested under some hypothesizes. We give the basic concepts, main contents and usual design methods of sliding variable structure control and fuzzy control, and then we make out the detailed design process of the missile attitude fuzzy variable structure control system. We can obtain new model reference variable structure control system of second order linear reference model system with common form according to the math model of usual non-linear system. In order to design better control law, we can make non-linear transformation for the model to let the model have the form of an affine non-linear system. According the requirements of control system, we set up non-linear sliding mode, and select fuzzy reaching law to calculate system's control law in order to eliminate the twitter. We make the control torque as the input, and then we translate it into the deflection of the control fin.