Research On Variable Structure Guidance Law Of Air-to-ground Guided Missile Based On Attitude Feedback

The core of missile precision guidance research is the researh of missile guidance law.The most widely used guidance method in engineering is proportional guidance method.Because proportional guidance method always tends to guide the missile motion to the direction where the line of sight angular rate of missile target system converges to zero,it is easy to cause the jump of missile control command at the end of terminal guidance when the target maneuvers,Threaten the stability of missile system,and then increase the miss distance.Secondly,the proportional guidance method has a small angle of attack at the end of terminal guidance,which cannot give full play to the overall damage efficiency of the missile.In addition,although the flight trajectory of the missile using proportional guidance method is relatively flat,the trajectory of the missile in space is easy to be predicted and the escape ability of the missile is poor.In order to solve the above problems,this paper first proposes the attitude feedback proportional guidance method,which introduces attitude feedback based on the proportional guidance method in order to improve the anti-target maneuverability of the guidance law.Then,in order to effectively solve the problem of guidance command jump caused by target maneuvering,this paper creatively puts forward the attitude feedback variable structure guidance law,which relies on the characteristics of variable structure control to suppress the sudden change of terminal guidance command,and further improve the anti-target maneuverability and anti-jamming of the guidance law.Finally,by introducing the over gravity compensation,the attitude feedback variable structure guidance law with over gravity compensation is proposed,which increases the attack angle of the terminal guided missile and improves the damage ability of the guided missile.The main work of this paper is as follows:(1)The classical guidance law is deeply studied and analyzed,and the variable structure control theory and over gravity compensation theory are studied.The common coordinate system in the process of establishing the mathematical model of missile target relative motion is studied.Through the coupling mode of pitch plane and yaw plane,the relative motion model between missile target in three-dimensional space,the parameter relationship between three-dimensional space and two-dimensional plane and the angle of attack of guidance terminal are analyzed and studied.(2)In view of the poor maneuverability of the proportional guidance method against the target,this paper proposes the attitude feedback proportional guidance method,which optimizes the performance of the proportional guidance method by introducing the missile attitude feedback.The attitude feedback proportional guidance method weakens the sudden change of the guidance control command at the guidance end,and can promote the convergence of the line of sight rate between the missile and the target.The data simulation shows that the attitude feedback proportional guidance method has better dynamic performance in the target maneuvering scene.(3)Aiming at the poor anti-jamming performance of attitude feedback proportional guidance method,this paper proposes an attitude feedback variable structure guidance law.Different from the traditional variable structure guidance law,the traditional variable structure guidance law only selects the projectile line of sight rate and a state quantity to complete the guidance law design in the sliding surface design process.This method redesigns the sliding mode surface by selecting a number of state variables correctly,so as to ensure that the dynamic performance of the sliding mode surface of the attitude feedback variable structure guidance law is improved.In addition,the adaptive approach law and relay function are selected to optimize the variable structure guidance law to weaken the chattering effect of the attitude feedback variable structure guidance law,and the guidance command design and simulation verification are completed on the basis of reconstructing the sliding mode surface,so as to further solve the problem of normal overload and jump required to control the terminal missile caused by target maneuver.Because the sliding mode variable structure control idea is introduced,the attitude feedback variable structure guidance law has certain anti-interference.The smooth motion of the guidance command in the phase plane optimizes the problem of poor anti-interference of the attitude feedback proportional guidance method.Finally,the simulation results show that the method has better dynamic performance.(4)Aiming at the problem of small terminal angle of attack of attitude feedback variable structure guidance law,an attitude feedback variable structure guidance law with over gravity compensation is proposed in this paper.In this paper,by introducing the over gravity compensation term and changing the trajectory shape,the escape ability of the missile is enhanced and the falling angle of the guided terminal missile is increased,so as to improve the damage ability of the missile.Finally,the simulation results show that the introduction of over gravity compensation can increase the terminal attack angle of missile terminal guidance and enhance the escape ability of missile without changing the guidance and control method.