Study Of Variable Structure Guidance Law For Interceptor Using Head Pursuit Interception

KKV(Kinetic Kill Vehicle) is a general interceptor used to intercept the tactic ballistic missile, and infrared sensor is applied to detect the target. To reduce the perturbation of interceptor detection induced by aerodynamic heating which is brought by high speed of the interceptor at the endgame guidance stage at atmosphere, a novel interception method, head pursuit interception is provided in this paper. Based on this advanced interception technology, the corresponing guidance law and tracking differentiator are studied using Lyapunov stability theory. The whole trjectory simulation is performed in the end.Head pursuit interception is a new missile interception technology which has been developped recently. For head pursuit interception, the interceptor is guided ahead of the target along the target's flight trajectory, so that the interceptor and the target fly in the same direction. The three-dimensional kinematics model is presented considering the motion of the interceptor and the target based on simplified interception model. According to the performance of head pursuit interception, the head pursuit guidance model is founded and the condition of head pursuit interception is discussed, at the same time the parameters and initial conditions for this kind of interception are provided.There are many uncertainties for the guidance and control of missile including aerodynamics, target maneuvering and outer disturbance. Three-dimensional head pursuit interception model is a nonlinear and uncertain system, and variable structure control method has the character of robustness for system diturbances. So based on Lyapunov stability theory a nonlinear finite-time stability variable structure control guidance law is designed considering the unknown accelerations of the target, which can satisfy the requirement of head pursuit interception. At the same time, an adaptive variable structure control guidance law is presented to eliminate the effect of uncertain item using the adaptive uncertain boundary method.High-order sliding mode control method is introduced according to differential inclusions and homogeneity theory. The main advantage of high-order sliding mode is being able to reduce the control discontinuity of sliding mode control while keeping the advantage of the sliding mode control. So a kind of second order sliding modes algorithm and head pursuit interception guidance law are presented, and smooth second order sliding mode head pursuit interception guidance law with an observer is provided to eliminate the control discontinuity. Simulation is performed using smooth second-order sliding mode head pursuit intercepion as an example.Tracking differentiator is a general method to get signal differentiator information in engineering, which can be used to track the signal of LOS(line of sight) angle and it's derivative. Nonlinear sliding mode control is an important method for tracking differentiator design, especially high order sliding mode control has been widely used, which has the character of less perturbation and high robustness. A second-order sliding mode tracking differentiator as well as it's improved algorithm are presented using Lyapunov stability theory on the basis of nonlinear second order sliding mode control theory. Integrating the character of linear and nonlinear tracking differentiator, this tracking differentiator can track and differentiate any signal. At the same time it has a simple form and is easy to be applied.The mathematic model used to depict the motion of missile is a multi-input multi-output system including dynamical equations, kinematic equations, geometric equations and control equations. So a variable structure control method is designed to control the interceptor attitude stability considering the on-off control of attitude engine. Finally, according to the algorithms designed above, a head pursuit interception numerical simulation is done considering the missile model, aerodynamics, mass variablity and target maneuvering, using second order sliding mode guidance law, variable structure attitude control theory. Simulation results verified the effectiness of the three-dimensional guidance model, the guidance law and the attitude control algorithm.