Research On Guidance And Control Law For Exo-Atmospheric KKV Based On Predictive Control

Advanced target detection and direct lateral force technology of fast response performance is the key to realizing direct hit. Because of using infrared imaging seeker, only the LOS angle is available. In order to get the relative distance and velocity required for advanced guidance law, the estimation of relative distance and velocity must using measurements of seeker. The observability cannot be ensured, the estimation precision is limited. Therefore, the robust guidance law should be designed to estimation errors. Moreover, the attitude control and translation control of interceptor is realized by pulse thrusters allocated on the body, which can only provide constant force, so this constraint on the inputs should be considered in the design procedure. Existing literature reveals that Model Predictive Control (MPC) is the most effective method to solve constrained control problem. Furthermore, predictive guidance law is a novel and excellent one for the exo-atmospheric interceptor. The research on guidance and control problem based on predictive control method plays a crucial role on theoretical and engineering. Therefore, On-Off guidance and control method based on prediction is focused on this dissertation. The main contributions are the following:Firstly, combining the characteristics of structure and actuator of exo-atmospheric interceptor, the mathematical model of guidance and control problem is established. In the attitude dynamics, the disturbance moments caused by thrust misalignments of divert thrusters and drift of mass center is considered. The line-of-sight (LOS) and LOS rate reconstruction method are given according to operation mechanism of strapdown seeker.Secondly, the observability of passive ranging is analyzed using observability analysis method for nonlinear system. The relationship between observability and singular value is revealed. The calculation method of error bounds for estimation of relative distance is proposed. Based on this, the selection of parameters of filter is researched.Thirdly, the predictive control methods for uncertain and constrained linear systems with On-Off control inputs are proposed. By appropriate adjustment of constraint set using constraint tightening approach, the robustness of algorithm can be guaranteed. The computational complexity of the new algorithms decreases drastically. The construction method of feasible solution is derived with On-Off control inputs, and the step is determinated for finite-time arrival to arbitrary target set. In order to guarantee the stability of systems with On-Off input, the construction method of robust control invariant sets is proposed. The On-Off attitude control law is designed by proposed method. In the course of design of attitude control law, the restriction on the seeker field of view is considered, which can avoid losing lock on the target.Fourthly, the predictive control methods are investigated for an uncertain nonlinear system with On-Off control input. The Fliess function expansion of nonlinear system with On-Off input is used to describe the relationship between predictive outputs and current states, uncertainties and On-Off inputs. Based on this, the optimazation problem in the MPC is obtained by choosing quadratic cost function. Considering the bounded uncertainty, the method that adopts nonlinear programming to solve problem of optimization is given to effectively solve the problem of designing of nonlinear systems with On-Off control input. The On-Off guidance law is designed by proposed method. The error is considered for estimation of relative distance and measurements noise of seeker. The On-Off threshold of divert thrusters is given. Based on this, the finite-time stability proof of guidance systems is given by Lyapunov method.Lastly, the main parameters are determinated in design of control law by system parameters and performance requirments. Based on this, the proposed methods are applied to a guidance and control design of exo-atmospheric interceptor, where the effect of thrust misalignments, drift of center of mass and measurements noise on guidance and control systems is investigated. We compared the proposed methods with the existing ones. Simulation results show the effectiveness and advantage of the proposed methods.