Indirect robust control of interceptors with tail fins and pulse thrusters

An interceptor missile with tail fins and pulse thrusters has two different control inputs: one is continuous and the other one is discontinuous. This brings some challenges to the autopilot design and stability analysis. Indirect robust control strategy is applied to handle this problem. Based on the nonlinear dynamics of the interceptor, a nonlinear system for tracking acceleration commands is presented. Treating the error between the actual inputs and the computed inputs as input uncertainty, a robust control problem is formed. It is equivalent to an optimal control problem of the nominal system with a modified cost functional. The state-dependent Riccati equation approach is applied to solve the nonlinear optimal control to obtain a solution to the robust control problem. Numerical results show the effectiveness of the proposed strategy.