Designing a robust controller for a missile autopilot based on Loop shaping approach

In this paper, a robust autopilot is designed for a missile autopilot, such that the system stability is guaranteed in low altitude and short-range conditions. First, using the v-gap metric, the system is linearzed around the equilibrium point. Then, the robust $H_\infty$ loop shaping controller is built for the linear model. The proposed approach does not utilize the gain scheduling method, and guarantees the system stability throughout the flight envelope. Particle Swarm Optimization (PSO) algorithm is used along with the control approach to reduce the complicated tuning process of the weight functions. The weighting functions are optimized throughout the evolutionary algorithm to maximize the stability margin. From the simulations, it is proved that the stability margins achieved guarantees the stability of interceptor throughout the whole flight envelope.