APPLICATION OF H-INFINITY CONTROL TO PITCH AUTOPILOT OF MISSILES

The pitch rate control of a missile is analyzed by an H-infinity contr oller. The system dynamics governing the aerodynamic stability derivat ives and airframe structure vibration is formulated in a generalized s tate space realization form. This formulation facilitates the gamma-it eration method in solving the associated Ricatti equation of the 4-blo ck H-infinity control problem. It is shown that the H-infinity control ler, because of its loop shaping capabilities, can provide improved tr acking performance and stability robustness compared with H-2 (linear- quadratic-Gaussian (LQG)) and classical proportional-integral-derivati ve (PID) controller in the rigid airframe model. When airframe flexibi lity effect is considered, the H-infinity controller is also shown to be robust under structure natural frequency variations.