Application of H/sup /spl infin// control to pitch autopilot of missiles

The pitch rate control of a missile is analyzed by an H ^∞ controller. The system dynamics governing the aerodynamic stability derivatives and airframe structure vibration is formulated in a generalized state space realization form. This formulation facilitates the γ-iteration method in solving the associated Ricatti equation of the 4-block H ^∞ control problem. It is shown that the H ^∞ controller, because of its loop shaping capabilities, can provide improved tracking performance and stability robustness compared with H ₂ (linear-quadratic-Gaussian (LQG)) and classical proportional-integral-derivative (PID) controller in the rigid airframe model. When airframe flexibility effect is considered, the H ^∞ controller is also shown to be robust under structure natural frequency variations.