Missile autopilot design via output redefinition and gain optimization technique

The autopilot for missile systems should be designed to provide satisfactory stability, performance, and robustness for all flight conditions which may occur in probable engagements. In this paper, dynamic inversion approach based on output redefinition is applied to the missile autopilot design. The redefined output is selected as a linear combination in the ratio of pitch rate and angle-of-attack. Using this redefined output, the proportional and integral gains for the outer-loop autopilot can be systematically determined and, simultaneously, possible to reflect the variation of missile dynamic. However, it is difficult to choice the combination ratio of two state variables, i.e., pitch rate and angle-of-attack, guaranteeing the design criteria of the resulting autopilot. In this paper, a parameter optimization technique is applied to design the autopilot with the dynamic inversion based inner-loop controller using the redefined output. Here, CEALM algorithm is adopted as an optimizer to effectively handle the constraints. Numerical results show that the pitch-channel autopilot designed by the proposed approach presents a satisfactory performance, stability, and robustness against inversion error and parameter uncertainty.