Robust Autopilot for a Short Range Surface-to-Surface Skid-to-Turn Homing Missile

This paper demonstrates a robust autopilot design for a surface-to-surface skid-to-turn homing missile. The whole design has been carried out in two stages. Input-output feedback linearization(FBLC) has been proposed based on the highly nonlinear and nominal plant model. This control law, designed based on the nominal plant, does not handle the plant uncertainties associated with aerodynamic coefficients and the disturbances like wind gust, fin misalignment, shifting of center of gravity etc acting on the missile body during the flight. To get rid of this problem, an H_infin autopilot design based on mixed sensitivity formulation in a linear matrix inequality (LMI) framework has been carried out. As the control law computation needs all state variables, this paper proposes a nonlinear reduced order Luenberger observer for estimating the unmeasured states. It is shown through realistic practical and comparative 6-DOF simulation results that the robust design has superior performance over a nominally designed FBLC in presence of aerodynamic uncertainties and various disturbances and thus demonstrates a robust feedback linearization approach for a high maneuvering missile.