High gain H/sub ∞/ feedback control for an anti-air missile

Abstract

A singular perturbation approach is applied to characterize the properties of linear time invariant high gain feedback systems with additive disturbance. Using the two time scale property of the high gain system, the near optimum high gain H/sub /spl infin// state regulator is the composition of the slow subsystem H/sub /spl infin// state regulator and the fast subsystem LQ state regulator. This approach is used to design an angle of attack command autopilot for an anti-air missile. The solution to the near optimal high gain H/sub /spl infin// state feedback is shown to be equivalent to the solution of the slow H/sub /spl infin// state feedback problem and the fast LQ state feedback problem. For sufficiently large /spl gamma/, the conditions for the existence of solutions are shown to be equivalent to the existence conditions for the high gain LQ problem. Moreover, the optimality of H/sub /spl infin// composite control system with respect to the H/sub /spl infin// performance measure is equivalent to the optimality of the LQ composite control with respect to the LQ performance measure, for /spl epsiv/ sufficiently small. Finally, the simulation results show that the high gain H/sub /spl infin// autopilot is comparable to the high gain LQ autopilot. However, for the 180/spl deg/ manoeuvre in the presence of turbulence the H/sub /spl infin// autopilot exhibits slightly better disturbance rejection properties. >