Linear-Parameter-Varying/Loop-shaping H-infinity synthesis for a missile autopilot

The design of a gain-scheduled autopilot for a bank-to-turn missile over a wide operating range is considered. The main steps to obtain such a control ler are explained. From a modeling point of view, the required linear fract ional transformation of the gain-scheduled model is obtained by using polyn omial expressions for each varying coefficient and a multivariable reductio n procedure. Then a multivariable linear parametrically varying synthesis i s performed in the spirit of the H-infinity/loop-shaping approach: the perf ormance of the closed-loop system is defined by the use of compensators tha t depend on the altitude; this framework allows for adaptation to enhance t he performance of the system because the specifications change considerably over the flight envelope. The gain-scheduled controller is then obtained b y solving linear matrix inequalities and then reducing using again the mult ivariable reduction procedure. Lots of time- and frequency-domain analyses allow one to check the specifications: robust stability and performance ana lyses are proceeded by use of the structured singular value; nonlinear simu lations using a six-degree-of-freedom model are also performed.