Periodic Model-Following For The Control-Configured Helicopter

A technique for designing flight control systems for rotorcraft that allows inclusion of the periodic terms in the rotor dynamics equations is described. The method is based upon an extension of optimal control theory, and permits incorporation of desired response behavior in terms of a dynamic model of the ideal closed-loop system. It is shown that the procedure is numerically simple, requiring at most two integration passes through the linearized dynamics equations, representing two rotor cycles. Sample calculations are presented for a simplified two-bladed helicopter indicating the various trends with choice of response model structure. Finally, implementation issues concerning the resulting periodic feedback structures are discussed.