Fuzzy gain scheduling for flight control laws

The state-of-the-art methodology for the design of digital flight-by-wire flight control laws is based on dimming and linearization of a nonlinear aircraft model at selected operating points and subsequent tuning of linear control laws. Despite recent advances in the development of computer-aided control design toots, selection of the operating points and the design of the gain schedule still has to be done manually, in a heuristic manner. In order to reduce the design effort, an automated procedure has been developed. The number of operating points and their locations are determined automatically on the basis of the changes in the aerodynamics over the flight envelope, by using fuzzy clustering. This approach also directly provides the interpolation mechanism (membership functions) for the local control law parameters. The procedure has been developed in close cooperation with airframe and control system manufacturers and was evaluated in pilot-in-the-loop flight simulator tests.