Identification of F/A-18 model from flight tests using the fuzzy logic method

A mathematical model relating control to structural deflections of an F/A-18 modified aircraft was determined in the Active Aeroelastic Wing technology program. Five sets of signals from flight flutter tests corresponding to the excited inputs were measured at NASA Dryden Flight Research Center. These inputs were: differential ailerons, collective ailerons, collective stabilizers, differential stabilizers, and rudders. The signals used to build this new model are of two types: control deflections and their corresponding structural deflections on the wing and trailing edge flap’s time histories. The fuzzy logic method was used for the identification of the aircraft nonlinear model for sixteen flight test cases dependent on Mach numbers between 0.85 to 1.30, and altitudes between 5,000 and 25,000 ft. Based on comparisons between the results obtained with four different input data systems (six, twelve, fifteen and twenty-one), we conclude that the best results, in terms of our pre-established specifications, were obtained for the twelve-input system.