An MRAC System for Aircraft Longitudinal Control

The paper proposes a scheme for implementing an adaptive controller design based on Lyapunov stability critarion. Aircraft T.F. consisting of one zero and a complex conjugate pair of poles is considered. The model has also similar structure but the poles are based on HQR considerations. The controller uses analog filters for generating derivatives whereas the parameters are computed and updated by a digital means. The scheme is thus differentiator free. The performance of the scheme has been evaluated by simulating aircraft dynamics plus filters on an Analog computer and then interfacing it to a general purpose Instrumentation & Control digital computer. The results show satisfactory response under widely different Aircraft T.F. including one having an unstable pole.