BIFURCATION-ANALYSIS OF EIGENSTRUCTURE ASSIGNMENT CONTROL IN A SIMPLENONLINEAR AIRCRAFT MODEL

Aircraft systems are highly nonlinear and time varying. High-performan ce aircraft at high angles of incidence experience undesired coupling of the lateral and longitudinal variables, resulting in departure from normal controlled flight. The construction of a robust closed-loop co ntrol that extends the stable and decoupled flight envelope as far as possible is pursued. For the study of these systems, nonlinear analysi s methods are needed. Previously, bifurcation techniques have been use d mainly to analyze open loop nonlinear aircraft models and to investi gate control effects on dynamic behavior. Linear feedback control desi gns constructed by eigenstructure assignment methods at a fixed flight condition are investigated for a simple nonlinear aircraft model. Bif urcation analysis, in conjunction with linear control design methods, is shown to aid control law design for the nonlinear system.