Bifurcation-induced limits of a controller-reconfigured F-16 subject to actuator failures

Abstract

Complex systems like the F-16 when subject to actuator failures operate in nonlinear regimes and probably in the vicinity of bifurcation points. Therefore in designing reconfigured controllers a designer must be aware of all bifurcation points, and their characteristics, within the impaired flight envelope. This work is the first step in that direction. The other limitations that were identified are the stability limits and the control saturation points. We considered both the nominal system, and the reconfigured system with the left elevator stuck. The nominal controller is designed according to the guidelines in the literature. The reconfigured controller is designed as a regulator with disturbance rejection capabilities. The bifurcations are associated with attempting to regulate the velocity and orientation of the aircraft. The main issues at the bifurcation points, in both the nominal and reconfigured system, are that the aircraft becomes uncontrollable and the control inputs become dependent.