A new approach for fault tolerance/disturbance rejection control

A new scheme of incorporating the fault tolerance and disturbance rejection in an existing flight control system is proposed. Method to design a standalone compensator is suggested which is added to the original system in order to guarantee the system stability and performance in the presence of fault or disturbances. Thus the controller, which is designed separately considering all the design parameters giving desired closed loop system response, has been augmented for the larger range of disturbances/fault. The degraded system performance is compensated by the compensator which comes into effect only after the fault / disturbance residual error increases to a certain pre-defined level. Neural network control is utilized to develop the compensator in order to introduce the dynamical handling of the error. This new controller scheme solves the traditional control conflict between the high performance and robustness. It also guarantees the stability of the system in presence of the disturbances. Longitudinal model of a unmanned aerial vehicle (UAV) is chosen for the simulations and the results prove the efficacy of the new approach.