UAV fault-tolerant control by combined L1 adaptive backstepping and fault-dependent control allocation

This paper presents an approach to obtain fault tolerance in the nonlinear longitudinal motion control of an aircraft. The approach uses an L₁ adaptive backstepping controller and fault-dependent control allocation to obtain such tolerance. In the nominal fault-free case, only the elevator will be active. The L₁ adaptive backstepping controller provides some robustness to the system by handling uncertainties, which is utilized for fault accommodation if a partial fault occurs. Also, control allocation is used to redistribute control to other available healthy actuators to make the system fault tolerant against more severe faults and even to a total loss of the elevator. Simulations have been conducted on a model of a Cessna 182 and show excellent results for both the nominal and faulty scenarios.