Fault Tolerant Control Based on Thau Observer of a Reconfigurable Quadrotor with Total Loss of Actuator

In this paper, we propose a Fault Tolerant Control (FTC) strategy for a reconfigurable quadrotor with foldable arms, to deal with a total loss of one of its rotors. The proposed strategy allows adapting the configuration of the quadrotor when one of its rotors is lost. It consists of: (i) a Fault Detection and Isolation (FDI) module, (ii) a robust controller, and (iii) a reconfiguration module. The FDI module is designed based on the nonlinear Thau observer in order to detect and identify the rotors faults. Once a rotor fault is detected based on the residual analysis, the quadrotor changes its shape by rotating the two adjacent arms in the direction of damaged one in order to form a trirotor configuration. This transformation induces a variation of vehicle's center of gravity (CoG), inertia, and consequently the control matrix. To deal with this issue, a sliding mode controller (SMC) is designed based on the control allocation matrix, where the control efforts are redistributed among healthy actuators. Numerical simulations are carried out to verify the effectiveness of the proposed approach. The obtained results show that the proposed strategy is successful in controlling the damaged quadrotor by trajectory tracking.