Fault - tolerant Flight Control of Quad-rotor UAV Based on Sliding Mode Theory

An active and passive sliding-mode-theory-based fault tolerant flight controller is figured out and exerted for a certain Quad-rotor UAV with propeller malfunction in this paper. First of all, the mathematical model of quad-rotor unmanned aerial vehicle (UAV) with actuator failures is deduced by Newton's Second Law of motion and Euler dynamics. Secondly, according to the different situations of actuator failures, by using integral sliding mode theory, a passive fault-tolerant flight control method is developed which include the position, altitude and attitude control loops. On this basis, an active fault-tolerant flight control method is proposed in which a failure observer is applied to real-time detect when the actuator failure will happen, and the control law is reconfigured and compensated as long as actuator failure happened in order to strengthen the fault-tolerant capability. Finally, we testify the validation of the controller by digital simulation analysis and practical flight test in the case of partial failure of the blade. The results show that both of the fault-tolerant control algorithms have strong fault tolerance performance. Whereas, compared with the passive one, the active fault-tolerant control algorithm can lower the system instability caused by the fault, it has better stability and stronger fault-tolerant capability.