The Research Of Fault Tolerant Control Method For Unmanned Aerial Vehicle

In the process of flight and mission, unmanned aerial vehicle(UAV) attitude dynamics will inevitably be subjected to faults which can be caused by actuators, sensors or system components. Research into fault diagnosis and fault tolerant control for UAV dynamic systems has long been recognized as one of the important aspects in seeking effective solutions to an improved reliability of fault systems. This paper focuses on the investigation of the fault-tolerant control and finite-time control problems for the longitudinal model of UAV both with external disturbance, model uncertainties, input constraints and actuator faults. In this case, a fault-tolerant control approach is designed using sliding mode and adaptive techniques to guarantee the stability of the faulty UAV systems, whose faults are unknown constant actuator failures with an unknown occurred time.Firstly, a non-linear mathematical model of UAV is developed, and an analysis of the characteristics of the longitudinal model is made. Secondly, an adaptive sliding mode fault tolerant control approach is proposed for the system with actuator faults. In order to solve the problem of input constraints, a fault compensation method based fault-tolerant control law is designed. Then the proposed method is extended to the trajectory tracking control problem. To solve the time uncontrollable problem for the fault tolerant control, a terminal sliding mode control method based on finite time is designed, which realizes the track angle and speed commands tracking. Finally, aiming at the terminal sliding away from the equilibrium point of convergence speed and the actuator input constraints, an adaptive fast terminal sliding mode is investigated, which can be used to track angle command tracking. The simulation results show that the proposed control law can effectively reduce the influence of parameter uncertainties, external disturbances and actuator faults, and track to the desired trajectory fastly and accurately. It indicated that the control law has a good command tracking control performance, which provides some ideas about fault tolerant control for the UAVs with actuator faults.