In this paper, fault detection and fault-tolerant control strategies are proposed to handle the issues of both actuator faults and disturbances in a hexacopter. A dynamic model of a hexacopter is first derived to develop a model-based fault detection system. Secondly, the altitude control based on a sliding mode and disturbance observer is presented to tackle the disturbance issue. Then, a nonlinear Thau observer is applied to estimate the states of a hexacopter and to generate the residuals. Using a fault detection unit, the motor failure is isolated to address the one or two actuator faults. Finally, experimental results are tested on a DJI F550 hexacopter platform and Pixhawk2 flight controller to verify the effectiveness of the proposed approach. Unlike previous studies, this work can integrate fault detection and fault-tolerant control design as a single unit. Moreover, the developed fault detection and fault-tolerant control method can handle up to two actuator failures in presence of disturbances.
Keywords: Thau observer; fault diagnosis; fault-tolerant control; hexacopter; sliding mode control.