Control of centrally-powered variable pitch propeller quadcopters subject to propeller faults

Research into variable pitch propeller (VPP) quadcopters has seen a marked increase in recent years which is due to their enhanced dynamic capabilities compared to conventional fixed pitch propeller quadcopters. Adding actuators to control the pitch angles of the propellers increases the mechanical complexity and hence may increase the risk of faults. In this paper, the flight control of a centrally-powered VPP quadcopter in the presence of a propeller fault is studied. This problem has not been studied in the literature. In this paper firstly the balance trajectory is analysed. The uncontrollable mode is identified next. Finally, a linear controller is proposed. It is shown that the yaw angle and angular velocity become uncontrollable in the presence of a VPP fault, yet the quadcopter can still accurately track a desired trajectory. It is also discovered that the quadcopter exhibits different and favourable behaviour, such as slow self-spinning speed. The relationship under certain parameter conditions is analysed and the parameter conditions that lead to zero self-spinning are identified. Our analysis could contribute to the development of high-performance quadcopters that are both agile and robust with respect to faults. Simulation results are presented to verify the theoretical findings.