Actuator Fault Detection in Centrally Powered Variable-Pitch Propeller Quadrotor Vehicles

Centrally powered variable-pitch propeller(VPP) quadrotors have a single motor that transfers power to all four rotors through a transmission mechanism. All four rotors have their respective blade pitch servo motors controlling the pitch of rotor blades. Unlike conventional quadrotors, these quadrotors are controlled only by varying the pitch angle of each propeller blades. In this work, we have focused on two types of actuator faults common in these type of quadrotors: a Lock-in-Place(LIP) type of failure in rotor blades and Loss of Effectiveness(LoE) of rotor blades. In a LIP failure, the servo motor controlling the blade pitch angle freezes at a position. It does not respond to commands from the flight controller, making the thrust from that rotor constant. In Loss of Effectiveness failure, the actuator responds less or more to the commanded signal. To detect such faults under hover and normal flight conditions, we propose a non-linear observer-based fault detection method. In this method, we design a Thau observer-based residual generator where the generated residuals are used to detect the actuator fault in the quadrotor. The proposed method is simulated under different levels of fault conditions, and the presented results show the designed method’s efficacy.