Disturbance Observer-based Control of Quadrotors with Motor Response Delay and Throttle Nonlinearity

This paper proposes a nonlinear disturbance observer-based controler (NDOBC) for quadrotors considering the motor response delay and the throttle nonlinear. A simplified quadrotor dynamic model which includes the attitude model and propulsion system is used to design the nonlinear disturbance observer. The NDOBC is sensitive to the motor response delay, which is founded by the experiment. Furthermore, if this is not handled appropriately, the system might go unstable. An equivalent motor response delay module is inserted between the observer and the controller output. To eliminate the influence of the throttle nonlinearity, a method is given by solving quadratic functions about the pseudo throttle. The simulation results show that the proposed method can guarantee the system stability and get a well noise suppression capability. In addition, a higher attitude control accuracy is achieved by eliminating the throttle nonlinearity.