Flight Control for Quadrotor Safety in the Presence of CoG Shift and Loss of Motor Efficiency

In this paper, a safety control strategy based on a novel Nonlinear Disturbance Observer (NDO) and geometric control is developed for a quadrotor Unmanned Aerial Vehicle (UAV), subject to the disturbances caused by Center-of-Gravity (CoG) shift and Loss of Motor Efficiency (LoME). The NDO is designed to estimate the disturbances in the rotational loop. The geometric attitude control approach is exploited in the rotational loop, where the desired angular velocity and acceleration are obtained by differential flatness theory. The stability of the resulting rotational close-loop is analyzed and a bounded steady-state error is achieved under derivative bounded sustained disturbances. Experiments are carried out to demonstrate the performance of the proposed safety control strategy, showing that the anti-disturbance performance can be significantly enhanced.