Test Bench Study on Attitude Estimation in Ground Effect Region Based on Motor Current for In-Flight Inductive Power Transfer of Drones

To overcome the short flight duration of drones, research on in-flight inductive power transfer has been recognized as an essential solution. Thus, it is important to accurately estimate and control the attitude of the drones which operate close to the charging surface. To this end, this paper proposes an attitude estimation method based solely on the motor current for precision flight control in the ground effect region. The model for the estimation is derived based on the motor equation when it rotates at a constant rotational speed. The proposed method is verified on the simulations and experiments. It allows simultaneous estimation of altitude and pitch angle with the accuracy of 0.30$\hspace{0.5mm}$m and 0.04 rad, respectively. The minimum transmission efficiency of the in-flight power transfer system based on the proposed estimation is calculated as 95.3 %, which is sufficient for the efficient system.