Basic Study on Regenerative Air Brake Using Observer-based Thrust Control for Electric Airplane

Research and development have been very active in electric airplanes (EAs). EAs use electric motors as the power source; therefore, EAs are expected to achieve more secure, more efficient, and more eco-friendly aviation. The conventional airplanes use mechanic air brakes such as spoilers to adjust the descent angle; however, they are difficult to control even for a skilled pilot. Previous research showed that electric motors enable EAs to regenerate their potential energy while descending as the windmilling propeller produces negative torque and thrust. This negative thrust works as a substitute air brake, called regenerative air brake. This paper proposes the thrust control method of regenerative air brake for automatic descent. Furthermore, the observer-based thrust estimation method is also proposed since adding force sensors decreases the stiffness of the thrusters. The effectiveness of the proposed method is verified by simulations and experiments in the wind tunnel.