Active Autorotation of Micro Aerial Vehicle with Foldable Winged Shell for Impact Mitigation during Free Fall

Drop mitigation is an important function of micro aerial vehicles (MAVs) that are used for internal inspections of enclosed and cluttered structures (height: 5-10 m). The mechanism also allows continuous operation of drones, prevents the downtime required for maintenance and repair and also provides a safer environment for workers who are working below the drones. Some solutions include parachutes, auto-rotors, and active auto-rotors. However, these are inapplicable to MAV s with a protector shell because of their size and payload. We herein propose a new rapid response drop mitigation method for MA V s involving active autorotation with bendable wings and shells. Active autorotation enables faster deceleration during dropping motion as compared to parachutes or passive autorotation. Bendable wings can ensure optimal flight performance and enable sufficient deceleration during falling motion. This newly proposed fixture was shown to reduce the impact impulse by 32.2 % and horizontal oscillation by 34.4 %. From our flight tests conducted at heights of 5 m and 10m in both outdoor and indoor environments, the measured impact impulse for both profiles were attained at 0.93 N s. The minimum impact impulse that can cause harm to the human eye, which is the most vulnerable part, is 2 N s. Thus, this mechanism was successfully proven to provide a greater safety buffer based on the drop test conducted. We envision this mechanism to provide greater safety to drone operating environments in relevant fields involving indoor and urban drone flights. Furthermore, it can reduce damage to drones and structures and avoid injuries arising from drone crashes.