Autonomous swing-angle estimation for stable slung-load flight of multi-rotor UAVs

This paper presents a practical swing-angle estimation method for slung load operations of the multi-rotor unmanned aerial vehicle (UAV), which is essential to maintain the safety during the operation. In order not to rely on extra sensors for monitoring the swing angle, the proposed method in this paper offers an autonomous swing-angle estimation using only an inertial measurement unit (IMU) and a single load cell attached to the slung load. The disturbance observer (DOB) derived external force estimation is performed to estimate the swing angle. The unique structure of the proposed DOB-based disturbance force estimation technique utilizes the IMU data only. Both simulation and actual experiment are performed to validate the feasibility of the proposed algorithm.