Autonomous Control of UAV for Proximity Tracking of Ground Vehicles with AprilTag and Feedforward Control

Recently, various tracking flight techniques of unmanned aerial vehicle (UAVs) have been developed and used in various applications. However, a proximity tracking flight is still challenging because accurate estimation of the position and velocity of a target ground vehicle (GV) is difficult. This paper presents an autonomous UAV system that can fly close to GVs. If the relative position between the UAV and GV was used for flight control and velocity was not used, the tracking can be unsuccessful. To address this issue, the speed of the ground vehicle was also estimated, and it was feedforwarded into the control loop. Real flight experiments showed that this approach greatly improved the tracking performance; the UAV tracked the GV driving at approximately 4 m/s with an average displacement error of less than 1 m.