A Fuzzy Control Strategy for UAV Perching using Varying Tau-dot
Wanchao Chi, Kin Huat Low, K.H. Hoon · 2016
Tau theory has been studied and applied to guide unmanned aerial vehicles (UAVs) during landing or perching in some literatures. The time derivative of tau, tau-dot, is commonly kept constant between 0 and 0.5 such that the UAV reaches the target position with its velocity and acceleration reduced to zero at the same time. In this paper, the perching flights of three parrots are first evaluated and the tau-dot is examined for each perching flight. It is found that a varying tau-dot is more likely to be observed from these perching parrots and it even varies up to 1. The varying patterns of tau-dot are further justified by the comparison between our experimental data and the theoretical formulas from literature, which shows such patterns make birds approach the target more quickly, with an acceptable final impact though. A fuzzy logic is then designed to vary the tau-dot of a perching quadrotor in real time to achieve faster safe perching. Perching experiments with a quadrotor are conducted to verify the performance of the fuzzy logic, and the applicability of the varying tau-dot as a control strategy for UAV perching is validated.