Dodging Like A Bird: An Inverted Dive Maneuver Taking by Lifting-Wing Multicopters

It is crucial for hybrid unmanned aerial vehicles, such as lifting-wing multicopters, to plan a continuous, smooth, and collision-free trajectory to avoid obstacles. Unlike quad-copters, which typically work in indoor environments, lifting-wing multicopters typically fly at a high altitude with a high cruising speed, requiring higher maneuverability in the vertical direction. Inspired by birds, lifting-wing multicopters can take an inverted flight maneuver to gain more maneuverability than the corresponding multicopter owing to the additional lifting wing. In this paper, a rotation-aware collision-free motion planning strategy is proposed that takes aerodynamics into consideration and allows lifting-wing multicopters to fly at large rotation angles, even in inverted postures. Specifically, a collision-free state sequence is found using rotation-aware primitives by solving a graph search problem. The sequence is then refined with B-spline into smooth trajectories to be tracked by the differential flatness-based controller for lifting-wing multicopters. We analyze the proposed motion planning algorithm in different scenarios and demonstrate the feasibility of the generated trajectories in simulation and real-world experiments. Video: https://youtu.be/n87jK81zg_I