Multi-rotor Vehicle Collision Recovery Strategies Based on Mosquitoes Survival in Raindrop Collisions

Multi-rotor vehicles are always facing the threat of collision due to the nature of low altitude flight, common solutions are perceptual obstacle avoidance algorithms and propeller protection structures, however these also fail in the event of unavoidable collisions therefore, it is necessary to study the recovery of the vehicle after a collision. In this paper, a low-cost and fast collision recovery framework is proposed, which uses extended state observer (ESO) to estimate the wrench caused by a collision and then performs collision detection and determines the type of collision based on the vehicle state. Inspired by the recovery manoeuvre of mosquitoes hit by raindrops, three new bionic-based collision recovery strategies: rolling with the trend, admittance control and collision escape are proposed to cope with different types of collisions, which enable the vehicle to present suppleness like a mosquito after a collision and mitigate the impact of the collision, and the applicable scenarios and implementation details of each collision recovery strategy are elaborated. These strategies solve the problem of active and passive collisions for most vehicles. Finally, a series of convincing collision experiments for both under-actuated and over-actuated vehicles are designed, and the vehicles are able to perform collision detection and collision recovery reasonably, and the experimental results verify the effectiveness of the collision recovery strategies.