Aerial Regrasping: Pivoting with Transformable Multilink Aerial Robot

Abstract: Regrasping is one of the most common and important manipulation skills used in our daily life. However, aerial regrasping has not been seriously investigated yet, since most of the aerial manipulator lacks dexterous manipulation abilities except for the basic pick-and-place. In this paper, we focus on pivoting a long box, which is one of the most classical problems among regrasping researches, using a transformable multilink aerial robot. First, we improve our previous controller by compensating for the external wrench. Second, we optimize the joints configuration of our transformable multilink drone for stable grasping form under the constraints of thrust force and joints effort. Third, we sequentially optimize the grasping force in the pivoting process. The optimization goal is to generate continous grasping force whilst maximizing the friction force in case of the downwash, which would influence the grasped object and is difficult to model. Fourth, we develop the impedance controller in joint space and admittance controller in task space. The advantages of aerial pivoting are twofold: saving strength for payload-limited aerial robots with ground contact; enlarging vertical workspace comparing to other manipulator. As far as we know, it is the first research to achieve extrinsic contact- aware regrasping task on aerial robots.