Path planning for 3-D in-hand dexterous micro-manipulation in presence of adhesion forces

Robotic manipulation of micro-objects is usually disturbed by forces that are predominant at the micro-scale such as capillary and electrostatic forces. Dexterous micro-manipulation methods that consider these effects are currently limited to planar manipulation of complex objects or 3-D manipulation of objects with simple shapes. This paper presents an original method able to generate optimal fingers trajectories for 3-D in-hand micro-manipulation of complex micro-objects. Since adhesion forces in micro-scale are usually difficult to predict, the proposed method considers the worst case where adhesion forces are overestimated when they have a disturbing effect and neglected when they contribute to stabilising the grasps. A graph of interconnected stable and accessible grasps is then built. Finally, the optimal trajectories are generated using the A* algorithm. When compared to the case where adhesion forces are neglected, the simulation results show that the computation time is shorter while the generated trajectories require more operations because of the excluded risky grasps.