Robotized peg-in-hole task involving the needle-like and pill-like objects with tight tolerances

Handling and assembly of the needle-like and pill-like objects is a delicate task, particularly if tight clearances are involved. In both cases the key issue is a compromise between the opposite requirements of holding firmly the object and, at same time, allowing it to have the adequate properties of passive compliance. In this paper we describe our approach to achieving this for both type of objects using the sensors with soft contact surfaces (SwSCS). For insertion of needle-like objects we take advantage of using soft rubber layers placed on top of the sensors composed in such a way to ensure the object's desired behaviour. During assembly we applied variable grasping force to overcome critical situations when the object motion inside the hole is limited by clearance while the resolution of the robot's motion is lower compared to it. In case of the pill-like object we constructed a special device for parallel grasping, to decouple the sensor cells for sensing forces in the grasping phase from those involved in the assembly itself. Both approaches were successfully tested by experiment.