Compliant Peg-in-Hole Assembly Using a Very Soft Wrist

This paper proposes to use a high-compliance soft wrist to improve the performance of robotic peg-in-hole in uncertain environments. In contrast to past research in this field, in which force control with relatively low compliance has been used, we propose a method that searching and aligning motions can be easily realized by taking advantage of high compliance wrist under gravity. Our proposed PiH strategy is completely passive: After the peg is trapped into the hole during the hole-searching process using the spherical helix trajectory, it is guaranteed that the peg can automatically be inserted into the hole due to the effect of gravity and wrist compliance if the configuration of the peg is included in the no-escapable area. The no-escapable area can be obtained based on the potential analysis considering the contact state combined with the wrist compliance space. The effectiveness of the proposed method is experimentally verified by using the peg with various shapes and sizes.