Compliance-Based Robotic Peg-in-Hole Assembly Strategy Without Force Feedback

The peg-in-hole assembly is a representative robotic task that involves physical contact with the external environment. In this paper, in contrast to past research in the area, which has involved the utilization of such expensive devices as force/torque sensors or remote compliance mechanisms, an inexpensive method is proposed for peg-in-hole assembly without force feedback or passive compliance mechanisms. The method consists of an analysis of the state of contact between the peg and the hole as well as a strategy to overcome the inevitable positional uncertainty of the hole incurred in the recognition process. A control scheme was developed to yield compliant behavior from the robot with physical contact under the condition of hybrid position/force control. The effectiveness of the proposed method was experimentally verified using a robot manipulator with 8-degrees of freedom and a peg-in-hole apparatus with a small clearance (0.1 mm).