External force control of an industrial puma 560 robot

Abstract

Abstract Deformations occurring in a robot working in contact with a rigid environment is a real problem in the industrial world. This problem can be solved by taking into account forces undergone by the robot at the end‐effector level. The first part of this article is aimed at determining a force control scheme that satisfies this constraint and that can be implemented on a non‐modified industrial robot controller. Various existing force control schemes are investigated and the reasons for discarding them are given. Then, the emphasis is put on a so‐called external force control scheme, which seems to be a solution to our problem. The control law appearing in such a scheme is determined by means of a realistic robot simulator developed on a SUN workstation. A simple integral term on the force error gives acceptable results in various robot configurations. This is illustrated in the form of graphs. In a second part, the implementation of this external control scheme in a real PUMA 560 robot's UNIMATE controller is presented. Certain software issues and implementation solutions are pointed out. Several experiments are described. Once again, graphs are used to show the experimental results. © 1994 John Wiley & Sons, Inc.