A robot compliant wrist system for automated assembly

Abstract

A compliant wrist combining passive compliance and a displacement sensor has been developed for a robot manipulator to be used in assembly operations. The wrist provides the necessary flexibility to accommodate transitions as the robot makes contact with the workpiece, to correct positioning error, and to avoid high impact forces in automatic assembly. Sensing from the device makes it possible to actively control the contact forces or to compensate the positioning error during motion and contact. The design features of two prototypes of the device are described. A hybrid position force control scheme using the device and incorporating the passive compliance in the design is presented. Two basic primitives in the assembly process, edge tracking and insertion operation with the compliant wrist, are investigated. A fuzzy controller is presented to assign velocity instead of evaluating force zones in insertion. The experimental results show that the system provides a feasible and economical solution to the provision of necessary compliance in automated assembly and manufacturing.