Adaptronic Revolute Joints for Parallel Robots Based on Simultaneous Quasi-Statical Axial and Radial Clearance Adjustment

Robots based on parallel kinematics feature low moved masses, allowing for better dynamic performance compared to serial mechanisms. Otherwise, the known drawbacks, like occurrence of singularities or bad radio of work space to installation area, hinder their fully industrial establishment. In order to overcome some of these drawbacks, development of specific and optimized robot components, like rods or joints, becomes necessary. Development of joints for parallel robots is determined by numerous contradictory requirements which cause different goal conflicts. In this work, possibilities for dissolving of such goal conflicts by means of adaptronic joints (joints with integrated piezo-actuators) are discussed. To deal with these complex issues this paper focuses on three major areas: firstly, conventional joint concepts, including their main flaws; secondly, new, adaptronic joint concepts based on quasi-statical clearance adjustment with two laboratory prototypes and their improvements over the old solutions; thirdly and finally, some of possible consequences of the new joint concepts for the overall performance of parallel robots. By drawing on experimental results derived from laboratory tests, it is possible to show how implementation of the developed joint prototypes could influence friction characteristic of the whole robot system.Copyright © 2008 by ASME