The effects of joint clearance on position and orientation deviation of linkages and manipulators

The paper presents a novel and simple approach to identify the worst position and direction errors due to the joint clearance of linkages and manipulators. It shows and proves that in a single loop linkage, joint clearances with the same value contribute equally to the direction deviation, and when used as a manipulator, the position error due to the joint clearance is always within an area enclosed by two four-bar coupler curves and two circular arcs. The method offers a geometrical model to explain and assess the output position or direction variation, to predict the limit of position uncertainty, to determine the maximum clearance, and hence to warranty the safety or precision of a mechanism. It can be used directly in any single closed loop linkage or manipulator and can also be extended to some multiloop linkages, (C) 1999 Elsevier Science Ltd. All rights reserved.