Analysis of Positional Error due to Joint Clearances in Four Bar Mechanism

摘要

Closed link mechanisms are widely used in machines and manipulators. The presence of clearance at the joints in mechanisms is inevitable. Joint clearance produces positional deviation along with other effects like vibration and wear. It is needed to study its effect as positional deviation caused due to it is unpredictable and random. It is needed to model possible highest positional error due to joint clearance and identify respective positions of mechanisms in workspace. This paper presents formulation of joint clearances in single-DOF planar mechanism. An orientation of coupler and follower is obtained for respective position of input link. Each clearance link is allowed to rotate fully about respective pivot centre. Shift in joint positions and mathematical expression of its motion is obtained. Formulation is implemented through soft computing. Highest positional deviation of coupler point with and without joint clearance is anticipated. It is observed that maximum error at any point on coupler is almost equal to sum of error due to individual joint clearances with almost equal contribution of all joint clearances in total error.