Investigation of Positional Error in Two Degree of Freedom Mechanism With Joint Clearance

Abstract

Closed chain mechanisms are used as robotic manipulators with special features. A planar two-DOF closed loop mechanism provides desired position of an end effecter in a confined workspace with two input motions. Position of end effecter depends on various factors including joint clearance. Positional accuracy forms important parameter for kinematic analysis of mechanism. This paper presents simple approach for quantifying error due to joint clearance in a two-DOF mechanism. Generalized scheme for positional deviation with and without clearance at joint is presented. Orientation of clearance links for maximum positional error is identified. Error at various positions is quantified in relation with clearance link length. Computer programming is used as a tool to workout positional analysis of mechanism. Results show that error is independent of magnitude of clearance, however, a function of location of end effecter in workspace.

Pick and place trajectory planning of planar 3-RRR parallel manipulator in the presence of joint clearance

“…Therefore, one can assume the continuous contact model, and neglect the friction in such a joint. 1,3,11 Assuming continuous contact model, joint clearance can be defined as the difference of the radii of pin and socket. In other words, we model joint clearance as a vector, which corresponds to a massless virtual link with the length equal to the joint clearance ( Fig.…”

“…The dependency on the applied loads and dynamics as well as the discontinuities make the calibration difficult. 3,11 The effects of joint clearances on mechanism dynamics were also investigated by many researchers. 2,12 Zhang et al 13 investigated the dynamics of a planar 3-RRR parallel manipulator with multiple clearance joints.…”

“…We assume a continuous contact model at the joints, where the joint forces act in the direction of the common normal of the pin and the hole. 1,3,11 The joint clearances are modeled by some virtual links, the directions of which are determined by the Newton-Euler equations. Li et al 29,30 showed that it is accurate to approximate the angular displacement of a virtual link with the joint force direction of the corresponding ideal mechanism.…”

Force analysis as a support to computer-aided tolerancing of planar linkages

“…The screw-theory model has been extended with virtual links [43][44][45][46] and by an analogy with Kirchhoff's laws of electrical circuits [47]. Other approaches emphasizing the treatment of joint clearances include rotatability [48][49][50], dual algebra [51] and inverse kinematic [52,53]. Besides influencing the stackup of deviations, joint clearances have also a complex influence on jerk, impact and vibration of mechanisms, as widely discussed in the contexts of kinematic and dynamic analysis [54][55][56][57][58][59][60][61].…”

Deployment accuracy analysis of cable-strut deployable mechanism with joint clearances and forces constrained

“…Plenty of researchers have been devoted to studying the influence of joint clearance. Most of the studies concentrated on single-loop linkage [15][16][17][18][19][20], but the common deployable mechanisms are multi-loop linkages that have loop constraints coupling and complicated topology structure [21,22]. The analytical method used in single-loop linkage may not be applicable to it on account of challenges of highly nonlinear and strong coupling.…”