Analytical modeling and analysis of the clearance induced orientation error of the RAF translational parallel manipulator

Abstract

SUMMARYThis paper deals with the analytical modeling and the analysis of the orientation error of the RAF translator due to the clearances in the joints. This model presents the orientation error as a function of the nominal pose, the external load applied to the platform, the manipulator structural parameters, and the joints clearances. Based on this model, an algorithm is developed in order to map the pose error within a desired workspace of the manipulator. It is shown that the orientation error variation depends essentially on the parallelogram configuration of the passive legs out of its plane. The orientation error magnitude is mainly caused by the parallelogram revolute joints radial clearances. Moreover, the orientation error around the z-axis presents some discontinuities due to the contact mode change of the parallelogram revolute joints.

Precision comparison of two 3-DoF translational parallel manipulators based on the orientation errors due to joint clearances

“…For the RAF manipulator, the static model is already developed ( [11,29] present more details). If a τ ext = [F M] T is applied to O p , the forces will be transmitted by the SPS legs and the moments will be supported by the PKL legs (Fig.…”

“…The accuracy of parallel mechanism can be altered by the uncertainties of the geometric parameters, joint clearances or both of them [4,5,[8][9][10][11][12][13][14]. Indeed, Al-Widyan et al [4] proposed a statistical approach to determine the optimum clearances of the unactuated cylindrical joints for the 3-DOF spherical manipulators.…”

“…In fact, the Interval Analysis method has been used to verify the efficiency of this method. The static model of the isostatic parallel manipulator and the virtual work principle have been adopted to determine an analytical model of the pose error of the platform due to the clearance in the passive joints [2,[9][10][11]. Sun et al [12] considered the epistemic and random uncertainty to introduce a general method of kinematic accuracy analysis of mechanisms with clearance.…”

Motion Reliability Analysis of the Delta Parallel Robot considering Mechanism Errors

“…The paper addressed the kinematic accuracy problem of the proposed new parallel robot with three legs due to the location of the U joint errors, clearance, and driving errors. Chouaibi's paper showed that the orientation error variation depends essentially on the parallelogram configuration of the passive legs out of its plane [13].…”

The effects of joint clearance on the dynamics of the 3RRR planar parallel manipulator

“…The problem of modeling joints with clearance in the context of multibody dynamics has been the subject of extensive studies during the last few decades. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Dubowsky and Freudenstein 16,17 formulated an impact pair model to predict the dynamic response of an elastic mechanical joint with clearance. Earles and Wu 18 introduced a model based on permanent contact condition.…”