Journal of the Japan Cociety for Precision Engineerig, Vol.65, No. 2 (1999) 288-292.

New Coordinate Measuring Machine using Parallel Mechanism (2nd Report)
-Link Layout Design and Error Analysis-

Takaaki OIWA, Naomichi KURI and Shuhei BABA

Abstract

This study proposes a new coordinate measuring machine (CMM) based on a parallel mechanism consisting of closed loop link mechanism. The use of this mechanism will potentially improve the stiffness, accuracy and efficiency of the CMM. This report describes link layout design for isotropic measuring resolutions. Moreover, error analysis was performed to obtain tolerances of various mechanical parameter errors. The obtained main results are as follows. (1) When three straight lines between three spherical joints and a probe tip are perpendicular to each other, the measuring resolutions become isotropic. (2) Overlapping between the struts and those lines, the resolution variation is minimized. (3) Increase of the base radius and decrease of the stage radius and the probe length reduce the resolution variation. (4) Maximum measurement error varies in proportion as the measuring length is multiplied by the parameter error.

Key words

coordinate measuring machine, parallel mechanism, closed loop mechanism, link layout design, error analysis, isotropic point, parameter error