Analysis and optimization of measuring space for the 3-PSS parallel CMM

A new type coordinate measuring system based on 3-PSS parallel mechanism was proposed in this paper, which could realize 3D measurement with only one linear grating and one precision guideway. Firstly, 6-bar forward kinematic model was achieved as CMM measurement model. Then, the workspace of the parallel CMM was discussed in detail. As parallel structure, the workspace was worked out by the limit boundary searching method. Theory and experiment has verified that different point in workspace carries different measuring accuracy in the CMM, so, the paper explored measuring space based on the workspace with an of 0.02mm measurement accuracy as target. Finally, structural parameters of the parallel CMM was researched and optimized, which keeps balance between measurement accuracy and big measuring space. Compared to the manufactured prototype parallel CMM, the new design can generally enlarge 130% the cross-sectional area of measuring space.