Distribution of position and orientation errors for a 6-UPS parallel machine tool

Abstract

A forward kinematics analysis for Stewart mechanism was extremely difficult, so the error analysis can not be carried out easily because it depended on forward kinematics solutions. To estimate the manufacturing accuracy of 6-UPS parallel machine tool BJ-04-02(A), which adopted a cross-link variation of Stewart mechanism as feeding mechanism, the principle of reverse thinking was adopted, thus the accuracy can be reflected by the change of link length for given pose(position and orientation) errors of cutter-platform. For each position point and orientation in workspace, the length changes of six actuating links were calculated for given pose errors of cutter-platform. Then the pose error limits of cutter-platform caused by link length unit error were obtained by extremum and reciprocal calculation. Finally the distributions of pose errors in workspace were provided.