Kinematics automatic calibration method for parallel machine tool

Taking Stewart Parallel Machine Tool(PMT) as object,a novel automatic calibration strategy was proposed to improve the efficiency of calibration.The ball bar was designed to obtain the errors of the distance between two spheres throughout the PMT's workspace,and then the error transformation model was set up which was used to relate the errors of the distance between two spheres to PMT's geometrical parameter errors.Scheme of the automatic data acquisition was presented and the special calibration software was developed to realize the integration of data acquisition,data processing analysis and PMT parameter compensation.Above-mentioned studies were applied in calibration of the Stewart-based PMT used for machining the turbine vane.After two calibrations,the kinematics position errors of the PMT were controlled within 0.02mm in the workspace.