Accuracy Evaluation of Parallel Mechanism Using Laser Tracking Coordinate Measuring System

In this paper, we experimentally evaluate the accuracy of parallel mechanism using Laser Tracking Coordinate Measuring System. The system has 4 tracking laser interferometers to measure the distance from retroreflector incrementally. Redundant 4 measurements enable us to identify relative location of each laser. Then the coordinate of retroreflector can be estimated precisely. We test the repeatability of parallel mechanism, and find that positioning error is less than 0.099mm. Then we calibrate the kinematic model of parallel mechanism to improve its absolute accuracy. The positions and poses of the endplate are measured and used for reference data of calibration and the kinematic parameter is modified to minimize the positioning error. Its maximum error is 0.98mm.