Development and error analysis of metamorphic parallel manipulators

A new type of hyper-redundant metamorphic parallel manipulator arm was proposed. It was based on the 3-PUPS parallel mechanism and it could change its configuration by locking driving joints. Error modeling and analysis of the manipulator were done, and the positioning error of the manipulator's experimental prototype was measured by a calibration system. First, the design idea of manipulator metamorphosis by locking driving joints was proposed so it could change its configuration and performance according to the requirements of the task. Then, using the closed loop vector loop method with error sources, the manipulator's error vector model was established, and the influence of each error source on the moving platform's output errors was analyzed. In addition, according to the influence of each error source on the output errors, the machining accuracy, grade, and tolerances of the manipulator's parts were determined. Based on these, the manipulator's experimental prototype was developed. Finally, the experimental prototype's errors were measured by a high precision calibration system for industrial robots. The experimental results show: the position errors of the manipulator's moving platform were between 0.005 mm and 0.003 8 mm, and the attitude errors were between 0.010° and 0.044°. The position errors were slightly higher than the position repeatability (0.05 mm) of the general industrial robot, and the attitude errors were equivalent to the attitude repetition positioning accuracy (0.045°) of the general industrial robot. © 2018, Science Press. All right reserved.