Position error modeling and accuracy evaluation of n-DoF translational parallel manipulators that can be transformed into n four-bar mechanisms based on motion/force transmissibility

Abstract

Accuracy is one of the most important properties for manipulators, and sensitivity analysis combined with tolerance allocation is usually used for ensuring their accuracy in the design stage. However, the improvement of tolerance grade is limited by manufacturing cost and processing technology level. For parallel manipulators, there are generally more joints than the serial ones, and the requirement for cost-efficient design is in urgent need. This paper focuses on error modeling, evaluating and improving the accuracy of parallel manipulators. Firstly, the error models based on motion/force transmissibility are established for translational parallel manipulators. The influence of motion/force transmissibility on theoretical accuracy is revealed. The result indicates that the position error of the parallel manipulator is inversely correlated with the output transmissibility of each limb. According to the established error models, the accuracy evaluation indices are proposed and used for accuracy optimization of the parallel manipulator via dimensional synthesis. The comparison before and after optimization shows that the optimized parallel manipulator has higher simulation accuracy. This work provides a new idea for the accuracy investigation of parallel manipulators.