A study on tolerances design of parallel link robots based on mathematical models

Abstract

Parallel link robots are now being applied to various assembling tasks for small products and components. One of the important issues for design of the parallel link robots is to improve their kinematic motion deviations due to the complex link structures. The kinematic motion deviations of the parallel link robots are deeply influenced by the geometric deviations of the components, such as joints and links. A systematic design method is required for specifying suitable geometric tolerances of the joints and the links, in order to improve the kinematic motion deviations of the parallel link robots. The objective of the present research is to establish a computer-Aided design system for specifying a suitable set of the geometric tolerances of the components considering the trade-off between the requirements on the kinematic motion deviations and the ease of the manufacturing processes. A mathematical model is formulated to represent the standard deviations of the kinematic motions of the end effectors, based on the tolerance values of the joints and the links. A systematic method is proposed here, by applying an optimization method, to determine a suitable set of the tolerance values of all the joints and the links under the constraints on the kinematic motion deviations of the end effectors. The method is applied to some design problems of the geometric tolerances of the parallel link robots.