MOTION CONTINUITY AND BRANCH IDENTIFICATION OF TWO-DOF SEVEN-BAR PLANAR PARALLEL MANIPULATORS AND LINKAGES

Jun Wang, Kwun-Lon Ting, Yajing Gong, and Hongxiu He

Keywords

Mobility, branch, motion continuity, multiple-loop linkages, two-DOF seven-bar parallel manipulators, joint rotation space

Abstract

Motion continuity or branch identification is a troublesome topic in manipulators and linkages design as well as robot navigation programming and motion control. A manipulator or linkage must be transformed continuously between discrete positions or configu- rations. The paper presents a simple model based on joint rotation space (JRS) and followed by algebraic expressions to explain and describe the formation and identification of branches (i.e., circuits, assembly modes or configuration spaces) and motion discontinu- ity of two-DOF planar seven-bar parallel manipulators. It also presents an algorithm for branch or motion continuity automatic identification among discrete positions. The branches of all three types of seven-bar chains may be understood and identified by this method. The analytical approach can be implemented with automated computer-aided motion continuity rectification, which is explained with examples. The research can be used to design the two-DOF parallel manipulators with desire workspace or for precise motion control.

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