Workspace and Mobility of a Closed- Loop Manipulator

Abstract

This paper examines the geometry of a group of closed-loop manipulators with structures based on a planar, revolute jointed, five-bar chain. Of primary interest is the influence of the link lengths on the reachable workspace of the manipula tor. Unlike the commonly used open-loop manipulators, the entire workspace for a closed-loop manipulator will not be freely reachable, in general. The issues pertaining to the independent mobility of the driving links are discussed at length. A classification is made based on mobility criteria, and these mechanisms are further categorized into two types depending upon the influence of the link lengths on the ma nipulator's workspace. Based on this analysis, some general guidelines are laid down to assist the designer in making rational choices in selecting manipulator link lengths.