Task-oriented structure synthesis of a class of parallel manipulators using motion constraint generator

•Structure synthesis of parallel robots with motion constraint leg is presented.•The motion space of end-effector is fully defined by the motion constraint leg.•The synthesized mechanisms are non-overconstrained.

This paper presents a systematic approach for the structure synthesis of a class of parallel manipulators with a motion constraint leg, which is so-called the motion constraint generator. Based on the given number of degrees of freedom, the motion type, and the specific motion requirements of the end-effector, a family of parallel manipulators made of one motion constraint leg and a set of auxiliary actuation legs can be systematically generated. Since the synthesis method adheres to the general mobility criterion throughout the design procedure, all the obtained PMs are naturally non-overconstrained. A number of examples for synthesizing some 2-, 3-, 4-, and 5-DOF parallel manipulators are provided. It shows that the synthesis procedure is fairly simple owing to the design concept of constructing the parallel mechanisms from its serial counterparts. Such a concept also suggests a rational way for the decoupled design of parallel manipulators.