Type Synthesis of a Novel Class of One-DOF Multi-Mode Parallel Mechanisms

Abstract

Multi-mode parallel mechanisms (PMs) are a class of reconfigurable mechanisms that can switch between different operation modes without the need for disconnection and reassembly. Although a number of multi-DOF multi-mode PMs have been presented in the literature, very few 1-DOF multi-mode PMs have been proposed. This paper deals with the type synthesis of a novel class of 1-DOF multi-mode PMs, which have one 1-DOF translation mode and at least one 1-DOF planar motion mode, using a construction method by leveraging symmetry of mechanisms and merging two multi-mode mechanisms. By inserting a revolute (R) joint into Sarrus-6R like six-joint mechanisms, 1-DOF two-mode two-legged PMs, which are composed of a moving platform and a base connected by one three-joint leg and one four-joint leg, are constructed first. From each 1-DOF two-mode two-legged PM, one can construct a 1-DOF two-mode three-legged PM by adding a third four-joint leg which is the mirror image of the four-joint leg about the plane of motion of the three-joint leg. Subsequently, 1-DOF three- and four-mode three-legged PMs are constructed by merging two 1-DOF multi-mode three-legged PMs. The instantaneous DOF of the above multi-mode PMs in a transition configuration is analyzed using screw theory. This work complements the existing approaches to the type synthesis of multi-mode PMs and hybrid reconfigurable mechanisms.