Type Synthesis of 3-DOF multi-mode translational/spherical parallel mechanisms with lockable joints

Xianwen Kong,Yan Jin

doi:10.1016/j.mechmachtheory.2015.04.019

Xianwen Kong, Yan Jin

Open Access

https://doi.org/10.1016/j.mechmachtheory.2015.04.019

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Abstract

A 3-DOF (degrees-of-freedom) multi-mode translational/spherical PM (parallel mechanism) with lockable joints is a novel reconfigurable PM. It has both 3-DOF spatial translational operation mode and 3-DOF spherical operation mode. This paper presents an approach to the type synthesis of translational/spherical PMs with lockable joints. Using the proposed approach, several 3-DOF translational/spherical PMs are obtained. It is found that these translational/spherical PMs do not encounter constraint singular configurations and self-motion of sub-chain of a leg during reconfiguration. The approach can also be used for synthesizing other classes of multi-mode PMs with lockable joints, multi-mode PMs with variable kinematic joints, partially decoupled PMs, and reconfigurable PMs with a reconfigurable platform.

Highlights

To develop reconfigurable manufacturing systems with a short changeover time, multi-mode PMs ( PMs with multiple operation modes or disassembly-free reconfigurable PMs) have received much attention from researchers since 2007 [1,2,3,4,5,6,7,8]
The DIRECTOR has two 3-DOF operation modes: Operation Mode 1 — PPR equivalent mode — in which the moving platform rotates about an axis parallel to Y-axis that translates along the O-YZ plane, and Operation Mode 2 — E equivalent mode — in which the moving platform undergoes planar motion or rotates about an axis parallel to X-axis that translates along the O-YZ plane
Step 2c For each set of mc non-lockable joints obtained in Step 2b, insert 1(=mA − mc = 5 − 4) lockable joint, denoted by A, that together with the 4 non-lockable joints satisfy the conditions for legs for translational PMs and 1(=mB − mc = 5 − 4) lockable joint, denoted by B, that together with the 4 non-lockable joints satisfy the conditions for legs for spherical PMs

Summary

Introduction

To develop reconfigurable manufacturing systems with a short changeover time, multi-mode PMs (parallel mechanisms) ( PMs with multiple operation modes or disassembly-free reconfigurable PMs) have received much attention from researchers since 2007 [1,2,3,4,5,6,7,8]. The approach to the type synthesis of multi-mode PMs without lockable joints [4,8] and single-loop mechanisms with two operation modes [17] will be further developed for synthesizing multi-mode PMs with lockable joints During reconfiguration, such multi-mode PMs may avoid both constraint singular configurations, which multi-mode PMs without lockable joints suffer [4,8], or self-motion of a sub-chain, which the metamorphic PMs using reconfigurable joints or variable-axis joints [12,13] encounter. S virtual chain (a) Spatial translation pattern: PPP (b) Spherical motion pattern: S virtual chain As it will be shown, the approach can be extended for synthesizing multi-mode PMs with variable kinematic joints, partially decoupled PMs, and reconfigurable PMs with a reconfigurable platform. There is no upper bound on m in theory, it is recommended to set m ≤ minðmA þ mB; 6Þ: ð5Þ

Center of rotation

Discussion

Conclusions