New Family of 3-DOF UP-Equivalent Parallel Mechanisms with High Rotational Capability

Wei Ye,Qin-Chuan Li,Xin-Xue Chai

doi:10.1186/s10033-018-0201-1

Wei Ye, Qin-Chuan Li + Show 1 more

Open Access

https://doi.org/10.1186/s10033-018-0201-1

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Abstract

Parallel mechanisms (PMs) having the same motion characteristic with a UP kinematic chain (U denotes a universal joint, and P denotes a prismatic joint) are called UP-equivalent PMs. They can be used in many applications, such as machining and milling. However, the existing UP-equivalent PMs suffer from the disadvantages of strict assembly requirements and limited rotational capability. Type synthesis of UP-equivalent PMs with high rotational capability is presented. The special 2R1T motion is briefly discussed and the fact that the parallel module of the Exechon robot is not a UP-equivalent PM is disclosed. Using the Lie group theory, the kinematic bonds of limb chains and their mechanical generators are presented. Structural conditions for constructing such UP-equivalent PMs are proposed, which results in numerous new architectures of UP-equivalent PMs. The high rotational capability of the synthesized mechanisms is illustrated by an example. The advantages of no strict assembly requirements and high rotational capability of the newly developed PMs will facilitate their applications in the manufacturing industry.

Highlights

Among the various lower mobility parallel mechanisms(PMs), those with two rotational and one translational motion(2R1T) are useful and can be implemented in many applications
A PU-equivalent Parallel mechanisms (PMs) can perform three degrees of freedom (3-DOF) motion that is identical to the end motion
There were few PU-equivalent PMs until the authors of this paper systematically investigated their type synthesis [5]

Summary

Introduction

Among the various lower mobility parallel mechanisms(PMs), those with two rotational and one translational motion(2R1T) are useful and can be implemented in many applications. We attempt to invent new architectures of UP-equivalent PMs with high rotational capability and low geometrical condition requirements. Considerable progress has been made in terms of the general method for type synthesis of lower-mobility PMs [14,15,16,17,18,19,20,21,22,23,24,25,26,27], and some 3T or 3T1R PMs with specified kinematic properties have been proposed [28,29,30,31,32], few architectures of UP-equivalent PMs without spherical joints and strict assembly requirement have been disclosed.

Special 2R1T Motion

Special Case

Limb Bond of UP‐Equivalent PMs

Inverse Position Solutions and Jacobian Matrix

Conclusions