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Research Papers

Mobility Change in Two Types of Metamorphic Parallel Mechanisms

[+] Author and Article Information
Dongming Gan

 Beijing University of Posts and Telecommunications, Beijing 100876, P. R. C.; King’s College London, University of London, Strand, London WC2R2LS, UK

Jian S. Dai

King’s College London, University of London, Strand, London WC2R2LS, UK

Qizheng Liao

 Beijing University of Posts and Telecommunications, Beijing 100876, P. R. C.

J. Mechanisms Robotics 1(4), 041007 (Sep 18, 2009) (9 pages) doi:10.1115/1.3211023 History: Received December 11, 2008; Revised May 18, 2009; Published September 18, 2009

This paper presents a new joint coined as the rT joint and proposes two types of metamorphic parallel mechanisms assembled with this rT joint. In the first type, the mechanism changes its topology by turning the rT joints in all limbs into different configurations. This change in mobility is completed by two cases illustrated by a 3(rT)PS metamorphic parallel mechanism having variable mobility from 3 to 6 and a 3(rT)P(rT) parallel mechanism having various configurations including pure translations, pure rotations, and mobility 4. In the second type, a central strut with the rT joint is added in a parallel mechanism. The variable mobility of the mechanism results from the topological change of the central (rT)P(rT) strut. This is illustrated in a 3SPS-1(rT)P(rT) metamorphic parallel mechanism, which changes its mobility from 4 to 5. It is demonstrated in mobility analysis that the change in local mobility of each limb results in the change in the platform mobility that a metamorphic process can be achieved. This particular analysis leads to advancement of improved Grübler–Kutzbach criterion by introducing the local mobility factor in the mobility analysis.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

Grahic Jump Location
Figure 1

A traditional Hooke’s joint

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Figure 3

Groove-fixed and bracket-fixed configurations of the rT joint

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Figure 4

3(rT)b2PS parallel mechanism

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Figure 5

The coordinate systems and (rT)b2PS limb

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Figure 6

Summary of the topological changes of 3(rT)PS

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Figure 7

1(rT)b1PS-2(rT)b2PS parallel mechanism and (rT)b1PS limb

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Figure 8

3(rT)g1P(rT)g3-pure rotation

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Figure 9

3(rT)g1P(rT)g2-pure translation

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Figure 11

3SPS-1(rT)b2P(rT)b2 parallel mechanism and (rT)b2P(rT)b2 central strut

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Figure 12

3SPS-1(rT)b1P(rT)b1 and (rT)b1P(rT)b1 central strut

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