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Research Papers: Design of Mechanisms and Robotic Systems

Position-Space-Based Compliant Mechanism Reconfiguration Approach and Its Application in the Reduction of Parasitic Motion

[+] Author and Article Information
Haiyang Li

Student Member of ASME
School of Engineering,
University College Cork,
Cork T12K8AF, Ireland
e-mail: haiyang.li@umail.ucc.ie

Guangbo Hao

Mem. ASME
School of Engineering,
University College Cork,
Cork T12K8AF, Ireland
e-mail: G.Hao@ucc.ie

Richard C. Kavanagh

School of Engineering,
University College Cork,
Cork T12K8AF, Ireland
e-mail: r.kavanagh@ucc.ie

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received September 4, 2015; final manuscript received June 14, 2016; published online July 21, 2016. Assoc. Editor: Charles Kim.

J. Mech. Des 138(9), 092301 (Jul 21, 2016) (13 pages) Paper No: MD-15-1618; doi: 10.1115/1.4033988 History: Received September 04, 2015; Revised June 14, 2016

This paper introduces a position-space-based reconfiguration (PSR) approach to the reconfiguration of compliant mechanisms. The PSR approach can be employed to reconstruct a compliant mechanism into many new compliant mechanisms, without affecting the mobility of the compliant mechanism. Such a compliant mechanism can be decomposed into rigid stages and compliant modules. Each of the compliant modules can be placed at any one permitted position within its position space, which does not change the constraint imposed by the compliant module on the compliant mechanism. Therefore, a compliant mechanism can be reconfigured through selecting different permitted positions of the associated compliant modules from their position spaces. The proposed PSR approach can be used to change the geometrical shape of a compliant mechanism for easy fabrication, or to improve its motion characteristics such as cross-axis coupling, lost motion, and motion range. While this paper focuses on reducing the parasitic motions of a compliant mechanism using this PSR approach, the associated procedure is summarized and demonstrated using a decoupled XYZ compliant parallel mechanism as an example. The parasitic motion of the XYZ compliant parallel mechanism is modeled analytically, with three variables which represent any permitted positions of the associated compliant modules in their position spaces. The optimal positions of the compliant modules in the XYZ compliant parallel mechanism are finally obtained based on the analytical results, where the parasitic motion is reduced by approximately 50%. The reduction of the parasitic motion is verified by finite-element analysis (FEA) results, which differ from the analytically obtained values by less than 7%.

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Figures

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Fig. 1

One degree-of-freedom translational compliant mechanisms: (a) basic parallelogram compliant mechanism, (b) compound basic parallelogram compliant mechanism, (c) basic parallelogram compliant mechanism being actuated at its stiffness center, and (d) basic parallelogram compliant mechanism with smaller in-plane thickness and larger spanning size

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Fig. 2

An XYZ compliant parallel compliant mechanism and its decomposition: (a) XYZ compliant parallel compliant mechanism, (b) BCMs and their rigid stages, (c) C-BCMs and their rigid stages, (d) basic decomposition pattern, (e) nonbasic decomposition pattern 1, and (f) nonbasic decomposition pattern 2

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Fig. 3

The global and local coordinate systems of the decomposed XYZ compliant parallel mechanism

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Fig. 4

Illustration of principal wrenches in the coordinate system O-XYZ: (a) principal wrenches and (b) linear combination of the principal wrenches

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Fig. 5

The demonstration of the possible positions of the three nonbasic ICMs through the rotations about the local X-axes: (a) the rotation of compliant module-X about the local X-axis and (b) the rotations of compliant module-X, compliant module-Y and compliant module-Z about the local X-axes

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Fig. 6

Sum of the absolute values of the parasitic rotations, ξm-rxyz, with the rotation angle α: (a) only X direction force applied, (b) only Y direction force applied, and (c) only Z direction force applied

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Fig. 7

Sum of the absolute values of the parasitic rotations, ξm-rxyz, with the rotation angles α and β: (a) only X-direction force applied (fx = 2, fy = 0, and fz = 0), (b) only Y-direction force applied (fx = 0, fy = 2, and fz = 0), and (c) forces in X-and Y-directions applied (fx = 2, fy = 2, and fz = 0)

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Fig. 8

Reconfigured XYZ compliant parallel mechanism with smaller parasitic motions

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Fig. 9

Analysis and FEA results: (a) fy = 0 and fz = 0, (b) fy = 1 and fz = 0, and (c) fy = 1 and fz = 1

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Fig. 10

An optimal design based on the reconfigured XYZ compliant parallel mechanism

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Fig. 11

An XY compliant mechanism and its basic composition pattern: (a) the XY compliant mechanism and (b) the basic composition pattern

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Fig. 12

An XY compliant mechanism reconfigured from the XY compliant mechanism shown in Fig. 11(a), via the translations of the ICMs

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Fig. 13

An XY compliant mechanism reconfigured from the XY compliant mechanism shown in Fig. 11(a), via the rotations of the ICMs

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Fig. 14

Comparison between the parasitic rotations of the XY compliant mechanisms shown in Figs. 11(a) and 13

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Fig. 15

Planar parallelogram compliant mechanism and the defined coordinate systems

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