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RESEARCH PAPERS

Optimal Synthesis of Compliant Mechanisms Using Subdivision and Commercial FEA

[+] Author and Article Information
Patrick V. Hull

 NASA/Marshall Space Flight Center, Huntsville, AL 35812

Stephen Canfield

Department of Mechanical Engineering, Tennessee Technological University, Cookeville, TN 38505scanfield@tntech.edu

J. Mech. Des 128(2), 337-348 (May 06, 2005) (12 pages) doi:10.1115/1.2159026 History: Received July 02, 2004; Revised May 06, 2005

The field of distributed-compliance mechanisms has seen significant work in developing suitable topology optimization tools for their design. These optimal design tools have grown out of the techniques of structural optimization. This paper will build on the previous work in topology optimization and compliant mechanism design by proposing an alternative design space parametrization through control points and adding another step to the process, that of subdivision. The control points allow a specific design to be represented as a solid model during the optimization process. The process of subdivision creates an additional number of control points that help smooth the surface (for example a C2 continuous surface depending on the method of subdivision chosen) creating a manufacturable design free of some traditional numerical instabilities. Note that these additional control points do not add to the number of design parameters. This alternative parametrization and description as a solid model effectively and completely separates the design variables from the analysis variables during the optimization procedure. The motivation behind this work is to create an automated design tool from task definition to functional prototype created on a CNC or rapid-prototype machine. This paper will describe the proposed compliant mechanism design process and will demonstrate the procedure on several examples common in the literature.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Subdivision process in defining a smooth surface from minimal number of parameters

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Figure 2

Current state of the art approach for designing distributed compliant mechanisms

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Figure 3

Outline of proposed compliant mechanism optimal synthesis tool

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Figure 4

Design domain and problem parameters

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Figure 5

Control points (numbered in boxes) and control mesh (numbered in circles)

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Figure 6

(a) Singularity condition created by two blocks and (b) subdivision to recapture the shape

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Figure 7

(a) Checkerboard mesh topology, (b) subdivided checkerboard mesh topology

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Figure 8

Example of a 3D subdivided shape (a) 3D control mesh formulation, (b) subdivided control mesh

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Figure 9

Initial setup for gripper problem, BC’s, force locations and finite areas

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Figure 10

(a) Optimum initial control mesh solution, (b) optimum subdivided solution and (c) optimum subdivided, FEA meshed and deformed solution

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Figure 11

Optimization of an inverter problem with minimum objective values

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Figure 12

(a) Initial setup for inverter problem, (b) symmetric simplification of the problem

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Figure 13

(a) Optimum solution in initial control mesh, (b) optimum subdivided solution, and (c) optimum subdivided, FEA meshed and deformed solution

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Figure 14

Optimization of an inverter problem with minimum objective values

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Figure 15

(a) Initial setup for inverter problem, (b) symmetric simplification of the problem

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Figure 16

(a) Optimum solution in initial control mesh, (b) optimum subdivided solution and (c) optimum subdivided, FEA meshed and deformed solution

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Figure 17

Optimization of a gripper problem with minimum objective values

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Figure 18

Prototype of compliant gripper

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Figure 19

Comparison of FEA model and prototype response

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Figure 20

(a) Midpoint vertices, (b) new vertexes calculated from midpoints

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Figure 21

(a) Midpoint vertices, (b) new vertexes calculated from midpoints

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Figure 22

(a) Midpoint vertices, (b) new vertexes calculated from midpoints

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