Research Papers

Dynamic Modeling of Damping Effects in Highly Damped Compliant Fingers for Applications Involving Contacts

[+] Author and Article Information
Chih-Hsing Liu

 Singapore Institute of Manufacturing Technology, Singapore 638075 chliu@simtech.a-star.edu.sg

Kok-Meng Lee1

 The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 –0405 kokmeng.lee@me.gatech.edu


Corresponding author.

J. Dyn. Sys., Meas., Control 134(1), 011005 (Dec 02, 2011) (9 pages) doi:10.1115/1.4005270 History: Received July 02, 2010; Revised July 31, 2011; Published December 02, 2011; Online December 02, 2011

In many industries, it is often required to transfer objects using compliant fingers capable of accommodating a limited range of object shapes/sizes without causing damage to the products being handled. This paper presents a coupled computational and experimental method in time domain to characterize the damping coefficient of a continuum structure, particularly, its applications for analyzing the damping effect of a highly damped compliant finger on contact-induced forces and stresses. With the aid of Rayleigh damping and explicit dynamic finite element analysis (FEA), this method relaxes several limitations of commonly used damping identification methods (such as log-decrement and half-power methods) that are valid for systems with an oscillatory response and generally estimate the damping ratio for a lumped parameter model. This damping identification method implemented using off-the-shelf commercial FEA packages has been validated by comparing results against published data; both oscillatory and nonoscillatory responses are considered. Along with a detailed discussion on practical issues commonly encountered in explicit dynamic FEA for damping identification, the effects of damping coefficients on contact between a rotating compliant finger and an elliptical object has been numerically investigated and experimentally validated. The findings offer a better understanding for improving grasper designs for applications where joint-less compliant fingers are advantageous.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 9

Experiment Setup for simulating contact between rotating finger and elliptical object

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Figure 10

Reaction force from the contact between rotating finger and elliptical object

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Figure 11

Simulation and experimental results of finger-contact deformation

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Figure 12

Simulated snapshots illustrating the finger deformation (α = 180 s−1 )

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Figure 13

Initial and final contact (α = 7.5, 180 and 600 s−1 )

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Figure 14

Effect of finger damping coefficient on maximum finger/object stresses and reaction force

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Figure 1

Frequency effect of proportional damping on damping ratio

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Figure 2

Coupled computational and experimental damping identification (CCEDI) method

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Figure 3

Impulse response with initial guessed and critical damping coefficients (αcr  = 30 s−1 , ζ= 0.0055)

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Figure 4

Comparison of simulation and published experimental data (α = αcr ζ = 0.165 s−1 )

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Figure 5

Setup for damping identification of the compliant finger

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Figure 6

Effect of FEA models (4.5-in. finger, α = 180 s−1 )

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Figure 7

Effect of α on tip response (4.5-in finger)

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Figure 8

Damping coefficients of compliant fingers



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