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Research Papers

Modeling and Verification of an Innovative Active Pneumatic Vibration Isolation System

[+] Author and Article Information
H. Porumamilla1

Department of Mechanical Engineering, Calpoly, San Luis Obispo, CA 93410hporumam@calpoly.edu

A. G. Kelkar

Department of Mechanical Engineering, Iowa State University, Ames, IA 50011akelkar@iastate.edu

J. M. Vogel

Department of Aerospace Engineering, Iowa State University, Ames, IA 50011

1

Corresponding author.

J. Dyn. Sys., Meas., Control 130(3), 031001 (Apr 09, 2008) (12 pages) doi:10.1115/1.2807049 History: Received August 23, 2005; Revised March 26, 2007; Published April 09, 2008

This paper presents a novel concept in active pneumatic vibration isolation. The novelty in the concept is in utilizing an air-spring-orifice-accumulator combination to vary the natural frequency as well as inject damping into the system per requirement, thereby eliminating the need for a hydraulic cylinder or a magnetorheological damper. This continuously variable natural frequency and damping (CVNFD) technology is aimed at achieving active vibration isolation. For analysis purposes, a particular application in the form of pneumatic seat suspension for off-road vehicles is chosen. A mathematical model representing the system is derived rigorously from inertial dynamics and first principles in thermodynamics. Empirical corelations are also used to include nonlinearities such as friction that cannot be accounted for in the thermodynamic equations. An exhaustive computational study is undertaken to help understand the physics of the system. The computational study clearly depicts the CVNFD capability of the vibration isolation system. An experimental test rig is built to experimentally validate analytical and simulation modeling of the system. Experimental verification corroborated the variable natural frequency and damping characteristic of the system observed through computational simulations.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Human body schematic

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Figure 2

Health guidance caution zones for driver and passenger

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Figure 3

Transmissibility curves for a suspended mass with base excitation

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Figure 4

Typical air spring used in pneumatic isolator systems

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Figure 5

CVNFD isolator depicting air spring, variable orifice, and accumulator

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Figure 6

Accumulator volume modulator

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Figure 7

Schematic of seat suspension

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Figure 8

Schematic of D/P meter

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Figure 9

Time constant for the CVNFD suspension

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Figure 10

Change in ωn and ζ for fixed accumulator volume and varying orifice area

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Figure 11

Change in ωn and ζ for fixed orifice area and varying accumulator volume

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Figure 12

Experimental test-rig

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Figure 13

Step response for full orifice opening

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Figure 14

Step response for 15% orifice opening

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Figure 15

Experimental corroboration of CVNFD dynamics

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Figure 16

Transfer function fits

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Figure 17

Change in ωn and ζ for fixed orifice area and varying accumulator volume

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