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Research Papers

The Effect of Dual-Rate Suspension Damping on Vehicle Response to Transient Road Inputs

[+] Author and Article Information
T. P. Waters

Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton SO17 1BJ, UKtpw@isvr.soton.ac.uk

Y. Hyun

 Corporate Research and Development Division, Hyundai and Kia, 772-1 Jangduk-Dong, Hwaseong-Si, Gyeonggi-Do 445-706, South Koreajiny@hyundai-motor.com

M. J. Brennan

Institute of Sound and Vibration Research, University of Southampton, Highfield, Southampton SO17 1BJ, UKmjb@isvr.soton.ac.uk

J. Vib. Acoust 131(1), 011004 (Jan 05, 2009) (8 pages) doi:10.1115/1.2980370 History: Received March 13, 2007; Revised May 27, 2008; Published January 05, 2009

The acceleration response of road vehicles to shock inputs from road irregularities such as bumps and hollows is an important consideration in the design of vehicle suspensions and damping characteristics, in particular. In this paper, the influence of the damper on the shock response of a simple vehicle model is considered. An analysis is presented of a single degree-of-freedom model subjected to a transient displacement input. Simple approximate expressions are given for the peak acceleration during an impulse of both short and long durations compared to the natural period, from which the role of the damper is clearly apparent. For impulses of short duration the peak acceleration occurs during the impulse and is shown to be approximately proportional to the damping ratio. Corollary to this, the peak acceleration can be reduced by switching the damper to a lower value during the impulse. The potential benefits of doing so are illustrated through numerical simulation, and a simple formula is given for the maximum possible reduction in peak acceleration. The results are also contrasted with those of a conventional dual-rate automotive damper model. The switchable damper is found to offer sufficient benefit to warrant further investigation.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

A damped SDOF system subject to a versed sine-shaped base displacement

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Figure 2

Transient response of a SDOF system with a natural period of 5 times the impulse duration (r=5) and a damping ratio of 0.25 to a versed sine base displacement input. (a) Displacement input, (b) displacement response, (c) relative displacement response, and (d) acceleration response.

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Figure 3

Acceleration time response of a SDOF system with a natural period of 5 times the impulse duration (r=5). (–) exact and (--) approximation. (a) ζ=0.25, (b) ζ=0.50, and (c) ζ=0.75.

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Figure 4

Peak normalized acceleration as a function of the ratio of the natural period to the impulse duration for a damping ratio of 0.25. (–) exact solution, (--) second order approximation (Eq. 17), and (⋅-⋅-⋅) first order approximation (Eq. 19).

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Figure 5

Schematic of the relationship between the damping force and the relative velocity: (—) typical automotive damper and (--) piecewise linear damping model. (Note that the gradient is less for negative relative velocity compared with that for positive relative velocity.)

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Figure 6

Transient response to a versed sine base displacement of a SDOF system with a piecewise linear damper. Damping ratios of 0.50 in extension and 0.20 in compression. The natural period is such that r=5. (a) damping ratio, (b) relative velocity across damper, and (c) acceleration of mass.

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Figure 7

Transient acceleration response to a versed sine base displacement of a SDOF system with a switchable damper. Damping ratios of 0.20 during impulse and 0.50 after impulse. The natural period is such that r=5.

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Figure 8

Peak acceleration as a function of damping reduction factor for a SDOF system with a natural period such that r=10. ((–) piecewise linear damper and (--) switchable damper.) (a) Ξ=0.25 and (b) Ξ=0.50.

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Figure 9

Reduction factor in peak acceleration by switching off the damper during the impulse compared with a linear damper. (a) Numerical integration and (b) simple approximation, 1∕ζr.

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