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TECHNICAL PAPERS

Analysis and Strategy for Superharmonics With Semiactive Suspension Control Systems

[+] Author and Article Information
Xubin Song

 Eaton Corporation, Eaton Innovation Center, 26201 Northwestern Highway, Southfield, MI 48076

Mehdi Ahmadian

 Center for Vehicle Systems and Safety, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24060-0238

Steve Southward

 Virginia Institute for Performance Engineering and Research, Department of Mechanical Engineering, Virginia Tech, Danville, VA 24540

J. Dyn. Sys., Meas., Control 129(6), 795-803 (Jan 19, 2007) (9 pages) doi:10.1115/1.2789470 History: Received January 26, 2006; Revised January 19, 2007

This paper focuses on an experimental implementation of a semiactive seat suspension using magnetorheological (MR) dampers. We first introduce the nonlinear dynamics phenomena induced by skyhook control. Skyhook control has been widely applied to applications ranging from structural vibration suppression to commercialized vehicle suspensions. Unfortunately, skyhook control generates superharmonic dynamics; yet, this issue has not been clearly addressed in such vibration control systems. This paper will attempt to explain how superharmonics are created with skyhook controls through analysis of test data. Furthermore, a nonlinear model-based adaptive control algorithm is developed and evaluated for reducing the negative impact of the superharmonics. Based on an empirical MR damper model, the adaptive algorithm is expanded mathematically, and the system stability is discussed. Then in the following sections, this paper describes implementation procedures such as modeling simplification and validation, and testing results. Through the laboratory testing, the adaptive suspension is compared to two passive suspensions: hard-damping (stiff) suspension with a maximum current of 1A to the MR damper and low-damping (soft) suspension with a low current of 0A, while broadband random excitations are applied with respect to the seat suspension resonant frequency in order to test the adaptability of the adaptive control. In two separate studies, both mass and spring rate are assumed known and unknown in order to investigate the capability of the adaptive algorithm with the simplified model. Finally, the comparison of test results is presented to show the effectiveness and feasibility of the proposed adaptive algorithm to eliminate the superharmonics from the MR seat suspension response.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Experimental system of an MR seat suspension.

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Figure 2

Isringhausen seat suspension: (a) closeup of seat suspension and (b) schematic of scissors seat suspension

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Figure 3

Implementation of skyhook control on seat suspension

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Figure 4

Power spectrum of ISO2 excitation

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Figure 5

A sample time history of ISO2 displacement

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Figure 6

The skyhook-controlled seat acceleration with ISO2 excitation in frequency domain

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Figure 7

Acceleration frequency spectrum for skyhook and passive damping with pure-tone excitation

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Figure 8

Current supplied to the MR damper for pure-tone excitation in time domain

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Figure 9

Power spectrum of the electrical current to the MR damper for skyhook control

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Figure 10

Signal flow for semiactive skyhook control

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Figure 11

Adaptive magneto-rheological seat suspension

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Figure 12

Identify M & K by applying RLS algorithm

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Figure 13

The simplified seat suspension model

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Figure 14

Evaluation of the simplified MR damper model by using the virtual vertical damping force for the simplified seat suspension

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Figure 15

Block diagram of forced nonlinear system

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Figure 16

Stable time-invariant system with memoryless nonlinearity of Φ̂MR(∙)∊[0,β–α]

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Figure 17

Illustration of sector condition for ΦMR(∙)

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Figure 18

Frequency spectrum of ISO excitations

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Figure 19

Time trace of ISO excitations for system testing

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Figure 20

Seat accelerations with response to ISO excitations

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Figure 21

Comparison of gradient and currents with ISO excitations

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Figure 22

System identification values with ISO excitations

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Figure 23

ISO1 induced seat acceleration in frequency domain

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Figure 24

ISO2 induced seat acceleration in frequency domain

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Figure 25

ISO3 induced seat acceleration in frequency domain

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Figure 26

ISO4 induced seat acceleration in frequency domain

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