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MODEL VALIDATION & IDENTIFICATION

Comparison of Linear, Nonlinear, Hysteretic, and Probabilistic Models for Magnetorheological Fluid Dampers

[+] Author and Article Information
Corina Sandu1

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 104 Randolph Hall, Blacksburg, VA 24061csandu@vt.edu

Steve Southward

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, IALR Office 112K, Danville, VA 24540scsouth@vt.edu

Russell Richards

 General Motors Powertrain Global Headquarters, 823 Joslyn Road, Pontiac, MI 48340russel.j.richards@gm.com

1

Corresponding author.

J. Dyn. Sys., Meas., Control 132(6), 061403 (Nov 09, 2010) (9 pages) doi:10.1115/1.4002480 History: Received September 19, 2008; Revised May 17, 2010; Published November 09, 2010; Online November 09, 2010

Magnetorheological (MR) fluid dampers have a semicontrollable damping force output that is dependent on the current input to the damper, as well as the relative velocity. The mechanical construction, fluid properties, and embedded electromagnet result in a dynamic damper response. This study evaluates four modeling approaches with respect to predicting the multi-input single-output behavior of an experimental MR damper when the inputs are band-limited random signals typically encountered in primary suspension applications. The first two models in this study are static in the sense that there is a unique output for any given set of inputs and no dynamics is present in either model. The third model incorporates a dynamic filter with the nonlinear model to exhibit hysteretic effects, which are known to exist in actual MR dampers. The fourth model is probabilistic and illustrates the dynamic nature of an actual MR damper. The results of this study clearly show the importance of nonlinear and dynamic effects in magnetorheological damper response. This study also highlights the importance of characterizing magnetorheological dampers using excitation signals that are representative of an actual implementation.

Copyright © 2010 by American Society of Mechanical Engineers
Topics: Force , Fluids , Dampers , Signals
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References

Figures

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Figure 1

Force-velocity-current characterization data for an ML-430 MR damper

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Figure 2

Behavior of MR fluid. (a) The fluid contains iron particles that under normal conditions, act as a Newtonian liquid. (b) When a magnetic field is applied, the iron particles act as dipoles and align with the magnetic flux.

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Figure 3

Typical schematic of a MR damper. Note that the activated region is very small compared with the volume of fluid. The lines of constant flux approximate straight lines due to the very small fluid gap.

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Figure 4

Physical model of the Spencer damper model. This model is based on observation of the MR damper operation and data from a Lord MR damper.

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Figure 5

Model of damper with hysteresis included by placing a spring in series with the damper

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Figure 6

Sample input signals of velocity and current showing the type of distribution used in the experiment. The spectral bandwidths of each signal account for the more rapid oscillation in velocity than in current.

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Figure 7

Distribution of a sample velocity signal (left) and a sample current signal (right). The current signal especially shows the effect of a filter to the original uniform distribution.

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Figure 8

Relative position, force, and relative velocity of the damper; current input to the damper and the original control signal

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Figure 9

Relationship of force to current and velocity from experimental data

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Figure 10

Plot of the PDF at the current bin ranging from 1.8 A to 2.0 A

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Figure 11

Plot of the PDF at the current bin ranging from 0.9 A to 1.0 A

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Figure 12

Plot of the PDF at the velocity bin at 0.1 m/s

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Figure 13

Force response of the actual MR damper and the nonlinear static model

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Figure 14

Nonlinear static model evaluated at a current of 1.5 A overlaid on the empirical PDF data for the current bin ranging from 1.4 A to 1.6 A

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Figure 15

Force response of the actual MR damper and the hysteretic model

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Figure 16

PDF comparison of experimental data (a) with the hysteretic model (b) at the current bin ranging from 1.6 A to 1.8 A

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Figure 17

PDF comparison of experimental data (a) with the hysteretic model (b) at the current bin ranging from 0.4 A to 0.6 A

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Figure 18

Plot of the PDF of force versus current at the zero velocity bin

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