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Research Papers

Lateral Load Transfer Effects on Bifurcation Behavior of Four-Wheel Vehicle System

[+] Author and Article Information
Vincent Nguyen

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742vince1@umd.edu

Gregory Schultz

U.S. Army Aberdeen Test Center, Aberdeen Proving Grounds, Aberdeen, MD 21005gregory.schultz@atc.army.mil

Balakumar Balachandran

Department of Mechanical Engineering, University of Maryland, College Park, MD 20742balab@umd.edu

J. Comput. Nonlinear Dynam 4(4), 041007 (Aug 25, 2009) (12 pages) doi:10.1115/1.3192128 History: Received March 23, 2008; Revised March 10, 2009; Published August 25, 2009

In this article, vehicle handling behavior of a nonlinear four-wheel vehicle system is studied. Bifurcations with respect to vehicle speed and roll moment distribution are examined for innate understeering and oversteering models. Lateral load transfer effects are investigated, and these effects are shown to alter the bifurcation locations for oversteering vehicles when the roll moment distribution is adjusted. When the roll moment distribution is used as a control parameter, transitions between bifurcation behavior characteristic of oversteering systems and bifurcation behavior characteristic of understeering systems are observed. This effort provides a framework for developing a complete vehicle handling assessment in terms of nonlinear regions of performance, transient behavior, and lateral load effects.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

SAE representation of the four-wheel model

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Figure 2

Tire diagram for α=90 deg, expected tire lateral force direction is perpendicular to tire heading rather than velocity direction

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Figure 3

Tire lateral force model output and empirical data for 50 psi tires

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Figure 4

(αr−αf) versus normalized tire force for the HLV four-wheel model

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Figure 5

Phase portrait for the HLV four-wheel model at V=10 m/s and δf=0.015 rad

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Figure 6

Vehicle orientation plot for equilibrium points of the HLV model at 10 m/s

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Figure 7

Phase portrait for the HLV four-wheel model at V=25 m/s and δf=0.015 rad

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Figure 8

Vehicle orientation plot for equilibrium points of the HLV model at 25 m/s

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Figure 9

Phase portrait for the HLV four-wheel model at V=40 m/s and δf=0.015 rad

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Figure 10

Bifurcation diagram for the HLV four-wheel model, equilibrium values of β versus speed

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Figure 11

Bifurcation diagram for the HLV four-wheel model, equilibrium values of r versus speed

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Figure 12

Phase portrait for an understeering system at V=10 m/s and δf=0.015 rad

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Figure 13

Phase portrait for an understeering system at V=30 m/s and δf=0.015 rad

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Figure 14

Bifurcation diagram for an understeering system, equilibrium values of β versus speed

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Figure 15

Bifurcation diagram for an understeering system, equilibrium values of r versus speed

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Figure 16

Vehicle roll axis

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Figure 17

Unsprung mass free-body diagram

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Figure 18

Sprung mass free-body diagram

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Figure 19

Diagram of the iterative solver

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Figure 20

Bifurcation diagram for the HLV four-wheel model, equilibrium values of β versus speed with lateral load transfer effects

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Figure 21

Bifurcation diagram for the HLV four-wheel model, equilibrium values of r versus speed with lateral load transfer effects

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Figure 22

Tire lateral force versus tire vertical load at 10 deg slip angle

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Figure 23

Bifurcation diagram for the HLV four-wheel model, equilibrium values of β versus speed with lateral load transfer effects; 75% roll stiffness at rear

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Figure 24

Bifurcation diagram for the HLV four-wheel model, equilibrium values of r versus speed with lateral load transfer effects; 75% roll stiffness at rear

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Figure 25

Bifurcation diagram for the HLV four-wheel model, equilibrium values of β versus rear roll stiffness ratio with lateral load transfer effects

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Figure 26

Bifurcation diagram for the HLV four-wheel model, equilibrium values of r versus rear roll stiffness ratio with lateral load transfer effects

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Figure 27

Saddle-node bifurcation points in the space of vehicle speed and rear roll stiffness ratio

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Figure 28

Bifurcation diagram for the HLV four-wheel model, equilibrium values of β versus speed with lateral load transfer effects; 30% roll stiffness at rear

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Figure 29

Bifurcation diagram for the HLV four-wheel model, equilibrium values of r versus speed with lateral load transfer effects; 30% roll stiffness at rear

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Figure 30

Phase portrait for the HLV four-wheel model at V=7 m/s and δf=0.015 rad; 30% roll stiffness at rear and 30% additional total roll stiffness

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Figure 31

Phase portrait for the HLV four-wheel model at V=25 m/s and δf=0.015 rad; 30% roll stiffness at rear and 30% additional total roll stiffness

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