Editorial Type:
Article Category: Other
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Online Publication Date: 01 Apr 2015

Experimental Study of Tire-Wheel-Suspension Dynamics in Rolling over Cleat and Abrupt Braking Conditions

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Page Range: 42 – 71
DOI: 10.2346/tire.15.430102
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ABSTRACT

The braking performance of recent vehicles is controlled by the interaction between the antilock braking system (ABS) and the transmitted force between road and tire. Because of tire and suspension elasticity, an abrupt braking or the ABS regulation initiates tire belt and wheel axle oscillations, which lead to a closed loop of acceleration and force transmission in the tire-wheel-suspension assembly in both translational and rotational directions. As a result, the oscillation of wheel slip and wheel load can influence the force transmission potential in the contact patch and thus the braking distance as well. The objective of the presented study is to investigate the influence of the tire-wheel-suspension dynamics on the force transmission potential between tire and road.

To obtain acceleration and force dynamics in the tire-wheel-suspension assembly without inducing the influence from other vehicle components, a McPherson suspension was isolated from a real car and adapted to the inner drum test bench at the Karlsruhe Institute of Technology, Institute of Vehicle System Technology. After mounting different tires, measurements were carried out under various driving conditions. First, tire measurements with a measuring hub were done on the test bench to obtain both quasistatic characteristics and dynamic response in rolling over cleat. Second, different tire-wheel-suspension assemblies were driven on the test bench while the wheel brake was initiated by a hydraulic braking system based on a modified ESP control unit. This modified unit allows generation of abrupt braking pressure slopes by a direct control of the valves. The accelerations of different wheel-suspension components and forces in the links were measured.

In this article, the experimental study of the dynamics of a run-flat and a standard tire and their respective coupled assembly with the suspension excited by rolling over cleat and abrupt braking is presented. After a description of the experimental setup, the results of tire-wheel-suspension dynamics of two different tires will be analyzed, interpreted, and compared. Furthermore, a simulation model of the tire-wheel-suspension assembly with the FTire model and dynamic models of suspension components will be built up.

Keywords: run-flat tire; tire-wheel-suspension; hydraulic braking system; rolling over cleat; abrupt braking; wheel axle movement; longitudinal slip oscillation; suspension load
FIG. 1
FIG. 1

Analytical quarter car model.

FIG. 2
FIG. 2

Linearization of the μ-slip-curve (left) and the chosen stationary operating points for deriving the transfer functions (right).

FIG. 3
FIG. 3

Bode diagram of the brake torque variation–induced longitudinal force variation (left) and wheel axle acceleration (right) at different operating states.

FIG. 4
FIG. 4

Bode diagram of the brake torque variation–induced vertical force variation (left) and wheel axle acceleration (right) at different operating states.

FIG. 5
FIG. 5

Bode diagram of the road unevenness–induced longitudinal force variation (left) and wheel axle acceleration (right) at different operating states.

FIG. 6
FIG. 6

Bode diagram of the road unevenness–induced vertical force variation (left) and wheel axle acceleration (right) at different operating states.

FIG. 7
FIG. 7

Overall concept of the experimental study.

FIG. 8
FIG. 8

Hydraulic braking system on the test bench.

FIG. 9
FIG. 9

Comparison of the stiffnesses between the run-flat and standard tire.

FIG. 10
FIG. 10

Comparison of the μ-slip-curve between the run-flat and standard tire.

FIG. 11
FIG. 11

Measurement of acceleration.

FIG. 12
FIG. 12

Measurement of forces, wheel speed, and brake pressure.

FIG. 13
FIG. 13

Global coordinate system in the measurement.

FIG. 14
FIG. 14

Power spectral density of the concrete road profile.

FIG. 15
FIG. 15

Power spectral density of the measured acceleration on wheel carrier at wheel load 2845 N, 60 km/h.

FIG. 16
FIG. 16

Stationary operating points on the μ-slip-curve in the measurement.

FIG. 17
FIG. 17

Measured acceleration and force on the wheel carrier in the standard tire quarter car assembly in the free rolling and braking state.

FIG. 18
FIG. 18

Measured acceleration and force on the wheel carrier in the run-flat tire quarter car assembly in the free rolling and braking state.

FIG. 19
FIG. 19

Power spectral density of the measured acceleration and force variation on the wheel carrier in the standard tire quarter car assembly in the free rolling and braking state.

FIG. 20
FIG. 20

Power spectral density of the measured acceleration and force variation on wheel carrier in the run-flat tire quarter car assembly in the free rolling and braking state.

FIG. 21
FIG. 21

Influence of the stationary operating points and the tire on the acceleration, force, and braking slip variation in different frequency ranges while rolling on the concrete road surface.

FIG. 22
FIG. 22

Longitudinal slip oscillation at the operating state (3/4)μmαx.

FIG. 23
FIG. 23

Influence of the tire on suspension loads in the braking state while rolling on the concrete road surface.

FIG. 24
FIG. 24

Geometry and arrangement of the single cleat on the inner drum.

FIG. 25
FIG. 25

Measured acceleration and force on the wheel carrier in the standard tire quarter car assembly in rolling over cleat with and without braking.

FIG. 26
FIG. 26

Measured acceleration and force on the wheel carrier in the run-flat tire quarter car assembly in rolling over cleat with and without braking.

FIG. 27
FIG. 27

Zoomed comparison of the acceleration and force on the wheel carrier in the standard tire quarter car assembly in rolling over cleat with and without braking.

FIG. 28
FIG. 28

Zoomed comparison of the acceleration and force on the wheel carrier in the run-flat tire quarter car assembly in rolling over cleat with and without braking.

FIG. 29
FIG. 29

Power spectral density of the measured acceleration and force on the wheel carrier in the standard tire quarter car assembly in rolling over cleat with and without braking.

FIG. 30
FIG. 30

Power spectral density of the measured acceleration and force on the wheel carrier in the run-flat tire quarter car assembly in rolling over cleat with and without braking.

FIG. 31
FIG. 31

Influence of the stationary operating points and the tire on the acceleration and force variation in different frequency ranges while rolling over cleat.

FIG. 32
FIG. 32

Influence of the tire on suspension loads in abrupt braking while rolling over cleat.

Contributor Notes

2 Corresponding author. Email: yaoqun.zhou@kit.edu
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