Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 27 Jan 2024

Identification of Characteristic Tire Parameters for the Virtual Steering System Design

,
,
, and
Page Range: 262 – 284
DOI: 10.2346/tire.22.22002
Save
Download PDF

ABSTRACT

The virtual design of steering systems requires suitable premises for predicting realistic steering rack forces. This includes the proper tire used for the parking maneuver. It is important to select the tire from a portfolio that generates the highest rack forces at the vehicle, so that the electro-mechanical dimensioning of the steering system can be safeguarded for all tires of a vehicle. To avoid time-consuming and expensive full vehicle measurements, drilling torques of tires are measured on a Flat-Trac to determine the so-called worst-case tire. However, the determined drilling torques do not correlate with the measured rack forces.

This work therefore investigates the suitability of a Kinematics & Compliance test rig converted to a tire test rig. First, it is investigated whether the wheel movements from the parking maneuver can be decomposed into their individual elements on the test bench. In addition, reproducibility studies are carried out and three different methods for determining the aligning torque under camber are presented. Furthermore, measurements for static and dynamic friction values, as well as stiffnesses and the contact patch, are integrated into the new measurement procedure. It becomes apparent that temperature and wear level of the tire play a major role in the reproducibility of the measurements. If the measurement procedure described in this paper is followed exactly, the scatter of the drilling torque can be reduced by up to 24% compared to the old procedure. For the dynamic and the static friction values, the scatter is reduced by about 17% and 22%, respectively. Stiffness scatter can be reduced by up to 16%.

With the new measurement procedure, the worst-case tire can be reliably determined. The drilling torques correlate with the rack forces and the additional tire characteristics permit finer resolution. After evaluation and interpretation, recommendations for future developments are discussed.

Keywords: tire measurement; tire wear; contact patch; parking maneuver; steering system design; steering system layout; drilling torque; tire characteristic values; aligning torque
FIG. 1 —
FIG. 1 —

Areas of steering system application in various vehicle and performance classes according to [1].

FIG. 2 —
FIG. 2 —

Composition of Pitman Arm Torque Magnitude during the parking maneuver according to [10].

FIG. 3 —
FIG. 3 —

Definition of steering variables with “fixed” steering axis according to [11].

FIG. 4 —
FIG. 4 —

Wheel Control of front axle according to [11].

FIG. 5 —
FIG. 5 —

Steering rack force with and without applied brakes.

FIG. 6 —
FIG. 6 —

K&C Tire Test Rig schematic representation (left), real implemented system (right).

FIG. 7 —
FIG. 7 —

Changes in drilling torque for different tire wear level.

FIG. 8 —
FIG. 8 —

Normalized drilling torque for different steering angles.

FIG. 9 —
FIG. 9 —

Drilling torque structured into four curve sections over tire wear level.

FIG. 10 —
FIG. 10 —

Longitudinal force over longitudinal displacement.

FIG. 11 —
FIG. 11 —

Comparison of pressure distribution 0° (left) and 9° (right).

FIG. 12 —
FIG. 12 —

Method 2: relative movement of the center of force with respect to the wheel contact point resulting from the steering process.

FIG. 13 —
FIG. 13 —

Comparison of the three measurements with influence of camber angle.

FIG. 14 —
FIG. 14 —

Comparison of Drilling Torque on a Flat-Trac and on the K&C tire test rig compared to the steering rack force at full vehicle level.

FIG. 15 —
FIG. 15 —

Resulting drilling torque for inverted motion of full vehicle measurement on K&C Tire Test Rig.

Contributor Notes

1 Corresponding author. University Duisburg-Essen, BMW Group, Petuelring 130, Munich, Bavaria 80809, Germany. Email: dominic.neumann@de.bosch.com
2 Hochschule für Angewandte Wissenschaften Hamburg, Stiftstraße 69, Hamburg 20999, Germany.
3 BMW Group, Petuelring 130, München 80809, Germany.
4 University Duisburg-Essen, Forsthausweg 2, Duisburg 47057, Germany.
  • Download PDF