Rack Force Estimation Method using a Tire Mesh Model

Kim, Minjun; Chang, Sehyun; Lee, Byungrim; Park, Young‐Dae; Cho, Hyunseok

doi:10.7467/ksae.2014.22.3.130

Transactions of the Korean Society of Automotive Engineers

2014

DOI: 10.7467/ksae.2014.22.3.130

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Rack Force Estimation Method using a Tire Mesh Model

Minjun Kim¹,

Sehyun Chang²,

Byungrim Lee³

et al.

Abstract: : In this paper, a new estimation method is proposed to calculate steering rack axial force using a 3 dimensional tire mesh model when a car is standing on the road. This model is established by considering changes of camber angle and contact patch between the tires and the ground according to steering angle. The steering rack bar axial force is estimated based on the static equilibrium equations of forces and moments. A tire friction force is supposed to act on the center point of the contact patch, and the p… Show more

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Parking-Specific Parameterization Method for FTire

Neumann¹,

Friederichs²,

Harris³

et al. 2023

Tire Science and Technology

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Virtual steering system layout in the early development phase requires adequate tire models to predict realistic steering rack forces. An accurate representation of parking is particularly important, as the largest steering rack forces occur during this maneuver. Physical tire models are mainly parameterized for rolling conditions. Since the tire exhibits different mechanical behavior under nonrolling conditions, this article introduces a new parameterization procedure for the physical tire model FTire that characterizes the conditions during parking maneuvers. To this end, an additional full vehicle measurement setup is used to understand the tire motions, forces, and torques during parking. It is also shown that a tire model based on a standard parameterization procedure results in steering speed-dependent parking torque deviations of up to 17.5% when compared with component measurements. Thus, new measurement methods are developed to help parameterize the tire model for this maneuver. A linear friction tester is used to determine the friction interaction between tire and road at the relevant relative velocities. In addition, measurements are performed on a tire stiffness test rig, in which translatory and rotatory movements are overlaid. Furthermore, the contact patch shape, ground pressure distribution, and tire outer contour are digitalized and added into the model. A tire model based on the new parking optimized parameterization is then compared with the standard tire modeling approach and component measurements as well as the full vehicle measurements. In conclusion, improvements of up to 12% for drilling torque, up to 15% for longitudinal force, a more realistic lateral stiffness, a more realistic pressure distribution, and improvements of up to 8% when simulating the steering rack force can be stated. After the results are evaluated and interpreted, recommendations for future developments of this parameterization procedure and an extension of the virtual tire model are discussed.

show abstract

Parking-Specific Parameterization Method for FTire

Neumann¹,

Friederichs²,

Harris³

et al. 2023

Tire Science and Technology

View full text Add to dashboard Cite

show abstract

Identification of Characteristic Tire Parameters for the Virtual Steering System Design

Neumann¹,

Ahmadi²,

Weinberger³

et al. 2023

Tire Science and Technology

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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.

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Sensitivity Analysis of Steering Wheel Return-ability at Low Speed

Cho¹,

Lee²,

Chang³

et al. 2017

KSAE

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Rack Force Estimation Method using a Tire Mesh Model

Cited by 3 publications

References 0 publications

Parking-Specific Parameterization Method for FTire

Parking-Specific Parameterization Method for FTire

Identification of Characteristic Tire Parameters for the Virtual Steering System Design

Sensitivity Analysis of Steering Wheel Return-ability at Low Speed

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