System for virtual prediction of road loads

• US 20070074565A1
• Filed: 09/30/2005
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Ford Motor Company
• Original Assignee: Ford Motor Company
• Inventors: Dhir, Anil, Ranganathan, R., Balendran, Bala, Berzeri, Marcello, Jayakumar, Paramsothy
• Granted Patent: US 7,363,805 B2
• Time in Patent Office: Days
• US Class Current: 73/146
• CPC Class Codes: B60C 99/006 Computer aided tyre design or simulation
• CPC Class Codes: G06F 30/15 Vehicle, aircraft or watercraft design
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]

Abstract

A system is provided for full-vehicle analytical road-loads prediction, which reduces the time and cost of modeling tires and tire-road interface, using road load simulations rather than actual measurements. The system includes a method to perform tire tests in a virtual environment, a road-load tire model for simulations in multibody environments; a tire model for FE simulations; and a comprehensive graphical user interface to support the user in all the steps of the analytical process.

Claims

1. A method for predicting road loads on vehicle components and systems, comprising the steps of:

(A) producing a set of data defining preselected physical characteristics of a tire on the vehicle;

(B) generating an analytical model of the tire using the data produced in step (A); and

,

(C) simulating road loads on the vehicle using the analytical tire model generated in step (B).

2. The method of claim 1, wherein step (B) includes performing virtual tests on the tire using nonlinear finite element simulations and the data set provided in step (A), and recording responses to the virtual tests.

3. The method of claim 2, wherein the tests include at least one of the following tests:

tire mass and inertias calculation, modal frequency tests, three directional quasi-static flat-plate tests, vertical wedge tests, longitudinal slip tests, and lateral or side slip tests.

4. The method of claim 2, wherein the recorded responses include wedge quasi-static force deflection data in the radial direction of the tire.

5. The method of claim 3, wherein the recorded responses further include at least one of the following:

tire mass and inertias;

modal frequencies, contact patch lengths on a flat-surface, flat-surface quasi-static force-deflection data in the X, Y &

Z-directions, flat-surface dynamic force-slip data in X-direction, flat-surface dynamic Y-force and aligning moment compared to slip angle data.

6. The method of claim 1, wherein step (B) includes modeling the contact between the tire and the road in three dimensions, and the modeling is performed by—

calculating a plurality of two dimensional slices of the contact between the road and the tire, wherein each of the slices is perpendicular to the axis or rotation of the tire,

determining the shape of the deformation of the tire due to contact with the road, and,

determining the resultant force between the tire and the road.

7. The method of claim 1, wherein step (B) includes modeling the contact between the tire and the road in three dimensions based on random undulations in the road surface, wherein the modeling includes—

generating a profile of each of a plurality of undulations in the road,

generating a plurality of slices of the tire that will interact with a corresponding one of the profiled undulations,

calculating the resultant force imposed on each the tire slice by the corresponding profiled undulation, and

calculating an overall resultant contact force imposed on the tire using the calculated resultant forces imposed on the tire slices.

8. The method of claim 2, wherein step (B) includes simplifying the finite element description by selectively reducing the number of characteristics of the tire used to generate the analytical tire model.

9. The method of claim 8, wherein the set of data defining the physical characteristics of the tire includes multiple layers of elements corresponding to multiple layers of material in the tire, and the selective reduction of the number of characteristics is performed by reducing the number of layers of elements to a single layer that substantially approximates the physical tire characteristics.

10. The method of claim 8, wherein reduction of the number of characteristics includes using parametric geometry to describe the cross section of the tire, and selecting tire characteristics matching features of the cross section described by the parametric geometry.

11. A method for generating a tire model for use in multibody simulations for vehicles, comprising the steps of:

(A) producing a set of data defining preselected physical characteristics of the tire; and

,

(B) developing a set of analytical road load tire parameters describing the tire model, using nonlinear finite element simulations and the data produced in step (A).

12. The method of claim 11, wherein the finite element simulations include generating data defining quasi-static force deflection of the tire in radial direction of the tire resulting from tire contact with a wedge shaped surface.

13. The method of claim 11, wherein the finite element simulations include determining the longitudinal and torsional stiffness of the tire by simulating the preload of the tire on a flat surface with a preselected vertical load, longitudinally displacing the surface, measuring the longitudinal force for each incremental deflection of the tire, and recording the longitudinal force at the center of the tire.

14. The method of claim 11, wherein the finite element simulations include determining the total lateral and sidewall lateral and conical stiffness parameters of the tire by preloading the tire with a preselected vertical load on a flat movable surface, incrementally displacing the flat surface laterally relative to the tire, and measuring the lateral force on the tire for each incremental deflection of the tire.

15. The method of claim 11, wherein the finite element simulations include determining the dynamic radial stiffness of the tire by forcing the tire against a triangular wedge, measuring the force in the vertical direction for each incremental deflection of the tire.

16. A method of building a virtual road load model for designing vehicles, comprising the steps of:

(A) generating a virtual model of a vehicle tire having a set of known characteristics;

(B) modeling the response of the virtual model tire to a set of predetermined road conditions; and

,

(C) developing the road load model using the response modeled in step (B).

17. The method of claim 16, wherein step (A) includes representing the dynamics of the virtual model tire using multiple rigid body modes, and the rigid body modes include radial, torsional, lateral and steering direction.

18. The method of claim 16, wherein step (A) includes characterizing the sidewall stiffness of the virtual model tire in a plurality of directions.

19. The method of claim 16, wherein step (A) includes 3D modeling of the interaction of the virtual model tire with a rough road, wherein the 3D modeling of the interaction is performed using discrete undulations in the road.

20. The method of claim 16, wherein step (C) includes determining the shape of the in-plane deflection of the tire due to engagement of the tire with a non-deformable road surface obstacle using second order polynomials approximations.