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Fraunhofer researchers develop tire simulation software for virtual testing; realtime application coming

Researchers at the Fraunhofer Institute for Industrial Mathematics ITWM in Kaiserslautern have developed a software tool—CDTire/3D—enabling the realistic simulation of tires for use in virtual testing on vehicle designs. The software takes into account the heat that is generated during driving and how the properties of the tires change.

The simulation of an automobile is well-understood; however, tires remain a challenge because they behave in a complex, non-linear manner. The calculation is either very drawn out, computationally intensive, and cannot be easily incorporated into the overall model, or it provides inexact results. CDTire/3D addresses these issues.

We have used technology to find a good balance between computation time and accuracy. Instead of mapping it as a volumetric model, we represent the tire as a shell—and that saves a great deal of simulation time, yet still takes into account all of the properties.

—Dr. Manfred Bäcker, head of tire and vehicle simulation at ITWM

First, the researchers calculate individual shells for every functional ply of the real tire: one for every steel belt ply, one for the cap ply, and so on. They subsequently bring these together into a single shell. The model also takes into account the sidewall. In usual simulations, the automobile manufacturers need to completely re-adjust the parameters as soon as the tire width changes in the simulation or the tire pressure varies.

We completely separated geometry from material properties so that you can alter the tire geometry without having to match the computer model to it.

—Dr. Bäcker

The simulation tool is already in use world-wide, including at Toyota and Daimler.

Additionally, the scientists now incorporate temperature into the simulation. This is important because the tire is dynamically deformed during driving and because the brakes give off heat. As a result, the tire warms up, and its properties change.

The researchers first save the results from CDTire/3D in the temperature model. Then, with the help of these calculations, they simulate how the heat travels in the tires, and finally couple the results back into the structural model. The Swiss Formula-1 Team Sauber wants to employ the temperature model in the future to make their race cars faster in the turns.

Since the system is modularly constructed, we can couple the temperature model to any simulation tool you want.

—Dr. Bäcker

As a result, it can also be connected to the “CDTire/Realtime” tool. This software can also be employed for example during the design of an electronic control system like the Electronic Stability Program, or ESP for short. If a car starts to loose traction or slide, the ESP selectively applies the brakes of the individual wheels. In about one or two years, Bäcker said, CDTire/Realtime will be able to be deployed using microcontrollers installed in the car to increase the accuracy of the ESP while driving.


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