Abstract
In order to develop vehicles which have maximum active safety, car manufacturers need information about the so-called force and moment properties of tyres. Vehicle manufacturers, tyre suppliers and automotive research organisations have advanced test equipment to measure the forces between a tyre and a road surface under a variety of loading conditions. However, because of the large differences in the test equipment and the measurement procedures used, the consistency of the force and moment properties determined with the different test devices is a major problem.
In the scope of the EC Standards, Measurements and Testing Research programme (DG XII) 14 automotive partners, under which the six main European tyre manufacturers and three European car manufacturers, started the project TIME, aiming at the development of a common tyre measurement procedure for steady state cornering that will be reliable and consistent with realistic driving conditions.
First, the differences between results obtained with the 11 different tyre test devices have been investigated, followed by a parameter sensitivity study in order to explain the differences between the results obtained with the different devices. Especially test surface curvature and test surface properties appear to have a large effect on the tyre F&M properties. Next step was the determination of the force and moment properties of different types of tyres under realistic vehicle driving conditions in order to establish reference measurements. Vehicle steady state cornering testing showed that ISO testing may produce not-realistic tyre testing conditions in terms of tyre temperature and tyre wear. A cruising type of test, with alternating left and right curves of different radii and vehicle speed, creates more realistic conditions for a tyre. The reference measurements have been used as a basis for developing the new tyre measurement procedure. Correlation of tyre test results of the 11 different tyre test devices with the reference measurements was the first part of the validation of the new measurement procedure. In addition, tyre test results coming from the new test procedure have been used in tyre models as a part of full vehicle dynamic simulation models in order to judge the procedure's validity and usefulness. Some of the test benches especially those who succeeded in implementing completely the TIME procedure allow the prediction of the vehicle steady state cornering behaviour within a range of 10%, when a direct implementation of tyre TIME measurements into a vehicle&tyre model is applied, without any further adjustment. The approach used in the TIME project to come to a common tyre test procedure for steady state cornering has resulted in a test method that aims at making people, involved in F&M tyre testing, more aware of the importance of both realistic tyre test conditions and vehicle test conditions.
It is expected that a common use of the TIME procedure will improve the efficiency of the co-operative (virtual) prototyping work of tyre and vehicle manufacturers. The wide support within the project consortium by the automotive industry already indicates that the common test procedure for steady state tyre testing, can be seen as a basis for a next generation of tyre test procedures.