Comparative Analysis of Tire Evaluation Methods for an Indirect Tire Pressure Monitoring System (iTPMS)

Starting from the USA and followed by the European Union, legal requirements concerning "Tire Pressure Monitoring Systems" (TPMS) for passenger cars and light trucks will be introduced in China as well and therefore in the third of the three largest automobile markets worldwide. Changes of pressure dependent physical tire properties such as dynamic roll radius and a certain tire eigenfrequency, which are included in the ESC-wheel speed signals, indicates pressure loss in an indirect manner. Systems with corresponding working principles are called "indirect Tire Pressure Monitoring System" (iTPMS). Since the tire is a structural element with varying characteristics according to the design parameters, the roll radius and frequency behavior due to pressure loss is variable as well. As a consequence, tires have to be evaluated regarding there compatibility to iTPMS during the vehicle development process. In order to firstly reduce the testing effort on the complete vehicle and secondly to perform the evaluation at an earlier stage in the development process, tires shall be tested on external drum test rigs. This paper researches the systematic differences between the tire evaluation at whole vehicle driving tests on road and at tire test rigs. Based on testing results and simulation models the interaction of tire vibration behavior and suspension influences is analyzed as well as excitation characteristics of roads and cleat crossings.