Extension of the nondimensional tire theory to general operating conditions
Kasprzak, Edward M
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Advances in computing technology have led to an increase in the use and complexity of automotive vehicle simulations. The limiting factor in the accuracy and speed of these simulations is often the detail and complexity incorporated into the tire model. There is a need for compact, efficient tire models for use in vehicle simulations. There is also a need for broader access to raw tire force and moment data which, necessarily, creates a need for more engineers who are familiar with handling tire data. The Radt/Milliken Nondimensional Tire Theory is an incomplete tire model whose unique approach of data compression to single curves in nondimensional space shows promise of being a very compact and efficient tire model. The problem is that the model only applies for select combinations of tire operating conditions. It does not address the full combination of tire operating conditions---normal load, slip angle, slip ratio and inclination angle. In this dissertation the Nondimensional Tire Theory is extended for use in general operating conditions. A universal nondimensionalization technique based on the parameterization of secondary variables is identified. This technique treats not only this combination of operating conditions, but also allows expansion of the model to include new variables. It is used to add inflation pressure as a variable into the Nondimensional Tire Model for the first time, thus extending the definition of general operating conditions. The new Nondimensional Tire Theory fills a gap in the tire modeling spectrum located between the accurate but physically-meaningless mathematical tire models (e.g. Pacejka) and the inaccurate but physically-meaningful simple mechanical tire models (e.g., Fiala). It includes the best qualities of both groups, making it a model well-suited for use in vehicle simulations. The model structure is even shown to provide opportunities to improve the efficiency of tire testing due to the unique combinations of measured data required to populate the model. The need for greater access to tire data and engineers familiar with tire data is addressed through the establishment of the Formula SAE Tire Test Consortium. This organization collects a modest fee from registered members, all of whom are colleges and universities participating in the international Formula SAE competitions. The consortium organizes tire force and moment tests and then distributes the raw data to all registered members. It is the first time that low-cost, high-quality tire force and moment data has been available to academia. Thus, the two major contributions of this dissertation are the extension of the Radt/Milliken Nondimensional Tire Theory to general operating conditions and the establishment of the Formula SAE Tire Test Consortium.