Riassunto analitico
In this thesis we aim at the measurement of the drag coefficient CxS of a racing car using track data. Existing methods isolate the aerodynamic drag from the overall resistance, either in an un-powered deceleration (coastdown) or in constant speed conditions. In these methods, the overall resistance is obtained by calculating the inertial force or by directly measuring the tractive torque, respectively. In both cases, the isolation of drag requires models for other resistances, namely the component of weight in longitudinal direction, the mechanical resistance of the driveline and the rolling resistance of the tyres. The proposed methodology allows to model those resistances from bespoke experimental measurements to be conducted in conjunction with the aerodynamic tests, by employing data and sensors commonly available in any racing car, thus without resorting to physical models provided by third-party suppliers. For those models, several simplifying assumptions were made, to minimize their sensitivity to potential measurement errors while focusing on the most relevant factors for racing cars.
The procedure, as concerns the coastdown method, was validated on a real racing car at the end of its development, with results being repeatable and coherent with other measurement tools. In general, calculated errors are small; moreover, the methodology was further validated by comparison against results of vehicle dynamics simulations.
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