Correlation and Accuracy of a Wheel Force Transducer as Developed and Tested on a Flat-Trac® Tire Test System 1999-01-0938

The wheel force transducer has been proven to be a cost and time effective tool for vehicle load data acquisition and simulation testing. The accuracy of wheel force transducers is typically given in terms of a static calibration, or a quasi-static system generated load case. The actual use of a wheel force transducer often involves high speed rotation, varying camber and steer of the tire on the vehicle, and other dynamic and rim related variations which deviate from the standard laboratory calibration. The Flat-Trac proves to be an excellent tool in the design process and evaluation of the wheel force transducer because it accurately controls and simulates the loading of a rotating wheel assembly. Through Flat-Trac System testing, issues that are critical to the use, accuracy, and integrity of data acquired through a wheel force transducer can be evaluated. Using this knowledge, a wheel force transducer can be developed which has low sensitivity to rim and boundary variations, high accuracies, and low errors including low modulation (spinning transducer coordinate system to non-spinning load coordinate outputs) error. These errors are typically encountered in actual usage of a wheel force transducer, but often are neglected or very difficult to analyze. In an actual road test, errors described above are very difficult or impossible to distinguish from other real outputs such as those caused by surface variations, tire non-uniformity, and driver variability. The Flat-Trac System provides a means to conveniently apply controlled loading and acquire data from realistic loads on a spinning wheel, while controlling the variables in the test, acquiring tire orientation data, and accurately measuring the static (vehicle coordinate) load vector through a Flat-Trac Transducer. The verification of the MTS Spinning Wheel Integrated Force Transducer * (SWIFT™) has shown that through a good sensor body design, these errors can be reduced to give highly accurate wheel force transducer data. This is critical in acquiring accurate data results, as well as for ensuring correlation of the durability and simulation tests to the actual loads occurring in durability road tests.