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Measurement of the Forces from the Ground on the Tires for a Baja SAE Vehicle
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on November 30, 2020 by SAE International in United States
Knowledge of the forces on the vehicle is necessary for designing most of the vehicle subsystems, however little knowledge of the dynamic forces on small off-road vehicles is available. To measure the vertical and longitudinal forces on the tires of an off-road vehicle, a custom strain gauge system was designed and combined with Quarq tire pressure sensors while running in off-road conditions. The strain gauge system consisted of a carefully calibrated half-bridge Wheatstone bridge of 350 Ohm resistors in bending, feeding the change in voltages into the 20-bit ADC of a Cypress Semiconductor PSoC 5LP microcontroller for data interpretation and then recorded onto an SD card for later analysis. The Quarq Tyrewiz tire pressure sensors were placed on both the front and rear tires and the recorded pressures were converted to forces on the tire through calibration and helped remove the uncertainty of certain strain gauge values. Experimental data was found to agree with suspension models. Data from the strain gauges and tire pressure sensors are in agreement and when used to measure the forces on a 470 lbf Baja SAE vehicle with a driver inside, the dynamic bump forces were found to be as high as three to four times the static corner weight of the vehicle.