Wheel Fight Objective Metric Development

Wheel Fight is the undesirable rotational response of a vehicle's steering wheel due to road input at any or all of the road/wheel tire patches. The type of road input that will cause wheel fight comes in two forms: continuous rough road surfaces such as broken concrete or transient inputs such as pot-holes and tar strips. An objective method to quantify a vehicle's wheel fight sensitivity would be of great value to the vehicle development engineer. To that end, a study was conducted on Ford's Vehicle Vibration Simulator (VVS) to gather subjective responses and use those as a basis for correlation to an objective metric. One road surface known to induce wheel fight consists of using a rubber strip and driving over it while impacting only one side of the vehicle. Under this condition, steering wheel data was acquired on five different light trucks from which paired comparison studies were conducted. Correlation of the subjective results showed that the subjective responses to the front impacts were most correlated to the overall impression; however, there was also a large degree of correlation between the front and rear impact evaluations indicating the possibility of temporal masking of the rear impact by the front. Some evidence of this effect was observed in-that the vehicle with the longest wheel base did not fit the general correlation trend observed with the other vehicles. Finally, peak-to-peak velocity of the front impact was found to correlate well to the overall subjective evaluation results. This is consistent with the results of other research dealing with human sensitivity to steering wheel rotational vibration.