March 23, 2017
Dr. Graeme Fowler of Exponent's Vehicle Engineering practice recently co-authored the article, "All-Terrain Vehicle (ATV) Handling and Control, Analysis of Objective Data." The article was included in the SAE International Journal of Vehicle Dynamics, Stability, and NVH.
Because the great majority of All-Terrain Vehicles (ATVs) use a solid rear axle for improved off-road mobility, these vehicles typically transition from understeer to oversteer with increased cornering severity in tests customarily used by automobile manufacturers to measure steady-state vehicle handling properties. An oversteer handling response is contrary to the accepted norm for on-road passenger vehicles and, for this reason, has drawn scrutiny from numerous researchers.
In this paper, an evaluation of ATV handling is presented in which 10 participants operated an ATV that was configured to have two different steady-state cornering characteristics. One configuration produced an approximately linear understeer response (labeled US) and the other configuration transitioned from understeer to oversteer (labeled US-OS) with increasing lateral acceleration in constant-radius turn tests conducted on a skid pad. After operating the ATV on a closed dirt track the participants were questioned about the handling qualities of each configuration. Participants found that the ATV with either the US or US-OS steady-state handling characteristic would be satisfactory for their typical use of an ATV; however, participants overwhelmingly preferred the US-OS Configuration.
No participant reported that either configuration was unpredictable, although the US-OS configured ATV was rated as more comfortable and received better steering feedback ratings for tight turns compared to the US Configuration. A detailed discussion of the participant responses is provided, while the objective steering and vehicle response data and video collected in the study is the focus of this paper. Consistent with the participant's feedback, the objective data did not indicate that there was a control issue associated with the ATV configured to have an understeer/oversteer steady-state handling response.
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