Recreational Off-Highway Vehicle (ROV) Handling and Control 2012-01-0239

Through testing conducted by multiple facilities, it has been observed that the class of compact two-person vehicles designed exclusively for off-road operation known as Recreational Off-Highway Vehicles (ROVs) exhibit a range of steady-state handling characteristics - including both understeer and understeer transitioning to oversteer as measured in circle-turn tests similar to those set forth in SAEJ266. This handling characteristic is different from on-road passenger cars and light trucks which, under all but heavy loading conditions, exhibit linear range and limit understeer steady-state cornering behavior. Limit understeer is considered desirable for on-road vehicles because it provides a directionally stable and generally predictable control response.

In the research presented in this paper, the handling qualities, including controllability, of a ROV which was modified to have different steady-state handling characteristics ranging from understeer to oversteer is examined. Specifically, this research examines how drivers adapt to and/or utilize the vehicle's different handling characteristics through comparisons of driver control inputs and vehicle response on an off-road riding course that includes a range of turning maneuvers and speeds. Five drivers operated the vehicle in the same course with the vehicle configured to be heavily understeer, moderate understeer, and to transition to oversteer. Based on the control strategies used and resulting vehicle response in the different configurations, the effect of a vehicle's steady state handling behavior in transient maneuvers is evaluated.

This study demonstrated that the test vehicle in all three configurations could be controlled safely when operated with only moderate levels of tire slip on the test course utilized for this study. When the vehicle was driven more aggressively, the stock configuration with moderate understeer and the transitional oversteer configuration provided sufficient feedback to allow the driver to maintain control of the vehicle. In the more heavily understeer modified configuration, the feedback from the vehicle as the front tires approached saturation was difficult to interpret and made the task of maintaining the vehicle on the test course more difficult, especially when the vehicle was operated in an intentionally aggressive manner.