Identification of Tire Force and Moment (F&M) Characteristics That Improve Combined Slip Handling Performance

Abstract

Since tires generate the control forces required for the operation of a vehicle, the tire force and moment (F&M) characteristics have to be designed such that the vehicle can easily be kept under driver control under many driving conditions. However, the relationship between F&M characteristics and vehicle handling performance is not well understood for many driving maneuvers. A better understanding of this relationship would thus provide insight into how to improve the matching between tires and vehicles for increased vehicle stability. Building a large number of tires with different characteristics would be too expensive and time consuming, so an investigation using simulations is preferred. However, one problem with simulations is that handling performance cannot be evaluated by a professional driver (subjective metrics), unlike in outdoor tests. A way of evaluating handling performance in simulation through objective metrics is therefore necessary. In this study, the focus is on vehicle handling performance during simultaneous cornering and braking. Desirable F&M metrics were identified using the following process: Handling simulations were validated using instrumented vehicle measurements of handling behavior at outdoor test facilities. An objective handling metric (peak body slip angle) was identified that has high correlation with professional driver ratings (subjective metric) of combined slip handling performance. The objective metric could therefore be used with simulations to predict the professional driver rating. Many virtual tires were generated by changing F&M characteristics of Pacejka tire models. These virtual tires were used in simulations of combined slip handling maneuvers and evaluated for performance using the objective handling metric. By identifying which changes to F&M metrics had high correlation to changes in handling performance, the primary influencing characteristics were determined. These results were also confirmed by looking at the correlation between F&M metrics of actual tires and their subjective ratings.