Motion Perception and Tire Models for Winter Conditions in Driving Simulators

Licentiate thesis, 2016

Many traffic accidents happen due to winter conditions, like slippery roads and limited visibility. The road administrators put a lot of effort into snow removal and deicing the roads. The vehicle manufacturers have been working with functionality to support drivers in winter conditions (studded tires, ABS, ESC, etc.) for decades. Many issues with driving in winter condition originate in drivers’ behaviors, such as risk taking and lack of awareness. By studying drivers’ behavior in winter condition in general and, the effect of various countermeasures of the vehicle, it is possible to reduce accident risks. Motion base driving simulators are commonly used tools for driver behavior research. The validity of the results of such studies depends on a large extent on the realism of the simulation. The aim of this research is to improve the realism of the driving in winter condition in driving simulators. Driving in winter conditions is in many ways different from driving in summer conditions. The difference originates mostly from differences in the tire to road interaction. Winter condition driving is typically characterized by softer motion and softer development of tire forces. With a focus on motion, two aspects have been studied: the motion feedback in the simulator and tire models for tire to snow behavior. Vehicle motion during winter driving is characterized by large yaw motions. It is shown through an experimental study that yaw motion feedback in the driving simulator is valuable for the perception of motion. Furthermore, a correct representation of the momentary center of rotation in the simulator can be important to the driver as it contains information on the vehicle state. The main differences in the force generation of tires between asphalt and snow surfaces are due to the friction levels and the shearable properties of snow. These differences are of importance for driver’s perception in driving simulators, which was confirmed by a subjective experiment. A physically based model was derived for tire behavior on snow and validated with real life measurements. It can be concluded that the there is a difference between driving in summer and winter conditions in terms of vehicle yaw motion and tire to road interaction. Conducted studies showed that these differences can be represented in the motion base driving simulator. Representing these difference increases the realism of the winter driving simulations.