Kaneko Tetsuya

This study deals with road friction in snowy countries in winter, which is one of the major issues in traffic safety, as a first step toward building a forward road friction estimation system. To achieve this purpose, in previous research we proposed a new method that can continuously measure the peak μ in μ-s characteristics and presented measurement results on different road surfaces. Based on these results, in this paper we measured the friction characteristics of snowy and icy surfaces maintained at proving ground, and showed the continuous μ-s characteristics on the surfaces and the peak μ region on each road surface. Furthermore, measurements are taken on ordinary roads under snow-covered conditions, and comparisons with these areas showed that the dynamics of μ-s characteristics should be considered.

This study focuses on changes in the friction characteristics of paved roads under various conditions from the viewpoint of traffic safety. In general, the braking characteristics of road vehicles are examined using the μ–s characteristics of the tires. Therefore, in our research, we used three types of limited datasets and identified them using the Magic Formula proposed by Prof. Pacejka. Based on various experiments, it was shown that changes in the road surface environment, such as dry and wet conditions, significantly affect the μ–s characteristics, and this influence varies significantly depending on the pavement conditions. In this study, as the first stage of the analysis of these influences, it was clarified that the difference in the friction characteristics of wet and dry road surfaces varies significantly depending on the pavement surface, which is based on experimental results obtained using actual roads. As this variation is closely related to the safety of actual road traffic, we used a brush model, which is a dynamic model of the road surface and tires, to clarify the differences in this characteristic.

Using the road friction measurement method constructed in previous our studies, the measurement results of friction characteristics on dry and wet surfaces are shown. From this comparison, it is confirmed that the characteristics of the wet and dry roads studied so far can be expressed. Next, we study the velocity dependence of these properties. As a result, it is shown that the velocity dependence of μ-s characteristics on ordinary roads is almost non-existent. Finally, a method of expressing μ-s characteristics obtained by continuous friction measurement, which is a feature of this measurement system, is presented. And, it is shown the peak μ and lock μ obtained from these, and also shown the superiority of this measurement method.

The Personal Mobility Vehicle (PMV), which has an inward-tilting angle, turns with lateral force due to a large camber angle, so it is necessary to consider the lateral movement of the tire vertical load axis during turning. Although the steering torque mechanisms are very different from those of automobiles, there are not many studies of the steering torque mechanisms of PMVs. In this paper, based on the effects of the force of six components acting on the tires, a method for setting the steering axis specifications is derived, including the geometrical minimization of steering moment disturbance due to the vertical load reaction force during turning. Automobile tires have a significant ground camber angle when traveling on rutted roads, but they do not have it on slanted roads because the vehicle body tilts along the road surface. On the other hand, in PMVs, the vehicle body always keeps upright when traveling both on slanted roads and on rutted roads. Therefore, the tires have ground camber angles on both types of road surface. We study the straight running ability under such road surface disturbances based on the geometrical minimization of steering moment disturbance due to the vertical load reaction force during turning. This straight running ability can be a remarkable strong point of PMVs with an inward tilt mechanism. In this study, it was proved that the steering axis parameters can be derived uniquely by taking into consideration the requirement to zero the moment (disturbance) around the steering axis due to the reaction force against the vertical load at all internal tilt angles.

This study focuses on the possibility of constructing a database on friction coefficients for actual roads from the viewpoint of traffic safety. A measurement algorithm is established to construct a road friction-measuring device. Next, the tires are selected for use in the measurements and their characteristics are measured using a bench tire characteristic tester. The measuring device is designed and constructed based on these characteristics. Finally, using this device, the measurement results of the road friction characteristics for two types of road surfaces are presented.