Measurement on Friction Coefficients of Tire Grounding Surface in Arbitrary Directions under High-Load

In order to measure friction coefficients of tire grounding surfaces in car running, a simple cantilever-type tactile sensor that can detect the vertical load and friction force applied to the sensing part as well as direction of the friction force, simultaneously, has been proposed. The present study equips the proposed sensor to a tire and confirms that the sensor can measure the friction coefficient of the tire grounding surface. For this purpose, measurements in this study were conducted using a sensor under a similar load as that of a common automobile travelling in an arbitrary direction. In order to perform the experiments under a high load in an arbitrary direction, we developed a parallel mechanism-type tire-driving device. The developed device can apply a high load to the tire in an arbitrary direction and can measure the vertical load, friction force, and the direction of the friction force applied to the tire involving the sensor. Thus, the measurement accuracy of the proposed sensor can be verified by comparing the output of the sensor to that of the driving device. As a result of this study, we clarified that the measurement values of the sensor are affected by the deformation of the tire, and proposed a method for correcting the effect of the tire deformation. By introducing the proposed correction method to the measurement of the sensor, it was confirmed that the friction coefficients of various surfaces can be measured with sufficient accuracy under a practical high-load condition.