An Estimation Method of Ski Friction Coefficients in Ski Running on Actual Snow Fields by Sensor System

Abstract

This paper proposes an estimation method of ski friction coefficients in ski running by using sensor system. It is important for development of skies, ski waxes to obtain ski friction coefficient in ski running on actual snow filed. The ski friction coefficients are assumed as the sum of the Coulomb friction coefficient and the viscous friction coefficient of a ski. The ski friction coefficients are estimated using the Kalman filter by the information of reaction force from snow surface and gliding velocity in ski's coordinate. The reaction force from snow surface was measured by 6-axis force sensor installed to between ski and binding, and the direction and vertical components of reaction force from snow surface are used for estimation of ski friction coefficient. The gliding velocity was estimated by the 3D posture and the acceleration of ski boot, and the 3D position. The 3D posture was estimated by using the sensor fusion from the angular velocity of gyro sensor and the acceleration of accelerometer attaching the ski boot. The 3D position was obtained by GPS receiver attaching to top of head. We used the estimation method of ski friction coefficients to measurement information obtained by the skier conducting carving turns on an actual snow field, and we obtained the ski friction coefficients varying from moment to moment on an actual snow field. The estimation results of ski friction coefficients fitted for the previous reference. Therefore, the proposed method can use to evaluation of skies, ski waxes.