Measurement of Friction Coefficient Between Shoe Sole and Floor Surface during Walking Using Sensor Shoe System

Abstract

Slip-related falls accounts for approximately 25% of falling accidents in work places. Therefore, it is required to know the places in workplace where floor friction is low. Because slip-related falls are likely to occur on icy road surfaces in winter, we aimed to investigate the friction coefficient between a shoe and icy surface using a sensor shoe system in which miniature tri-axial force sensors and inertial measurement units (IMUs) are installed in the outsole. Four tri-axial force sensors were place on the heel, ball, hypothenar, and toe positions, and two IMU were installed on the rear and fore foot parts. An adult male participant was asked to take a step forward with his right foot wearing the sensor shoe system on the icy surface of ice-skating link. The environmental temperature and relative humidity were 2.5℃ and 55%RH, respectively, and temperature of the ice surface was -4.2℃. The step length was 0.6 m or 0. 8 m. The sliding velocity and distance were estimated by integral of acceleration data obtained from IMUs. The friction coefficient at each force sensor position was calculated from the normal and horizontal forces obtained by each force sensor. The results indicated that the peak sliding velocity and sliding distance were not affected by the step length condition. The friction coefficient at the heel and hypothenar was lower than that at the ball and exhibited low values less than 0.1 or 0.05, which was related to large normal force at these locations.