Estimation of coefficient of static friction with one-axis force sensor by observing peripheral local slips on elastic hemisphere

Abstract

With the development of aging societies, medical costs due to slip-related-falls (SRFs) continue to increase. In order to monitor the accidents, wearable shoe systems to detect slips are promising tools to prevent SRFs in daily activities. However, a complex and heavy construction is a bottleneck of the shoe systems. In this paper, a simple sensor mechanism capable of detecting static coefficient of friction (SCOF) only by a one-axis force sensor with elastic hemisphere is proposed. In order to investigate design guidelines for the slip sensor, we experimentally evaluated (i) the Young's modulus of the elastic hemisphere and (ii) the ratio of the hemisphere diameter to the one-axis force sensor diameter. These results indicate that the proposed sensor detects the SCOF by only one-axis force sensor with soft elastic hemisphere. Furthermore, the best diameter ratio of one-axis force sensor and elastic hemisphere is 1/3 with a measurement range from 70 to 230 $\mathrm {kPa} $, which range is suitable for sensor-embedded systems.

Keywords

• slip detection sensor
• static coefficient of friction (scof)
• peripheral local slips (plss)
• slip-related falls (srfs)
• fall prevention