Development of Wearable Sheet-Type Shear Force Sensor and Measurement System that is Insusceptible to Temperature and Pressure

Abstract

A sheet-type shear force sensor and a measurement system for the sensor were developed. The sensor has an original structure where a liquid electrolyte is filled in a space composed of two electrode-patterned polymer films and an elastic rubber ring. When a shear force is applied on the surface of the sensor, the two electrode-patterned films mutually move so that the distance between the internal electrodes of the sensor changes, resulting in current increase or decrease between the electrodes. Therefore, the shear force can be calculated by monitoring the current between the electrodes. Moreover, it is possible to measure two-dimensional shear force given that the sensor has multiple electrodes. The diameter and thickness of the sensor head were 10 mm and 0.7 mm, respectively. Additionally, we also developed a measurement system that drives the sensor, corrects the baseline of the raw sensor output, displays data, and stores data as a computer file. Though the raw sensor output was considerably affected by the surrounding temperature, the influence of temperature was drastically decreased by introducing a simple arithmetical calculation. Moreover, the influence of pressure simultaneously decreased after the same calculation process. A demonstrative measurement using the sensor revealed the practical usefulness for on-site monitoring.

Development of Thin Shear Force Sensor Aimed at Improving QOL for Persons with Disabilities

“…The sensor was prepared by the method written in our previous paper [6]. We prepared all the parts in our laboratory.…”

“…The measurement system consists of a portable measuring circuit and a notebook computer. The configuration and functions of a single sensor system are described in the reference [6], and we explored it as a multi-sensor measurement system. The main part of the circuit was a tiny microcomputer board.…”

“…Response evaluation of the sensor was performed by a self-made evaluation apparatus [6]. This apparatus includes a fixed plate and a movable plate, and a wire cable is connected to the movable plate via a pulley.…”

“…Although raw current data between electrodes are influenced by temperature and pressure, it was possible to almost eliminate their influences by simple calculation. The corrected data showed a linear response to the shear force [6].…”

“…Though research to measure the shear force applied to the human body surface has been done before, most of these experiments are performed by preparing dedicated measuring instruments, since the shear force sensor becomes bulky. Therefore, we have developed thin shear force sensor [5,6]. This makes it possible to measure shear forces between the instruments used by persons with disabilities and the body without modification of the instrument.…”