Development of a Wearable Sensors System to Monitor Foot-Transmitted Vibration

Exposure to mechanical vibration may lead to harmful effects on the human body if it does not occur within a controlled environment. ISO 2631-1 regulates how to measure the vibration exposure and provides safety limits. According to this standard, the acceleration signals should be measured at the interface between the vibrating surface and the human body for a time interval long enough to represent a whole working shift. This is impossible to achieve in the case of foot-transmitted vibration, as standard equipment cannot fit between the foot and the floor. For this reason, a new system of sensors has been developed to be small enough to fit inside a regular foot insole. This system is powered through batteries and transmits the data to a cellphone through the Bluetooth connection, thus enabling a precise and continuous measurement. After production, the system has been validated by comparing the vibration exposure measured with the insoles to the vibration measured by standard piezo-electric accelerometers. The validation process took place both in laboratory controlled conditions and in real, outdoor conditions. The experimental results show a root-mean-squared error in the evaluation of vibration exposure lower than 0.1 m/s2, thus proving the potential of the proposed system.