Development of a Motion Estimation Method Using a Piezoelectric wire sensor.

Numerous studies have aimed to create an electric prosthesis that allows free finger movement without delay. However, a device with these capabilities has yet to be developed. Research on electric prostheses has been conducted not only with myoelectric prostheses but also with other biological signals. Our focus was on muscle sounds detectable on the skin during mechanical activity. Muscle sound, a biological signal, remains unaffected by skin impedance and can be measured on the skin surface. This study defined Muscle Vibration as the amalgamation of muscle sound and bulge, both detected as micro-vibrations during muscle deformation. Motion was estimated utilizing a piezoelectric wire sensor with a diameter of 0.5 mm. However, using muscle sound for motion estimation is a concern because ambient sound changes may reduce the accuracy of discrimination. Thus, this study aimed to compare the accuracy of motion estimation using a piezoelectric wire sensor. Even amid an ambient noise level of 80 dB, an average discrimination rate of 85.7% was achieved. Discriminators developed under different ambient noise conditions also exhibited a discrimination rate exceeding 90% for movements. Therefore, ambient noise does not affect motion estimation using a piezoelectric wire sensor. In conclusion, an electric prosthesis that uses Muscle Vibration measured with a piezoelectric wire sensor is a robust measurement model that is unaffected by changes in environmental sounds during use and discrimination.