Biological Signal Measurements for Automatic Driving System by PZT/PZT Sol-Gel Composite

Abstract

Automatic driving system will be overspread over the world in the near future and biological signal measurement of driver will be mandatory. High sensitivity piezoelectric sensors embedded in the car sheet could be one of the solutions. However, high signal to noise ratio (SNR) requirement of sensors is much demanded. Since the SNR of PVDF is low, development of new sensors for biological signal measurement has been desired. In this study, PZT/PZT piezoelectric film sensors were made by automatic spray coating method. 90pm thick PZT/PZT piezoelectric film ware fabricated on a 60pm thick stainless substrate by an automatic spray coating machine. Also, biological signal was measured by sensors embedded in the chair on two conditions of rest state and utterance state. Measurements by Electrocardiogram (ECG) and respiration sensor were also carried out simultaneously for comparison purpose. PZT/PZT piezoelectric sensors had higher SNR than PVDF sensor on rest state, so it peaks from pulse wave and respiration were clearly observed. The error rates of PZT/PZT sensors compared with ECG was lower than that of PVDF sensor. Also, in utterance state, peak intervals of and PZT/PZT piezoelectric film sensor were similar with R-R interval as well as rest state. However, clear peaks at regular intervals could not be confirmed from the signal obtained from PVDF sensor. From these results, PZT/PZT piezoelectric film sensors can monitor heart rate variability better than PVDF due to higher SNR.