應用於手腕橈動脈脈搏波量測之壓電感測器結構設計與訊號特性分析

Abstract

本研究旨在針對手腕橈動脈量測之壓電感測器進行結構設計與訊號特性分析，探討壓電感測元件形狀、支撐結構與探頭設計對輸出訊號之影響。由於手腕橈動脈量測環境中，感測器需在有限空間內穩定感測橈動脈脈搏所造成之微小變形，因此壓電元件之固定方式與接觸面皆可能影響輸出電壓大小與訊號穩定性。 為建立可重複量測之測試條件，本研究設計並製作一組壓電感測器測試平台，利用伺服馬達搭配連桿機構驅動探頭進行週期性下壓，以模擬脈搏輸入作用於感測器之情形。壓電元件之輸出訊號透過示波器擷取，並經由訊號處理計算平均峰值與平均響應時間差，作為比較不同結構設計下訊號強度與穩定性之依據。 圓形壓電感測元件方面，本研究利用3D列印製作多種支撐結構之感測器基座，並比較其對輸出訊號之影響。結果顯示，環形支撐結構可提供較穩定之支撐條件。後續進一步探討探頭硬度與長時間重複下壓對訊號表現的影響。本研究亦針對陶瓷層同側配置之雙層圓形壓電片進行理論分析，探討其對輸出訊號提升之影響，作為圓形壓電感測元件結構優化之參考。矩形壓電感測元件方面，本研究針對不同寬度之矩形壓電片進行測試，並透過理論推導與有限元素模擬分析壓電陶瓷長度對輸出電壓之影響。後續進一步製作可實際配戴於手腕之壓電感測器，進行初步脈搏訊號量測，並透過探頭形狀與配置設計，提升訊號量測穩定性。 綜合實驗、理論分析與數值模擬結果，本研究探討壓電感測元件於手腕橈動脈脈搏波量測中之訊號表現，並分析支撐結構、壓電元件配置與探頭設計對輸出訊號之影響。研究結果可作為後續壓電感測元件形狀選擇、支撐結構設計與探頭配置優化之參考。

This study focuses on the structural design and signal characteristic analysis of piezoelectric sensors for radial artery pulse wave measurement at the wrist. The effects of piezoelectric sensing element geometry, support structure, and probe design on the output signal were investigated. In wrist-based radial artery measurement, the sensor must detect small mechanical deformations induced by arterial pulsation within a limited space. Therefore, the fixed structure and contact surface of the piezoelectric element may significantly affect the output voltage and signal stability. To establish repeatable testing conditions, a piezoelectric sensor testing platform was designed and fabricated. A servo motor combined with a linkage mechanism was used to drive the probe for periodic pressing, simulating pulse input applied to the sensor. The output signal of the piezoelectric element was recorded using an oscilloscope, and signal processing was performed to calculate the mean peak value and mean response time difference. These parameters were used to compare the signal strength and stability of different structural designs. For circular piezoelectric sensing elements, various sensor bases with different support structures were fabricated using 3D printing, and their effects on the output signal were compared. The results showed that the ring-shaped support structure provided more stable support conditions. The effects of probe hardness and long-term repeated pressing on signal performance were further investigated. In addition, a theoretical analysis was conducted on a double-layer circular piezoelectric disk with ceramic layers arranged on the same side to evaluate its potential for enhancing the output signal. For rectangular piezoelectric sensing elements, piezoelectric plates with different widths were tested. The influence of piezoelectric ceramic length on output voltage was analyzed through theoretical derivation and finite element simulation. A wearable piezoelectric sensor for wrist measurement was further fabricated for preliminary pulse signal measurement. The probe shape and configuration were designed to improve signal measurement stability. Based on experimental results, theoretical analysis, and numerical simulation, this study investigates the signal performance of piezoelectric sensing elements for wrist radial artery pulse wave measurement and analyzes the effects of support structure, piezoelectric element configuration, and probe design on the output signal. The results can serve as a reference for future selection of piezoelectric sensing element geometry, support structure design, and probe configuration optimization.