- 學位論文
壓電式超音波快速感測系統
Fast-response ultrasonic sensor system for piezoceramics
摘要
本論文結合超音波飛行時間法(ToF / Time of Flight)與相位偵測法(PD / Phase Detection)之優點，並討論一種新的超音波訊號處理方法。此方法引進非連續脈寬調變(DPWM / Digital Pulse-Width-Modulation)為代表，超音波感測系統可以透過此法，去捉取超音波的回波時間，並透過卡爾曼數位濾波器(Kalman Filter)預測並降低誤差，其中也包括處理壓電片阻抗的模擬(Impedance Simulation)。在此由透過數位編碼與數值方法的建立，將可使感測器應用於實際測試中，達到高效能與高可靠度的資料。 本文主體分為超音波致動器(Ultrasonic Actuator)、超音波感測器(Ultrasonic Sensor)、電路模擬(Circuit Simulation)、電路設計(Circuit Design)、訊號處理(Signal Process)，五大部份所組成。首先由電路模擬的部份開始建立一個壓電致動器模型，由材料製程常數來決定最佳驅動頻率與最佳驅動電壓，還有提供了壓電片感值與容值的電抗性分析，進而開始使用FSK(Frequency Shift Keying)訊號調變的方式，或是DPWM(Digital Pulse Width Modulation) 訊號調變的方式，來進行超音波訊號發送，完成一個完整的超音波發送過程。 在超音波接收電路方面，先由麥克風模型建立一個簡單的聲音感測器，再由電路模擬的部份開始建立一個壓電感測器模型，透過電路分析設計軟體(PSpice / HSpice)，建立功率放大器(OPA / Operation Amplifier)接收電路，或是建立一個NPN型BJT(Bipolar Junction Transistors)電晶體之共射極電壓增益CEVG(Common-Emitter Voltage Gain)，來進行交流與直流分析(AC and DC analysis)，最後將輸出導入訊號截取卡(Data Acquisition Card)，透過卡爾曼數位濾波器來預測，得到最終的輸出結果。 透過本文可以快速的了解超音波感測器基本原理，並由本系統的脈寬調變法，去驅動一組超音波致動器與感測器。在實際測試之中所得到的數值資料，此方法將是一個最可靠而且最有效率的方法。本論文的優點是可以縮短超音波測距的反應時間(Response time)，透過超音波資料串流模式(Ultrasonic data stream)，在中長遠距離之中快速的得到精確的資訊。
並列摘要
A new digital-signal-processing method combining ultrasonic time-of-flight with phase detection estimation is presented. The method uses the digital pulse width modulation to acquire ultrasonic signal in order to accurately estimate the responding time of the echo. It is also possible to assure reduced bias and uncertainty in digital filtering measurements, such as those involving low measurement errors of echo signal. A number of numerical tests are conducted on simulated signals with the aim of the good performance when operating in real-time conditions. There are five topics in the thesis, including ultrasonic transducer, ultrasonic sensor, circuit simulation, circuit design, and signal process. Users could follow the steps in the chapter to realize the system working stage. Results attained in DPWM-based distance measurements will finally give the top reliability and max efficiency in the actual ultrasonic tests. The main contributions of this distance measurement system reduce the responded time and get powerful information in long distance. It is easily achieved by supersonic data stream model to build up the target.