實現於STM32微控制器的超音波二維風速儀

A Two Dimensions Ultrasonic Anemometer Base on the STM32 Microcontroller

鄭丁睿(Ding-Ruei Jheng)

指導教授 ： 宋家驥

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903285

摘要

在這個科技發展快速，且綠色能源與環保議題受到重視的時代，風已經不僅僅只是一個自然現象，作為一個乾淨的再生能源，風能的利用日益受到關注。為了要有效率的利用風能，少不了測量環境的風速與風向。相較於傳統的機械式風速計，超音波式風速計有速度快、精確度高、耐用、適應惡劣環境等優點。本研究期望以相較市售風速儀相對低廉的價格成本，實現與市售風速儀媲美的高精度風速儀。
量測系統透過超音波在順逆風下傳播的時間差(Time of Flight)計算單維度風速，並以向量合成的方式演算合成二維風速與風向。整體系統以超音波換能器為感測元件，搭配STM32微處理器作為核心，可以大量收發訊號，並且擷取訊號與前處理。後續於電腦端開發風速演算法，以訊號處理中常用於計算訊號延遲時間的互相關(Cross-correlation)函數為理論，精確計算順逆風下之訊號延遲。最終研究達成運用換能器收發一體之架構，並且由微控制器控制系統，使系統能夠獨立發收訊號，能夠在短時間內擷取大量數據並且平均，之後傳送至電腦加以運算輸出風速與風向資料。

關鍵字

超音波 ； 風速 ； 時差法 ； 風速儀 ； 互相關函數 ； STM32微處理器

並列摘要

Wind is not just a nature phenomenon in this high tech and rapid-changing generation. As a clean and renewable energy, wind energy draws more attention while the environmental issues are highly concerned. To take advantage of the wind energy, monitoring the local wind speed and direction is an important part of the beginning.
Ultrasonic anemometers possess some advantages of resisting extreme weather, shorter responding time, silence, and simple operation over traditional wind speed measuring instruments. Moreover, ultrasonic anemometers are not assembled by many parts, that can reduce the wear and tear of the instruments.
To provide an accurate measurement of wind speed, the ultrasonic anemometer is presented in this paper, which applies the property that the time of flight (ToF) of ultrasound between two transducers depends on the environmental air flow. The system takes ultrasonic transducer as the sensor, and the STM32 F303ZE microcontroller as the control core to command the system. The system can transmit and receive massive signal and captures the signal in the head wind and tail wind. After collecting the signals, the microcontroller will send the data to the computer and do the further algorithm. The algorithm is bases on the cross-correlation theorem, which is frequently used to verify the time delay of two signals. Finally, the wind speed and direction information are obtained by the vector calculation. The system is capable of switching the transducer between transmit mode and receive mode only by digital control, and be able to transmit and receive the signal independently.

並列關鍵字

ultrasonic ； anemometer ； time of flight ； cross-correlation ； STM32

參考文獻

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