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標題: | 智慧生活科技用自組態無線感測器網路的研製與開發:
聲波與射頻定位 Autonomous WSN for Smart Living Technology Application: Acoustic & Radio Frequency Positioning |
作者: | Ji-De Huang 黃繼德 |
指導教授: | 葉超雄 |
關鍵字: | 無線感測器網路,時間同步,超音測距,抵達時間測量,同步接收器, WSN,Time Synchronization,Ultrasonic Ranging,TOA,Synchronized Receivers, |
出版年 : | 2011 |
學位: | 博士 |
摘要: | WSN (Wireless Sensor Network)結合了無線射頻與感測器技術,可以將分散於各處的感測節點 (Sensor Node)所蒐集到的資訊,透過無線技術於集中於電腦端。這項技術在自動化量測、智慧家庭、無線生醫檢測、災害預警、建築物結構自動監控等領域,皆有實際應用的價值。WSN只要改變感測器的種類,便能替換於各類的應用情境,故成為國內外眾多學者的研究方向。
然而要WSN的學習曲線並不平緩,開發人員除了須了解無線與感測技術的特性之外,還必須開發嵌入式系統的韌體來控制整套系統;除此之外,WSN的硬體價格居高不下,亦提高了入門門檻。而對實際佈建WSN來說,則有兩項基本需求,第一是時間同步,第二是定位能力。時間同步讓節點可以規劃運作與休眠時間,在保持周期性工作的情況下依然能正確的交換資料;定位能力則讓使用者得知感測資料來自何處,以及節點目前所在位置。這篇論文先以WSN的硬體設計為出發,接續討論WSN時間同步與定位機制。 WSN隨著時間的推演逐漸成熟,然而開發工具的價格與學習曲線卻令人止足不前。2006年在國科會的支持下,本論文開發了兩種不同的教學用WSN硬體,並設計各自的韌體函式庫以便於使用。有需要的研究團隊只需向計畫辦公室登記,便能獲得這套硬體進行開發,期望能以此帶動台灣的WSN發展。 由於現有同步機制無法套用於這兩種具備CSMA/CA的IEEE802.15.4硬體,因而本論文設計了一個時間同步機制;此同步機制利用微控制器的計時功能記錄誤差,再利用程式修正回去;這個機制只需單向廣播即可完成,因而適用於大規模網路。實驗證實,該同步機制在跨越三層網路的情況下,依然讓誤差維持在±0.88us以內。 節點定位這部分包含了有線超音波、RF搭配超音波,以及純RF定位這三部分。在有線超音波這部分,本論文開發了一個新的測距方法。這個方法發送兩個經過振幅與相位調變的超音波脈衝訊號,並在接收端發生自我干涉,藉由偵測自我干涉現象來達到測量TOA(Time of Arrival)的目的。實驗證實這個方法在2000mm的範圍內,依然保有標準差在0.15mm以內的精密度。在RF與超音波測距這部分,本論文沿用有線超音波測距的成果,搭配WSN時間同步,設計了二維超音波WSN節點定位系統。雖然因時間同步誤差的關係而降低系統表現,但在線性測量下,此系統依然具有1000mm內標準差為0.32mm的精密度。 在純RF定位這部分,本論文發現將多顆收發晶片的時脈同步,可以獲得比單純取平均更好的TOA結果。以此想法為基礎,本論文開發了同步相位測距系統。此系統包含多個經過同步化的接收器,這些接收器彼此間距固定相位差,且同時偵測同一封包的SFD(Start Frame Delimiter)事件。此系統在室內與室外100m的距離下,確認具有3.4m的精密度,而系統的RMS誤差則分別為5.03m與6.86m。 WSN是一個分散式系統,可應用於各式各樣的情境,下至個人化的生醫檢測,上至國家規模的環境檢測皆能運用;但若成本考量、學習困難或技術問題而不去開發與應用,那實在是浪費這個優秀的概念。本論文詳述了WSN硬體平台的開發要點,並在時間同步與定位的研究上,獲得不錯的成果。希望藉由本論文所呈現的成果,讓WSN不再只限於學術研究,而能實際投入於民生應用與產業發展上。 There are several requirements for wireless sensor network deployment. First is time synchronization and second is locatization capability. With time synchronization functioin, nodes can maintain active and sleeping sequence as well as keep working periodically to make sure data exchange correctly. Locatization capability provides the user with a way to identify where sensing data is collected and where the nodes are located. This thesis took WSN hardware/firmware design as the starting point followed by discussing the synchronization and locatization of Wireless Sensing Network (WSN). As time goes by, WSN becomes more and more mature. Nevertheless, the development tools are still too expensive and the learning curve remains steep. In 2006, this thesis was based on two newly developed WSN hardware platforms sponsored by Taiwan’s National Science Council. The handly firmware library for each of these hardware platforms were also developed then. It is due to the ease of implementation, open source software and open source hardware configurations of these two platforms, these platforms were distributed to groups who determined to advance the application of WSN. The outcome of this action led to significant advancement of WSN technology and application in Taiwan. During the year 2007 period, time synchronization methods cannot work properly in the two WSN hardware platforms mentioned above due to CSMA/CA function of IEEE802.15.4. To resolve this limitation, a new synchronization method was developed and detailed in this thesis. This method records timing error by utilitizing timer function in microcontroller and corrects it by using compensating method. With only single direction broadcast required to process the compensation, this method is sutiable for large network applications. Experimental results showed that this method is capable of keeping error under ±0.88us over three hops. Locatization technology developed during the course of this research and presented in this thesis contains wired ultrasonic ranging, wireless ultrasonic ranging, and pure RF ranging. In wired ultrasonic ranging section, a new ranging system was developed. Two ultrasonic pulses with AM and PM are sent in this system, which interfere with respect to each other at the receiver end. By detecting the interference signal, system can precisely measure Time of Arrival (TOA). Experimental results showed this system can keep Standard Deviation error (STD error) under 0.15mm over 2000mm range. In the wireless ultrasonic ranging section, a 2D ultrasonic WSN location system based on localization and time synchronization was developed and detailed. Although the performance is reduced by the synchronization error, this system still has precision up to 0.32mm over 1000mm range in linearity test. In pure RF ranging section, multi-receivers with same clock source were found to achieve better TOA data than receivers with difference sources. Base on this idea, a synchronized phase ranging system was developed. In this system, all receivers were clocked by the same souce. Same phase shift between each other and SFD (Start Frame Delimiter) event detection from the same RF package were adopted. This system was examed in 100m indoor and 100m outdoor cases; results showed this system has precision of 3.38m with RMS error of about 5.03m and 6.86m respectively. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/10124 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 應用力學研究所 |
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