無線電力驅動感測器網路研製

Design and Implementation of Wireless Powered Sensor Networks

劉昱宏(Yu-Hong Liu)

指導教授 ： 林啟瑞

國立臺北科技大學/機電學院/機電整合研究所/碩士(2012年)

摘要

近年來無線通訊技術的發展，省略了訊號線的配置，使感測器網路更易於安裝和應用，然而，感測器網路節點上電力的需求，無論是使用電力配線或者以電池供應電力，仍然妨礙了感測網路的分佈，降低其應用性。本研究提出一項以無線電力驅動感測器網路之技術，搭配使用標準之無線射頻識別讀取器，在符合FCC規範條件下，以902~928 MHz超高頻電磁波作為電力傳輸媒介，透過電磁波共振技術達成高效率之無線電力傳輸，以提供電力給遠端感測網路節點，達成無線資料傳輸與無線電力傳遞之操作，發展一易於分散配置之感測器網路。研究中包括開發：無線電力傳輸模組 與 無線感測器節點模組，其中感測器節點模組上為能精確量測相關物理量除整合IC封裝之溫度感測器、照度感測器與相對濕度感測器，更配置本實驗室利用微機電技術開發之微結構風速感測器，以用於空間中之物理量監測蒐集乃至於舒適度指標之推估計算。其檢測精度、線性度與動態範圍，分別與實驗室等級量測儀器測量比對，均能符合工業用所需；為作進一步的確效與驗證，最終將所開發之無線電力驅動感測器網路應用於室內環境的舒適度量測，並驗證其適用於舒適度指標推估之用。總結相關實驗結果，發現電磁波發射源使用線極化天線時，無線電力最大有效傳輸範圍可達約3.5公尺；利用感測器網路與實驗室等級量測儀器測量空間中定點PMV值，其相差在±5%內，尤其風速感測器只有0.01 m/s以下之差距，證實感測器網路配置之IC型感測器與自行開發之微機電型風速感測器均有良好精度，以無線電力驅動無線感測器配置之感測器足以有效用於空間中相關資訊之蒐集；另一實驗則以本研究之無線電力驅動感測器網路量測舒適度，並與室內人員舒適度投票值CSV相比較，信賴水準達93.3%，互相關值約在3%內，此一實驗結果顯示了無線電力驅動感測器網路能夠有效收集室內舒適度指標，與人體感受趨於一致，並可由此建議，作為環境監控用之節電回路規劃參考，更可望在未來配合控制器的研發，實現以節能為主的無線控制網路操作，用於工業與民生各項控制，達成智慧型舒適感測調整乃至於節約省能之目標。

關鍵字

無線電力傳輸 ； 無線射頻識別 ； 電磁共振 ； 回波耦合 ； 無線功率傳輸 ； 無線感測器網路 ； 舒適度量測 ； 非接觸技術

並列摘要

Recent technological advances in wireless communications have been enabled to easily install and apply sensor networks. Today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on. However, the sensor node’s power supply which rely power line or battery will obstruct the sensing system distribution and applications. In this paper, the feasibility of wireless power transfer is investigated. The construction is based on the reference design of the wireless identification and sensing platform (WISP) from Intel. The wireless power transmission system works with a standard UHF RFID reader, using the electromagnetic wave (EM wave) with the central frequency between 902 to 928 MHz - the allowed ISM band at FCC. The electric power is transferred to remote sensor nodes by Electromagnetic Resonance and a matched resonant antenna. The technique will be able to supply enough power to drive remote sensor nodes and the low-power circuits. The sensor networks which powered by the wireless power transfer will be constructed to achieve wireless power transmissions and wireless data communications, as well as be more easily to distribution. The study includes design and implement wireless power transfer module and sensor node module. After checking precision and effective working range, we find they are suitable for industrial use. In order to get the more detailed test and verify, I use a demo case to do thermal comfort measurements with using the wireless powered sensor networks(WPSN). The thermal comfort measurements are influenced by thermal, humidity and flow. To get the measurements are more accurate, the sensing node module integrates an IC-based temperature sensor, the radiation thermometer, the relative humidity sensor, a MEMS flow sensor and the PIC16F690 microprocessor for predicted mean vote (PMV) calculation. The 433 MHz band RF module was employed for the wireless data communication with the specific protocol based on the Modbus communications protocol.
Moreover, in the wireless power transfer the efficiency is the more significant parameter. The study also focuses on the efficiency of remote charging and the effective distance. In this paper, the wireless power transmission system has been proved to achieve 70% power conversion efficiency and it collects the power by setting the distance at 3.5m. Although we expect that the effective distance with wireless power transfer could have reached to fifteen meters, yet the electric power has to be limited in accordance with the legal emission power from the RFID reader, which is ask by National Communication Council. With experimental results prove that this technique is quite suitable for low input power transmission. Finally, the outcomes of the evaluation inspire us to utilize the technique in a demo case of the thermal comfort measurements. The wireless powered sensor networks are able to gather the indoor comfort sensing index in good agreement with the comfort sensing vote (CSV) of a human being and the experimental results within the environment suggest that the sensing system can be used in air conditioning system to realize the comfort-optimal control strategy.

並列關鍵字

Wireless Power Transfer(WPT) ； Radio Frequency Identification system(RFID) ； Electromagnetic Resonance ； Backscatter Coupling ； Wireless Power Transmittion ； Wireless Sensor Networks(WSNs) ； Thermal comfort ； PMV ； Contactless Technique

參考文獻

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