可回復之無線被動式微慣性開關的研發

Abstract

無線(wireless)在感測器上的使用越來越多，可減少線材的耗費，且無線感測器可應用於惡劣環境的監控，如高溫或是強酸鹼之環境，並且不用接線也使得安裝上更為方便。被動式(passive)感測器之特點為，在量測時由外部給予能量，此特點有以下三個優點，一為外部給予能量之維持與維修較容易；二為需要量測時，才需由外部給予能量量測，這說明了被動式感測器有很大的節能潛力；三為可安裝置不易安裝電池之地點，如地底下、結構內部，或精密儀器之內部。微慣性卡榫式開關(Micro Inertial Switches)可記憶最大的加速度狀態，適合被動式量測；而開關式之訊號變化大，便於人們判讀。 本論文研究重點在於研發可回復之無線被動式微慣性開關，以往的相關文獻尚無提出，其設計包含LC無線電路、微慣性開關、及微熱致動器所組成，利用微慣性開關記錄不同之加速度狀況，再利用LC無線電路感測其電路共振頻率，間接得知所紀錄之最大加速度；微熱致動器的作用是使微慣性開關能夠回復，利用LC無線電路無線傳輸能量至微熱致動器，達到微熱致動器產生位移，使卡在卡榫上之懸臂樑能夠脫落回到原始位置。 實驗架構分為三部分進行可行性驗證，一為無線被動式微慣性開關，已可透過無線量測其LC共振頻率判斷是否有latch，尚未latch時，其共振頻為9.388 MHz，第一段加速度閾值量測值為32.78 G，共振頻為7.974 MHz，，第二段加速度閾值之量測值為47.69 G，共振頻為7.075 MHz，；二為無線熱致動器，已可透過LC電路無線傳輸能量至熱致動器，所使用之電路電容值為4.4 uF，電感值為14.315 uH，電路共振頻為20.054 kHz，在輸入頻率為20 kHz時有最大之互感電流，成功無線驅動熱致動器；三為可回復之無線被動式微慣性開關，目標在透過LC電路無線驅動熱致動器使微慣性開關能回復，但因質量塊觸底問題，目前尚無法使懸臂樑回到原始位置。

Wireless sensors are popular recently, and it can reduce the cost of wires. Wireless sensors can monitor the environments in the high temperature or acid, and it is convenient to install due to its wire-free. The character of the passive sensors is, its energy is given from outside when measuring. There are three benefits with passive sensors. First, energy instrument is easier to fix and maintain outside. Second, it can save energy because it needs energy only when measuring. Third, it doesn’t need the batteries. And the Micro Inertial Switches can record the maximum acceleration, so it is good for passive measuring. The Signal of the switches is big enough to tell when switching. This thesis focuses on Developing of Reversible, wireless and Passive Micro Inertial Switches. And it contains the LC wireless circuit, micro inertial switches and the thermal actuators. It can record the maximum acceleration by measuring the resonance frequency with the LC circuits, then it can reversible with the thermal actuators. The results are divided into three parts: First, the wireless micro inertial switches can record the different acceleration by LC circuits wirelessly. When it is unlatching, its resonance frequency is 9.388 MHz; when it is on the first latch, its acceleration is 32.78 G, and its resonance frequency is 7.974 MHz; when it is on the second latch, its acceleration is 47.69 G, and its resonance frequency is 7.075 MHz Second, the wireless thermal actuators can be driven by LC circuits wirelessly. Its capacitance is 4.4 uF, and its inductance is 14.315 uH, its resonance frequency is 20.054 kHz. When the entering frequency is 20 kHz, it can produce the maximum current by mutual inductance, and it can drive the thermal actuator wirelessly. Third, Reversible, wireless, and Passive Micro Inertial Switches, it can be driven by the LC circuits. And the displacement of the cantilever beam’s end is 17 um. It can unlatch but can’t be reversible because the mass touches the substrate.