電子信息工程外文資料翻譯---壓電式加速度傳感器及其應用

1、<p>　　畢業(yè)論文(設計)外文資料翻譯</p><p>　　The piezoelectric acceleration sensor and its application</p><p>　　Abstract: in recent years the piezoelectric acceleration sensor got bigger development, this

2、 article expounds the piezoelectric acceleration sensor principle and constitute element, and the analysis of its frequency characteristics and sensitivity, exploring the error formation factors, summarizes its applicati

3、on in the field of engineering control. </p><p>　　One, the piezoelectric acceleration sensor principle </p><p>　　The piezoelectric acceleration sensor and says piezoelectric accelerometer. It al

4、so belongs to the inertial sensor. It is the use of certain substances, such as quartz crystal's piezoelectric effect, in the accelerometer, quality by vibration of piezoelectric element and in the force changed also

5、. When measured vibration frequency is far lower than the natural frequency of the accelerometer, the change of force by using is proportional to the acceleration. </p><p>　　Because of the piezoelectric sens

6、or output signal is weak charge, and sensor itself has a great internal resistance, so little, the output energy behind the circuit to bring certain difficulties. Therefore, usually the sensor signal to lose to high inpu

7、t impedance of the preamplifier. After impedance transformation can be used in the future, amplification, detection circuit will signal loss to indicating meter or recorder. </p><p>　　Second, the piezoelectr

8、ic acceleration sensor constitute elements </p><p>　　(a) center installation compression type (b) ring shear (c) triangle shear</p><p>　　Commonly used the piezoelectric accelerometer structure

9、 form shown in figure 13.18. S is spring, M is the mass, B is base, P is piezoelectric element, R is clamping ring. Figure 13.18 a is the central Ann loaded compressed type, piezoelectric element-quality piece of-spring

10、system installed in the circular center struts, supports and base connection. This structure has high resonant frequency. However base B and the testing to like connection, if base B are the deformation will directly inf

11、luenc</p><p>　　Three, the piezoelectric acceleration sensor amplitude frequency characteristics </p><p>　　The use of accelerometer ceiling depends on the amplitude frequency curve frequency reso

12、nant frequency map (figure 13.19). General small damping (z < = 0.1) of the accelerometer, upper limit for the resonant frequency if the frequency of a third, can guarantee amplitude error is less than 1 dB (12%); If

13、take for 1/5 of the resonant frequency are guaranteed amplitude error is less than 0.5 dB (6%), and phase shift less than 30. But the resonant frequency and accelerometer fixed condition, acceler</p><p>　　Fi

14、gure 13.20 a of the steel bolt, is to make the resonant frequency can achieve the best way out of the resonant frequency. Bolt may not all shake screw holes into the base, lest cause base deformation, the influence of th

15、e accelerometer outputs. In the installation of layer of the tu yi on silicon grease can increase the uneven surface of the installation of the connection reliability. Need can be used when insulation insulation bolts an

16、d mica washer to fixed accelerometer (figure 13.20 b), but</p><p>　　Four, the piezoelectric acceleration sensor sensitivity </p><p>　　The piezoelectric accelerometer, the sensitivity of piezoele

17、ctric accelerometer is power type, can see it as a sensor voltage source or charge source, the sensitivity and charge voltage sensitivity has two said method. The sensitivity The former is the accelerometer output voltag

18、e (mV) and are under the acceleration than; The latter is accelerometer output charge and are under the ratio of acceleration. Acceleration unit for m/s2, but in vibration measurement often use standard gravity accelerat

19、</p><p>　　Piezoelectric crystal accelerometer transverse sensitivity says it lateral (in vertical axis) accelerometer sensitive degree of transverse vibration, the sensitivity to the Lord sensitivity (that i

20、s often accelerometer voltage sensitivity or charge sensitivity) percentage said. In general on the shell marked by a red dot minimum horizontal direction, a good and the sensitivity of the accelerometer transverse sensi

21、tivity should be less than 3% of the Lord sensitivity. Therefore, the piezoelectric</p><p>　　Five, the piezoelectric acceleration sensor error formation factors analysis </p><p>　　Piezoelectric

22、accelerometer preamplifier piezoelectric element stress the creation of charge after amount, this very weak charges boundary and then piezoelectric element on the boundary conductor charged to the voltage U = q/Ca (here

23、is the accelerometer Ca in capacitance). To determine the charge so weak (or voltage) is the key to prevent wire, the measurement circuit and accelerometer itself of charge of the leakage. In other words, piezoelectric a

24、ccelerometer used the preamplifier should have</p><p>　　From the piezoelectric sensor mechanics model of the look, it is "low pass" characteristics, the original extremely low frequency vibration m

25、easurement. But in fact because of low frequency especially small amplitude vibration acceleration, the sensitivity of the sensor is small, limited, so the output signal will be weak and signal-to-noise ratio was low; Ad

26、ditional charge, the drift integral leakage circuit (used for measuring vibration velocity and a move), the noise of the device is inevitab</p><p>　　Five, the piezoelectric acceleration sensor of practical a

27、pplication </p><p>　　At present the latest IBM Thinkpad laptops in the built-in acceleration sensors, dynamic monitoring out to use notebook in the vibration, and according to the vibration data, the system

28、will be intelligent choice closed or let it continue to run hard drive, so can the greatest degree of protection because, for example, the turbulence vibration work environment, or accidentally fell off the computer to d

29、o damage caused by the hard disk, the greatest degree of protection in the inside of the data.</p><p>　　Generally speaking, acceleration sensor can be used in the control, the handle vibration and shaking, i

30、nstruments, the brake start testing, testing, earthquake warning system, toys, structures, environmental monitoring, engineering geological exploration, vibration measurement, railway, Bridges, DAMS vibration test and an

31、alysis; The mouse, high-rise building structure dynamic characteristics and security vibration on reconnaissance. </p><p>　　Six, the piezoelectric acceleration sensor of practical application </p><

32、;p>　　At present the latest IBM Thinkpad laptops in the built-in acceleration sensors, dynamic monitoring out to use notebook in the vibration, and according to the vibration data, the system will be intelligent choice

33、 closed or let it continue to run hard drive, so can the greatest degree of protection because, for example, the turbulence vibration work environment, or accidentally fell off the computer to do damage caused by the har

34、d disk, the greatest degree of protection in the inside of the data.</p><p>　　Generally speaking, acceleration sensor can be used in the control, the handle vibration and shaking, instruments, the brake star

35、t testing, testing, earthquake warning system, toys, structures, environmental monitoring, engineering geological exploration, vibration measurement, railway, Bridges, DAMS vibration test and analysis; The mouse, high-ri

36、se building structure dynamic characteristics and security vibration on reconnaissance. </p><p>　　壓電式加速度傳感器及其應用</p><p>　　摘要：近年來壓電式加速度傳感器得到了較大的發(fā)展，本文重點闡述了壓電式加速度傳感器的原理及其構成元件，分析了其頻率特性和靈敏度，探究了其誤差形成因素

37、，概述了其在工程控制領域中的實際應用。</p><p>　　一、 壓電式加速度傳感器原理</p><p>　　壓電式加速度傳感器又稱壓電加速度計。它也屬于慣性式傳感器。它是利用某些物質如石英晶體的壓電效應，在加速度計受振時，質量塊加在壓電元件上的力也隨之變化。當被測振動頻率遠低于加速度計的固有頻率時，則力的變化與被測加速度成正比。</p><p>　　由于壓電式傳感

38、器的輸出電信號是微弱的電荷，而且傳感器本身有很大內阻，故輸出能量甚微，這給后接電路帶來一定困難。 為此，通常把傳感器信號先輸到高輸入阻抗的前置放大器。經過阻抗變換以后，方可用于一般的放大、檢測電路將信號輸給指示 儀表或記錄器。 </p><p>　　二、壓電式加速度傳感器構成元件</p><p>　　常用的壓電式加速度計的結構形式如圖13.18所示。S是彈簧，M是質塊，B是基座，P是壓電元

39、件，R是夾持環(huán)。圖13.18a是中央安 裝壓縮型，壓電元件—質量塊—彈簧系統(tǒng)裝在圓形中心支柱上，支柱與基座連接。這種結構有高的共振頻率。然而基座B與測試對 象連接時，如果基座B有變形則將直接影響拾振器輸出。此外，測試對象和環(huán)境溫度變化將影響壓電元件，并使預緊力發(fā)生變化， 易引起溫度漂移。圖13.18c為三角剪切形，壓電元件由夾持環(huán)將其夾牢在三角形中心柱上。加速度計感受軸向振動時，壓電元件承 受切應力。這種結構對底座變形和溫度變化有極好的

40、隔離作用，有較高的共振頻率和良好的線性。圖13.18b為環(huán)形剪切型，結構簡單，能做成極小型、高共振頻率的加速度計，環(huán)形質量塊粘到裝在中心支柱上的環(huán)形壓電元件上。由于粘結劑會隨溫度增高而變軟，因此最高工作溫度受到限制。</p><p>　　三、壓電式加速度傳感器幅頻特性</p><p>　　加速度計的使用上限頻率取決于幅頻曲線中的共振頻率圖（圖13.19）。一般小阻尼(z<=0.1)的

41、加速度計，上限頻率若取為共振頻率的 1/3，便可保證幅值誤差低于1dB（即12%）；若取為共振頻率的1/5，則可保證幅值誤差小于0.5dB（即6%），相移小于30。但共振頻率與加速度計的固定狀況有關，加速度計出廠時給出的幅頻曲線是在剛性連接的固定情況下得到的。實際使用的固定方法往往難于達到剛性連接，因而共振頻率和使用上限頻率都會有所下降。加速度計與試件的各種固定方法見 圖13.20。</p><p>　　其中圖1

42、3.20a采用鋼螺栓固定，是使共振頻率能達到出廠共振頻率的最好方法。螺栓不得全部擰入基座螺孔，以免引起基座 變形，影響加速度計的輸出。在安裝面上涂一層硅脂可增加不平整安裝表面的連接可靠性。需要絕緣時可用絕緣螺栓和云母墊片來 固定加速度計（圖13.20b），但墊圈應盡量簿。用一層簿蠟把加速度計粘在試件平整表面上（圖13.20c），也可用于低溫（40℃以下）的場合。手持探針測振方法（圖13.20d）在多點測試時使用特別方便，但測量誤差較大，

43、重復性差，使用上限頻率一般不高于 1000Hz。用專用永久磁鐵固定加速度計（圖13.20e），使用方便，多在低頻測量中使用。此法也可使加速度計與試件絕緣。用硬性粘接螺栓（圖13.20f）或粘接劑（圖13.20g）的固定方法也長使用。某種典型的加速度計采用上述各種固定方法的共振頻率分別約為：鋼螺栓固定法31kHz，云母墊片28kHz，涂簿蠟層29kHz，手持法2kHz，永久磁鐵固定法7kHz。</p><p>　　

44、四、壓電式加速度傳感器的靈敏度</p><p>　　壓電式加速度計的靈敏度 壓電加速度計屬發(fā)電型傳感器，可把它看成電壓源或電荷源，故靈敏度有電壓靈敏度和 電荷靈敏度兩種表示方法。前者是加速度計輸出電壓（mV）與所承受加速度之比；后者是加速度計輸出電荷與所承受加速度之比。 加速度單位為m/s2，但在振動測量中往往用標準重力加速度g作單位，1g= 9.80665m/s2。這是一種已為大家所接受的表示方式，幾

45、乎所有 測振儀器都用g作為加速度單位并在儀器的板面上和說明書中標出。對給定的壓電材料而言，靈敏度隨質量塊的增大或壓電元件的增多而增大。一般來說，加速度計尺寸越大 ，其固有頻率越低。因此選用加速度計時應當權衡靈敏度和結構尺寸、附加質量的影響和頻率響應特性之間的利弊。</p><p>　　壓電晶體加速度計的橫向靈敏度表示它對橫向（垂直于加速度計軸線）振動的敏感程度，橫向靈敏度常以主靈敏度（即加速度計的電壓靈敏度或電荷

46、靈敏度）的百分比表示。一般在殼體上用小紅點標出最小橫向靈敏度方向，一個優(yōu)良的加速度計的橫向靈敏度應小于主靈敏度的3％。因此，壓電式加速度計在測試時具有明顯的方向性。</p><p>　　五、壓電式加速度傳感器誤差形成因素分析</p><p>　　壓電加速度計的前置放大器 壓電元件受力后產生的電荷量極其微弱，這電荷使壓電元件邊界和接在邊界上的導體充電 到電壓U=q/Ca（這里Ca是加速度計的

47、內電容）。要測定這樣微弱的電荷（或電壓）的關鍵是防止導線、測量電路和加速度計本身的電荷泄漏。換句話講，壓電加速度計所用的前置放大器應具有極高的輸入阻抗，把泄漏減少到測量準確度所要求的限度以內，壓電式傳感器的前置放大器有：電壓放大器和電荷放大器。所用電壓放大器就是高輸入阻抗的比例放大 器。其電路比較簡單，但輸出受連接電纜對地電容的影響，適用于一般振動測量。電荷放大器以電容作負反饋，使用中基本不受 電纜電容的影響。在電荷放大器中，通常用高質

48、量的元、器件，輸入阻抗高，但價格也比較貴。</p><p>　　從壓電式傳感器的力學模型看，它具有“低通”特性，原可測量極低頻的振動。但實際上由于低頻尤其小振幅振動時，加速度值小，傳感器的靈敏度有限，因此輸出的信號將很微弱，信噪比很低；另外電荷的泄漏，積分電路的漂移（用于測振動速度和位 移）、器件的噪聲都是不可避免的，所以實際低頻端也出現“截止頻率”，約為0.1～1Hz左右?！?lt;/p><p&

49、gt;　　六、壓電式加速度傳感器的實際應用</p><p>　　目前最新IBM Thinkpad手提電腦里就內置了加速度傳感器，能夠動態(tài)的監(jiān)測出筆記本在使用中的振動，并根據這些振動數據，系統(tǒng)會智能的選擇關閉硬盤還是讓其繼續(xù)運行，這樣可以最大程度的保護由于振動，比如顛簸的工作環(huán)境，或者不小心摔了電腦做造成的硬盤損害，最大程度的保護里面的數據。另外一個用處就是目前用的數碼相機和攝像機里，也有加速度傳感器，用來檢測拍攝