超聲波在空氣中超聲測距計畢業(yè)論文外文文獻翻譯及原文

1、畢業(yè)設(shè)計（論文） 外文文獻翻譯文獻、資料中文題目：在空氣中超聲測距文獻、資料英文題目：文獻、資料來源： 文獻、資料發(fā)表（出版）日期：院（部）：專 業(yè)： 班 級：姓 名：學 號：指導教師：翻譯日期：2017. 02. 14附錄a英文原文ultasonic ranging in airg. e. rudashevski and a. a. gorbatovudc 534,321.9:531.71.083.7one of the most important problems in instrumentation technology is the remote,contactless measur

2、ement of distances in the order of 0.2 to 10 m in air.such a problem occurs，for instance,when measuring the relativethre edimensional position of separate machine members or structural units.interesting possibilities for its solution are opened up by utilizing ultrasonic vibrations as an information

3、 carrier.the physical properties of air,in which the measurements are made,permit vibrations to be employed at frequencies up to 500 khz for distances up to 0.5 m between a member and the transducer，or up to 60 khz when ranging on obstacles located at distances up to 10 m.the problem of measuring di

4、stances in air is somewhat different from other problems in the a -pplication of ultrasound. although the possibility of using acoustic ranging for this purpose has been known for a long time,and at first glance appears very simple,nevertheless at the present time there are only a small number of de

5、velopments using this method that are suitable for practical purposes.the main difficulty here is in providing a reliable acoustic three-dimensional contact with the test object during severe changes in the airs characteristic.practically all acoustic arrangements presently known for checking distan

6、ces use a method of measuring the propagation time for certain information samples from the radiator to the reflecting member and back.the unmodulated acoustic(ultrasonic)vibrations radiated by a transducer are not in themselves a source of information.in order to transmit some informational communi

7、cation that can then be selected at the receiving end after reflection from the test member，the radiated vibrations must be modulated.in this case the ultrasonicvibrations are the carrier of the information which lies in the modulation signal，i.e.，they are the means for establishing the spatial cont

8、act between the measuring instrument and the object being measured.this conclusion,however,does not mean that the analysis and selection of parameters for the carrier vibrations is of minor importance.on the contrary,the frequency of the carrier vibrations is linked in a very close manner with the c

9、oding method for the informational communication，with the passband of the receiving and radiating elements in the apparatus,with the spatial characteristics of the ultrasonic communication channel,and with the measuring accuracy.let us dwell on the questions of general importance for ultrasonic rang

10、ing in air，namely:on the choice of a carrier frequency and the amount of acoustic power received.an analysis shows that with conical directivity diagrams for the radiator and receiver，and assuming that the distance between radiator and receiver is substantially smaller than the distance to the obsta

11、cle,the amount of acoustic power arriving at the receiving area pr for the case of reflection from an ideal plane surface located at right angles to the acoustic axis of the transducer comes to2pr4ltgad1where prad is the amount of acoustic power radiated,b is the absorption coefficient for a plane w

12、ave in the medium,l is the distance between the electroacoustic transducer and the test me mber，d is the diameter of the radiator(receiver)，assuming they are equal,and cis the angle of the directivitydiagram for the electroacoustic transducer in the radiator.fia 9.ymln (200 khz)hg. 3both in eq.(l)an

13、d below,the absorption coefficient is dependent on the amplitude and not on the intensity as in some worksl，and therefore we think it necessary to stress this difference.in the various problems of sound ranging on the test members of machines and structures,the relationship between the signal attenu

14、ations due to the absorption of a planewave and due to the geometrical properties of the sound beam are,as a rule，quite different.lt must be pointed out that the choice of the geometrical parameters for the beam in specific practical cases is dictated by the shape of the reflecting surface and its s

15、patial distortion relative to some average position.let us consider in more detail the relationship betweenthe geometric and the power parameters of acoustic beams for the most common cases of ranging on plane and cylindrical structural members.it is well known that the directional characteristic w

16、of a circular piston vibratingin an infinite baffle is a function of the ratio of the pistons diameter to the wavelength d/x as found from the following expression:sma70：ltsin a(2)where j1 is a bessel function of the first order and a is the angle between a normal to the piston and a line projected

17、from the center of the piston to the point of observation(radiation).from eq.(2)it is readily found that a t w o-t o-o n e reduction in the sensitivity of a radiator with respect to sound pressure will occur at the angle0.76 義6r0 5 = arcsinfor angles a<20.eq.(3)can be simplified to0.76ca)5«f

18、dwhere c is the velocity of sound in the medimaa and f is the frequency of the radiated vibrations.it follows from eq.(4)that when radiating into air where c=330 m/s e c，the necessary diameter of the radiator for a specified angle of the directivity diagram at the0.5 level of pressure taken with res

19、pect to the axis can befound to be 1400(5)where disincmf is in khz，and ot is in degrees of angle.curves are shown in fig.l plotted from eq.(5)for six angles of a radiators directivity diagram.the directivity diagrm needed for a radiator is dictated by the maximum distance to be measured and by the s

20、patial disposition of the test member relative to the other structural members.in order to avoid the incidence of signals reflected from adjacent members onto the acoustic receiver,it is necessary to provide a small angle of divergence for the sound beam and,as far as possibles small-diameter radiat

21、or.these two requirements are mutually inconsistent since for a given radiation frequency a reduction of the beams divergence angle requires an increased radiator diameter.in fact,the diameter of thesonicatedspot is controlled by two variables,namely:the diameter of the radiator and the divergence a

22、ngle of the sound beam.in the general case the minimum diameter of thensonicatedf,spot dmin on a plane surface normally disposed to the radiators axis is given byd-=min6cl(6)where l is the least distance to the test surface.the specified value of dmin corresponds to a radiator with a diameter .5cl(7

23、)d =as seen from eqs.(,6)and(7)，thelinimum diameter of thensonieated"spot at the maximum required distancecannot be less than two radiator diameters.naturally.withshorter distances to the obstacle the size of themsonicatedn surface is less.let us consider the case of sound ranging on a cylindri

24、cally shaped object of radius r.the problem is to measure the distance from the electroacoustic transducer to the side surface of the cylinder with its various possible displacements along the x and y axes.the necessary angleaof the radiators directivity diagram isr + lmin(8)given in this case by th

25、e expressiona > arcsinwherea is the value of the angle for the directivity diagram,ymax is the maximum displacement of the cylinders center from the acoustic axis,and lmin is the minimum distance from the center of the electroacoustic transducer to the reflecting surface measured along the straig

26、ht line connecting the center of the m e m b e r with the center of the transducer.it is clear that when measuring distance，thef,runningntime of the information signal is controlled by the length of the path in a direction normal to the cylinders surface，or in other words，the measure distance is alw

27、ays the shortest one.this statement is correct for all cases of specular reflection of the vibrations from the test surface.the simultaneous solution of eqs.(2)and(8)when w=0.5 leads to the following expression:d =(9)yin the particular case where the sound ranging takes place in air having c=33o m/s

28、ec，and on the asstunption that l min«r，the necessary diameter of aunidirectional piston radiator d can be found from the fomula25 r(10)where d is in cm and f is in khz.curves are shown in fig.2 for determining the necessary diameter of the radiator as a function of the ratio of the cylinders ra

29、dius to the maximum displacement from the axis for four radiation frequencies.also shown in this figure is the directivity diagram angle as a function of r and yrnax for four ratios of minimum distance to radius.the ultrasonic absorption in air is the second factor in determining the resolutionof ul

30、trasonic ranging devices and their range of action.the results of physical investigations concerning the measurement of ultrasonic vibrations air are given inl-3.up until now there has been no unambiguous explanation of the discrepancy between the theoretical and expe -rimental absorption results fo

31、r ultrasonic vibrations in air.thus，for frequencies in the order of 50 to 60 khz at a temperature of+25°c and a relative humidity of 37%the energy absorption coefficient for a plane wave is about 2.5db/m while the theoretical value is 0.3 d b/m.the absorption coefficient b as a function of freq

32、uency for a temperature of+25°cand a humidity of 37%according to the data in2can be described by table 1.the absorption coefficient depends on the relative humidity.thus，for frequencies in the order of 10 to 20khz the highest value of the absorption coefficient occurs at 20%humidity3，and at 40%

33、humidity the absorption is reduced by about two to one.for frequencies in the order of 60 khz the maximum absorption occurs at 30.7o humidity，dropping when it is increased to 98% or lowered to 10%by a factor of approximately four to one.the air temperature also has an appreciable effect on the ultra

34、sonic absorption 1 .when the temperature of the medium is increased from+10 to+30，the absorption for frequencies between 30 and 50 khz increases by about three to one.taking all the factors noted above into account we arrive at the following approximate values for the absorption coefficient:at a fre

35、quency of 60 khz /3min=0.15 m"1 andmaxzo.sat a frequency of 200 khz/min=0.6 m1 and bmax=2 m'1.the relationships under consideration are shown graphically in fig.3.in the upper part of the diagram curves of g=f(l)are plotted for five values of the total angle in the radiators directivity dia

36、gram，where(11)thevaluesfortheminimum minandrnaxil-nummaxntransmittancencoefficients were obtained in the a bsence of aerosols and rain.their difference is the result of the possible variations in temperature over the range from -3 0 to+50and in relative hmnidity over the range from 10 to 98%.the ove

37、rall value of thentransmittanceuis obtained by multiplying the values of g and 0 for given values of l，f，and d.literaturecited1 .l.bergman，ultrasonicsrussian translation jzd.inostr.lit.?moscow(l 957).2. v.a.krasilnikov，sonic and ultrasonic wavesin russian,f i z m a t g i z?moscow(1960).3. m.mokhtar

38、and e.richardson，proceedings of the royal society, 184( 1945).附錄b中文翻譯在空氣中超聲測距g. e. rudashevski and a. a. gorbatovudc 534,321.9:531.71.083.7在儀器技術(shù)中遠程是最重要的一個問題。在空氣中，從0.2米至10米非接 觸式測量距離時，涉及到了這個問題，例如，在測量時個別機件或結(jié)構(gòu)單位的相 對三維位置。有趣的是，是利用超聲振動作為信息運輸工具，開啟了解決辦法的 可能性.在空氣這個自然道具中，進行測量的是雇用成員和傳感器之間距離0.5 米的時候，允許振動頻率高達500千

39、赫，或當與障礙物之間修正距離延仲達10 米時候，振動頻率高達60千赫茲。應(yīng)用超聲波在空氣中測量距離不同丁其他的問題。雖然能否利用聲波修正 測距的可行性己經(jīng)研宄了很長一段時間，乍一看似乎很簡單，但是目前只有為數(shù) 不多的新發(fā)明使用這種適合實際目的方法，主要困難是在有嚴重特有變化的空氣 中提供一個可靠試驗對象去接觸三維聲波。幾乎所有的目前己知用來校驗距離使用的，都是為了某些來自用來反射成員 和后面的散熱器信息樣本，測量傳播時間解決聲音的辦法。該未解調(diào)的聲（超聲）振動由傳感器輻射的，本身并不是一個信息來源.在接收 端，來自測試會員反射后，為了傳遞一些情報信息，因而被選定后，輻射振動一 定會被調(diào)制。在這

40、種情況下，超聲波振動是在于調(diào)制信號的信息的承運人，即他 們就是在測量儀器和測量穩(wěn)定的對象之間建立了空間三維接觸的手段。這一結(jié)論，但是，并不意味著分析和選擇的參數(shù)承運人振動重要性小.正相 反，承運人振動頻率與信息溝通編碼方法，與接收通頻帶和儀器中的輻射元素， 與超聲波空間特有的溝通渠道，以及測量精度是具有非常密切的聯(lián)系方式。 讓我們談具有普遍意義的空氣中超聲波測距問題，即：載波頻率和的被普遍認為 標準的聲音數(shù)額的選擇。<v14ltga(1)在pfad輻射聲功率，b是平面波在介質(zhì)中吸收系數(shù)為，l是聲電傳感器和 測試箱之間的距離，d是散熱器（接收）的直徑，c是的電聲換能器的散熱 器方向性閣的角

41、度。在均衡器（1 ）及以下，和作品1一樣，吸收系數(shù)依賴于振幅和而不是 強度，因此，我們認為有必耍強調(diào)這種差異。d. cm圖2在聲音的各種問題上，包括成員測試設(shè)備和結(jié)構(gòu)的關(guān)系，由于信號衰減吸收 的平面和適當?shù)膸缀涡再|(zhì)的聲束是，作為一項規(guī)則，一定是相差甚遠的.需要指 出的是，選擇的實際情況中光束具體的幾何參數(shù)，是基于形狀的反射面和空間的 一些失真相對平均排布。讓我們考慮一下更詳細的幾何關(guān)系和聲束的動力參數(shù)這個最常見包括平面 和圓柱結(jié)構(gòu)的成員情況。7id . sin a眾所周知，定向特性瓦的一個圓形活塞振動無限擋板是一個活塞比例函 數(shù)，d/ x為下列表達式基礎(chǔ)：2j'w =(2)從均衡器(2

42、 )中很容易發(fā)現(xiàn)，在減少兩到一個敏感性散熱器方面，聲壓級角度將會引起注意aq5 = arcsin0.76ad(3)表1fdkhz10203040506080100150200300500p()db/m1.522.63.546916400.76cld(4)其中c是中期聲速，f是輻射震動的頻率它遵循均衡器（4 ）,當輻射到空中，其中c = 300米/秒，在0.5級的壓 力面，散熱器為采取的軸的直徑用于指定角度的方向性閣上是必耍的1400(4(5)其中d是厘米，khz是千赫，（x是度角。在閣1中顯示的曲線閣是均衡器（5 ）中6個角度散熱器的方向性閣。事實上，直徑的“超聲波降解標本”現(xiàn)場控制的兩個變量，即：直徑的散熱器和發(fā)散角的聲音束.一般情況下，最小直徑的“超聲波降解標本”在現(xiàn)場飛機 表面處理，通常傾向于散熱器的軸心。min(6)l是測試表面最小的距離。對應(yīng)的散熱器直徑d =（7）作為從均衡器（6 ）及（7 ）, “聲振”現(xiàn)場最小直徑，最高耍求 散熱器直徑距離不得少于2.自然的，以短距離的障礙的大小，“聲振“表面