電氣類外文翻譯----光電編碼器的特性及應(yīng)用

1、<p>　　The properties and application of photoelectric encoder </p><p>　　The working principle, photoelectric encoder</p><p>　　Photoelectric encoder, is a kind of photoelectric transformatio

2、n through the machine will output shaft geometric displacement convert pulse or digital sensors. This is the most sensor, photoelectric encoder and grating is by photoelectric detection device. Grating is in certain part

3、s of the diameter of the circular plate to open several rectangle hole. Caused by the code, motor and motor coaxial rotates grating and motor rotate speed, with the light emitting diode and other electronic components<

4、;/p><p>　　According to the measuring principle, encoder can be divided into optical and magnetic type, inductive and capacitor. According to the calibration method and the signal output form, can be divided int

5、o incremental, absolutely and hybrid three.</p><p>　　Incremental encoder</p><p>　　Incremental encoder is directly for the use of photoelectric pulse output three square principle of A and B and

6、Z, A and B group phase, pulse 90 º can easily identify rotation direction, and for every turn A phase Z benchmark for positioning. Pulse, Its advantages are simple structure, mechanical principle, average life expec

7、tancy in tens of thousands of hours, strong anti-jamming capability, high reliability, suitable for long distance transmission. Its defect is not the absolute output shaft r</p><p>　　圖1 光電編碼器的遠(yuǎn)離示意圖</p>

8、;<p>　　Absolute photoelectric encoder</p><p>　　Absolute encoder is direct digital output sensor, in its circular yards on several concentric yards along the radial direction of every faith, by perviou

9、s to light and not pervious to light, the sector and the adjacent code number of sectors, encoder is double the code number of bits of it in the code of digits, light source, the other side is one word has a correspondin

10、g yard photosensitive components, When the code in different position, the dish by various photosensitive components according </p><p>　　Single channel absolute photoelectric shaft encoder is using the natur

11、al binary or circular binary (Gregory yards) manner photoelectric conversion. Absolute photoelectric encoder and incremental encoder differs not pervious to light on the disk, the line, absolute encoders may have graphic

12、s, according to the number of code read code on coding, detection absolute position. Code design can use binary code, circulation, binary complement, etc. Its features are:</p><p>　　Can read Angle of absolut

13、e coordinates directly.</p><p>　　No accumulative error. </p><p>　　Power excision location information would be lost. But the resolution is determined by the binary digits, i.e., precision depend

14、s on the median 10, 14 etc. </p><p>　　Hybrid absolute encoder.</p><p>　　Hybrid absolute encoders, its output of two groups: a group of information, information for testing poles with absolute in

15、formation function, Another group of incremental encoder is completely with the output information.</p><p>　　Photoelectric encoder is an Angle (angular velocity) detection device, it will input shaft Angle f

16、or, using the principle of photoelectric convert electrical or digital accordingly, small size, high accuracy, high reliability, digital interface, etc. It is widely applied in nc machine tools, turning machine, servo dr

17、ive, robots, radar and military targets were needed in the Angle of device and equipment.</p><p>　　Applied circuit of photoelectric encoder</p><p>　　EPC - 755A application of photoelectric encod

18、er</p><p>　　EPC - 755A photoelectric encoder and the use of good performance in Angle measurement, displacement measurement, and has strong anti-jamming capability of the output pulse signal is stable and re

19、liable, and the pulse signal can be obtained by counting were measured after the digital signal. Therefore, we in the car driving simulators, steering wheel rotation Angle measurement chooses EPC - 755A photoelectric enc

20、oder, the output circuit as sensors, choose open collector output resolution selectio</p><p>　　圖2 光電編碼器鑒相計(jì)數(shù)電路</p><p>　　When the photoelectric encoder clockwise, channel, A leading channel outpu

21、t waveform of output waveform B 90 °, D flip-flop output waveform W1) for Q (high level, Q (W2) for low-level waveform cross-coupled nand gates, open, counting pulse waveform W3) by (bidirectional, send to the 74LS1

22、93 counter CU input pulses, add count, At this time, below, its output cross-coupled nand gates close for high level (waveform W4). When the photoelectric encoder counter-clockwise, channel A output waveform of </p>

23、;<p>　　Steering wheel clockwise and counter-clockwise, the maximum rotation Angle for two laps, choose resolution for 360 pulse/circle of the output pulse coder, its biggest for 900, Actual use three slices of cou

24、nts circuit 74LS193 component in the system of initialization, the signal reset (CLR), the initial set for 800H, namely 2048 (LD); the signal, So, when the steering wheel clockwise, count the output circuit for 2048 ~ 29

25、48, when steering counter-clockwise, count the output circuit for 2048-804</p><p>　　In practice, the steering wheel frequently made clockwise and counterclockwise rotation, because existence, work longer qua

26、ntization error after a period of time, the steering wheel when the output of a circuit to count, but may not 2048 several words deviation, To solve this problem, we added a steering wheel to detect circuits, systems, da

27、ta processing circuit after work on the operation state in the simulator, system test in the back, if detection circuit in the back wheel, and counts circuit</p><p>　　Photoelectric encoder gravity measuremen

28、t instrument in the application</p><p>　　The rotary photoelectric encoder, the shaft and gravity measuring instrument for knob shaft. Gravity measurement of the angular displacement volume knob compensation

29、for a signal is transformed, Rotary photoelectric encoder and absolute encoder two points and incremental encoder.</p><p>　　Incremental encoder is the output pulse form, its code plate sensor than absolute e

30、ncoder code easier to disk and higher resolution. Generally need only three barcode, here's code has not actually had word of absolute encoder code, but produce counting pulse. It's code of WaiDao and middle way

31、has the same number of uniform distribution of not pervious to light and sector (raster), but is two sector mutual stagger half area. When the code salver, turning the output signal is A difference for 90 </p><

32、;p>　　圖3 增量光電編碼器基本波形和電路</p><p>　　圖4 四倍計(jì)數(shù)方式的波形和電路</p><p>　　Figure 4 is a can prevent error and can improve the resolution of the pulse frequency subdivision circuit four times. Here, the func

33、tion of memory is D flip-flop and clock generator. Figure 4 shows, by every two D flip-flop, so take in the clock pulse, the interval of two Q end (such as the corresponding B 74LS175 2, 7 foot) maintain two clock period

34、, if both input status, said the change in, Otherwise, can according to the relationship between the changes from the party, which is "to" or "backw</p><p>　　Application problem analysis and i

35、mprovement measures</p><p>　　Application problem analysis</p><p>　　Photoelectric detection devices transmit and receive devices are installed in the production and use of exposed many defects, i

36、ts internal factors have external factors, which is mainly embodied in the following aspects:</p><p>　　Devices or accept device for mechanical vibration, caused by the shift or offset, receiving devices not

37、reliable to receive light signals, but cannot produce signals. For example, Photoelectric encoder used in steel rolling speed regulation systems, because of photoelectric encoder is bolted directly in motor shell, photoe

38、lectric encoder shaft through hard shrapnal and motor rotor connections, because motor with load is a load of impact, while rolling steel rotor motor will have caused the shell</p><p>　　Because of photoelect

39、ric detection device installed in production, production environment factors in photoelectric detection devices not reliable work. Such as the installation position of high temperature, humidity, photoelectric detection

40、device to internal electronic components characteristics change or damage. For example in continuous caster send analyzed.essential tracking system, because of photoelectric detection equipment installation location near

41、 the slab, high temperature environment</p><p>　　Production site for all kinds of electromagnetic interference source photoelectric detection device, of interference, photoelectric detection device of output

42、 waveform distortion distortion occurs, the system maloperation accident or production. For example, Photoelectric detection device installed in the production equipment of the signal, the body to the control system of t

43、he cable transmission distances in 20-100 meters, cable, although usually choose multiple shielded cable conductor, but du</p><p>　　Measures for improvement</p><p>　　Change of photoelectric enco

44、der installation. Photoelectric encoder is not installed in motor shell, but in the motor based on a fixed bracket to independent installation photoelectric encoder, photoelectric encoder axis and motor shaft center must

45、 at the same level, two axis adopt soft rubber or nylon hose connection, to reduce the impact of photoelectric encoder motor load of mechanical shock. By this way after vibration testing, the vibration velocity to 1.2 mm

46、/s.</p><p>　　Reasonable choice of photoelectric detection device, the output signal transmission medium by twisted-pair cable instead of ordinary shield cable. Twisted-pair cable has two important characteri

47、stics of cable, one is by electromagnetic interference with strong protection ability, because the space of electromagnetic interference current online can cancel each other out. Twisted-pair cable is another technical c

48、haracteristics of two mutually twisted line spacing is small, after two lines of inter</p><p>　　Using PLC software to monitor or interference. In the continuous process analyzed.essential photoelectric detec

49、tion device has the timing signal, at the same time, the whole process of signal and corresponding different stages. As shown in figure 5.</p><p>　　圖5 送引錠過程和光電信號(hào)關(guān)系</p><p>　　1 send analyzed.esse

50、ntial before starting the process, photoelectric signal 1 "1".</p><p>　　2 after the start sending analyzed.essential process, in A stage, roller, start sending bar. When the lever block photoelectr

51、ic device analyzed.essential emit light, the photoelectric signal for "0", When light guide bar through central 2 small round hole, photoelectric device sends a signal to 2 and 3, "1". </p><

52、;p>　　3 analyzed.essential sent in B stage, the process of photoelectric signal for "0", roller suspension bar, stop sending, fan-shaped 10 section pressure straightening machine, pull. "and" 1 &quo

53、t;, synchronous bar to give.</p><p>　　4 analyzed.essential sent in C stage, process, and no longer bar ceiling light, photoelectric signal four blocks for "1", "2", "stop synchronous

54、 synchronous 1," lead bar to give. This work is over optoelectronic device.</p><p>　　According to the light of electrical device testing work process, as long as the scene of sending analyzed.essential

55、each photoelectric signal process, based on the time analyzed.essential process and photoelectric signal relationship, using PLC application of relevant data, prepare to meet the requirements of PLC program, PLC program

56、output signal input to the input module, instead of PLC original photoelectric signal input signal. The program diagram shown in figure 6.</p><p>　　Conclusion</p><p>　　Photoelectric detection de

57、vice is itself by electronic components, it is certain to installation environment of technical requirements, especially in a bad environment, should take corresponding measures to protect the photoelectric detection dev

58、ice to make the product requirements in the work condition, can play the technical characteristics of the device. Otherwise, the service life of photoelectric detection device and reliability of work may be subjected to

59、the influence of different level. </p><p>　　光電編碼器的特性及應(yīng)用</p><p>　　光電編碼器的工作原理</p><p>　　光電編碼器，是一種通過光電轉(zhuǎn)換將輸出軸上的機(jī)械幾何位移量轉(zhuǎn)換成脈沖或數(shù)字量的傳感器。這是目前應(yīng)用最多的傳感器， 光電編碼器是由光柵盤和光電檢測(cè)裝置組成。光柵盤是在一定直徑的圓板上等分地開通若干

60、個(gè)長方形孔。由于光電碼盤與電動(dòng)機(jī)同軸，電動(dòng)機(jī)旋轉(zhuǎn)時(shí)，光柵盤與電動(dòng)機(jī)同速旋轉(zhuǎn)，經(jīng)發(fā)光二極管等電子元件組成的檢測(cè)裝置檢測(cè)輸出若干脈沖信號(hào)，其原理示意圖如圖1所示；通過計(jì)算每秒光電編碼器輸出脈沖的個(gè)數(shù)就能反映當(dāng)前電動(dòng)機(jī)的轉(zhuǎn)速。此外，為判斷旋轉(zhuǎn)方向，碼盤還可提供相位相差90º的兩路脈沖信號(hào)。 </p><p>　　根據(jù)檢測(cè)原理，編碼器可分為光學(xué)式、磁式、感應(yīng)式和電容式。根據(jù)其刻度方法及信號(hào)輸出形式，可分為增量式

61、、絕對(duì)式以及混合式三種。 </p><p><b>　　增量式編碼器</b></p><p>　　增量式編碼器是直接利用光電轉(zhuǎn)換原理輸出三組方波脈沖A、B和Z相；A、B兩組脈沖相位差90º，從而可方便地判斷出旋轉(zhuǎn)方向，而Z相為每轉(zhuǎn)一個(gè)脈沖，用于基準(zhǔn)點(diǎn)定位。它的優(yōu)點(diǎn)是原理構(gòu)造簡(jiǎn)單，機(jī)械平均壽命可在幾萬小時(shí)以上，抗干擾能力強(qiáng)，可靠性高，適合于長距離傳輸。其缺點(diǎn)是

62、無法輸出軸轉(zhuǎn)動(dòng)的絕對(duì)位置信息。</p><p>　　圖1 光電編碼器原理示意圖</p><p><b>　　絕對(duì)式編碼器</b></p><p>　　絕對(duì)編碼器是直接輸出數(shù)字量的傳感器，在它的圓形碼盤上沿徑向有若干同心碼道，每條道上由透光和不透光的扇形區(qū)相間組成，相鄰碼道的扇區(qū)數(shù)目是雙倍關(guān)系，碼盤上的碼道數(shù)就是它的二進(jìn)制數(shù)碼的位數(shù)，在碼盤的一

63、側(cè)是光源，另一側(cè)對(duì)應(yīng)每一碼道有一光敏元件；當(dāng)碼盤處于不同位置時(shí)，各光敏元件根據(jù)受光照與否轉(zhuǎn)換出相應(yīng)的電平信號(hào)，形成二進(jìn)制數(shù)。這種編碼器的特點(diǎn)是不要計(jì)數(shù)器，在轉(zhuǎn)軸的任意位置都可 讀出一個(gè)固定的與位置相對(duì)應(yīng)的數(shù)字碼。顯然，碼道越多，分辨率就越高，對(duì)于一個(gè)具有 N位二進(jìn)制分辨率的編碼器，其碼盤必須有N條碼道。目前國內(nèi)已有16位的絕對(duì)編碼器產(chǎn)品。</p><p>　　絕對(duì)式編碼器是利用自然二進(jìn)制或循環(huán)二進(jìn)制（葛萊碼）方式

64、進(jìn)行光電轉(zhuǎn)換的。絕對(duì)式編碼器與增量式編碼器不同之處在于圓盤上透光、不透光的線條圖形，絕對(duì)編碼器可有若干編碼，根據(jù)讀出碼盤上的編碼，檢測(cè)絕對(duì)位置。編碼的設(shè)計(jì)可采用二進(jìn)制碼、循環(huán)碼、二進(jìn)制補(bǔ)碼等。它的特點(diǎn)是： </p><p>　　可以直接讀出角度坐標(biāo)的絕對(duì)值； </p><p><b>　　沒有累積誤差； </b></p><p>　　電源切除后

65、位置信息不會(huì)丟失。但是分辨率是由二進(jìn)制的位數(shù)來決定的，也就是說精度取決于位數(shù)，目前有10位、14位等多種。 </p><p><b>　　混合式絕對(duì)值編碼器</b></p><p>　　混合式絕對(duì)值編碼器，它輸出兩組信息：一組信息用于檢測(cè)磁極位置，帶有絕對(duì)信息功能；另一組則完全同增量式編碼器的輸出信息。 </p><p>　　光電編碼器是一種角

66、度（角速度）檢測(cè)裝置，它將輸入給軸的角度量，利用光電轉(zhuǎn)換原理 轉(zhuǎn)換成相應(yīng)的電脈沖或數(shù)字量，具有體積小，精度高，工作可靠,接口數(shù)字化等優(yōu)點(diǎn)。它廣泛應(yīng)用于數(shù)控機(jī)床、回轉(zhuǎn)臺(tái)、伺服傳動(dòng)、機(jī)器人、雷達(dá)、軍事目標(biāo)測(cè)定等需要檢測(cè)角度的裝置和設(shè)備中。</p><p>　　光電編碼器的應(yīng)用電路</p><p>　　EPC－755A光電編碼器的應(yīng)用</p><p>　　EPC－755A

67、光電編碼器具備良好的使用性能，在角度測(cè)量、位移測(cè)量時(shí)抗干擾能力很強(qiáng)，并具有穩(wěn)定可靠的輸出脈沖信號(hào)，且該脈沖信號(hào)經(jīng)計(jì)數(shù)后可得到被測(cè)量的數(shù)字信號(hào)。因此，我們?cè)谘兄破囻{駛模擬器時(shí)，對(duì)方向盤旋轉(zhuǎn)角度的測(cè)量選用EPC－755A光電編碼器作為傳感器，其輸出電路選用集電極開路型，輸出分辨率選用360個(gè)脈沖/圈，考慮到汽車方向盤轉(zhuǎn)動(dòng)是雙向的，既可順時(shí)針旋轉(zhuǎn)，也可逆時(shí)針旋轉(zhuǎn)，需要對(duì)編碼器的輸出信號(hào)鑒相后才能計(jì)數(shù)。圖2給出了光電編碼器實(shí)際使用的鑒相與雙向

68、計(jì)數(shù)電路，鑒相電路用1個(gè)D觸發(fā)器和2個(gè)與非門組成，計(jì)數(shù)電路用3片74LS193組成。</p><p>　　圖2 光電編碼器鑒相計(jì)數(shù)電路</p><p>　　當(dāng)光電編碼器順時(shí)針旋轉(zhuǎn)時(shí)，通道A輸出波形超前通道B輸出波形90°，D觸發(fā)器輸出Q(波形W1)為高電平，Q(波形W2)為低電平，上面與非門打開，計(jì)數(shù)脈沖通過(波形W3)，送至雙向計(jì)數(shù)器74LS193的加脈沖輸入端CU，進(jìn)行加法

69、計(jì)數(shù)；此時(shí)，下面與非門關(guān)閉，其輸出為高電平(波形W4)。當(dāng)光電編碼器逆時(shí)針旋轉(zhuǎn)時(shí)，通道A輸出波形比通道B輸出波形延遲90°，D觸發(fā)器輸出Q(波形W1)為低電平，Q(波形W2)為高電平，上面與非門關(guān)閉，其輸出為高電平(波形W3)；此時(shí)，下面與非門打開，計(jì)數(shù)脈沖通過(波形W4)，送至雙向計(jì)數(shù)器74LS193的減脈沖輸入端CD，進(jìn)行減法計(jì)數(shù)。</p><p>　　汽車方向盤順時(shí)針和逆時(shí)針旋轉(zhuǎn)時(shí)，其最大旋轉(zhuǎn)角度

70、均為兩圈半，選用分辨率為360個(gè)脈沖/圈的編碼器，其最大輸出脈沖數(shù)為900個(gè)；實(shí)際使用的計(jì)數(shù)電路用3片74LS193組成，在系統(tǒng)上電初始化時(shí)，先對(duì)其進(jìn)行復(fù)位(CLR信號(hào))，再將其初值設(shè)為800H，即2048(LD信號(hào))；如此，當(dāng)方向盤順時(shí)針旋轉(zhuǎn)時(shí)，計(jì)數(shù)電路的輸出范圍為2048～2948，當(dāng)方向盤逆時(shí)針旋轉(zhuǎn)時(shí)，計(jì)數(shù)電路的輸出范圍為2048～1148；計(jì)數(shù)電路的數(shù)據(jù)輸出D0～D11送至數(shù)據(jù)處理電路。</p><p>

71、　　實(shí)際使用時(shí)，方向盤頻繁地進(jìn)行順時(shí)針和逆時(shí)針轉(zhuǎn)動(dòng)，由于存在量化誤差，工作較長一段時(shí)間后，方向盤回中時(shí)計(jì)數(shù)電路輸出可能不是2048，而是有幾個(gè)字的偏差；為解決這一問題，我們?cè)黾恿艘粋€(gè)方向盤回中檢測(cè)電路，系統(tǒng)工作后，數(shù)據(jù)處理電路在模擬器處于非操作狀態(tài)時(shí)，系統(tǒng)檢測(cè)回中檢測(cè)電路，若方向盤處于回中狀態(tài)，而計(jì)數(shù)電路的數(shù)據(jù)輸出不是2048，可對(duì)計(jì)數(shù)電路進(jìn)行復(fù)位，并重新設(shè)置初值。</p><p>　　光電編碼器在重力測(cè)量?jī)x中的

72、應(yīng)用</p><p>　　采用旋轉(zhuǎn)式光電編碼器，把它的轉(zhuǎn)軸與重力測(cè)量?jī)x中補(bǔ)償旋鈕軸相連。重力測(cè)量?jī)x中補(bǔ)償旋鈕的角位移量轉(zhuǎn)化為某種電信號(hào)量；旋轉(zhuǎn)式光電編碼器分兩種，絕對(duì)編碼器和增量編碼器。</p><p>　　增量編碼器是以脈沖形式輸出的傳感器，其碼盤比絕對(duì)編碼器碼盤要簡(jiǎn)單得多且分辨率更高 。一般只需要三條碼道，這里的碼道實(shí)際上已不具有絕對(duì)編碼器碼道的意義，而是產(chǎn)生計(jì)數(shù) 脈沖。它的碼盤的外道

73、和中間道有數(shù)目相同均勻分布的透光和不透光的扇形區(qū)（光柵），但 是兩道扇區(qū)相互錯(cuò)開半個(gè)區(qū)。當(dāng)碼盤轉(zhuǎn)動(dòng)時(shí)，它的輸出信號(hào)是相位差為90°的A相和B相脈沖 信號(hào)以及只有一條透光狹縫的第三碼道所產(chǎn)生的脈沖信號(hào)（它作為碼盤的基準(zhǔn)位置，給計(jì)數(shù) 系統(tǒng)提供一個(gè)初始的零位信號(hào)）。從A，B兩個(gè)輸出信號(hào)的相位關(guān)系（超前或滯后）可判斷旋轉(zhuǎn)的方向。由圖3（a）可見，當(dāng)碼盤正轉(zhuǎn)時(shí)，A道脈沖波形比B道超前π/2，而反轉(zhuǎn)時(shí) ，A道脈沖比B道滯后π/2。圖3（b

74、）是一實(shí)際電路，用A道整形波的下沿觸發(fā)單穩(wěn)態(tài) 產(chǎn)生的正脈沖與B道整形波相‘與’，當(dāng)碼盤正轉(zhuǎn)時(shí)只有正向口脈沖輸出，反之，只有逆向口脈沖輸出。因此，增量編碼器是根據(jù)輸出脈沖源和脈沖計(jì)數(shù)來確定碼盤 的轉(zhuǎn)動(dòng)方向和相對(duì)角位移量。通常，若編碼器有N個(gè)（碼道）輸出信號(hào)，其相位差為π/ N，可計(jì)數(shù)脈沖為2N倍光柵數(shù)，現(xiàn)在N=2。圖3電路的缺點(diǎn)是有時(shí)會(huì)產(chǎn)生誤記脈沖造成誤差， 這種情況出現(xiàn)在當(dāng)某一道信號(hào)</p><p>　　圖3

75、增量光電編碼器的基本波形和電路</p><p>　　圖4 四倍計(jì)數(shù)方式的波形和電</p><p>　　圖4是一個(gè)既能防止誤脈沖又能提高分辨率的四倍頻細(xì)分電路。在這里，采用了有記憶功能 的D型觸發(fā)器和時(shí)鐘發(fā)生電路。由圖4可見，每一道有兩個(gè)D觸發(fā)器串接，這樣，在時(shí)鐘脈 沖的間隔中，兩個(gè)Q端（如對(duì)應(yīng)B道的74LS175的第2、7引腳）保持前兩個(gè)時(shí)鐘期的輸入 狀態(tài)，若兩者相同，則表示時(shí)鐘間隔中無

76、變化；否則，可以根據(jù)兩者關(guān)系判斷出它的變化方 向，從而產(chǎn)生‘正向’或‘反向’輸出脈沖。當(dāng)某道由于振動(dòng)在‘高’、‘低’間往復(fù)變化 時(shí)，將交替產(chǎn)生‘正向’和‘反向’脈沖，這在對(duì)兩個(gè)計(jì)數(shù)器取代數(shù)和時(shí)就可消除它們的影 響（下面儀器的讀數(shù)也將涉及這點(diǎn)）。由此可見，時(shí)鐘發(fā)生器的頻率應(yīng)大于振動(dòng)頻率的可能 最大值。由圖4還可看出，在原一個(gè)脈沖信號(hào)的周期內(nèi)，得到了四個(gè)計(jì)數(shù)脈沖。例如，原每 圈脈沖數(shù)為1000的編碼器可產(chǎn)生4倍頻的脈沖數(shù)是4000個(gè)，其分辨

77、率為0.09°。實(shí)際上 ，目前這類傳感器產(chǎn)品都將光敏元件輸出信號(hào)的放大整形等電路與傳感檢測(cè)元件封裝在一起 ，所以只要加上細(xì)分與計(jì)數(shù)電路就可以組成一個(gè)角位移測(cè)量系統(tǒng)(74159是4-16譯碼器)。</p><p>　　應(yīng)用中問題分析及改進(jìn)措施</p><p><b>　　應(yīng)用中問題分析</b></p><p>　　光電檢測(cè)裝置的發(fā)射和接

78、收裝置都安裝在生產(chǎn)現(xiàn)場(chǎng)，在使用中暴露出許多缺陷，其有內(nèi)在因素也有外在因素，主要表現(xiàn)在以下幾個(gè)方面：</p><p>　　發(fā)射裝置或接受裝置因機(jī)械震動(dòng)等原因而引起的移位或偏移，導(dǎo)致接收裝置不能可靠的接收到光信號(hào)，而不能產(chǎn)生電信號(hào)。例如；光電編碼器應(yīng)用在軋鋼調(diào)速系統(tǒng)中，因光電編碼器是直接用螺栓固定在電動(dòng)機(jī)的外殼上，光電編碼器的軸通過較硬的彈簧片和電動(dòng)機(jī)轉(zhuǎn)軸相連接，因電動(dòng)機(jī)所帶負(fù)載是沖擊性負(fù)載，當(dāng)軋機(jī)過鋼時(shí)會(huì)引起電動(dòng)機(jī)

79、轉(zhuǎn)軸和外殼的振動(dòng)。經(jīng)測(cè)定；過鋼時(shí)光電編碼器振動(dòng)速度為2.6mm/s，這樣的振動(dòng)速度會(huì)損壞光電編碼器的內(nèi)部功能。造成誤發(fā)脈沖，從而導(dǎo)致控制系統(tǒng)不穩(wěn)定或誤動(dòng)作，導(dǎo)致事故發(fā)生。</p><p>　　因光電檢測(cè)裝置安裝在生產(chǎn)現(xiàn)場(chǎng)，受生產(chǎn)現(xiàn)場(chǎng)環(huán)境因素影響導(dǎo)致光電檢測(cè)裝置不能可靠的工作。如安裝部位溫度高、濕度大，導(dǎo)致光電檢測(cè)裝置內(nèi)部的電子元件特性改變或損壞。例如在連鑄機(jī)送引錠跟蹤系統(tǒng)，由于光電檢測(cè)裝置安裝的位置靠近鑄坯，環(huán)境

80、溫度高而導(dǎo)致光電檢測(cè)裝置誤發(fā)出信號(hào)或損壞，而引發(fā)生產(chǎn)或人身事故。</p><p>　　生產(chǎn)現(xiàn)場(chǎng)的各種電磁干擾源，對(duì)光電檢測(cè)裝置產(chǎn)生的干擾，導(dǎo)致光電檢測(cè)裝置輸出波形發(fā)生畸變失真，使系統(tǒng)誤動(dòng)或引發(fā)生產(chǎn)事故。例如；光電檢測(cè)裝置安裝在生產(chǎn)設(shè)備本體，其信號(hào)經(jīng)電纜傳輸至控制系統(tǒng)的距離一般在20—100米，傳輸電纜雖然一般都選用多芯屏蔽電纜，但由于電纜的導(dǎo)線電阻及線間電容的影響再加上和其它電纜同在一起敷設(shè)，極易受到各種電磁干擾

81、的影響，因此引起波形失真，從而使反饋到調(diào)速系統(tǒng)的信號(hào)與實(shí)際值的偏差，而導(dǎo)致系統(tǒng)精度下降。</p><p><b>　　改進(jìn)措施</b></p><p>　　改變光電編碼器的安裝方式。光電編碼器不在安裝在電動(dòng)機(jī)外殼上，而是在電動(dòng)機(jī)的基礎(chǔ)上制作一固定支架來獨(dú)立安裝光電編碼器，光電編碼器軸與電動(dòng)機(jī)軸中心必須處于同一水平高度，兩軸采用軟橡膠或尼龍軟管相連接，以減輕電動(dòng)機(jī)沖擊負(fù)

82、載對(duì)光電編碼器的機(jī)械沖擊。采用此方式后經(jīng)測(cè)振儀檢測(cè)，其振動(dòng)速度降至1.2mm/s。</p><p>　　合理選擇光電檢測(cè)裝置輸出信號(hào)傳輸介質(zhì)，采用雙絞屏蔽電纜取代普通屏蔽電纜。雙絞屏蔽電纜具有兩個(gè)重要的技術(shù)特性，一是對(duì)電纜受到的電磁干擾具有較強(qiáng)的防護(hù)能力，因?yàn)榭臻g電磁場(chǎng)在線上產(chǎn)生的干擾電流可以互相抵消。雙絞屏蔽電纜的另一個(gè)技術(shù)特點(diǎn)是互絞后兩線間距很小，兩線對(duì)干擾線路的距離基本相等，兩線對(duì)屏蔽網(wǎng)的分布電容也基本相同

83、，這對(duì)抑制共模干擾效果更加明顯。</p><p>　　利用PLC軟件監(jiān)控或干涉。在連鑄生產(chǎn)的送引錠過程要求光電檢測(cè)裝置產(chǎn)生有時(shí)序性的電信號(hào)，同時(shí)，該信號(hào)與整個(gè)過程不同階段相對(duì)應(yīng)。如圖5。</p><p>　　圖5 送引錠過程和光電信號(hào)關(guān)系</p><p>　　①送引錠過程啟動(dòng)前，光電信號(hào)1為“1”。</p><p>　?、谒鸵V過程啟動(dòng)后，

84、在A階段，輥道啟動(dòng)，引錠桿上送。當(dāng)引錠桿擋住光電裝置發(fā)射出的紅外光時(shí)，光電信號(hào)為“0”；當(dāng)紅外光透過引錠桿中部2個(gè)小圓孔時(shí)，光電裝置發(fā)出信號(hào)2和3，均為“1”。</p><p>　?、鬯鸵V過程在B階段，光電信號(hào)為“0”，輥道停下，引錠桿暫停上送，扇形10段壓下，啟動(dòng)拉矯機(jī)和“同步1”，引錠桿繼續(xù)上送。</p><p>　　④送引錠過程在C階段，引錠桿上送，并不再擋住紅外光，光電信號(hào)4為“

85、1”，啟動(dòng)“同步2”，停下“同步1”，引錠桿繼續(xù)上送。至此光電裝置工作過程結(jié)束。</p><p>　　根據(jù)光檢測(cè)電裝置的工作過程，只要現(xiàn)場(chǎng)測(cè)定送引錠過程中各個(gè)光電信號(hào)發(fā)生的時(shí)間，結(jié)合送引錠過程與光電信號(hào)的關(guān)系，利用PLC應(yīng)用程序中的相關(guān)數(shù)據(jù)，編制符合要求的PLC程序，將PLC程序輸出信號(hào)輸入至PLC的輸入模塊，替代原光電信號(hào)的輸入信號(hào)。其程序框圖如圖6所示。</p><p><b&g

86、t;　　圖6 程序框圖</b></p><p><b>　　結(jié)束語</b></p><p>　　光電檢測(cè)裝置本身是由電子元器件構(gòu)成，它對(duì)安裝環(huán)境有一定的技術(shù)要求，特別是在較惡劣環(huán)境下使用，要采取相應(yīng)的保護(hù)措施，以使光電檢測(cè)裝置工作在其產(chǎn)品要求的技術(shù)條件下，才能發(fā)揮裝置的技術(shù)性能。否則光電檢測(cè)裝置的使用壽命及其工作的可靠性都將受到不同程度的影響。結(jié)合光電檢