外文翻譯--數(shù)字控制的發(fā)展及數(shù)控用傳感器

1、<p><b>　　英文原文：</b></p><p>　　The development of NC</p><p>　　and Transducers for NC machine Tools</p><p>　　The first NC machines used vacuuin tubes ,electrical relays

2、,and complicated machine-control interfaces.The seciond generation of machines utilized improved miniature electronic tubes,and later solid -state circuits .As computer techonology improved,NC underwent one of the most r

3、apid changes known in history .The third generation used much improved integrated circuits .Computer hardware became progressicelu less expensive and more reliable and NC control builders introduced for the first time Re

4、a</p><p>　　A set of preprogrammed subroutines ,named canned cycles ,were developed for yse in routine operations .They were recorded into the ROMs and remained there even after power was shut off.For the fir

5、st time ,this concept made it possible to read the machinging program into memory and to operate the machine from memory .In addition to the advantages of editing ,the problems caused by erroneous tape reading disappear

6、ed .</p><p>　　Along with the many canned cycle options ,CNC builders introdyced displays for visual editing of part programs in memiry .Various in-cycle problems generated alarms and hundreds of diafnostic m

7、essages which could be displayed as applicable .Practically every function of the machine was tied into the system and monitored during operation .A constant surface speed control was incorporated and continuously antic

8、ipated the most efficient spindle speed of the next cut to minimize time lost for spind</p><p>　　The improvement in drives was as important for the system as the contribution of the microprocessor or the min

9、icomputer.</p><p>　　The feed drives ,usually known as servodrives, consist of a motor and its control which receives its motion instructions from the CNC. their performance is essential to the accuracy ,reli

10、ability ,and flexibility of the CNC system.</p><p>　　The open-loop system is normally used in simple point-to-point,or positioning systems,although improvements in technology have made it possible to inst

11、all the system in contiuring systems as well.</p><p>　　The closed-loop configuration is more accurate and reliable ,as reflected by its higher cost .</p><p>　　Although many CNC system still use

12、hydraulic or pules motors, the DC drives have gained dominance on a much larger scale .In most cases ,the drive packages are purchased from specialized drive system builders .These direct current (DC) permanent -magnet

13、wound field serviomators range from 3,000 revolutions per minute to less than 1 rpm wethout stalling .They develop peak torque capabilities with high slide acceleration and low inertia for optimized system response.Most

14、drive systems offer a cho</p><p>　　The fourth -generation microprocessor CNC incorporated in many cases the controversial bible memory .The bibles are magnetic garnet crystals grown on nonvolatile data stora

15、ge. Although at this stage it is not competitive in the large computers,the bible memory is closing the cost gap with disk storage devices .Insensitive to adverse temperature changes ,dust ,and vebration ,the bubble me

16、mory has demonstrated superioe reliability in shop enveronment.General Numerics introduced its fourth-genera</p><p>　　Among the strengths of the fourth -generation mecroprocessor CNC(MCNC) are added part pr

17、ogram memory storage ,reduction of printed circuit boards , programmable interface ,faster memory access, parametric subroutines,and macro capabilities.</p><p>　　The system user can now write specific canned

18、 cycles directed to particular applications (user macros ), far more economical and efficient than conventional canned cycles .Mathematical calculations with do-loop subroutines using variables can now be incorporated in

19、 the part program .The microprocessor controls both computations and motion commands.Thus ,following an in-process gaging ,an out-of tolerance condition will be fed back ,and the tool offset will be automatically modifie

20、d to achieve th</p><p>　　Positioning feed back devices for NC can be classified into two groups,viz.rotary and linear transducers.Rotary transducers may be connected to the lead screweithyer directly or thro

21、ugh precision gearing . This feed back device measures indirectly the position of the slide as it measures some angle and the feed train ratio relates the Same to the linear movement of the slide.On the other hand ,linea

22、r transducers indicate the position of the slide directly. In this case one part of the transducer</p><p>　　Rotary Transducers </p><p>　　Rotary transducers are quite popular with NC machine manu

23、facturers because of their compact size and the flexibility with which these can be used.There are two primary types of rotary transducers:resolvers and encoders the resolver is an analog device whose output is converted

24、 to digital form , whereas the encoder is a numerical device that outputsdigital data directly.</p><p>　　Resolver:Resolverslike synchros are simple ,small,cylindrical ac motors in construction.The stator of

25、a simple synchro contains three windings 120apart while that of a resolver has two windings 90 apart .As the rotor turns,synchros and resolvers behave as rotating transformers and an inductive coupling exists between the

26、 stator and rotor.Typically, by exciting the rotor windings a voltage is induced in the stator windings.The magnitude of the induced voltage is proportional to the cosine of the </p><p>　　Rotary Inductosyn:I

27、t is like a resolver with a large number of poles (say 144 or 360 poles ) and with one rotor coil.Due to a large number of poles , the output signal cycles per revolution increase manifold, viz.half the number of poles a

28、s was mentioned earlier in the case of resolver.</p><p>　　Rotary Encoders:Rotary encoders are widely used widely used in NC machine tools as position and motion sensors.These can be classified as either incr

29、emental encoders or absolute encoders.</p><p>　　Incremental encoders (Pulse Generating Encoders ) The optical incremental encoder consists of a glass disc with accurately etched lines at regular intervals.Ty

30、pically the diameter of the discs may vary from 60 mm to 150 mm with lines 10 to 2500.The disc rotates between a light source and one or more of photodiodes.The lines make and break this photoelectric beam and the genera

31、ted pulse signal is amplified to give a square wave output. An encoder with 360 lines accordingly gives 360 pulses per re</p><p>　　Linear Transducers</p><p>　　The principles involved in the poer

32、ation of these transducers are quite similar to those discussed for rotary transducers. As these measure the position of the slide directly, these do not need highly precise intermediate members namely screw and nut , a

33、nd gearing .Further , the errors due to this interposing feed train are sent. Main types are described below;</p><p>　　Glass Scales with Line Grationg : The transparent index grating (sensing device )</p&

34、gt;<p>　　and the glass scales in this case have similar line graduation. The relative movement between the two scales results in alternate transparent and opaque regions . Typical width of the lines and spaces is

35、20 microns each . The light passing through these regions is sensed by photodiodes. The resistance of these photodiodes changes with the intensity of falling light resulting into electrical pulses . The periodic signals

36、are processed within the counter in such a manner that a single forward coun</p><p>　　Linear Inductosyn:It consists of a scale (usually fixed to the machine tool bed ) and a slider . The scale is made from s

37、teel or aluminium sections of about 250 mm length .An insulating layer covers this base material . The coil , in a continuous rectanguglar waveform pattern ( with a typical cyclic pitch of 2 mm) is bonded to the scale .

38、The slider about 100 mm long has two separate but identical coil tracks bonded to the surface that faces the scale . In operation , the inductosyn is like a mu</p><p>　　Alternatively , the slider coils may b

39、e excited with 90` phase shift and relate the linear movement to the phase shift of the output signal obtained at the scale coil. </p><p><b>　　中文譯文：</b></p><p>　　數(shù)字控制的發(fā)展及數(shù)控用傳感器</

40、p><p>　　第一代數(shù)控裝置采用的是真空管，繼電器及復(fù)雜的機(jī)械控制接口；第二代數(shù)控裝置則采用了小型電子管及后來(lái)的固體電路。隨著計(jì)算機(jī)技術(shù)的不斷發(fā)展，NC裝置以歷史上最快的速度得到了發(fā)展；第三代數(shù)控裝置采用了性能好得多的集成電路。隨著計(jì)算機(jī)的硬件越來(lái)越便宜，可靠性越來(lái)越好，數(shù)控裝置制造商首次引入ROM技術(shù)。在專用設(shè)備中，使用ROM來(lái)存儲(chǔ)程序，從而使CNC系統(tǒng)問(wèn)世。CNC系統(tǒng)成功的應(yīng)用于幾乎每一個(gè)制造工藝，如在加工中心

41、和車削中心上完成鉆、銑和車削加工，還應(yīng)用于玻璃切割、模型制造、電火花加工、鋼鐵廠軋軋輥磨削、坐標(biāo)測(cè)量、電子束焊接、彎管、制圖、印刷電路板、繞線、功能測(cè)試、機(jī)器人及許多其他的工藝。</p><p>　　研制開(kāi)發(fā) 了一套預(yù)先編制好的子程序，叫做固定循環(huán)供日常使用，這些程序記錄了在 ROM內(nèi)，失去電后仍然保存。加工程序可以存入存儲(chǔ)器，并從存儲(chǔ)器取出指令來(lái)操作機(jī)床；除具有編輯功能外，還可避免出現(xiàn)由讀帶錯(cuò)誤所產(chǎn)生的一些問(wèn)題

42、。</p><p>　　除有許多固定循環(huán)可供任選擇外，還設(shè)有顯示裝置（CRT)，可顯示存儲(chǔ)器內(nèi)零件程序的編輯，對(duì)各種循環(huán)內(nèi)出現(xiàn)的問(wèn)題可發(fā)出報(bào)警，并能顯示幾百個(gè)診斷信息。機(jī)床的幾乎每個(gè)功能均與系統(tǒng)連在一起，操作期間可進(jìn)行監(jiān)控，采用恒線速控制，能不斷使主保持在最佳切削轉(zhuǎn)速，從而使主軸加速時(shí)間減至最小。除傳統(tǒng)的直角座標(biāo)直線和圓弧插補(bǔ)外，還采用了極座標(biāo)和螺旋線插補(bǔ)；由編碼或內(nèi)部參數(shù)所設(shè)定的安全區(qū)域建立了電子防撞壁可防止刀

43、具碰撞，這些特性標(biāo)志著制造和金屬切削工業(yè)水平達(dá)到了高技術(shù)。</p><p>　　傳動(dòng)系統(tǒng)的改進(jìn)和采用微處理機(jī)或小型計(jì)算機(jī)一樣，對(duì)系統(tǒng)是最重要。進(jìn)給傳動(dòng)通常稱作伺服傳動(dòng)，它用電動(dòng)機(jī)和接收CNC運(yùn)動(dòng)指令的控制裝置組成。其性能如何將影響CNC系統(tǒng)的精度，可靠性和靈活性。雖然開(kāi)環(huán)系統(tǒng)經(jīng)技術(shù)改進(jìn)后可用于連續(xù)控制系統(tǒng)，但一般仍用于簡(jiǎn)單的點(diǎn)位或定位系統(tǒng)中。閉環(huán)系統(tǒng)比開(kāi)環(huán)系統(tǒng)更精確，更可靠，但成本也較高。盡管仍有許多CNC系統(tǒng)采

44、用液壓或肪沖馬達(dá)，但直流驅(qū)動(dòng)裝置已在相當(dāng)大蕩圍內(nèi)得到應(yīng)用。在多數(shù)情況下，驅(qū)動(dòng)設(shè)備是從專門(mén)經(jīng)營(yíng)驅(qū)動(dòng)系統(tǒng)的制造商處購(gòu)買(mǎi)。這些永久磁鐵磁場(chǎng)的直流伺服電機(jī)轉(zhuǎn)速范圍從3000轉(zhuǎn)/分到1轉(zhuǎn)/分也不失速。這些伺服電機(jī)具有性能好，峰值轉(zhuǎn)矩慣性低等特點(diǎn)，使系統(tǒng)響應(yīng)達(dá)最佳化。大多數(shù)驅(qū)動(dòng)系統(tǒng)可選用晶體管化的可控硅整流器或全程放大電壓的脈寬調(diào)制。它能驅(qū)動(dòng)任何絲杠，其內(nèi)部電流環(huán)響應(yīng)快，可對(duì)扭矩－負(fù)載失調(diào)進(jìn)行可靠調(diào)整，還有一個(gè)高增益的前置放大器，可用來(lái)接高帶寬速度

45、環(huán)。</p><p>　　直流驅(qū)動(dòng)裝置加上軸的固有剛度對(duì)CNC系統(tǒng)實(shí)現(xiàn)加減速，停止及恒速等功能是必不可少的。它還可應(yīng)用于機(jī)器人，傳送線，航模，繪圖儀等領(lǐng)域。由于這些驅(qū)動(dòng)裝置均為無(wú)級(jí)變速和全反饋，幫對(duì)各種規(guī)格的電機(jī)都可實(shí)現(xiàn)最佳控制。隨著齒輪箱和離合器的去除，第三代CNC系統(tǒng)驅(qū)動(dòng)裝置的成本也隨之大大減小。</p><p>　　第四代采用微處理機(jī)的CNC系統(tǒng)在許多情況下采用磁泡存儲(chǔ)器。磁泡是在非

46、磁性基片上造成的磁性石晶體，大小為2~3微米，可用作永久性數(shù)據(jù)存儲(chǔ)器。雖然目前磁泡存儲(chǔ)器在大計(jì)算機(jī)中還缺乏競(jìng)爭(zhēng)力。但其價(jià)格正在接近磁盤(pán)存儲(chǔ)器。它在車間環(huán)境中對(duì)溫度變化，防塵和防震要求低而可靠性又高，通用數(shù)字公司推薦使用磁泡存儲(chǔ)器的第四代CNC，而日立公司認(rèn)為磁泡用于數(shù)字控制（DNC）中比較經(jīng)濟(jì)。</p><p>　　第四代MCNC的優(yōu)點(diǎn)是增加了零件程序存儲(chǔ)器的儲(chǔ)存量，減少了印刷電路板，可編程接口，存儲(chǔ)器快速存取，

47、參數(shù)子程序，宏指令能力等功能。</p><p>　　用戶可將專用的固定循環(huán)直接寫(xiě)進(jìn)“用戶宏指令”中，這比通常的固定循環(huán)更經(jīng)濟(jì)，更有效?？蓪?duì)零件程序中帶D0循環(huán)的變量子程序進(jìn)行數(shù)學(xué)，微處理機(jī)可控制計(jì)算及運(yùn)動(dòng)指令。在加工過(guò)程中測(cè)出超差時(shí)將反饋，自動(dòng)對(duì)刀具補(bǔ)償值進(jìn)行修正以達(dá)到所要求的零件尺寸。</p><p>　　數(shù)控的位置裝置反饋裝置可分為兩大類，即旋轉(zhuǎn)型和直線型傳感器。旋轉(zhuǎn)型傳感器可直接或者

48、經(jīng)過(guò)精密傳動(dòng)裝置與絲杠相連。這種裝置通過(guò)測(cè)定角度來(lái)間接測(cè)出刀架的位置，而進(jìn)給傳動(dòng)比與刀架的直線運(yùn)動(dòng)相同。直線型傳感器則是指示刀架的位置，其傳感器的一部分固定在機(jī)床的部件上，而另一部分裝在可動(dòng)部件上。</p><p>　　這種傳感器由于其緊湊性以及靈活性而廣泛用于數(shù)控機(jī)床上。主要有分解器和編碼器兩種：分解器是一種將模擬量輸入轉(zhuǎn)換成數(shù)字量輸出的傳感器；而編碼器則直接輸出數(shù)字?jǐn)?shù)據(jù)。</p><p&g

49、t;　　結(jié)構(gòu)上與同步機(jī)相似。是一種小而簡(jiǎn)單的圓筒型交流電機(jī)，同步機(jī)定子由三個(gè)間隔120度的繞組組成，而分解器定子是由兩個(gè)間隔90度的繞組組成。轉(zhuǎn)子旋轉(zhuǎn)時(shí)候，同步機(jī)和分解器相當(dāng)于旋轉(zhuǎn)變壓器，定子和轉(zhuǎn)子間存在感應(yīng)耦合。勵(lì)磁轉(zhuǎn)子繞組時(shí)，在定子繞組中會(huì)產(chǎn)生一感應(yīng)電壓，這感應(yīng)電壓的大小與轉(zhuǎn)子線圈軸和定子線圈軸間夾角的余弦值成正比。</p><p>　　這種感應(yīng)同步器象一個(gè)帶多極（144或360極）和一個(gè)轉(zhuǎn)子線圈的分解器。由

50、于極數(shù)多，故每一轉(zhuǎn)的輸出信號(hào)大量增加（1/2極數(shù)）。</p><p>　　這種編碼器廣泛用于數(shù)控機(jī)床的位置和運(yùn)動(dòng)的檢測(cè)元件?？煞譃樵隽烤幋a器和絕對(duì)值編碼器兩種。</p><p>　　光增量編碼器由一個(gè)按一定間隔、精確刻線的玻璃盤(pán)組成。盤(pán)的直徑范圍為60~150mm刻線數(shù)為10~2500條。此盤(pán)在光源和單個(gè)或多個(gè)光電極管間旋轉(zhuǎn)，刻線使光電束通或斷，將所產(chǎn)生的脈沖信號(hào)經(jīng)過(guò)放大后以矩形波的形式輸

51、出，有360條刻線的編碼器沒(méi)轉(zhuǎn)產(chǎn)生360個(gè)脈沖，若將有2500條刻線的編碼器直接與一個(gè)螺距為25mm絲杠相連，則沒(méi)每個(gè)脈沖使刀架移動(dòng)0.01mm需要時(shí)，可通過(guò)齒條和小齒輪，精密傳動(dòng)裝置和調(diào)速皮帶等機(jī)械放大裝置來(lái)進(jìn)一步提高分辨率。用兩個(gè)軌跡的刻線就可檢測(cè)轉(zhuǎn)向，故可采用兩個(gè)光電管系統(tǒng)讀同一盤(pán)，在此情況下，兩組刻線相位差為90度。將兩個(gè)軌跡來(lái)的 信號(hào)送給可區(qū)分兩種信號(hào)的方向檢測(cè)邏輯線路，并檢測(cè)其相互關(guān)系。可采用指示脈沖作為零基準(zhǔn)位，就可對(duì)軸的

52、角度增量進(jìn)行記數(shù)。</p><p>　　這種傳感器的工作原理與旋轉(zhuǎn)型傳感器十分相似，由于它們是直接測(cè)量刀架位置，故不需要諸如絲杠和螺母副及傳動(dòng)裝置等精度高的中間環(huán)節(jié)，這樣就不存在由中間環(huán)節(jié)所產(chǎn)生的誤差。主要有以下幾種型式：</p><p>　　透明的指示光柵R和刻度光柵R的原理類似于直線分度。兩光柵R間的相對(duì)運(yùn)動(dòng)產(chǎn)生交替的明暗條紋（摩爾條紋）。明暗條紋的寬度為20微米，光電二極管用來(lái)檢測(cè)光

53、的通斷。其電阻隨光的強(qiáng)度而變，從而產(chǎn)生電脈沖。計(jì)數(shù)器按光柵R每移動(dòng)5或10微米產(chǎn)生一個(gè)計(jì)數(shù)脈沖，并對(duì)這些周期信號(hào)進(jìn)行計(jì)數(shù)，從而可確定總的行程。</p><p>　　它由一個(gè)通常固定在機(jī)床床身上的刻度尺和一滑尺組成，刻度尺由250毫米長(zhǎng)的鋼或鋁制成，外包絕緣層。波形為連續(xù)方波的線圈（周期節(jié)距一般為2毫米）和刻度尺相連。約100毫米長(zhǎng)的滑尺有兩個(gè)獨(dú)立的但相同的線圈軌道，線圈軌道和面向刻度尺的表面相連。</p&g