外文翻譯---控制系統(tǒng)的介紹

1、<p>　　Introduction to Control System</p><p>　　The design of people to control nature’s forces successfully has been the catalyst for progress throughout history. Our goal has been to control these force

2、s in order to help perform physical tasks, which were beyond our own capabilities. During the dynamic and highly motivated 20th century, the control-system engineering has transformed many of our hopes and dreams into re

3、ality. Control-system engineers have made very important contributions to our advancements. As we look back, control-syste</p><p>　　Yet all these types of control, if they are to be successful, have certai

4、n features in common. A control system is the collection of components connected in such a way as to effect control over certain aspects of the domain in which the system operate. In addition, Control systems exist that

5、require no human interaction, such as aircraft automatic plots and automobile cruise control system. In dealing with control system, particularly engineering control system, we will deal with a variety of co</p>&

6、lt;p>　　In general, control systems can be categorized as being either open-loop or closed-loop. The distinguishing feature between these two types of control system is the use of feedback comparison for closed-loop op

7、eration.</p><p>　　Open-loop Control System</p><p>　　Open-loop control systems represent the simplest form of controlling devices. Figure 2.1 illustrates a simple tank-level control system. We wi

8、sh to hold the tank level h within reasonable acceptable limits even though the outlet flow through value v1 is varied. This can be achieved by irregular manual adjustment of the inlet flow rate by value V2.</p>&

9、lt;p>　　The system is not a precision system, as it does not have the capability of accurately measuring the output flow rate through value V1, the input flow rate through value V2, or the tank level. Fig.2.2 shows the

10、 simple relationship that exists in this system between the input (the desired tank level) and the output (the actual tank level). </p><p>　　This signal-flow representation of the physical system is called a

11、 block diagram. Arrows are used to show the input entering and the output leaving the control system. This control system does not have any feedback comparison, and the term open loop is used to describe this absence.<

12、;/p><p>　　Fig2.3 illustrate a field-controlled dc motor turning a cutting wheel at a constant speed. When a piece of wood is applied to the surface of the cutting wheel, it acts as a disturbing torque of the mo

13、tor any results in a reduction of the speed of the cutting wheel, assuming that control signal remains constant. This situation can be represented as shown in Fig.2.4. The symbol appearing between the motor and the load

14、represents a substractor.</p><p>　　The effect of disturbance torques, or other secondary inputs, is detrimental to the accurate functioning of an open –loop control system, it has no way of automatically co

15、rrecting its output, because there is no feedback comparison.</p><p>　　Closed-loop Control System</p><p>　　Closed-loop control systems derive their valuable accurate reproduction of input from f

16、eedback comparison. An error detector derives a signal proportional to the differences between the input and output. The closed-loop control system drives the output until it equals the input and the error is zero. Any d

17、ifferences between the active and desired output will be automatically corrected in a closed-loop control system. Through proper design, the system can be made relatively independent of seconda</p><p>　　Fig.

18、2.5 illustrates an automatic tank-level control version of the system shown in Fig.2.1. It can maintain the desired tank level h within quite accurate tolerances even through the output flow rate through value V1 is vari

19、ed. If the tank level is not correct, an error voltage is developed. This is amplified and applied to a motor drive that adjusts value V2 in order to restore the desired tank level by adjusting the inlet flow rate. A blo

20、ck diagram analogous to this system is shown in Fig.2.6.</p><p>　　An automatic speed-control version of a filed-controlled dc motor, which was shown in Fig.2.7, is illustrated in Fig.2.4. This feedback syste

21、m has the capability of maintaining the output speed relatively constant even though disturbing torques may occur. A tachometer, which function as a transducer that transform speed to control system. Should the outpu

22、t speed differ from the desired speed, the difference amplifier develops an error signal, which adjusts the filed current of the motor in o</p><p>　　Feedback control system used to control position, velocity

23、, and acceleration are very common in industrial and military application. They have been given the special name of servomechanisms. With all their many advantages, feedback systems have a very serious disadvantage, beca

24、use the closed-loop system may inadvertently act as an oscillator. Through proper design, however, all the advantage of feedback can be utilized without having an unstable system. </p><p><b>　　譯文

25、：</b></p><p><b>　　控制系統(tǒng)的介紹</b></p><p>　　人們對自然力控制地成功設計，一直是整個歷史進程的催化劑。為了有助于完成物理學的重任，這些又遠遠超出我們?nèi)藫碛械哪芰?。我們的目標已?jīng)達到了控制這些力。在這具有極大活力和欲望的二十世紀，控制系統(tǒng)的設計已經(jīng)把我們的許多愿望和夢想變成了現(xiàn)實。控制系統(tǒng)設計人員對我們社會的發(fā)展，已經(jīng)成

26、為了非常重要的貢獻者。當我們回顧歷史，制系統(tǒng)設計人員，所做的貢獻，有機器人、太空飛行器系統(tǒng)，包括在月球上軟著陸的成功完成、直升飛機自動飛行和控制、輪船和潛水艇的控制系統(tǒng)以及水翼船的控制、高速鐵路自動控制系統(tǒng)，而且特別是最近以來，用于磁懸浮火車的鐵路系統(tǒng)的控制系統(tǒng)。</p><p>　　然而，如果說這些是成功的話，所有這些類型的控制存在著共同的特點。一個控制系統(tǒng)是由許多元件以一種方式連接在一起的集合，這種方式能夠影

27、響系統(tǒng)運行中占主導作用方面的控制。另外，控制系統(tǒng)要有無人操作的要求，以達到直升飛機的自動飛行和自動巡航控制系統(tǒng)。在處理控制系統(tǒng)時特別是引擎控制系統(tǒng)，我們要處理各類元件，暗示了這類學科是接受培訓的一類?？刂圃O計人員需要具有機械、電子、流體機械、熱力學、結構學、材料學等等方面的知識。計算機很廣泛地用于實現(xiàn)控制體系。日益俱增的技術信息和軟件設計的知識，也正成為控制設計人員的需要。很顯然，每一種控制系統(tǒng)不僅包括上面所述的一種因素，而且是包含很多

28、方面的因素。</p><p>　　總之，控制系統(tǒng)被分為開環(huán)系統(tǒng)和閉環(huán)系統(tǒng)，這兩類型的控制系統(tǒng)的根本性特征是用于閉環(huán)運行中有反饋比較的應用。</p><p><b>　　開環(huán)控制系統(tǒng)</b></p><p>　　開環(huán)控制系統(tǒng)代表了控制裝置的一種簡單形式，圖2.1表示了一種簡單的容器液位控制系統(tǒng)，我們希望使液位保持在合理的可能的范圍，即使通過變量V

29、1，泄露量一直在變化，這種狀態(tài)是通過變量V2的輸入流量速度，或容器的液位。</p><p>　　圖2.2表示了在輸入（所期望的容器液位）和輸出（實際的容器液位）之間的系統(tǒng)中存在的簡單關系。這種物理學系統(tǒng)中單一流向的描繪，稱為方框圖，箭頭被用來表明輸入口和輸出口控制系統(tǒng)。這個系統(tǒng)沒有任何反饋比較，術語開環(huán)被用來描述這種缺乏。</p><p>　　圖2.3描述了一個場控制的直流電機，此電機能以

30、恒定的速度帶動切割輪旋轉(zhuǎn)。當一塊木頭作用于這個切割輪表面，它對電機阻轉(zhuǎn)矩起到一種阻礙作用，結果切割輪速度降低。假定控制信號一直保持，這種情況可能是圖2.4所示，電機和負載之間表現(xiàn)出來的特征構成了減法器。</p><p>　　阻礙力矩的影響或者其它次要的輸入，對開環(huán)控制系統(tǒng)的準確性，是至關重要的，它沒有辦法糾正它的輸出，因為它沒有反饋比較。</p><p><b>　　閉環(huán)控制系統(tǒng)

31、</b></p><p>　　從反饋比較中得到系統(tǒng)動態(tài)的準確的輸入結果，一個不精確的探測器來說，對于不同的輸入和輸出，得到一個成比例關系的信號，直到閉環(huán)控制系統(tǒng)等于輸入或誤差為零時得到輸出。在實際和期望的輸出之間的任何相差，都將會在一個閉環(huán)系統(tǒng)中被自動地糾正。通過合理的設計，系統(tǒng)在元件性能中，能相對做到次要輸入和變化的獨立性。</p><p>　　圖2.5描述了一個自動液位控制

32、系統(tǒng)模型，也就是圖2.1所表示的圖形，它能得到所期望的液位h在相當精確的誤差之內(nèi)，即使輸出流量速度隨著變量V1而變化。如果液位是不精確的，則形成了一個錯誤的電壓，這是被放大了而且是適應變量V2的電機驅(qū)動，為回到所期望的容器液位，就通過調(diào)節(jié)輸入流量速度。圖2.6中的方框圖是對這個系統(tǒng)的分析，因為反饋比較的存在，這段閉環(huán)被用來描述系統(tǒng)的運行</p><p>　　圖2.7表示的是場控制的直流電機自動速度控制模型，這種模

33、型在圖2.4中很好地被描述了。反饋系統(tǒng)有能力一直保持相對的輸入速度，即使有干擾力矩發(fā)生。轉(zhuǎn)速計是這個反饋系統(tǒng)的一個元素，它的功能是作為一個轉(zhuǎn)換器，次裝置能把速度轉(zhuǎn)換成電壓。如果輸出速度和所期望的速度不同，那么不同倍數(shù)的放大器生成一個錯誤信號，此信號能夠調(diào)整電機的場電流，為了得到所期望的速度。</p><p>　　控制系統(tǒng)習慣于控制位置、速度、加速度，這在工業(yè)和軍事應用中是非常的普遍。它們都有伺服機構所給定的名字。