Обучение чтению литературы на английском языке по специальности «Системы автоматического управления» (120

ПРЕДИСЛОВИЕ

Второе пособие, написанное авторами по специальности «Системы автоматического управления», позволяет совершенствовать навыки чтения и перевода оригинальной научно-технической литературы в целях получения нужной информации и ее обобщения,

атакже приобрести навыки, необходимые для ведения бесед по темам прочитанных текстов.

Все тексты пособия взяты из оригинальной американской и британской литературы, они сокращены и в некоторых случаях незначительно адаптированы. Отобранные материалы посвящены различным проблемам классической и современной теории управления. В процессе работы студенты получат возможность овладеть терминологией, расширить и углубить знания по изучаемой специальности. Стилистическая разноплановость текстов и их объем,

атакже предполагаемые формы работы позволяют моделировать условия реальной информационно-поисковой деятельности специалиста.

Пособие состоит из трех разделов, каждый из которых содержит три учебных текста. Тексты А предназначены для формирования навыков изучающего чтения. Тексты В нацелены на развитие навыков чтения книг и достаточно больших и сложных в информативном и языковом планах научных статей для извлечения основной информации по определенному алгоритму и последующего ее устного обобщения в реферативной форме. Тексты С способствуют формированию навыков ознакомительного чтения и расширению словарного запаса.

Относящиеся к текстам упражнения направлены на усвоение активной лексики, закрепление грамматических конструкций и стилистических приемов, характерных для научно-технической литературы. В конечном счете эти упражнения нацелены на творческую работу с информацией, полученной из иностранных источников (монографий, статей, справочников).

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В конце каждого раздела дан словарь (Essential Vocabulary), содержащий новые для студентов специальные термины и общеупотребительную лексику, необходимые для понимания и перевода текстов. Разумеется, помимо этих словарей студентам следует использовать разнообразные словари, изданные как в нашей стране, так и за рубежом.

Пособие предназначено для студентов 3-го курса, обучающихся по специальности «Системы автоматического управления».

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UNIT 1

TASK 1. Read and translate the text using Essential Vocabulary and a dictionary.

Text IA. Control Theory

Control engineering has taken several major steps forward at crucial events in history. Each of these steps has been matched by a corresponding burst of development in the underlying theory of control.

Early on, when the compelling concept of feedback was applied, engineers sometimes encountered unexpected results. These then became catalysts for rigorous analysis. For example, if we go back to Watt’s fly-ball governor, it was found that, under certain circumstances, these systems could produce self-sustaining oscillations. Toward the end of the 19th century, several researchers (including Maxwell) showed how these oscillations could be described via the properties of ordinary differential equations.

The developments around the period of the Second World War were also matched by significant developments in Control theory. For example, the pioneering work of Bode, Nyquist, Nichols, Evans and others appeared at that time. This resulted in simple graphical means for analyzing single-input, single-output feedback control problems. These methods are now generally known by the generic term Classical Control theory.

Classical Control theory was naturally couched in the frequency domain and the s-plane. Relying on transform methods, it is primarily applicable for linear time-invariant systems, though some extensions to nonlinear systems were made using, for instance, the describing function.

The system description needed for controls design is the magnitude and phase of the frequency response. This is advantageous since the frequency response can be experimentally measured. The transfer function can then be computed. For root locus design, the transfer function is needed. An exact description of the internal system dynamics is not needed for classical design; that is, only the input/output behavior of the system is of importance. The design may be carried out by hand using graphical techniques. These methods impart a great deal of intuition and afford the controls designer with a range of design possibilities, so that the resulting control systems are not unique. The design process here is an engineering art.

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The 1960’s saw the development of an alternative state space approach to control. This followed the publication of work on optical estimation and control by Wiener, Kalman, etc. This work allowed multivariable problems to be treated in a unified fashion. This had been difficult, if not impossible, in the classical framework. This set of developments is loosely termed Modern Control theory. With all its power and advantages, modern control was lacking in some aspects. The guaranteed performance obtained by solving matrix design equations means that it is often possible to design a control system that works in theory without gaining any engineering intuition about the problem.

Another problem is that a modern control system with any compensation dynamics can fail to be robust to disturbances, unmodelled dynamics and measurement noise. On the other hand, robustness is built in with a frequency – domain approach using notions like the gain and phase margin.

Thus these various approaches to control reached a sophisticated level and emphasis then shifted to other related issues, including the effect of model error on the performance of feedback controllers. This can be classified as the period of Robust Control theory.

There have been numerous other developments including adaptive control, autotuning and intelligent control.

TASK 2. Read and translate the following words:

major, crucial, rigorous, circumstance, generic, exact, techniques, unique, disturbance, margin.

TASK 3. Complete the table:

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TASK 9. Translate the sentences into English.

1.При каких обстоятельствах это произошло?

2.Реакция протекает (to proceed) при нормальном давлении и при комнатной температуре.

3.Открытие было сделано при следующих обстоятельствах.

4.Радиосигналы посылались с постоянной частотой.

5.Этот закон справедлив только при некоторых условиях.

6.В нашем опыте газ находился под большим давлением.

TASK 10. Find English equivalents for the following phrases and word combinations:

to encounter unexpected results; to be couched in the frequency domain and the s-plane; to carry out the design by hand; engineering art; claimed theory; to shift emphasis to other reached issues.

TASK 11. Answer the questions.

1.What crucial events in history connected with control engineering can you name?

2.How could unexpected results sometimes become catalysts for new analysis?

3.In what way did the Second World War influence the developments in control theory?

4.Why can the frequency response be regarded as advantageous?

5.Why is intuition so important for controls designer?

6.Does Modern Control Theory have any disadvantages? Which ones?

7.Can you explain the necessity of Robust Control Theory?

8.What new control theory developments do you know?

TASK 12. Speak about different methods of Control Theory.

TASK 13. Read the text using Essential Vocabulary and a dictionary to know its content in detail. Complete the tasks that follow.

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Text IB. Basic Concepts of Control Theory

The concepts of control theory are simple and applicationindependent. This universality of control theory means that it is best considered as applied to an abstract situation called a system. It is this generality which constitutes the core idea of control theory: the high level of abstraction allows for control theory to be applicable to any situation with greater specificity.

Control theory concerns itself with means by which to alter the future behavior of systems (clearly the past cannot be influenced nor, since no response can take place in any system in zero time, can the present). Furthermore, the objective of any control system in every case is connected with the performance of the system over some period of time. For control theory to be successfully applied there needs to be at least two possible actions at any stage in the control system as the system would follow an unchangeable course otherwise. In addition, control theory also needs access to some means of choosing the correct (or most applicable) actions that will result in the desired behavior being produced.

Control theory was developed to support the emergent activity of automatic control. A central idea of control theory is the control loop, labeled as information channel in Fig. 1.

Fig. 1. Automatic process control using a negative feedback (control) loop

In the broadest form, a control loop operates on the principles of negative feedback. The effects of an action are reported to the controller through an information channel. The controller strives to minimize the error difference between the measured and the desired behaviors and commands the next action appropriately. A straight-forward example of this control concept is the cruise control feature of a car: if the

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measured speed of the car drops below the set speed (because of an uphill stretch), the cruise controller will accelerate; if the car rolls too fast, the controller will shift down in an attempt to minimize the discrepancy between the desired and the measured speeds.

Historically, automatic control was concerned with the replacement of a human worker in a manually controlled process with an automatic controller supervised by a human being. The control loop of the manually steered process was closed by the operator, who manipulated levers and switches in an attempt to assimilate the measured behavior (as displayed by the control panel) with the desired one. However, human control is expensive and subject to human errors. Furthermore, there exist a number of situations in which a human control loop is not possible, or at least not feasible, be it due to dangerous circumstances or small scales.

All control loops have the same basic form, regardless of the particular application area. Thus, control theory can be considered to concentrate on studying the universal situations that underlie all applications of quantitative control.

TASK 14. Thoroughly read paragraphs 1 and 2 and define their main points.

TASK 15. Thoroughly read paragraphs 3, 4 and 5 and condense their content.

TASK 16. Summarize paragraphs 1 and 2 in no more than three sentences. Begin with: The text provides information on…

TASK 17. Compress paragraphs 3, 4 and 5 into a statement begining with the phrases:

The text describes a central idea of…

It is reported that…

The text claims that...

TASK 18. After reading the following guidelines summarize the text.

Guidelines for Making Summaries

1. Read the text through carefully – the importance of this reading period cannot be overemphasized. You really need to “think yourself into the theme” of the text and ensure a complete grasp of the topic before continuing.

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