Elements and Structure of Automatic Control Systems

Automatic control is the use of means which can maintain physical variables, such as temperature or pressure, at a desired level automatically. Systems which perform the control of physical variables are called automatic control systems (ACS).

Automatic control systems may be classified as servo-mechanisms, process control systems and regulators, but whatever the classification be, the same principles of operation are common to them all. Every ACS should contain five main components. They are: a driver or reference input, an error detector, control elements, a controlled quantity and feedback path elements. The basic control system operation may be described by the simple block diagram:

The reference input or driver sets the desired level or position of controlled quantity C in this system. The controlled quantity C is the resulting level or position of variable parameter, which is the position to be controlled by this ACS. The feedback path elements H supply a feedback signal B that indicates the level of the controlled quantity C. The error detector receives the feedback signal B and compares it with the input command signal R; any error (or difference between B and R) produces an output or resulting signal E. Control elements G receive, amplify and transform the output signal E to maintain the controlled quantity at the desires level.

 

 

 

 

To produce an automatic control system it is necessary to use a lot of various elements. These are logical elements, relays, potentiometers, magnetic amplifiers, transducers and other devices. The basic components of every ACS are logical elements which may be deducted to transducers and servomotors. Relays are usually sensitive devices that can control the action of large or remote apparatus in circuits. A potentiometer consists basically of a variable resistor. If connected to a circuit the variable resistance makes it possible to vary the amount of voltage supplied to a load. Magnetic amplifiers belong to a large group of magnetically controlled devices. The principle of their operation is based on the process of magnetizing a core by varying a magnetomotive force periodically. Transducer is known as a converting device. Many well-known devices act as transducers, for example, an electric motor acts as a transducer converting electrical energy into mechanical one.

The application of automatic control systems covers a lot of spheres, ranging from the use for the guidance of space vehicles to the control of industrial processes.

 

3. Look through the text and answer the questions:

1) What is automatic control? 2) What are automatic control systems? 3) How can they be classified? 4) What components does an ACS consist of? 5) What is the function of a driver? 6) Try to describe the ACS control system operation. 7) What are the basic elements of any automatic control system? 8) What is the function of relays? 9) What is the principle of amplifiers operation based on? 10) What do transducers serve for?

 

4. Memorize the words:

a self-feeding process – процесс автоматической подачи

self- initiating – автоматическое включение

a float-type controller – поплавковый регулятор

a weaving loom – ткацкий станок

to suggest an idea to smb – натолкнуть на мысль

continuous cycle production – непрерывный производственный цикл

to direct on the correct path – направлять по заданной траектории

transfer machining – механическая перестановка

 

5. Read the text and explain the advantages of automation:

Automation

by Meriam J.L.

 

It is well known that since ancient times people have tried to construct automatic toys. Those toys were put into motion by hidden mechanisms of automatic devices. The mechanical wonders of the past indicated the road for developing automatic systems later. Clocks and watches, being the first automatic systems, suggested to people an idea of producing automata in industrial manufacture. The Frenchman Vaucanson built a weaving loom replacing fifty weavers. The talented Russian mechanic Ivan Polzunov invented a float-type controller for his steam engine. Steam engine found universal application due to the invention of the centrifugal speed governor, designed by the English inventor James Watt. Soon automation spread to all technological spheres and became a moving force of technological advance.

So, automation deals with the theory and construction of control systems which can function without man’s participation. It should be noted that modern automatic industrial process involves four independent components, each component becoming more powerful in the presence of the other. They are: transfer machining, automatic assembly, communication engineering and control engineering. These four components are linked together into a single process called automation. When two or more automatic machines are connected together with automatic controls, which may be mechanical, electrical or a combination of them, an automated control is formed. This system creates a self-feeding, self-initiating and self-checking process.

It should be noted that electronics has greatly extended the range of automatic control and has made the processing of information rapid and automatic. Electronic devices are able to respond very quickly to signals and take measurements and detect faults very accurately. So, they can effectively control many processes and machines working at high speeds. Due to the above – mentioned advantages automatic control systems find wide application in many fields of technology. Automatic controls relieve man of many monotonous activities. Besides, they can perform functions which are beyond the physical abilities of man.

People make great use of automation in industry; it is especially effective in continuous cycle production. Various kinds of electronic devices are applied in automatic aircraft pilots, as radio aids to air and marine navigation. Owing to automation special devices make precise calculations for space vehicle movement, help to launch missiles and to direct them to the correct path. Automatic interplanetary stations and space rockets are equipped with orientation systems, photo-television apparatus, special soft landing radio systems and movement control systems of high precision. These systems ensure safe returning and safe landing.

Automation to be developed successfully has become one of the main factors of engineering progress today.

 

6. Answer the questions:

1) How were the first automatic toys put into motion? 2) What were the first automatic systems? 3) Who was the first to show the advantages of automatic devices? 4) Due to what did steam engines find wide application? 5) What is automation? 6) What components does an automatic process include? 7) What conditions can an automatic control system be formed under? 8) What process does such system create? 9) What extended the range of automatic control? 10) What fields of technology are automatic control systems used in?

 

7. Translate and memorize the following word combinations:

To invent a float-type controller; centrifugal speed governor; to put into motion; self-initiating and self-checking process; to extend the range of automatic control; a steam engine; control engineering; mechanical wonders; transfer machining; to create a self-feeding; to extend the range of automatic control; to respond to signals quickly; to take measurements; to detect faults accurately; continuous cycle production; automatic aircraft pilot; radio aids; air and marina navigation; owing to automation; to make precise calculations; space vehicle movement; to launch and direct missiles on the correct path; to be equipped with orientation systems; movement control systems of high precision; to ensure safe returning and safe landing.

 

8. Find out the English equivalents for the following word combinations:

1) Автоматическая сборка; автоматизированные системы управления; натолкнуть на мысль; механическая перестановка; диапазон автоматического управления; создавать процесс автоматической подачи; обнаруживать погрешности с высокой точностью; автоматическое включение; техника регулирования; быстро реагировать; непрерывный производственный цикл; выполнять вычисления; направлять ракеты по заданной траектории; системы управления полетом высокой точности; приводить в движение; благодаря изобретению регулятора скорости; промышленное производство; автопилоты; радиосредства; паровой двигатель; техника связи.

2) Прибор по обнаружению ошибки; управляемая величина; задающее устройство; поддерживать физические переменные величины; подавать сигнал обратной связи; чувствительные приборы; периодическое намагничивание сердечника; усиливать; менять величину напряжения; подаваемого к нагрузке; любая погрешность; желаемый уровень; управление производственными процессами; принцип действия; переменное сопротивление.

 

9. Translate the verbs and their derivatives:

To feed – feedback; feed forward; feeder; feeding.

To indicate – indicated; indication; indicative; indicator; indicatory.

To transfer – transferable; untransferable; transferability; transferring; transference; transferor.

To govern – governor; governable; ungovernable; government; governmental.

To vary – variable; variability; invariability; variant; variation; variety; various

To detect – detectable; undetectable; detectability; detection; detector.

To control – controllable; incontrollable; controller; controlling.

 

10. Find out the synonyms from the texts for the followings:

- To mean; to connect; to provide; to build; to widen; to react; to connect; to install; to include; to manage; to show; to find out; to provide; to get; to fabricate; to use; to intensify; to convert; to operate; to change.

- Up-to-date; broad; on-going; main; different; quick; particular; distant; feasible; accurate.

- Motor; branch; airplane; progress; road; concept; convertor; regulator; production; movement; use; instruction; number; rate; type; mistake; value; element; standard; failure; work.

 

11. Translate the word combinations paying attention to the words in bold type

Error (ошибка, погрешность): access error; accidental error; admissible error; application error; calculation error; entry error; conversion error; common error; start-up error; connection error; operating error; error-prone; undetectable error; unexpected error.

Control (управление, регулирование): automatic control; distance/remote control; digital control; feedback control; error control; process control; keyboard control; manual control; on-line control; off-line control; power control; security control; precision control.

Level (уровень; степень; мера): level of sensitivity; desirable level; difficulty level; error level; output level; performance level; protection level; significance level; transmission level; software level.

Quantity (величина; значение; количество): absolute quantity; alternating /variable quantity; digital quantity; average quantity; random quantity; unknown quantity; directed quantity; constant quantity; derived quantity; digital quantity; switching quantity.

Variable (переменная величина; переменный, изменяющийся): complex variable; controlled variable; physical variable; dependent variable; independent variable; input variable; random variable; irregulated variable; reference variable; switching variable; replaceable variable.

 

12. Translate the following word combinations using the exercise 11:

Комплексная переменная; подверженный ошибкам; средства управления системой защиты; неизвестная величина; уровень чувствительности; изменяющаяся величина; переменная – переключатель; физическая переменная; ошибка доступа; сетевое управление; дистанционное управление; неизвестная величина; комплексная переменная; независимая переменная; уровень выходного сигнала; случайная переменная; незакономерно изменяющаяся величина; векторная величина; подверженный ошибкам; уровень сложности; степень быстродействия; непредусмотренная ошибка; программный уровень; управление производственным процессом; регулирование потребляемой мощности; входная переменная; допустимая ошибка; случайная погрешность; клавишное управление; степень значимости; производная величина; вспомогательная переменная; ошибка в прикладной программе; числовое значение; контроль за ошибками; заменяемая переменная; уровень передаваемого сигнала; распространенная ошибка; неправильное соединение; управление с использованием обратной связи; уровень защиты; ошибка из-за нарушений правил эксплуатации; управление точностью (вычисления); уровень ошибки; не обнаруживаемая ошибка; автономное управление.

 

13. Translate the text paying attention to the forms of the Infinitive:

Michael Faraday, one of the greatest men of science, had little chance to get an education. In his early youth Faraday had to save money to buy the apparatus necessary for his experiments. We know Faraday to have taken interest in many scientific and technical problems of his time. He took part in the creation of a safety lamp to be used in mines. To turn gases into liquids was one of numerous problems he worked at. For several years Faraday is known to have been working at the problem of a perfect optical glass that greatly improved the telescope. After a while Faraday set to work on another important problem, the problem of magnetism. These were many questions to be answered in the field of science. The main task of his work was to find out the nature of electricity and magnetism.

 

14. State the functions of the Infinitive and translate the following:

1) A. The instrument to be used; the problem to be solved; the new device to be introduced; the theory to be considered; the experiment to be carried out.

B. Kepler was the first to discover the exact laws governingthe movements of the planets. The fly-ball governor was a device to control the speed of steam engines.

2) The primary task is to maintain the output value in the presence of disturbances. We may consider the emergency control as an integrated system.

The function of the transmitter is to encode the messages.

3) To obtain the necessary data was difficult. To measure information means to define the logarithm of the number of available choices.

4) To meet the requirements the circuit must be assembled on the basis of current technology. Switches are used to open the circuit. To learn more about the space people launch spaceships.

5) It was decided to use “a bit” as a unit of information. To measure information means to define the logarithm of the number of available choices.

15. Translate the text paying attention to the functions of the Infinitive and its forms:

Business Systems

by K. Ogata

 

A business system may consist of many groups. Each task assigned to a group will represent a dynamic element of the system. Feedback methods of reporting the accomplishments of each group must be established in such a system for proper operation. The cross-coupling between functional groups must be made a minimum in order to reduce undesirable delay times in the system. The smaller this cross-coupling, the smoother the flow of work signals and materials will be.

A business system is a closed-loop system. A good design will reduce the managerial control required. Note that disturbances in this system are the lack of personnel or materials, interruption of communication, human errors, and the like.

The establishment of a well-founded estimating system based on statistics is mandatory to proper management. Note that it is a well-known fact that the performance of such a system can be improved by the use of lead time, or anticipation.

To apply control theory to improve the performance of such a system, we must represent the dynamic characteristic of the component groups of the system by a relatively simple set of equations.

Although it is certainly a difficult problem to derive mathematical representations of the component groups, the application of optimization techniques to business systems significantly improves the performance of the business system.

 

Ogata K. Modern Control Engineering. – 4^th Ed. – New Jersey: Prentice Hall, 2002. – 964 p. (P. 5).

16. Translate the text and speak about feed forward and feedback controllers: