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Elements and Structure of Automatic Control Systems
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| 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. R Reference input (commands) G Control elements C Controlled quantity E Error detector H Feedback path elements 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 Read the text and explain the advantages of automation: жүктеу/скачать 464,87 Kb. Достарыңызбен бөлісу:
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