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Control Systems

Control Systems. Chapter 1 Introduction to Control System. 1.1 Introduction Automatic control played a vital role in the advance of engineering and science. - Space-vehicle systems - Missile guidance systems - Robotics systems. Definition:

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Control Systems

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  1. ControlSystems

  2. Chapter 1 Introduction to Control System 1.1 Introduction Automatic control played a vital role in the advance of engineering and science. - Space-vehicle systems - Missile guidance systems - Robotics systems

  3. Definition: -Controlled variable: the quantity or condition that is measured and controlled - Manipulated variable: the quantity or condition that is varied by the controller so as to affect the value of the controlled variable - Plants: a piece of equipment, a set of machine functioning together to perform a particular operation. - Processes: any operation to be controlled such as chemical, economic and biological processes. - Systems: a combination of components that act together and perform a certain objective. - Disturbances: a signal that tends to adversely affect the value of the output of a system. Internal and external disturbances. - Feedback control: an operation that, in the presence of disturbances, tends to reduce the difference between the output of a system and some reference input.

  4. Closed-loop feedback control system

  5. Speed Control System 1.2 Examples of Control Systems

  6. Robot Control System

  7. Temperature Control System

  8. Temperature Control of Passenger Compartment of a Car

  9. Feedback Control Systems/Closed-Loop Control Systems - The actuating error (difference between the input signal and the feedback signal is fed to the controller to reduce the error and bring the output of the system to the desired value 1.3 Closed-Loop VS. Open-Loop Control

  10. Open-Loop Control Systems • The output has no effect on the control action. • The output is neither measured nor fed back for comparison with the input • The accuracy of the system depends on calibration. • In the presence of disturbances, the system will not perform the desired task. • Used, in practice, only if the relationship between the input and output is known and no internal/external disturbances • Example  Washing machine, Traffic control

  11. เปรียบเทียบClosed-Loop/Open-Loop Control Systems • An advantage of the closed-loop control system is the fact that the use of feedback makes the system response relatively insensitive to external disturbances and internal variations in system parameters. • Possible to use relatively inaccurate and inexpensive components to obtain the accurate control of a given plant, whereas doing so is impossible in the open-loop case. • From the point of view of stability, the open-loop control system is easier to build because system stability is not a major problem. On the other hand, stability isa major problem in the closed-loop control system, which may tend to overcorrect errors that can cause oscillations of constant or changing amplitude.

  12. ข้อดีของ Open-Loop Control Systems 1. Simple construction and ease of maintenance. 2. Less expensive than a corresponding closed-loop system. 3. There is no stability problem. 4. Convenient when output is hard to measure or measuring the output preciselyis economically not feasible. (washing machines, for example, measure cleanliness is not easy.)

  13. ข้อเสียของ Open-Loop Control Systems 1. Disturbances and changes in calibration cause errors and the output may be different from what is desired. 2. To maintain the required quality in the output, recalibration is necessary from time to time.

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