Control system in which the output has an effect on the input quantity in such a manner that the input quantity will adjust itself based on the output generated is called closed loop control system .
Open loop control system can be converted in to closed loop control system by providing a feedback. This feedback automatically makes the suitable changes in the output due to external disturbance. In this way closed loop control system is called automatic control system .
Figure below shows the block diagram of closed loop control system in which feedback is taken from output and fed in to input.
Practical Examples of Closed Loop Control System
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Automatic Electric Iron – Heating elements are controlled by output temperature of the iron.
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Servo Voltage Stabilizer – Voltage controller operates depending upon output voltage of the system.
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Water Level Controller – Input water is controlled by water level of the reservoir.
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Missile Launched & Auto Tracked by Radar – The direction of missile is controlled by comparing the target and position of the missile.
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An Air Conditioner – An air conditioner functions depending upon the temperature of the room.
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Cooling System in Car – It operates depending upon the temperature which it controls.
Advantages of Closed Loop Control System
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Closed loop control systems are more accurate even in the presence of non-linearity.
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Highly accurate as any error arising is corrected due to presence of feedback signal.
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Bandwidth range is large.
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Facilitates automation.
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The sensitivity of system may be made small to make system more stable.
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This system is less affected by noise.
Disadvantages of Closed Loop Control System
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They are costlier.
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They are complicated to design.
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Required more maintenance.
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Feedback leads to oscillatory response.
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Overall gain is reduced due to presence of feedback.
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Stability is the major problem and more care is needed to design a stable closed loop system.
Also Check : Closed Loop and Open Loop Animation