Open Loop and Closed Loop Control System

Oct 25 • Notes • 11157 Views • 1 Comment on Open Loop and Closed Loop Control System

In modern times, Control System play a very important role in our daily life. The concept of automatic control system are fundamental and well mixed in every aspects of our life. From a simple bread toaster to a complex modern power plant all comes under the sires of control system principle that affects our life. Advance example involves launching of a satellite, regulating the generation of power plant, tracking an enemy plane on radar are the example of a control system. The basic objective of these Control system is to calculate solution for the proper corrective action. Here in this post you will find the  details of Open Loop and Closed Loop Control System with example.

Requirements for a Good Control Systems:

a) Accuracy: Accuracy must be very high as error arising should be corrected. Accuracy can be improved by the use of feedback element.

b) Sensitivity: A good control system senses quick changes in the output due to an environment, parametric changes, internal and external disturbances.

c) Noise: Noise is a unwanted signal and a good control system should be sensitive to these type of disturbances.

d) Stability: The stable systems has bounded input and bounded output. A good control system should response to the undesirable changes in the stability.

e) Bandwidth: To obtain a good frequency response, bandwidth of a system should be large.

f) Speed: A good control system should have heigh speed that is the output of the system should be fast as possible.

g) Oscillation: For a good control system oscillation in the output should be constant and must follow Barkhausein’s Criteria.

Open Loop and Closed Loop Control System

Control action is the quality of a system which is responsible for activating the system in order to produce the output. The open loop and closed loop system are basically the parts of Control system. Depending on weather a control action performed should depends on the status of output, Control System are classified as

1) Open Loop Control System
2) Closed Loop Control System


An Open loop System is also known as the control system without feedback . These systems do not have any any portion of output feedback to the input for comparison and measurement. The components of these system are: input, processing system and output.

Open Loop Control System

Block Diaagram of Open Loop Control System

Advantages of Open loop Control System:

  • They are simple in constructions,
  • They are economical in nature.
  • Have stability problem.

Example of these systems are:

  1. Immersion rod: in this how much heating is required is not measured by the rod.
  2. Traffic Control System: this system is based upon the timer and not on the density of traffic.


These system are also known as the system with feedback.In this system a portion of output is feedback to the input side which is compared with the reference element and thus the error occurred at that time is filtered out and output is desire output. The components of these system are: input, reference element,controller, processing system and output.

Closed Loop Control System

Block Diagram of Closed Loop Control System

Advantages of Closed loop Control System:

  • They reduces the effect of non-linearities.
  • They are less economical in nature.
  • These system are highly stable.

Example of these systems are:

  1. Human Body: Human Body has the tendency to change its temperature and pressure is maintained according to the physiological change.
  2. Automatic Electric Irons: An automatic Iron regulates the temperature of iron such that for the given cloth selection the temperature remains a specified range.

For pdf, follow: Requirements for a Good Control Systems

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