Feedback Systems: Open & Closed Loop Types

BY ADMIN January 3, 2025

Feedback Systems: Open & Closed Loop Types – Explained

Feedback systems are used to regulate the behavior of a system based on its output. These systems can be classified into two types: Open-Loop Systems and Closed-Loop Systems. Let’s break them down in simple terms:

Open-Loop System

An Open-Loop System is a system that does not use feedback. In an open-loop system, the output is not measured or used to adjust the input. It’s like giving instructions without checking whether they were followed correctly.

How Does an Open-Loop System Work?

  • In an open-loop system, the input is given to the system, and the system does its job without checking if the result is what we want.
  • The system does not adjust itself based on the output.

Example of Open-Loop System:

  • Washing Machine:
    • A washing machine that runs for a set amount of time, regardless of whether the clothes are clean or not, is an open-loop system.
    • It just follows a pre-set program and does not check if the clothes are actually washed properly.

Pros and Cons of Open-Loop Systems:

  • Pros:
    • Simpler design and easy to implement.
    • Often cheaper and quicker.
  • Cons:
    • Less accurate, as there is no feedback to correct errors.
    • If something goes wrong, the system cannot correct itself. For example, if the washing machine has too many clothes inside, it may not clean them properly.

Closed-Loop System :

A Closed-Loop System uses feedback to adjust its performance. In a closed-loop system, the output is continuously measured and compared with the desired output, and adjustments are made to ensure the system behaves as needed.

How Does a Closed-Loop System Work?

  • The system measures the output (result) and compares it with the desired outcome.
  • If the output is different from the desired result, the system adjusts the input to correct the output.
  • This feedback loop helps the system stay accurate and stable.

Example of Closed-Loop System:

  • Thermostat (Room Heating/Cooling System):
    • If you set the temperature to 22°C, the thermostat continuously checks the room temperature (the output).
    • If the temperature falls below 22°C, it turns the heater on.
    • If the temperature goes above 22°C, it turns the heater off.
    • This feedback keeps the room temperature steady at the desired value.

Pros and Cons of Closed-Loop Systems:

  • Pros:
    • More accurate because the system can adjust itself.
    • Can correct mistakes and errors in real-time (self-regulating).
  • Cons:
    • More complex design and can be more expensive.
    • Requires sensors and additional components for feedback.

Open vs. Closed Loop Systems :

 

Feature Open-Loop System Closed-Loop System
Feedback No feedback is used. Feedback is continuously used to adjust the system.
Accuracy Less accurate. More accurate due to self-correction.
Complexity Simple and easy to design. More complex and requires sensors for feedback.
Cost Cheaper to build. More expensive due to added components.
Adjustment to Errors Cannot correct errors on its own. Can correct errors and adjust the output.
Example Washing machine, microwave oven. Thermostat, cruise control, elevator.

Open-Loop vs. Closed-Loop Systems

  • Use Open-Loop Systems when:
    • The process is simple, and you don’t need precise adjustments.
    • The system doesn’t require constant monitoring or correction (like a microwave that runs for a set time).
  • Use Closed-Loop Systems when:
    • Accuracy and stability are important.
    • The system needs to adjust based on feedback to maintain performance (like a thermostat controlling room temperature).

Real-Life Examples of Both Systems :

  • Open-Loop System:
    • Microwave Oven: You set the time and power, and the microwave runs for that set time without checking if the food is cooked properly.
    • Traffic Lights: A fixed timing system where the lights change at specific intervals, regardless of traffic conditions.
  • Closed-Loop System:
    • Cruise Control in Cars: The car’s speed is constantly monitored and adjusted. If the car slows down due to an incline, the system speeds it up again to maintain the set speed.
    • Refrigerator: A refrigerator checks the internal temperature and turns the compressor on or off to keep the temperature stable.

Summary :

  • Open-Loop Systems are simple and work without feedback. They follow preset instructions but cannot adjust based on results.
  • Closed-Loop Systems use feedback to ensure the system stays accurate and stable, adjusting the system based on real-time measurements.

 

 

 

 

 

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