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Control System Open-Loop, Closed-Loop, And Feedback-Loop

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Introduction:-

The Control System means by which any quantity of interest in a machine, Mechanism or another part of the machines is organized by a command in the desired manner. This is Called Control System. 

Definition of the Control system:-

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A control system may be a system of devices or sets of devices, that manages, commands directs or regulates the behavior of alternative devices or systems to realize desired results. In alternative words, the definition of a Control system may be simplified as a system, that controls alternative systems. As human civilization is being progressive day by day the demand for automation is increasing consequently. Automation extremely needs the management of devices.




Features of a control system:-

The main feature of a Control system is that there ought to be a transparent mathematical relationship between input and output of the Control system. once the relation between input and output of the Control system may be diagrammatical by a linear proportion, the system is termed a linear system. once more once the connection between input and output can't be diagrammatical by single linear proportion, rather the input and output are connected by some non-linear relation, the system is observed as a non-linear system.
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Requirements of a decent system:-

Accuracy:- Accuracy is that the activity tolerance of the instrument and defines the boundaries of the errors created once the instrument is employed in traditional in operation conditions. Accuracy may be improved by exploitation feedback components. to extend the accuracy of any system error detector ought to be a gift within the control system.

Sensitivity:- The parameters of a Control system are forever ever-changing with the modification in encompassing conditions, internal disturbance or the other parameters. this transformation may be expressed in terms of sensitivity. Any system ought to be insensitive to such parameters however sensitive to input signals solely.


Noise:- An unsought signal is understood as noise. a decent system ought to be able to cut back the noise impact for higher performance.

Stability:- it's a crucial characteristic of the Control System. For the finite signal, the output should be finite and if the input is zero then the output must be zero then such a Control system is alleged to be a stable system.

Bandwidth:- Operation frequency varies decides on the information measure of the system. information measure ought to be as massive as attainable for the frequency response of a decent system.


Speed:- It's the time taken by the system to realize its stable output. a decent system possesses high speed. The transient amount for such a system is extremely tiny.


Oscillation:- Constant oscillation of output tends to point the system to be stable.

Let us take an example of the straightforward temperature controller of the space, to clear the thought. Suppose there's an easy element, that is het up as long because the electrical power provide is switched on. As long because the power provides switch of the heater is on the temperature of the space rises and when achieving the specified temperature of the room, the ability provide is transitioned. once more thanks to close temperature, the space temperature falls and so manually the heater component is switched on to realize the specified temperature once more.

The Contol Systems are mainly 2 types 
  1. Open Loop Control System
  2. Close-Loop Control System

Open Loop Control System:-

Any Physical Control System Which doesn't automatically for variation in its output is called an open-loop control system. In this type of system, the output remains constant for constant output. The output can be changed by the desired input value. The Open-loop control system can be a function that can be tolerated or system components are designed and constructed are well controlled. The feedback can control the employed traffic.

Advantages of Open Loop system:-

  1. Simple in construction and style.
  2. Economical.
  3. Easy to keep up.
  4. Generally stable.
  5. Convenient to use as output is troublesome to live.
  6. Disadvantages of Open-Loop Control system
  7. They are inaccurate.
  8. They are unreliable.
  9. Any modification in output can't be corrected mechanically

Open Loop system Examples:-


Electric Hand Drier:- Hot air (output) comes out as long as you retain your hand beneath the machine, no matter what quantity your hand is dried.

Automatic washer:- This machine runs in keeping with the pre-set time no matter laundry is completed or not.

Bread Toaster:- This machine runs as per adjusted time no matter browning is completed or not.
Automatic Tea/Coffee Maker:- These machines conjointly operate for a pre-adjusted time solely.
Clothes Dryer:- This machine dries wet garments for pre-adjusted time, it doesn't matter what quantity the garments are dried.
Light Switch:- Lamps glow whenever a lightweight switch is on no matter light is needed or not.
Volume on the stereophonic system:- Volume is adjusted manually no matter the output volume level.

Close-Loop Control System:-

The Close-Loop Control system within which the output has a bearing on the input amount in such a way that the input quantity can regulate itself supported the output generated is termed a closed-loop system. The open-loop system may be born-again into a closed-loop control system by providing feedback. This feedback mechanically makes appropriate changes within the output thanks to external disturbance. during this method, a closed-loop system is termed an automatic control system. The closed-loop system within which feedback is taken from the output a fed into an input.

A close-loop Control System can be represented as a block diagram. 
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In this type of control system has 3 basic elements:
  1. Feedback Element
  2. Controller
  3. Controlled System

Feedback Element:- The feedback element is a device that converts the output variable c into another suitable variable, the feedback signal is b, which then is compared with the input signal.

Controller:- The controller consists of an error detector. The error detector compares the feedback signal with the input signal obtained to determine the theorem of the deviation known as the Actuating signal. It can suitably manipulate the controlled system.

Controlled System:- The controlled system is an essential part so it can be driven by the power stage of the actuating signal. It is a process or plant to produce the desired output. 


Example of Closed-loop system:-


Automatic electrical Iron:- Heating components are controlled by the output temperature of the iron.

Servo Voltage Stabilizer:- The voltage controller operates relying upon the output voltage of the system.
Water Level Controller:- Input water is controlled by the water level of the reservoir.
Missile Launched Measuring Instrument:- The direction of the missile is controlled by examination of the target and position of the missile.
An air conditioning:- An air conditioner functions relying upon the temperature of the space.
Cooling System in Motor:- It operates relying upon the temperature in the Motor that it controls.

Advantages of the closed-loop Control system:-

  1. Closed-loop control systems are a lot of correct even within the presence of non-linearity.
  2. Highly correct as any error arising is corrected thanks to the presence of a feedback signal.
  3. Bandwidth varies is massive.
  4. Facilitates automation.
  5. The sensitivity of the system is also created tiny to form the system a lot of stables.
  6. This system is a smaller amount stricken by noise.
  7. Disadvantages of the closed-loop Control system.
  8. They are costlier.
  9. They are difficult to style.
  10. Required a lot of maintenance.
  11. Feedback results in a periodic response.
  12. Overall gain is reduced thanks to the presence of feedback.
  13. Stability is that the major drawback and a lot of care are required to style a stable closed-loop Control system.

Feedback Loop of Control System:-

Feedback may be a common and powerful tool once coming up with an impression system. An electric circuit may be a tool that considers the system output and permits the system to regulate its performance to fulfill the specified results of the system.

In any system, the output is affected thanks to a modification in environmental conditions or any quite disturbance. therefore one signal is taken from the output and is fed back to the input. This signal is compared with a reference input and also the error signal is generated. This error signal is applied to controller and output is corrected. Such a system is termed a feedback system. 

Feedback system:-

When the feedback signal is positive then the system referred to as a feedback system. For a feedback system, the error signal is the addition of a reference signal and a feedback signal. once the feedback signal is negative then the system is termed a feedback system. For the feedback system, the error signal is given by the distinction of the reference signal and also the feedback signal.


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