Control System(Features, Types etc)

Hello everyone, Hope you all are doing good:) The topic on which we all are gonna discuss today is “Control System”. Have you ever thought about what is a Control system? what are its features? how does it work? and questions of the same type, if yes then you are at the right place.

What is a Control System?

Let’s start from the beginning that what is a basic control system?

However A control system is a system which manages, commands, directs, or regulates the behavior of other devices or systems using control loop.

Basic Block Diagram Of control system

Block diagram of control system

The above figure shows a basic block diagram of a control system.

A block diagram is a pictorial representation of the cause and the effect of the relation between the input and the output signal.

The basic elements of the block diagram are as shown:-

1.Refrence Point:

However, the reference point is mainly a junction where an external signal is given to the summing point of the system to subsequently get the required output by plant/process. The signal represents the desired output value of the controlled variable called SetPoint. Meanwhile, it is also known as the Input signal or reference variable.

2.Summing Point

Certainly, It has two or more inputs and a single output. Its main function is to perform the algebraic sum of the inputs ( subsequently which sums up to perform addition or subtraction of the inputs on the basis of the charges on it. )

3.Controller Element

The controller element is the component that is needed whenever we produce the desired signal by modulating the actuating signal. It is also known as Controller.


However, the plant is the part of the system through which a particular quantity or condition is been controlled. It is also known as a Process.


Certainly, the unwanted part of the input signal which upsets the value of the controlled variable is known as Disturbance. Element

Generally, it is a component used to identify the functional relationship between the feedback signal and the output variable.

7.Feedback Signal

It is a part of the output signal which is given back to the summing point of the system and algebraically added to the reference input to consequently get the actuating signal.

8.Output Variable

However, It is the quantity or condition of the plant which is been controlled.

9.Manipulated Variable

It is the variable of the process which generally acts upon to maintain the plant (Controlled variable) at the desired value.

Feature of Control System:-

Certainly, the most important feature of the control system is that there should be a clear mathematical relationship between the input and the output of the system.

Linear System

A linear system is a system in which can chiefly get a linear relationship between the input and the output.

Non-Linear system

Although a non-linear system is a system in which we cannot get a linear relationship between the input and the output. In other words, we can say that we get a non-linear relation between them.

Types of Control System:-

Based on some parameters we can classify the control system as:

Based on type of signal

  • Continuous time domain
  • Discrete time domain

On the bases of number of inputs and Outputs

  • SISO(single input single output)
  • MIMO(multiple input multiple output)

Based on Feedback Path

  • Open Loop System
  • Close Loop System

1. Open Loop Control System:-

In an open-loop control system, the control action by the controller is independent of the method of execution and also of the control variable. For example, the central heating boiler is controlled by a timer, washing machines, switches.

example of open loop control system


  • Firstly Simple in construction.
  • secondly Economical in nature.
  • and above all it has stability problem.


  • Inaccurate
  • less reliable
  • changes in the output cannot be corrected automatically because there is no sensors present.

2. Closed Loop Control System:-

In a closed-loop system, the control action from the controller is dependent on the desired and also of the actual process variable. For example the Voltage stabilizer, Auto Engine, Thermostat heater, Turbine water control system at power stations.

A close-loop controller has a feedback loop that makes sure that the controller exerts pressure on the control system so that the required output is obtained.


  • Reduces the affect of non linearity.
  • Less economical in nature.
  • Highly stable.
  • Facilitates automation.


  • Expensive.
  • Complicated construction.
  • Require more maintenance.
  • Reduces the Total gain.
  • Feedback leads to oscillatory action.

The closed-loop systems are also known as Feedback controllers.

block diagram of closed loop control system

Transfer Function

what is a transfer function?

A Transfer function mainly represents the relationships between the output signal and the input signal, for all possible values of input. however, the value of the output function is a multiple of the input function and transfer function.

It is a simple way to represent linear, time-invariant systems in terms of input-output. The main advantage of the transfer function is that they allow the engineers to use the algebraic equations for large and complex equations for designing the system.

It is interprets as the ratio of Laplace Transform of output to Laplace Transform of input where all initial conditions are zero;

Transfer function= Laplace Transform of output function

Laplace Transform of Input

Moreover, The T(s) appears for the Transfer function, the input function by R(s) while the output function by C(s).

Procedure for determining the transfer function of any given system

  • Form the equation form the given figure.
  • Now take the Laplace transform of the equation while assuming initial condition to be equal to zero.
  • Specify the input and the Output terms.
  • Take the ratio of output of Laplace transform to input of Laplace transform.
  • Now lastly write the equation of G(s) or T(s).

Poles and Zeroes

The poles and zeroes of a transfer function are the frequencies at which the value of the denominator and the numerator becomes equal to zero respectively. these values determine the stability and the quality of performance of the system. the physically realizable system must have poles greater than zeroes.

On-Off Control

However, an On-Off Controller is a kind of closed-loop controller which switches abruptly between the two states. For Example, the on-off controller is a pressure switch on an air compressor, Meanwhile, when the pressure drops below the subsequent setpoint the compressor is energize. the refrigerator and the vacuum pump have the same mechanism.

Requirement for a Good Control System


accuracy must be as high as possible and this can be obtain by including feedback elements in the path and by using an error detector in the control systems


The parameter of the control system keeps on changing with the changes in the surrounding, this changes can be termed as sensitivity. For instance, Internal, external changes, parametric changes, and temperature change does not affect a good control system.


Certainly, Noise is the disturbance in the signal and a good signal should be sensitive to such disturbances.


The bandwidth of the system must be large so that we can obtain a good frequency.


A good control system should have high speed.

Benefits of a Controlling System

Quality Assurance

Consistent quantity and quality are extremely important for the companies as while purchasing the costumer demand certain specifications/quality. control system and processor helps to maintain the quality and avoid human error.

Less Wastage

Industries can lead to the production of a large amount of waste due to over-processing, scrap, removal, etc. thus using a standardized approach could help in the reduction of waste production, material usage.

Lower operating cost

Making the operation more efficient and decreasing waste will reduce the cost of production.

Production Planning

It involves a strategic approach towards what a company wants.

Production Control

To achieve desired output variable we can include various control techniques. it processes the material until and unless the we get desired output.


Software Error

The error may occur because, of the complexity of the system which is executable by the algorithms only.

System Stability

The stability of the system decreases as it changes from continuous-time domain to digital time domain. Even a stable second-order system can get unstable during the conversion to a discrete system.

System Design

The mathematical analysis of the network is quite tedious and complex in nature.


As the is the system is complex in construction thus it requires frequent maintenance.


The cost of the system is quite high Because of the complex design and Structure the economical.


I hope that I have provided you with all the needed information about a control system. if you liked the blog then please make sure to share with others, and feel free to comment down if there’s any query regarding the topic, also I would be really happy to know which topic you would like to read next on.


Have a nice day 🙂

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  • Prakash Mishra February 12, 2021 at 1:06 pm Reply


  • Harshita February 12, 2021 at 1:06 pm Reply


  • Harsh February 13, 2021 at 8:50 am Reply

    It was really helpful for me 👍🏻

  • Jadhav Prathamesh February 22, 2021 at 2:42 pm Reply

    Amazing write up !

  • Yash March 1, 2021 at 11:20 am Reply

    Great work..

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