1 of 8

Control Systems

Mrunalini T

2 of 8

What is a System?

  • A system is a combination of a number of equipment or components connected in a sequence to perform a specific function
  • The meaning of control is to regulate or to direct or to command and therefore, a control system is an arrangement of distinct physical components connected in such a manner so as to regulate or to direct or to direct or to command itself or some other system

3 of 8

Introduction to Control System�

4 of 8

Basic components of a control system �

  • Plant
  • Feedback
  • Controller
  • Error detector
  • The combined unit or error detector, controller, plant, and feedback make a complete automatic control system.

​

5 of 8

Plant

  •  The portion of a system that is to be controlled or regulated is called a plant or process.
  • It is a unit where actual processing is performed and if we observe in the above figure, the input of the plant is the controlled signal generated by a controller.
  • A plant performs necessary actions on a controlled system and produces the desired output

​

6 of 8

Feedback

  •  It is a controlled action in which the output is sampled and a proportional signal is given to the input for automatic correction of any changes in the desired output.
  • The output is given as feedback to the input for correction i.e. information about the output is given to input for correcting the changes in output due to disturbances.
  • The feedback signal is fed to the error detector. Negative feedback is preferred as it results in better stability and accuracy. The other disturbance signals are rejected.

​

7 of 8

Error detector

  •  The function of the error detector is to compare the reference input with the feedback signal.
  • It produces an error signal which is a difference of two inputs which are a reference signal and a feedback signal.
  • The error signal is fed to the controller for necessary controlled action. This error signal is used to correct the output if there is a deviation from the desired value.

​

8 of 8

Controller

  • The element of a system within itself or external to the system which controls the plant is called as a controller.
  • The error signal will be a weak signal and so it has to be amplified and then modified for better control action.
  • In most of the systems, the controller itself amplifies the error signal and integrates or differentiates to generate a control signal.
  • An amplifier is used to amplify the error signals and the controller modifies the error signal.

​