Control System


What is Control System?

The main objective of control system is to achieve the objective in best possible way. To achieve an objective a system implies certain control strategies. For instance, an athlete running a 100m distance has the objective of running the distance in the shortest possible time. On the other hand, a marathon runner, not only run the distance as quickly as possible, but is doing so he or she must control the consumption of energy and devise the best possible strategy for this race. Here athlete and marathon runner represent the control system which is designed to perform the different task like cover a distance as quickly as possible and run the distance by maintaining the energy consumption and other factor which are their objectives. To achieve these objectives both the runners devise their certain control strategies.


Application of Control System

Control System are found in abundance in all sectors of industries, such as

  • Quality control of manufactured products
  • Automatic assembly line
  • Space Technology
  • Weapon System
  • Transportation System
  • Robotics


Types of control system

  • Open Loop Control System
  • Closed Loop Control System

Open Loop Control System

Open loop control system is also known as non-feedback control system in which control action is independent of output. Open loop control system is manually operated system means if the system output did not matched the desired output then it is operated manually to get the desired output.

Control System

Practical examples of open loop control system

  • Automatic Washing machine
  • Traffic Signal


Closed Loop Control System

A closed loop control system is also known as feedback control system in which control action is dependent on the output. Closed loop control system a self-corrected system. If the system’s output did not match the desired output then the feedback element measured the change in output and fed back to the input to achieve the desired output. Feedback employees measurement i.e. feedback elements are measuring element which are sensor or transducers.

Let us take an example of closed loop control system, consider an automatic water level controller whose control objective is to keep the water level at a height h. If water level changes from height h automatic controller shows an error (thus the output of an automatic controller is expressed as a function of error) then a feedback (measuring element) measures the level of water and compare with a set point then control element changes the water inlet or outlet accordingly.

Control System

Control Canonical Form

Control System

E(s) = R(s)  -  B(s)              (B(s)   =   C(s).H(s)   &   E(s)  =     C(s)/G(s))

Practical Example of Closed Loop Control System

  • Liquid Level Controller
  • Humidity Controller
  • Temperature Controller

Related Term

#-Block diagram Reduction Technique

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