Control engineering, as one of the cornerstones of automation, has contributed enormously to the development of modern industrial society. In the automation systems of today, control engineering remains one of the core functions. It ultimately enables actual automation tasks to be accomplished. Control system as the name suggest is used to direct, guide or manipulate the command as per the desired input. Controller is a brain of mechatronic system. To run a controller, control system has to play a vital role. It communicates with the various sensors as an input, scan the input thoroughly, make the decision on what to do and give respective signal to the actuator to take the particular action. Within this process if any feedback taken and if any error found between desired input and feedback, the control system has the capacity to rectify the error and give proper control action. The job of the controller is essentially to capture process variables -- either as a continuous process or at sufficiently short intervals -- and to compare them with set values. The controller uses the results of the comparison as the basis for intervention in the process being controlled, thus ensuring that in a steady state, process variables are in line with specified set values.

Controllers are therefore important for the running of a technical plant when the process to be managed is subject to influences that, without control, would cause the process variables to deviate from the set values. Where a technical process is to run automatically, the use of controllers is vital with respect to economy, reproducibility of product quality, service quality, safety and environmental protection.