Introduction

Control plays an important role in our lives. In all our actions we practice some kind of control. For instance consider that you want to go to a particular place. Then you will walk towards your desired place. Your eyes help to guide you in the desired direction. You can control your walking action towards the desired direction.

When practicing control we need a desired objective. Every controller tries to achieve this objective through its action. Some changes occur in the system due to these actions and thereby it is possible to achieve the final objective. Consider the walking example we discussed earlier. Suppose our objective is to walk to the particular place at a given time. Here, we change the speed of the walking action to achieve our objective.

We call variables associated with our objective as input variables or desired response. Output response after the control action is called as output response or actual response.

We come across innumerable examples of control systems in operation in our everyday lives. They occur in all 'disciplines', such as in engineering (the control of frequency of an electrical generator, the control of the speed of a vehicle, etc), ecosystems (the balance between the populations of different species), economic systems (control of the rate of inflation). The list is never ending. While there are wide differences in the way these different systems operate, there are also some underlying similarities in a coherent manner, and evolve a unified treatment spanning applications in the different fields.