Basic Structure of a closed loop control system

In this tutorial I will explain the basic blocks of a closed loop control system.

The system presented in the figure consist a controller, plant (The system we want to control), an output feedback path and the reference or desired input.

Plant : - The plant is the system or process that is to be controlled. Examples : Quadcopter, Aeroplane, Vehcile etc. The system is modeled in the form of a transfer function or state-space equations.

Sensor - The sensor measures the output quantity to provide the output feedback

Controller- It is the brain of the control system. It takes action based on the error signal which is the difference between reference and the measured output quantity.

Different types of controllers:

Proportional controller

Proportional + Integral Controller

Proportional + Derivative Controller

Proportional + Derivative + Integral Controller

Reference Input - It is the desired output that we want to achieve. For example in a temperature control system the 20 degree Celsius could be ref. input or in a Quadcopter altitude control system 10 m could be a reference input.