Control System

Control systems are an integral part of modern society.
Numerous applications are all around us.
The control systems also exist in nature such as the pancreas, which regulates our blood sugar.

Control System Definition


Consists of subsystems and processes (or plants) assembled for the purpose of controlling the output of processes.In other word, a control system provides an output or response for a given input or stimulus.

Advantages of Control System
-We can move large equipment with precision
-We can point huge antennas toward the farthest reaches of universe to pick up faint radio signals

We build control systems for four primary reasons:
-Power amplification
-Remote control
-Convenience of input form
-Compensation for disturbances


Response Characteristics and System Configurations





Response characteristic – input, output, transient response, steady-state response and steady-state error.

Input/stimulus – a desired response
Output – the actual response
Transient response – a gradual change before the steady-state response
Steady-state response – after the transient response, which is its approximation to the desired response
Steady-state error – the differences between input and output

There Two major system configurations of control systems :

Open-Loop Systems:

It consists of subsystems called an input transducer, controller and process or plant.
Input transducer converts the form of the input to that used by the controller. Controller drives a process or plant. Other signals, such as disturbances, are shown added to the controller and process outputs via summing junctions. The open-loop system cannot correct for these disturbances.
Examples – toasters, washing machine (washing process)

Closed-Loop (Feedback Control) Systems:

The disadvantages of open-loop systems may be overcome in closed-loop system as shown in Figure 1.3. An output transducer/ sensor, measures the output response and converts into the form used by controller. The closed-loop systems measured the output response through a feedback path, and comparing that response to the input at the summing junction. If there is any difference between the two response, the system drives the plant, via the actuating signal, to make a correction. If there is no difference, the system does not drive the plant.
Examples – air conditioning, lift, washing machine (water level control)