Control systems nagrath and gopal pdf

What is the theory of control and system engineering?
A control system is a set of mechanical or electronic devices that regulates other devices or systems by way of control loops.
Typically, control systems are computerized.
Control systems are a central part of production and distribution in many industries.
Automation technology plays a big role in these systems..
Who is the Indian author of control systems book?
Control theory is used in control system engineering to design automation that have revolutionized manufacturing, aircraft, communications and other industries, and created new fields such as robotics.
Extensive use is usually made of a diagrammatic style known as the block diagram..

What is the theory of control and system engineering?