Automatic control is the research area and theoretical base for mechanization and automation, employing methods from mathematics and engineering. A central concept is that of the system which is to be controlled, such as a rudder, propeller or an entire ballistic missile. The systems studied within automatic control are mostly the linear systems.

Automatic control systems are composed of three components:

• Sensor(s), which measure some physical state such as temperature or liquid level.
• Responder(s), which may be simple electrical or mechanical systems or complex special purpose digital controllers or general purpose computers.
• Actuator(s), which effect a response to the sensor(s) under the command of the responder, for example, by controlling a gas flow to a burner in a heating system or electricity to a motor in a refrigerator or pump.

A regulator such as a thermostat is a typical example of a device studied in automatic control.

See also

• process control
• control theory
• controller
• Control engineering