Controller - Definition and Overview

A controller is a person or device that exercises or attempts to exercise control or influence.

Control Theory

In control theory, a controller is a device that attempts to control states or outputs of a dynamic system. Generally, it accomplishes this using feedback to reject disturbances to the system: known as closed-loop control. Open-loop control also occurs: in systems sufficiently well-characterized to predict what inputs will necessarily achieve the desired states or outputs. For example, the velocity of a motor may be well-characterized for the voltage fed into it, in which case feedback may prove unnecessary.

Organisational Control

In business and administration, the controller is one of the most senior accountants in a firm or institution.

Controllers also feature commonly in the hierarchies of espionage networks.

See also: comptroller

Computing

In computing, especially in computer hardware, controllers occur commonly, often when interfacing with peripherals. See for example:

• disk array controller (a type of storage controller)
• disk controller (a type of storage controller)
• graphics controller or video display controller
• network controller (in Ethernet)
• keyboard controller
• interrupt controller
• RAID controller
• SCSI controller
• Terminal Access Controller

See Also

• Open-loop
• Closed-loop
• Process control
• Control theory
• Accountancy (Accounting)
• Microcontroller
• Programmable logic controller