Controllers

Controllers are devices, systems, or software components that manage the behavior of other systems by comparing a desired output with a measured variable and applying a corrective action. They are central to control theory and operate in feedback loops, though some controllers also work in open-loop configurations where the action is not adjusted based on the actual process.

In industrial and process control, controllers monitor variables such as temperature, pressure, or flow and adjust actuators to maintain target values. Programmable logic controllers (PLCs) and more specialized industrial controllers are common. Proportional-Integral-Derivative (PID) controllers provide a widely used generic algorithm that computes corrective actions from current error, accumulated error, and error rate of change. Microcontrollers and embedded controllers implement control logic in compact, low-power hardware and are used in consumer electronics, automotive systems, and robotics. Motor controllers regulate speed, torque, and direction; power controllers manage electrical power conversion and distribution.

In computing, a controller often refers to a software component that handles input, processes it, and updates the model or user interface, as in the model-view-controller (MVC) pattern. In hardware, a controller may refer to a device that interfaces with peripherals, such as disk, network, or USB controllers, which mediate communication between the system and devices.

In consumer electronics and gaming, a controller is an input device such as a gamepad, joystick, or remote control used to issue commands to a system or game.

Key considerations for controllers include feedback accuracy, latency, stability, robustness to disturbances, and safety, especially in critical applications such as aviation or medical devices.