control

Control is the regulation of a system’s behavior to achieve a desired performance. In engineering and applied sciences, control theory analyzes how to influence a dynamic plant with actuators and feedback. The concept also appears in social and organizational contexts, where governance, policies, and procedures aim to regulate activities and outcomes.

A typical control system comprises a plant, sensors that measure output, and a controller that computes corrective actions. In open-loop control, actions are applied without regard to the actual output. In closed-loop control, feedback continuously informs adjustments to reduce error between a reference signal and the measured output. Core ideas include stability, controllability, observability, and robustness. Controllers are designed using time-domain or frequency-domain models, often expressed as transfer functions or state-space equations. Proportional-Integral-Derivative (PID) controllers are widely used, while more advanced methods include model predictive control and adaptive control.

Applications span process industries, robotics, aerospace, automotive systems, energy grids, and consumer electronics. Effective control systems manage performance criteria such as speed, accuracy, energy use, and safety, while accounting for disturbances, delays, noise, and model uncertainties.

Beyond engineering, social and political control refers to mechanisms that guide or constrain behavior, including laws, incentives, surveillance, and organizational governance. The term also appears in psychology, with concepts such as locus of control describing perceived influence over events.