# Control Loop **Domain:** Control Theory / Cybernetics **Doc Type:** Canonical Technical Concept **Maturity:** Developed ## Definition A **control loop** is a feedback structure in which a system measures or estimates state, compares it with a reference or acceptable range and changes inputs to influence subsequent state. ## Historical Lineage Governors, thermostats and process controllers show that regulation can occur through continuous correction rather than detailed advance instruction. Cybernetics generalized this pattern across machines, organisms and organizations while requiring discipline about differences among those domains. ## Governing Variable The loop governs error between observed or estimated state and a desired condition. ## Material and Computational Manifestation Sensors, estimators, controllers and [[wiki/Actuator|actuators]] form the loop. Local loops can be nested beneath supervisory systems and [[wiki/Control Plane|control planes]] that revise setpoints, allocate resources or coordinate multiple processes. ## Relation to Governance [[wiki/Reconciliation Loop|Reconciliation Loop]] is the declarative computing form: compare actual and desired state, then perform bounded correction. The analogy to governance is useful only when authority, objective and rights remain visible; people are not interchangeable process variables. ## Constitutional Question and Failure Modes Who selects the target, which measurements count and how an actor can contest correction are more important than the loop's technical efficiency. Delay, noise, saturation, wrong objectives and unmodeled interactions can produce oscillation or harm. ## Related Ontology [[wiki/Telemetry|Telemetry]] · [[wiki/State Estimation|State Estimation]] · [[wiki/Actuator|Actuator]] · [[wiki/Reconciliation Loop|Reconciliation Loop]] · [[wiki/Algorithmic Homeostasis|Algorithmic Homeostasis]]