feedbackloops

A feedback loop is a process in which a portion of a system's output is routed back to influence subsequent input. In control theory and systems thinking, feedback loops connect the output to the input through a measurement and comparison, creating a closed circuit that can regulate, stabilize, or amplify behavior.

There are two main types: negative feedback, which counteracts deviations from a target and promotes stability; and positive feedback, which reinforces deviations and can lead to rapid change or runaway effects. Negative feedback examples include a thermostat maintaining room temperature by reducing heating when the temperature rises; positive feedback examples include processes like blood clotting where activation accelerates further clotting.

A typical feedback loop comprises a sensor (to measure the output), a comparator (to compare with a reference or setpoint), and an actuator or controller that adjusts the input based on the difference. When the system continuously samples and adjusts based on the difference, it is called a closed-loop system; without feedback, the system is open-loop.

Feedback loops appear across fields: in engineering for control systems and electronics; in biology for homeostasis and neural circuits; in ecology for population dynamics; in economics for price and demand feedback; in computing for adaptive algorithms and reinforcement learning. Climate feedback loops, such as ice-albedo effects or water vapor feedback, can alter climate trajectories.

Key considerations include stability, convergence to a setpoint, delays that can cause oscillations, and system gain. Understanding feedback loops helps analyze how systems respond to changes and maintain or transform their behavior.