Closed-loop control
Elementary
Think of a machine that is trying to reach a goal, like a heater warming a room. In closed-loop control, the machine checks the result and adjusts its action based on what it measures.
High school
Consider a controller that chooses the input to a system. In closed-loop control, the controller measures the result and adjusts the input to correct errors.
Undergraduate
Consider a control system $\dot x = f(x, u)$. In closed-loop control, the input $u$ is computed from measurements of the output (or state), forming a feedback loop. The closed-loop system is the plant together with its controller.
Examples
Examples
- A thermostat Elementary
- Steering a bike to keep from tipping over Elementary
-
Cruise control that uses both the speed error and a map of upcoming hills
High school
Cruise control that uses the speed error is closed-loop feedback control, because it corrects the measured speed error.
Non-examples
Things that may be mistaken for examples.
- A toaster that runs for a fixed time Elementary
Distinctions involving this term
- Types of control: A controller can decide its input with or without measuring what the system is doing. Open-loop control computes the input without measuring the output, and closed-loop (feedback) control uses the measured output to correct errors. Feedforward acts on a measured disturbance or a known reference before it affects the output, and is usually combined with feedback.