How does a closed-loop control system use feedback to adjust a process?

A closed-loop control system regulates a process by continuously monitoring its output and adjusting it to match a desired reference value, or set point. This process relies on five core components: an input (the desired value), the process being controlled, the output (the actual measured variable), sensing elements, and a controller with actuating devices.12

The system functions through a feedback loop:
* Measurement: Sensing elements monitor the current state of the output variable.2
* Comparison: The controller compares this measured value against the reference input.2
* Adjustment: The controller and actuating devices calculate the difference between the actual and desired values and initiate changes to the process to reduce that difference.23

For example, in a heating system, a thermostat measures room temperature. If the temperature falls below the set point, the controller activates the furnace; once the temperature exceeds the set point, it turns the heat off. To ensure stability and prevent overcorrection—a phenomenon known as hunting—systems often incorporate damping to smooth the response.23