How do controllers and actuators reduce the difference between actual and desired output?

In a closed-loop feedback control system, controllers and actuators work together to minimize the discrepancy between the desired operating value (input) and the actual measured value (output).1

The process functions through the following mechanism:

• Comparison: The controller continuously compares the measured output—monitored by sensing elements—against the reference input.1
• Determination: The rate at which energy is supplied to the system is determined by a function of the difference between these actual and desired values.2
• Action: Actuating devices, such as motors, valves, or switches, use power from a local source to influence the process. By adjusting the process based on this difference, the system drives the output toward the set point.12

This process is a form of negative feedback, which dampens the difference by applying the output against the initial conditions. To ensure stability and prevent overcorrection (a phenomenon known as hunting), systems often incorporate damping to slow the response and avoid excessive overshoot.32