How do controllers and actuators change the output of a feedback system?

In a closed-loop feedback control system, the controller and actuating devices function together to regulate the system's performance by minimizing the discrepancy between the desired input (set point) and the actual output.1

The process works as follows:

• Comparison: The controller continuously compares the measured output value—provided by sensing elements—against the reference input value.1
• Correction: If a difference is detected, the controller and actuator act as the mechanisms that influence the process to reduce that error.1
• Execution: These components utilize various mechanical and electrical hardware, such as motors, valves, switches, or pistons, to apply the necessary changes to the process, thereby adjusting the output variable to align with the desired set point.1

For example, in a thermostat, the controller and actuator detect when the room temperature falls below the set point and trigger the heating system to increase the output, turning it off once the target temperature is reached.1