SOLUTION

Closed-Loop Control

• A closed-loop control system utilizes a measure of the actual output to compare the actual output with the desired output response.
• The measure of the output is called the feedback signal. The elements of a general closed-loop feedback control system are shown in Figure.

• A closed-loop control system compares the measurement of the output with the desired output (reference or command input).
• The difference between the two quantities (the error signal) is then used to drive the output closer to the reference input through the controller and actuator.
• Often the difference between the output of the process under control and the reference input is amplified and used to control the process so that the difference is continually reduced.