In a closed-loop control system, which term identifies the speed value that is compared with the actual speed to produce an error signal?

• A. Setpoint speed value
• B. Reference speed
• C. Feedback
• D. Error signal

Answer: (A)

The main idea here is that a closed-loop system compares a desired target with what’s actually happening. The value used as the target for speed is the setpoint speed value. It represents the speed the system is aiming to reach, and it’s fed into the comparison against the real speed (the feedback). The difference between these two is the error signal, which the controller uses to adjust the output.

The other terms describe different things: the feedback is the measured actual speed, and the error signal is the result of the comparison (the difference). The reference speed is another common name for the target in some contexts, but the explicit term that matches “the speed value being compared” is setpoint.