Which statement best describes a hallmark of closed-loop control design?

• A. Emphasizes minimal sensor use
• B. Relies on accurate feedback and tuning to minimize error
• C. Prefers no feedback to avoid noise
• D. Does not require calibration

Answer: (B)

Closed-loop control relies on feedback to minimize error. The system continuously measures the output, compares it to the desired reference, and uses that difference to adjust the input so the discrepancy gets smaller over time. This happens effectively only when you have accurate feedback from sensors and you tune the controller (for example, the gains in a PID regulator) so the response reduces both steady‑state and transient error without becoming unstable. In practice, this feedback ability is what lets the system reject disturbances and model mismatches, maintaining the desired performance. The other ideas—avoiding sensors, avoiding feedback, or not needing calibration—conflict with how closed-loop control actually works, since measurements and proper tuning are essential for achieving and sustaining minimal error.