Which type of control is more robust to disturbances?

• A. Closed-loop
• B. Open-loop
• C. Neither
• D. Both equally

Answer: (A)

Using feedback makes a system more robust to disturbances because it continuously measures the actual output and adjusts the input to reduce any deviation from the desired value. When a disturbance pushes the output away from the setpoint, the controller sees the error and applies a corrective action that brings the output back toward the target. This ongoing correction is what provides disturbance rejection and keeps performance stable under changing conditions, payload variations, friction, or external forces. Open-loop control, on the other hand, applies a preplanned input without checking the result, so disturbances after actuation happen unchanged and the system may drift from the setpoint. Therefore, closed-loop control is better at handling disturbances.