Getting input from sensors in a control loop is typically required.

• A. It is never used
• B. It is a typical step
• C. It destroys data
• D. It only uses actuator data

Answer: (B)

Getting input from sensors is essential in a control loop because you need to know the system’s current state to decide how to act. The controller compares this measured state to the desired state and computes an error, then applies a control law (like PID) to generate actuator commands that reduce that error. This feedback mechanism lets the system correct for disturbances, model inaccuracies, and unknown dynamics, keeping performance on target. If sensor input isn’t used, you’d be operating open-loop, blindly following the command without knowing whether you’re achieving the goal, so disturbances would push the system off course and planning could’t compensate.

That’s why the idea that sensor input is never used, or that it destroys data, or that only actuator data is used, doesn’t fit real control practice—the feedback from sensors is what lets a control loop adjust and stay accurate.