Which motor is driven to a commanded angular position using feedback control to achieve precise motion?

• A. Stepper
• B. Servo
• C. Synchronous
• D. Induction

Answer: (B)

Closed-loop position control is what this item is about. A servo motor system uses feedback from an encoder or resolver to measure the actual shaft angle. The commanded position is compared to that feedback, and the controller adjusts the drive signal to minimize the error. This feedback loop lets the motor reach the exact angle and hold it accurately, even if there are disturbances or changes in load. While a stepper motor can position itself in steps and is sometimes used without feedback, it isn’t inherently defined by a feedback-driven command-to-angle approach the way a servo is. Synchronous and induction motors are typically used for speed or torque control rather than precise, closed-loop positioning, so they don’t fit the description as naturally as a servo does.