Which motor is typically used for precise open-loop positioning by stepping with digital pulses?

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

Answer: (B)

Open-loop positioning relies on counting input steps rather than using position feedback to correct errors. A motor that moves in fixed, repeatable increments in response to each digital pulse fits this approach: the stepper motor. Each pulse advances the rotor by a defined step angle, so a sequence of pulses yields a predictable position, and the motor can hold its position when energized. This makes precise positioning with digital pulses straightforward without feedback, as long as load, speed, and torque stay within the motor’s capability and steps aren’t skipped. Other motor types rely on feedback or continuous torque behavior and don’t provide the inherent fixed-step increments that enable reliable open-loop stepping, which is why they’re less suited for this requirement.