“…The Shinsei ultrasonic motor and Piezoelectric Ultrasonic Motor of Rotary (PUMR) series are commonly used in the MRI-compatible surgical robots hitherto developed. Ultrasonic motors have certain advantages, such as large torque [19], high holding torque (approximately 1.0 Nm) [20], compactness, lightness, zero backlash, an ability to operate in a strong magnetic field [21], absence of a generated magnetic field, quiet operation, simple structure [19], fast dynamic response, and high efficiency [21].…”