Efficiency index – stepper motor efficiency is about 60%, servo motor is about 80%; in actual use, it will be found that servo motors are expensive and much more expensive, so synchronous motors are more widely used, especially in synchronous motors that do not require very high positioning accuracy Stepper motors are often used in belt drives, flat belt conveyors and other occasions. Closed-loop stepper motor: In addition to the open-loop stepper motor, there is also a stepper motor that adds an encoder at the end of the motor to achieve closed-loop control. The closed-loop control of the stepper motor uses position feedback and (or) speed feedback to determine the phase transition suitable for the rotor position, which can greatly improve the performance of the stepper motor. Servo system with no out-of-step phenomenon.