The difference is that:

1. The control precision is different. The more the number of phases and beats of the stepping motor, the higher its accuracy. The servo motor is based on its own encoder, and the more scales of the encoder, the higher its accuracy.

2. The control methods are different; one is open-loop control and the other is closed-loop control.

3. The low-frequency characteristics are different; stepping motors are prone to low-frequency vibrations at low speeds. When they work at low speeds, damping technology or subdivision technology is generally used to overcome low-frequency vibrations. The servo motor runs very smoothly, even at low speeds. Vibration will occur. The AC servo system has a resonance suppression function, which can cover the lack of rigidity of the machine, and the system has a frequency analysis function (FFT) inside the system, which can detect the resonance point of the machine to facilitate system adjustment.

4. The torque-frequency characteristics are different; the output torque of the stepper motor will decrease with the increase of the speed, and the AC servo motor has a constant torque output.

5. The overload capacity is different; stepper motors generally do not have overload capacity, while AC motors have strong overload capacity.

6. The operating performance is different; the control of the stepping motor is an open-loop control. If the starting frequency is too high or the load is too large, it is easy to lose steps or stall. When the speed is too high when it stops, it is easy to overshoot. The AC servo drive system is closed-loop Control, the driver can directly sample the feedback signal of the motor encoder, internally constitutes a position loop and a speed loop, generally there will be no step loss or overshoot of the stepping motor, and the control performance is more reliable.

7. The speed response performance is different; the stepper motor needs hundreds of milliseconds to accelerate from static to working speed, while the acceleration performance of the AC servo system is better, generally only a few milliseconds, and can be used in control occasions that require fast start and stop.