Stepper Motor And Servo Motor

1. The control accuracy of stepper motors and servo motors is different. The step angle of a two-phase hybrid stepper motor is generally 1.8 °, while that of a three-phase hybrid stepper motor is 1.2 °. There are also some high-performance stepper motors with smaller step angles.

The control accuracy of the AC servo motor is ensured by the rotary encoder at the rear end of the motor shaft. For servo motors with standard 2500 line encoders, due to the use of quadruple frequency technology inside the driver, its pulse equivalent is 360 °/10000=0.036 °.

For the vast majority of users, both mechanical transmission accuracy and photoelectric sensor positioning accuracy are not as high as the physical accuracy of stepper motors and servo motors. It is unnecessary to pursue the highest accuracy of the motor unilaterally.

2. The torque frequency characteristics of stepper motors and servo motors are different.

The output torque of a stepper motor decreases with increasing speed and sharply decreases at higher speeds, so its maximum operating speed is generally between 0-900RPM. The AC servo motor has a constant torque output, which means it can output the rated torque within its rated speed (usually 1000-3000 RPM).

3. The overload capacity of stepper motors and servo motors is different.

4. The operating performance of stepper motors and servo motors is different. The control of the stepper motor is open-loop control. If the starting frequency is too high or the load is too large, it is easy to cause step loss or rotor blockage. If the speed is too high when stopping, it is easy to cause overshoot. Therefore, to ensure its control accuracy, the problem of speed increase and decrease should be handled well.,

5. The AC servo drive system adopts closed-loop control, and the driver can directly sample the feedback signal of the motor encoder, forming a position loop and a speed loop internally. Generally, there will be no loss of step or overshoot of the stepper motor, and the control performance is more reliable. The servo motor is a closed-loop system, and the servo driver can automatically correct lost pulses and provide timely feedback to the controller in case of rotor blockage. However, the stepper motor is an open-loop system and must have sufficient torque margin to avoid rotor blockage.

6. The speed response performance of stepper motors and servo motors is different.

7. It takes 100-2000 milliseconds for the stepper motor to accelerate from stationary to working speed. The acceleration performance of the AC servo system is good, and it only takes a few milliseconds from static acceleration to its rated speed of 3000RPM. It can be used in control situations that require fast start stop.