First, the control accuracy is different:
The step angles of the two-phase hybrid stepping motor are 3.6° and 1.8°, respectively, and the step angles of the five-phase hybrid stepping motor are 0.72° and 0.36°, respectively. There are also some high-performance stepping motors with smaller step angles. The rotary encoder at the back of the motor shaft ensures the control accuracy of the AC servo motor. Take the JYT all-digital AC servo motor as an example. Because the drive adopts quadruple frequency technology, for a standard 2500-line encoder motor, the pulse equivalent is 360°/10000≤0.036°. For a motor with a 17-bit encoder, the drive rotates 217 ≤131072 pulse motors, that is, the pulse equivalent is 360°/131072=9.89 seconds. It is 1≤655 equivalent to the pulse of a stepper motor, and the step angle is 1.8°.
2. Different low frequency characteristics:
Stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to the load and the performance of the drive. It is generally considered that the vibration frequency is half of the motor's no-load take-off frequency. This low-frequency vibration phenomenon determined by the working principle of the stepper motor is very unfavorable to the normal operation of the machine. When the stepper motor is working at low speed, damping technology should be used to overcome the phenomenon of low frequency vibration, such as installing a damper on the motor, or using subdivision technology on the driver, etc. Jinyuantai AC servo motor runs very smoothly, and there is no vibration even at low speed.
Third, the bending moment and frequency characteristics are different:
The output torque of a stepper motor decreases with the increase of the speed, and drops sharply at a higher speed. Therefore, the working speed of a stepper motor is generally between 300 and 600 rpm. AC servo motor is a kind of constant torque output, that is, within its rated speed (generally 2000 rpm or 3000 rpm), it can output rated torque, and output constant power beyond the rated speed.
Four. Different overload capacity
Stepper motors generally do not have overload capacity, and AC servo motors have strong overload capacity. Take the AC servo system as an example. It has the capability of speed overload and torque overload. The torque is three times the rated torque. It can be used to overcome the inertial torque of the inertial load at the beginning of the torque. It is often necessary to choose a large torque motor , During normal operation, there is no need for such a large torque, and there is a torque waste phenomenon.
Five. Different performance:
Stepper motor control is open-loop control. When the starting frequency is too high or the load is too large, it is easy to lose step or lock up. When the speed is too high, it is easy to overshoot. Therefore, in order to ensure the control accuracy of the stepper motor, the lifting problem must be dealt with. . The AC servo drive system is a closed-loop control. The drive can directly sample the feedback signal of the motor encoder to form a position loop and a speed loop. Generally, there will be no step loss or overshoot of the stepper motor, and the control performance is more reliable.
With the further development of the intelligent transformation of the manufacturing industry, the application range of robots has become wider and wider, the production mode has changed to flexible, intelligent, and refined, and the automatic control situation is generally applied to servo motors. If you want to know more about servo motors, please pay attention to us.