The servo motor is similar to the stepper motor in function and structure, but the performance of the servo motor is very different. What are the specific differences? What is the difference between servo motor and step motor in the application of precision machine tools?
First, the low frequency characteristics of servo motor and stepper motor are different.
Stepper motor is prone to low frequency vibration at low speed. The working principle of step motor determines that the low frequency vibration phenomenon is very unfavorable to the normal operation of the machine. Many step drivers automatically calculate their vibration points to adjust the control algorithm to suppress their vibration.
Ac servo motor runs very smoothly, even at low speed will not appear vibration phenomenon. Ac servo system has the function of resonance suppression, which can make up for the lack of rigidity of machinery, and has frequency analytic function (FFT) inside the system, which can detect the resonance point of machinery and facilitate system adjustment.
Second, servo motor and stepper motor performance is different.
The control of stepping motor is open loop control, the starting frequency is too high or the load is too large, and the phenomenon of overshoot or overshoot is easy to appear when the speed is too high, so in order to ensure its control accuracy, the problems of rising and falling speed should be dealt with well. The AC servo drive system is closed loop control. The driver can directly sample the feedback signal of the motor encoder. The position ring and the speed ring are formed inside. Generally, there is no step loss or overshoot of the stepping motor, and the control performance is more reliable.
Thirdly, the moment frequency characteristics of servo motor and stepper motor are different.
The output torque of the stepper motor decreases with the increase of the speed, and will decrease sharply at the higher speed, so the maximum working speed of the stepper motor is generally 300~600 RPM.. The output torque of the stepper motor will decrease sharply at the higher speed The AC servo motor is constant torque output, that is, within its rated speed (generally 2000 RPM or 3000 RPM), it can output rated torque and constant power output above rated speed.
Fourth, servo motor and stepper motor speed response performance is different.
A stepper motor takes 200~400 milliseconds to accelerate from rest to working speed, usually hundreds of revolutions per minute. The acceleration performance of AC servo system is good. Taking Mingzhi 400 W AC servo motor as an example, it takes only a few milliseconds to accelerate from static to its rated speed of 3000 RPM which can be used in the control situation which requires fast start and stop.
In some very demanding situations, servo motors with much higher performance than stepper motors must be used. Although China has the most complete industrial category in the world, most of them are in the field of “bold and free “, and there is still a big gap in the accumulation of high-end products.
Fifth, servo motor and stepper motor control accuracy is different.
The step angle of two-phase hybrid stepping motor is 1.8,0.9, and that of five-phase hybrid stepping motor is 0.72,0.36. However, the control accuracy of AC servo motor is guaranteed by the rotary encoder at the back end of the motor shaft. For the motor with 17 bit encoder, the
Post time: Sep-15-2020