Servo motor and stepper motor accuracy and low frequency difference

Update:27 Dec 2021

The control accuracy of the AC servo motor is guaranteed by the rotary encoder at the back end of the motor shaft. Take the fully digital AC servo motor as an example. For a motor with a standard 2000-line encoder, due to the quadruple frequency technology used in the drive, its pulse The equivalent is 360°/8000=0.045°. For a motor with a 17-bit encoder, every time the driver receives 131072 pulses, the motor makes one revolution, that is, its pulse equivalent is 360°/131072=0.0027466°, which is the pulse equivalent of a stepping motor with a step angle of 1.8° 1/655.
Stepper motors are prone to low-frequency vibration at low speeds. The vibration frequency is related to load conditions and drive performance. It is generally considered that the vibration frequency is half of the no-load take-off frequency of the motor. This low-frequency vibration phenomenon is determined by the working principle of the stepper motor. It is very unfavorable for the normal operation of the machine. When the stepper motor is working at low speed, damping technology should generally be used to overcome the low-frequency vibration phenomenon, such as adding a damper to the motor, or using subdivision technology on the drive.
The AC servo motor runs very smoothly, and there is no vibration even at low speeds. 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, which is convenient for system adjustment.

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