When the stepper motor runs at low speed, due to the speed impact and inertia caused by phase sequence conversion, the motor rotor repeatedly oscillates at the equilibrium position, affecting the operating accuracy. And produce relatively large noise.

There are two ways to solve this problem:

One method is to increase the number of phases of the stepper motor and reduce the angle of rotation of the rotor during phase sequence transformation; the other method is the stepping motor step angle subdivision control method proposed by American scholar T.R. Fredriksen in 1975. Practice has proved that the stepper motor subdivision drive control technology can reduce the step angle of the stepper motor, improve the stability of the motor operation, and increase the flexibility of control.

   The concept of stepper motor subdivision drive control:

The driving method of subdividing the "motor inherent step angle" into several small steps is called subdivision driving. The subdivision is realized by precisely controlling the phase current of the stepping motor through the driver, and has nothing to do with the motor itself. The principle is that the stator energized phase current does not rise to a certain level at one time, and the de-energized phase current does not drop to 0 at one time (the winding current waveform is no longer an approximate square wave, but an N-level approximate ladder wave), then the stator winding current The resulting magnetic field force will cause the rotor to have N new equilibrium positions (forming N step angles).

   Latest technological developments:

Research on subdivision drive technology is very active at home and abroad. High-performance subdivision drive circuits can be subdivided into thousands or even arbitrary subdivisions. At present, it has been possible to make the subdivided step angle uniform through complex calculations, which greatly improves the pulse resolution of the stepper motor, reduces or eliminates vibration, noise and torque fluctuation, and makes the stepper motor more efficient. "Servo-like" features.

a. The relationship between the use of subdivision technology and the improvement of stepper motor accuracy: The subdivision technology of stepper motors is essentially an electronic damping technology. Its main purpose is to weaken or eliminate the low-frequency vibration of the stepper motor and improve the operating accuracy of the motor. Just a by-product of subdivision technology. After subdivision, the resolution of each pulse is improved when the motor is running, but whether the running accuracy can reach or approach the pulse resolution depends on other factors such as the subdivision current control accuracy of the subdivision driver. The accuracy of subdivision drives from different manufacturers may vary greatly; the larger the number of subdivisions, the more difficult it is to control the accuracy.

b. Real subdivision requires very high technical and process requirements for the driver, and the cost will also be higher. Some drivers use "smoothing" to replace the subdivision of the motor phase current, which belongs to "false subdivision". "Smoothing" does not produce microsteps, but will cause the motor torque to drop. The real subdivision control will not cause the motor torque to drop, on the contrary, due to the reduction of vibration, the energy loss will be reduced, and the torque will increase.