Micro-step control of stepping motor

by:V&T Technologies     2020-01-12
The running performance of stepping motor is closely related to its stepping driver. The shortcomings of stepping motor can be overcome by improving driving technology. Compared with other driving methods, micro-step driving can not only reduce the stepping angle of the stepping motor, improve the resolution, but also reduce or eliminate low-frequency vibration, making the motor run more smoothly and evenly. In general, the micro-step driver has the best control performance. Since the common low-end stepping motor servo system does not have encoder feedback, the internal control current will decrease with the increase of motor speed, resulting in out-of-step. Therefore, in the field of low speed and precision, it is widely used and the driving precision is also very high. Micro-step is to drive each pulse from the upper device by the stepping driver, and divide the subdivision coefficient set by the device into coefficient pulse output, which means that if the stepping motor driver is subdivided, then every time the stepping motor turns into 200 pulses, it enters 32 bits, and the stepping motor driver needs to output 6400 pulses to turn the stepping motor once. Usually divided into 2, 4, 8, 16, 32, 62, 128, 256, 512. . . In foreign countries, for stepping systems, two-phase hybrid stepping motors and corresponding micro-stepping drivers are mainly used. However, in China, most users do not particularly understand'Subdivision' Some people just think that subdivision is to improve accuracy, but this is not the case. Subdivision is mainly to improve the operation performance of the motor. The explanation is as follows: the subdivision control of stepping motor is realized by accurately controlling the phase current of stepping motor by driver. Take a two-phase motor as an example. If the rated phase current of the motor is 3A, if a conventional driver (For example, the commonly used constant current chopping method) To drive the motor, the current in the winding of the motor will suddenly change from 0 to 3A or from 3A to 0 for each step of the motor. Great changes in phase current will inevitably cause vibration and noise of the machine. If a micro-step driver is used, the motor is subdivided into a drive state. For each micro step of the motor, the current change in the winding is only 0. 3A instead of 3A, and the current is sinusoidal and changeable, which greatly improves the vibration and noise of the motor. Therefore, the performance advantage is the real advantage of the motor. Subdivision. Since the subdivision driver must accurately control the phase current of the motor, the cost will be higher in order to have relatively high technical and technological requirements for the stepping motor driver. Please note that some drivers in China use'Smooth' Instead of subdivision, some are also called micro steps, but this is not a real subdivision. I hope most users must distinguish the essence of the two: 1. 'Smooth' The phase current of the motor cannot be accurately controlled, but the change rate of the current will only be slowed down, so'Smooth' No micro steps will be generated, and subdivided micro steps can be used for accurate positioning. 2. After smoothing the phase current of the motor, the motor torque will decrease, and subdivision control will not cause the motor torque to decrease. On the contrary, the torque will increase. TAG
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