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How to control the brushless DC motor
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- Time of issue:2021-08-09 15:34
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How to control the brushless DC motor
- Categories:News
- Author:
- Origin:
- Time of issue:2021-08-09 15:34
- Views:
The brushless DC motor, because of the brushless, the motor cannot complete the current commutation by itself, and must rely on an external control circuit to achieve the commutation. Therefore, there is no conventional DC control method. The external control circuit completes the commutation through the switch tube. Due to the flexibility of the switch circuit, it can easily achieve more functions than the simple commutation. Therefore, the chopper DC control method is adopted. Control the motor.
First of all, the brushless motor must be turned. The control unit must determine the order of turning on (or turning off) the power transistors in the converter, the upper arm power transistor and the lower arm power transistor according to the current position of the motor rotor sensed by the stator winding. , So that the current flows through the motor coils in order to generate a forward (or reverse) rotating magnetic field, and interact with the magnet of the rotor, so that the motor can rotate clockwise/counterclockwise. When the motor rotor rotates to the position where another set of signals is induced, the control unit turns on the next set of power transistors, so that the circulating motor can continue to rotate in the same direction until the control unit decides to stop the motor rotor, then turn off the power transistors (or Only the lower arm power transistor is turned on); if the motor rotor is to be reversed, the power transistors are turned on in the reverse order.
According to the commutation mode of the stator winding, the commutation control first finds out the state of the three rotor magnet position sensor signals H1, H2, H3, and the relationship between the six power tubes, and places them in the EEPROM of the single-chip microcomputer in the form of a table. . According to the status from H1, H2, and H3, 8751 can find the corresponding conductive power tube, and send it out through P1 port to realize the commutation of the DC brushless motor.
The speed control is in the normal operation of the DC brushless motor, as long as the output voltage U0 of the digital-to-analog converter is controlled, the current of the DC brushless motor can be controlled, and then the current of the motor can be controlled. That is, the 8751 single-chip microcomputer calculates the speed of the motor through the period of the sensor signal, and compares it with the given speed. If it is higher than the given speed, reduce the output value of port P2, reduce the motor current, and achieve the purpose of reducing its speed. . On the contrary, increase the output value of P2 port, and then increase the speed of the motor.
PWM control speed control can also be realized by PWM mode.
Variable structure control When the DC brushless motor is in the starting state or during the adjustment process, the operation mode of the DC brushless motor is adopted to realize the dynamic response speed. Once the motor speed reaches the given value, it is immediately transferred to synchronization Motor operation mode to ensure its steady speed accuracy. At this time, the computer only needs to control the commutation of the motor at a certain frequency. At the same time, the computer measures its speed through the signal cycle of the position sensor and judges whether it falls out of synchronization. Once it is out of cloth, immediately turn to the DC brushless motor to run, and pull it into synchronization again.
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Tel: +86 0519-81235785 Fax: +86 0519-81235782 E-mail: michelle@zz-motor.net Add: 4th Floor, Building 3, Rail Transit Industrial Park, No. 355 Longjin Road, Lucheng Street, Wujin District, Changzhou City, Jiangsu Province
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