How To Control Brushless DC Motor

1. After controlling the energization sequence of the coils, divide the opposite coils into several groups, and flow current at the same time to generate the same direction magnetic field.

     2. Since the maximum number of brushless DC motors is three, each pair of "magnetic poles" is turned on in a specific order to achieve the effect of magnetic field rotation. Under the action of the magnetic field, the central permanent magnet rotor always tends to keep the magnetic field in the same direction and rotate with the rotating magnetic field. Hall sensors are elements that detect magnetic fields, located in the air gap of the excitation coil, and can change the voltage depending on the direction of the magnetic field.

      3. De-energize the given stator coil, there must be a narrow angle between the rotor and the stator magnetic field. There is no need to judge whether the brushless DC motor has just started, just run the following command according to the running state returned by the Hall sensor:

      4. As the rotor turns, the induced potential of each coil is zero at the highest point and then in the opposite direction. When the coil is energized and reversed, the back EMF prevents the voltage from reversing, and a trapezoidal wave appears locally. Since the positive and negative voltages of this trapezoidal zero point are in opposite directions, the voltage comparator detects the positive and negative voltages to determine the working state of the motor stator.

      5. Determine the starting direction, first energize the coil in this direction, rotate the rotor to this starting position for a short time, and then stop energizing according to the following operations to make the motor rotate.