Five, the principle of the motor control of the hub motor
The principle of DC brushless control, the controller reads the Hall signal to determine the sector where the rotor of the motor is located, and determines the switching logic of the inverter bridge arm. The square wave control is essentially a relatively simple six-step commutation operation. At any moment, one phase of the stator winding is in forward conduction, that is, the phase current is flowing forward; the second phase stator winding is in reverse conduction, that is, the phase current is reversed. Inflow; the third group is not powered. The electromagnetic torque originates from the magnetic field generated by the stator winding and attracts the rotor magnetic field to continuously rotate. If the reluctance torque (surface-mount permanent magnet synchronous motor) is neglected, the AC-axis magnetic field generated by the stator winding generates all electromagnetic moments; When the rotor magnetic field coincides, that is, the interaction between the direct-axis magnetic field of the stator and the rotor magnet, the electromagnetic torque generated is zero. Therefore, it is necessary to constantly change the position of the stator magnetic field to drive the continuous rotation of the rotor magnet, and the control stator magnetic field always leads the rotor magnet.
The field is at a certain angle, so that the magnetic field that forms the permanent magnet is always chasing the winding synthetic magnetic field. The controller detects the sector in which the rotor's magnetic field is located, and then controls the winding to produce a magnetic field directed to the next sector. Controlling the rotor to rotate one revolution requires only changing the stator winding six times. However, since the number of pole pairs of the hub motor is usually not, each completion of one energization period means that the rotor is only rotated one turn of the electrical angle, and the mechanical angle of the rotor is not achieved one week. Therefore, the commutation period required for the rotor to rotate the mechanical angle for one week The number is the same as the pole pair.
This control mainly realizes the speed control of the motor. By reading the position signal of the Hall sensor, the rotor position is judged, and the motor speed controller performs closed-loop control on the motor speed. Since the voltage is proportional to the speed, the phase voltage of the output can be controlled to realize the speed control. This control method changes the armature magnetic field by a simple six-step commutation, leading the rotor to rotate, and only two phase windings are turned on at any time. The specific control process is as follows:
The square wave control uses a Hall element as a position sensor. The three Halls are respectively placed at positions of 0°, 120° and 240°, as shown in Fig. 8, and the 360° electrical angle is divided into six sectors. The controller detects the sector in which the rotor is located and controls the armature magnetic field to direct the rotor to the next sector.
