Brushless dc motor controller, because of the brushless motor controller can't do on its own their current commutation, must rely on external control circuit to realize the reversing. So there is no conventional dc control mode, the external control circuit to complete the reversing are implemented through the switch tube, due to the flexibility of switching circuit, can easily achieve more than just the reversing function, so the dc chopper control mode is used to control the motor controller. The first thing to turn, let the brushless motor controller control department must be based on the induction to the motor controller is the position of the rotor current, and then according to the stator winding decided to open (Or close)Inverter in the order of the power transistor, upper arm power transistor and the lower arm power transistor, the current flowing through the motor controller coil in a sequence downstream (Or the reverse)A rotating magnetic field, and interact with the rotor magnet, so can make the motor controller chronological/reverse rotation. When the rotor rotation to the induction motor controller out of position to another set of signals, control of open again the next set of power transistor, so the motor controller can continue to roll according to the same direction until the control department decided to rotor motor controller to stop the close power transistor (Or just open the arm power transistor); To the motor controller rotor opposite to reverse power transistor to open order. Commutation control according to the stator winding commutation way, first of all find out three magnetic steel rotor position sensor signal H1, H2, H3, and 6, the relationship between the power tube of a tabular form in the microcontroller block of the EEPROM. 8751 according to the state of the H1, H2, H3, can find the corresponding conduction of power tube, and through the P1 mouth out, commutation of brushless dc motor can be realized. Brushless dc motor speed control in normal operation in the process, as long as by controlling the da converter output voltage U0, can the current control of the brushless dc motor to control the current of the motor. 8751 single chip microcomputer through sensor signal cycle, calculate the speed of the motor, and comparing it with the given speed, such as higher than that of a given speed, the decrease P2 output value, reduce the motor current, to achieve the purpose of reduce its speed. On the other hand, increases the P2 output value of mouth, and then increase the speed of the motor. The PWM speed control can be controlled by PWM mode. When variable structure control for brushless dc motor in a starting state, or in the process of adjustment, adopt the mode of the brushless dc motor, in order to realize dynamic corresponding rapidity, once near the speed of the motor to the given value, immediately put it into synchronous motor running mode, to ensure its steady speed precision. The computer only need according to certain frequency control of motor commutation, at the same time, computer through position sensor signal cycle, to measure its size, speed and decide if it fell out of sync. Once lost, is immediately transferred to the brushless dc motor running, and again it back into synchronization.
