Let the motor rotation, the first control department must be based on the hall-sensor sensing the rotor to its current location, and then determined in accordance with the stator winding open (or off) converter (inverter) the order of the power transistor inverter in theAH, BH, CH (these are called the upper arm power transistors) and AL, BL, CL (these are called the power transistors of the lower arm), the current sequentially flows through the motor coil forward (or reverse) rotating magnetic field, and the rotormagnet interaction, and so will be able to motor along / reverse rotation. When the motor rotor rotation to the hall-sensor sensing the position of another set of signals, the Ministry of control again to open the next set of power transistors, so the cycle motor can continue according to the same direction, turn the power is turned off until the control department decided to be the motor rotor to stop transistor (or only open under the arm of power transistor); to the rotor reverse power transistor to open in reverse order.
Basically, the opening of the power transistor method can be for example as follows: BH, CL, AH, CL AH, BL a group → group → group → BH, AL group → CH, AL group → CH, BL group, but must not opening into the AH, AL or BH, the BL or CH, CL. In addition, electronic components, the response time of the switch power transistor in response time off and open the staggered parts of the time you want to be taken into account, when the upper arm (or arm) is not yet completely closed, the lower arm (or upper arm) had open the result is burned under the arm short-circuit leaving the power transistor.

When the motor rotation, control of the Ministry will be set by the drive speed and acceleration / deceleration rate of the composition of command (Command) than (or by a software algorithm) decided to come back from the next group (with the speed of the hall-sensor signal changes beAH, BL, or AH, CL, or BH, CL, or ...) switch is turned on, and turns on the length of time. Speed ??is not enough open, the speed is too far shortened, this part of the work done by the PWM. PWM is to determine the motor speed is fast or slow, how to generate the PWM is to achieve a more accurate speed control of the core

High-speed speed control must take into account the CLOCK resolution of the system is sufficient to master the software instructions, another hall-sensor signal changes in data access also affects the processor performance and to determine the correctness of the brushless DC motor
Real-time. As for the low-speed speed control, especially low-speed start because it is very important to return the hall-sensor signal changes more slowly, how to retrieve the signal to deal with timing and control parameters according to the appropriate configuration of the motor characteristics. Or speed of return to change the encoder changes as a reference, the signal resolution to increase in order to get better control. The motor can operate smoothly and a good response, PID control is appropriate or not can not be ignored. Mentioned before, the brushless DC motor closed-loop control, the feedback signal is tantamount to tell the control of the Ministry of the motor speed from the target speed is even worse how much, this is the error (Error). Know the error is naturally necessary to compensate for the way traditional engineering controls such as PID control. Status and environmental control in fact is complex and durable has to consider the factor to control is probably not the traditional engineering control can fully grasp, so fuzzy control, expert systems and neural networks will also be incorporated into intelligent type PID control theory.