Hi Pearl,
I think this is not the best place to ask this.
For more detailed answers you'd better ask or search for this in a motor control Forum.
Anyway, any BLDC motor control needs some sort of rotor position feedback in order to define the commutation, i.e. in which motor windings you must switch the current.
Digital Hall sensor is the standard and simplest solution.
More performance can be obtained with sinusoidal commutation, using analog Halls or, better, an encoder.
You can possibly operate the motor without a physical feedback device, by measuring the back emf and using it to obtain a raw rotor position (this is referred as sensorless control).
Which one of these? It depends on your control hardware, system capabilities, your design effort and what you need the motor for.
Regards
