Hello!
I felt lazy to make a drawing on a simple case, but I found that:
https://www.radiolocman.com/shem/schematics.html?di=150563
There is a description of the simplest possible BLDC. You have 3 sensors and their information
will generate 3 square signals as shown on the figure's top left. We'll call the coils black coil,
yellow coil and red coil.
Let's imagine that when you detect that south of the rotor is facing the black coil (exactly like
the drawing), let's imagine that you generate a north in the black coil. What would it do?
It wouldn't move at all.
Now from this position, imagine that you can turn your hall sensors set. There will be a point
where the motor starts to spin. Slowly first because the timing would be quite bad, and then if
you move further, the speed would increase until an optimal point as indicated by the coil
signals graphics on the left. I suppose that you can understand that the angle has an influence
on how optimal the switching will be.
In fact, there are other ways to spin a BLDC, there are even solutions without hall sensors
by sending a 3-phase signal in the 3 wires. This is a pure openloop system.
And there are also solutions using a high resolution encoder for a close loop system. In this
case, you measure the angle, and you calculate the 3 phases and their sine values to feed
into the motor. These days, you can have (relatively) cheap encoders with a resolution
around 20 bit (1 million values per turn) with which you can have a very smooth movement.
Dora.