I'm interested in the often repeated advantage number one. "AC can be more efficient". Why is this? Is it because the proximity from the winding to the pole is actual a perfect sinusoid? I have read that driving an AC motor with a square wave, or a 6-step is inefficient - isn't a DC motor just the same as an AC motor except that it mechanically transforms the DC signal into a square wave AC? (what's that part called, the commutator or something?)
This Field Oriented Control concept is very interesting. It would be worthwhile to design a controller that has all the inputs required to use FOC, but start with a simple Volts/Hz controller. That paper shows massive advantages to FOC over V/Hz - specifically, it shows "DC motor-like" low-end torque... which is one of the main benefits of a DC motor.
btw, LOVE the motor sound
