Alain:
The PWM is controlled by a Pot. I could also make a variable power supply and control directly the voltage on a SMPS circuit instead of PWM. More complicated.

Amgen:
It is easier on the unipolar mode. But gets difficult on bipolar drive having software to control both PWM, low freq signal and the control of the 4 MosFets transitors. Including deadtime.
Better, most if not all of this be done on hardware using NCO, CWG, CLC etc.

I believe that it is possible to do this as Richard is confident too. I just need more reading to understand how all these modules will work together.

Ioannis