This is the sort of sensing I'm aiming at:
Interestingly, he also demonstrates the effect of changing rotor field.
This is a good starting point for the Prius position sensors.
Simple initial circuit
As with the field control it's a good idea to start simple.
This means using reed switches and magnets for sensing position, and probably using a diode matrix as the logic to drive the outputs.
So going back to the simple relay-based controller and swapping out the reed relays with reed switches.
Since the relays are not a one-to-one with reed switches we need to introduce a diode matrix.