This week, I wrote an implementation of a flux observer for the janktroller. It uses an integrator to determine the flux that has been put into each phase, and reads the current currently in the phase to sense the ratio between them, which is the flux linkage. This varies as that magnets move around the stator, and with the three flux linkages and some trig you can calculate the electrical position of the rotor. A large benefit of a flux observer over something like a back-emf observer is that the flux linkage is not dependent on rotor speed, so ideally it allows for closed loop control at almost all speeds. Testing of this module is currently waiting on good adc data, which has to be sampled at very specific times.