MCF8329A: Motor parameters accuracy

The sensorless FOC control algorithm needs to know the BLDC motor coil resistance, inductance, and the motor's BEMF constant, in order to calculate the rotor position.  With what level of accuracy does each of these parameters need to be determined?  What are the observable effects when each of these is too far from the actual value?  Is it typically the case that for a specific motor design, unit-to-unit manufacturing variation will be unimportant?  Or is it necessary to characterize each individual motor for best performance?

What level of accuracy does the MPET function achieve for each of those parameters?  Do the best results come from using the built-in MPET, or from using (appropriately good) bench test equipment?