With the current sensors being so cheap, using a bunch of resistors and capacitors to proxy the phase current and then still needing the op-amps to amplify the current to feed into the MCU, then use an algorithm to estimate the phase current, I really don’t understand why so many people look at this as some kind of “holy grail” of motor control. It’s a really old, poor and cheap way to control a motor, harking back from the days of my grandpas when people didn’t really have FOC and used a simple “zero cross” commutation to control the motor speed. Whoever needs “sensorless FOC” probably only needs a really simple and cheap fan speed controller, not a modern control board with a FOC algorithm.
https://www.digikey.com/en/products/detail/allegro-microsystems/AMT49406GLPTR/10498761
Adding this to the library is certainly a very interesting and academically worthy exercise, however, I see very little practical applications, furthermore coupled with the fact that there are no commercial boards implementing the phase sensing using “sensorless approach”, that is, the resistor/capacitor schematics for sensing the phase current from the coils. They all use either shunt resistors or hall-current sensors. I looked into adding “sensorless” sensing (an oxymoron) and it was so messy and complicated that I gave up. Perhaps someone else could design a “sensorless” phase sensing board, for testing, it would be an interesting and intellectually challenging project in PCB routing.
For those interested in doing it, here is the “sensorless” schematics. As you can see, plenty of “sensing” going on, not quite simple and “sensorless”.
