Is Sensorless FOC (Back-EMF based FOC) in develepment?

[Rimbaldo]

@runger

Well, this makes sense, although 2K-5K RPM still isn’t so slow for SimpleFOC but I think this will be possible.
The faster your MCU, the faster you’ll be able to turn the motor in this kind of setup, so I would advise looking at one of the faster 32bit Arduinos like the Nano33s, or even a Nucleo 32 board if you like the Nano form-factor.

Great!

I’ve got no problem in turning the motor, even at 47K RPM in the Nano… but, if a better CPU is needed, could than an ESP32 be used then?

@runger

But I think your core problem will remain: having to work with <5% duty cycle makes the control more difficult, all the more so if PWM frequency is 61kHz… so you could experiment with adaptive PWM (its a thing ) where you lower the PWM frequency to give yourself more range to work with on the low duty cycles.

I’m reading about lowering the frequency at the lower end… Do you have any info, or direction on where to look for adaptive PWM?

@runger

Another idea to try is an adjustable PSU - using a switch mode DC-DC converter on the VS input path would allow you to regulate the voltage. I don’t know how much power your motor draws, but you can buy or implement reasonably sized switch mode power supplies up to 10A or so. If you have space, they can do a lot more, of course
Using an adjustable DC-DC converter and a digital potentiometer or something like this you could implement a variable DC supply scheme to reduce the motor voltage at low RPMs, allowing you to use higher duty cycles.

I did exactly this, but in a ready-made chinese driver. I managed to go lower than 5K by lowering the Voltage from 33V to 18V. But as the internal code (in the chinese driver) was not done to fast speed transitions, I coundn’t mantain high torque at low speeds even with PID.

But in my dev DRV8302 board I’m not being able so far to do it. I lower the voltage but in the end, I get to the same min speed, but with higher duty cycle… So far… Have to try more…

Thanks!