I spent some time looking at closed loop a couple of years ago (see the thread at Mechaduino experiment ). I believe Arksine also further extended that code ( GitHub - Arksine/klipper at work-mechaduino-updated ?).
Unfortunately, my experience led me to believe that implementing a traditional “closed loop” driver would be high effort and have a high risk of failure. My rough conclusion is that minor overshoot on typical stepper motors is common and correcting it with a closed loop feedback system will likely lead to “salmon skin” effects. That is, I fear correcting motor position is likely to result in worse quality.
That said, I think it may be possible to use the sensors to characterize a stepper motor driver and use that to calibrate the motion system to send slightly modified commands - so as to improve positional accuracy in a predictive way. (A kind of “feed forward” system.) Alas, this is likely very complex.
I’m not currently working on this and don’t have any short or medium term plans to work on it. I don’t know of anyone else currently working on it.
Cheers,
-Kevin