3) is interesting. Sensorless operation is common for running motors, but usually doesn't sense position when the motor is stopped, or being moved by external forces.
So if you put a carrier on the power signals, you can potentially sense position, even at zero speed? No need for even Hall sensors? There's a paper from 2001 on that.[1] But it doesn't seem to be a mainstream technique. Are there problems with that approach? If it worked well, you'd expect to see it built into common motor control ICs by now. This paper [2] indicates some of the problems. Detecting the sensing signals in the presence of noise is reported to be hard, especially for small motors. It's a PhD thesis topic.[3] Looking for info about this, I'm finding academic papers, but not IC data sheets.
It would sure be nice to have motors with full positional feedback and only 3 wires, instead of 16.
So if you put a carrier on the power signals, you can potentially sense position, even at zero speed? No need for even Hall sensors? There's a paper from 2001 on that.[1] But it doesn't seem to be a mainstream technique. Are there problems with that approach? If it worked well, you'd expect to see it built into common motor control ICs by now. This paper [2] indicates some of the problems. Detecting the sensing signals in the presence of noise is reported to be hard, especially for small motors. It's a PhD thesis topic.[3] Looking for info about this, I'm finding academic papers, but not IC data sheets.
It would sure be nice to have motors with full positional feedback and only 3 wires, instead of 16.
[1] http://ieeexplore.ieee.org/document/955987/ [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3231115/ [3] http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=10...