They are just a closed-loop stepper system with a higher resolution encoder that provides 32,000 pulses per rev which to be honest isn't really practical unless the drive allows electronic gearing because most controllers won't have the frequency or pulse width to drive it to its full potential. Just to get it to spin at 1500rpm you would need a frequency of 800Khz and most of the lower end controllers like UC300 are 100khz or at best 400Khz ie UC400.