[Frank Herrmann] had an interesting idea to turn a geared DC motor into a servo motor assembly ... pins hooked up to the motion controller upstream. The Arduino source for this can be found ...

[Cameron] has been hard at work at a low cost, closed-loop controller for the robotics community that will take a conventional BLDC airplane motor and transform it into a high end servo motor.

grbl is stepper motor controller firmware for three-axis cnc machines ... that are too powerful for the normal drivers included on grbl Arduino shields (or integrated Arduino+drivers equivalents), and ...