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

Brushless DC (BLDC) motors are standard ... and encapsulated it into a compact Arduino library, added a host of examples, and minted a stackable BLDC motor control shield to boot.

ClearCore CLCR-4-13 is an industrial IO and motion controller that can be programmed using the Arduino IDE. It handles up to four axes of step-and-direction motion control (500kHz max step rate), and ...

On the Arduino side, I have the bones of an idea ... For those interested, someone called H Holden has published a detailed analysis of a mosfet chopper style dc motor controller.