Sometime not all our problems have been dealt with with something on the web.

The problem with low speed running is what do you do while you wait for your speed sensor to tell you how fast you are going. In some ways a tacho generator is a good idea, but at low speeds they are very noisy device and suffer from commutation noise like servo motors. An optical encoder is a good way of doing it. Then you have two choices, to put the signal into an F to V converter or to create a Phased locked loop, either in software or hardware.

You are after a fairly extreme dynamic range for a DC drive really, at 1500:1

To be honest, a DC servo motor is so easy to drive with discrete electronics, and so well characterised I don't see any great benefits to using a microcontroller ! If, however you were working with AC servo motors, or induction motors, that would be very different and much much harder.

I sponsored a design project at Salford University on a DC motor servo design. The thesis was worse than useless, else I would send you the references.