Homegrown servo motor driver?

Howdy,

I'm preparing to build a small (<100W) DC motor controller for the
purpose of learning about the problems and solutions in such products.
While I've already done the basics (microcontroller driven h-bridge with
motor encoder feedback for velocity control), I have not yet tried to
directly control position. I'm also interested in how one should go
about choosing a PWM frequency and the benefits/trade offs of higher and
lower frequencies and how motor characteristics affect the decision.

I wonder if anyone could direct me to some resources for expanding my
knowledge in this area.

Thanks!
Dave K