Just wanted to add, that is a cool project on hack-a-day, but once you start looking at precision motion, or variable loads (eg. moving a robot arm), you start

Just wanted to add, that is a cool project on hack-a-day, but once you start looking at precision motion, or variable loads (eg. moving a robot arm), you start to become keenly aware of the physical imperfections of your motor and gear-box, and start having to think of things like cogging in the motor, or torque-ripple in the gearbox output and all that. The drive signals on those direct drive robots are NOT going to look like the perfect "3 sine-waves 120 deg out of phase" you see on wikipedia, and you need some damn good control software, and sensing of motor state to get good motion. I'm not trying to say it's impossible, or to knock anyones project or sounds argumentative. It's been done, as you pointed out! Just wanted to point out that while in theory it's much nicer to be able to do direct torque control on the motors, the headaches to become apparent in practice. (I still love the idea of direct drive :-D )