I was envisioning a controller that used a rotary encoder to keep track of the motor shaft - just like a brushless servo.
Regardless of the sensor or how it is mounted, as long as there is a way to get an absolute or relative (combined with some kind of start-up sequence) reading on the motor shaft commutation is possible. If I mounted the encoder in the gearbox backlash could be a problem but that's a separate issue.
There are a few products that can accomplish what I want but they are invariably giant expensive boxes intended for CNC or similar applications:
http://www.tolomatic.com/products/it...cfm?tree_id=92
The tolomatic box requires only an incremental encoder.
The more I search the more it looks like the best option is building it ourselves but every time I hear terms like flux vector I feel like it is a job better left to experts.
Of course, given the limited options I seem to have I'm willing to go with whatever I can get.