Options for Brushless Motor Control?

[r691175002]

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.

[Ether]

Backlash, torsional windup, and sensor resolution make a gearbox-mounted sensor a very poor choice for commutation. You want the commutation sensor mounted internally to sense the shaft position near the rotor for best results.

Trapezoidal commutation is not that hard to code if you are using motors with Hall commutation sensors. Interrupt on change of Hall states and flip the appropriate FETs in the 3-half-bridge driver circuit. Just make sure the rest of your code is written properly so that you have very low software latency.