Well, if you use your CNC controller to close the position loop, this means you will have more than one CPU involved in closing the servo loops (the position loop closed by the CNC controller, and the velocity/torque loops closed by the servo drive). But because the three servo loops are tightly interrelated (i.e., any change in one means a change in the others), ).
Not quite true, There are many systems that have used the same method as I have often done with a Galil Motion controller, there is only ONE CPU involved, that in the Galil Card.
The drives are simple torque mode, Transconductance amplifiers.
The applications achieved with Galil Controllers are some that demand very stringent requirements, and for the typical CNC machining accuracy, more than adequate. IMO.
Al.