Bob Engelhardt wrote:
Jon Elson wrote:
Of course these can be used for CNC. You just need a servo interface
that puts
out +/- 10 V analog velocity commands. ...

Then this amp would just be a driver, and its tach feedback/servo
circuitry wouldn't be used?

Bob
No. The CNC control looks at position, only, via the encoder signal.
The velocity servo amp looks at velocity via the tach signal. The CNC
control commands a particular velocity by an analog output, and the
servo amp adjusts motor current to exactly match the commanded velocity.
The velocity error amp in the servo compares commanded to actual
velocity and creates an error signal, which is used as a commanded motor
current. (Motor current equals torque.) That current command signal
goes to a current error amp, and the amp adjusts PWM duty cycle to give
the requested motor current.

This is the "classic" velocity servo scheme used since the late 1960's
on all manner of servo-driven machines.

Jon