Re: [CAD_CAM_EDM_DRO] Re: Big servo motors drive recommendations

Mark Vaughan wrote:

> I’ve wondered why they don’t copy some of the old analogue stuff.
>
> I suppose the issue is probably the fact that most digital engineers hate
> analogue work and so they keep clear, that little analogue I have seen on
> digital cards is very poorly done.

The smoothest and most stable performance is obtained with a
tachometer on the motor. This scares the average DIY
retrofitter beyond belief! And, for good reason, because to get
good performance, it takes an oscilloscope and a lot of fooling
around to tune the servo response. First you need to set the
bandwidth (compensation) for the torque (current) loop, then do
the same for the velocity loop. Then, you need to balance the
gains of the velocity (tach) feedback with the velocity command.
Finally, you need to tune the PID loop on the CNC computer.
That is a HELL of a lot of interacting adjustments! When one of
them is out of whack, it can take some time to figure out which
one it is.

Jon