> The motion controller copies feedback to command while in the machine
> off state.  The stepgen also updates its internal command position while
> it is disabled (which it should be in machine off).  The motion
> controller shouldn't do anything when it's enabled (it might, and that
> would be a valid bug), and it should only apply screw correction when it
> starts moving, since it doesn't know any direction until then.
>
> Of course, this will be a problem if the magnitude of screw compensation
> is larger than your following error setting.
>
> - Steve

This is why feeding the scale position into axis.N.joint-pos-fb would
be so elegant.  Because everything else would work correctly.

The only thing that would make it better is if the screw comp 'sensed'
direction change rather than taking a que from the motion controller.
Then if you move the machine manually, and re-enable the motors, the
screw comp will know what side of the screw it is on to start with.
Even without doing that, I suspect that the secondary feedback loop
would be sufficient to cover up that problem, and get things going
again.

Brian

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