Re: EMC handling backlash 2

[Doug Fortune <pentam-at-home.com>]

> Fred Proctor wrote:
> > Doug Fortune wrote:
> > > Maybe once we find a reasonably priced linear encoder (which
> > > of course directly senses table movement) then it will be
> > > feasible to have EMC directly characterize the backlash ...

Jon Elson wrote:

> This is kind of muddled.  Obviously, with a decent linear encoder, there
> is NO backlash.  What we got into was temporarily installing a linear
> encoder to characterize variations in backlash over the length of the screw.

Yes, obviously we can assume the linear encoder has no backlash.

The backlash is a combination of:
 - gaps between the nut threads/balls and the screw threads
 - slop in the end thrust bearings
 - compression effects of the screw (which vary according to where the nut is).

and of course all of the above may change slightly according to table
load (so maybe the automatic calibration should be run whenever drastically
changing the load on the table).

Doug