This article presents a partially worked out means of automatically reducing variable backlash in a CNC system. All was going just fine until I ran right into a bit of reality. However, others will hopefully see a good solution to the problem that blocked me and the scheme can be reduced to practice.
If you are interested, please see
http://rick.sparber.org/ABR.pdf
Your comments are welcome. All of us are smarter than any one of us.