@Peter: robust was the word I think you were looking for
. OP asked for alternate approaches: "How would you guys do this?"
OP is trying to calibrate a control system via a manual "training" procedure. The problem, which may be caused by friction as you suggest (although OP has neither confirmed nor denied that), is noise;
I don't mean noise in the measurement device (transducer, electronics, shot, etc.) itself, as that source of noise is obviously minimal in this case,
as you noted earlier. The noise comes from the operator/trainer's arm having too high a gain when trying to manually assert a steady position or pressure.
In my experience, multiple samples are the most robust way to beat down the noise.
A drunken monkey could play with the guide/shoe for several seconds, then the actual operator could replace the monkey, hold the shoe at two positions, and my method would take the monkey- and operator-driven data
in toto, and produce good results.
I am pretty sure just looking at the force and rate of change in the force will do the trick.
P.S. do you realize that my first approach did exactly that?
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