Richard
I am attempting to tune my machine, running rutex drives and emc2.
I command a drive to move 8 inches one direction reverse and return to zero.
G1 X-8.0 F10 G1 x0.0 F10. When I test with a dial indicator if the machine
returned I see that I over traveled .005". I retuned the drive and increased
the "i" value and adjusted p and d to reflect the increased i. I rerun my 8
inch test and find I returned to zero.
I then run the same test but with twenty inches of motion and find myself 2
thousands short. Just to see what would happen I increased my feed rate from 10
to 15ipm. Suddenly the machine returns to zero. I increased the feed to 30ipm
and I overshoot.
It appears that I have a velocity dependent situation.
You might like to investigate electrical noise. Speed will obviously cause
steppers to loose steps but I do not see how the servos would suffer. I have
only used the older Rutex drives but they allowed a massive 32k count following
error and more importantly would fault out if it was exceeded so you never got
lost steps that you did not know about (only following error!)
Noise on the encoder signals will confuse the drive about where the motor
actually is and, of course, noise on the step signal will alter the requested
steps.
You talk in terms of overshoot and undershoot but you do not really know which
direction of motion (or both) causes the errors so whether you are looking for
lost or gained steps. Can you use a setting bar to measure a one-way journey.
John Prentice
ps Out of interest, what was the reason for the "sudden death" you had or how
did you fix it?
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