RE: Accumulating position error with servo system

[Kurtis Martineau <klmartineau-at-shaw.ca>]

Jon,

 I'm just wondering if something
> else in the computer
> may be interfering with the I/O address of the Y axis encoder counter.
>  This is a pretty
> long shot.

I didn't mention it, but the pc was the first thing I changed. From a Compaq
350MHz to a PIII 667MHz.

> This really seems to implicate either the STG or the software.  Check 7
> seems to get the STG
> off the hook, so software begins to look very suspect.
>
> There was a problem some time ago, when using certain values of backlash
> compensation.
> Turn all the backlash values to 0.0 and try it again.

I have the values set to 0.000.  I will try 0.0 and 0 to see if this makes a
difference.

> It may have also reared its head in  relation to homing, so it gets more
suspicious.  One thing I might try
> is to move the machine manually, while in estop, and compare a dial
indicator with the screen display.

I have done this over only a small range (just a quick check, so I didn't
collect any real data) and dial indicator position seemed to compare with
the screen display.  I could try it again over the whole 1.00000 inch range
of the dial indicator.

> If there is no problem when manually moving, but you get errors when
moving under computer control, then there are only a couple of
possibilities.
> One is  a software problem (and the backlash bug did exactly this, I
recall) or there is  some electrical problem from servo amp noise that only
affects the Y axis encoder counter.
>
> You might also try STG's DOS diagnostic programs and see if they give an
error.


Kurtis