caxis.comp status

Can you see the position cmd and position actual in degreees ??? See if anything odf there. Set a hal scope trugger for the index pulse, see if it's got noisy signal ? If index was triggered i could see it dumping the known position and rolling over unexpectedly

@Tommy,
Re-reading the PID manual, deadband should be set slightly greater than 1/2 count to stop hunting.  Your example is (I suspect) referencing a linear axis where you've got a very high count-per-unit (like thousands of counts per mm or inch).  Just like my X/Z axes with 1um encoders where I've got ~25400 counts/inch.

My subspindle is a direct-drive rotary axis where units = degrees.  So I've got ~27 counts per degree; significantly coarser feedback per unit.

The encoder signal is output from the drive, and I've got it set as high a resolution as possible.

@Aciera,
I tried the PID autotune a couple times on my Z-axis a while ago and the results were just dumb.  While I may give it a try, I haven't read a single report on the forum where someone was pleased with the results.

@smc.collins,
I have the pos-cmd and pos-fb up in halshow, but haven't yet scoped them.  Nothing odd or way off during a programmed back-and-forth move.  It homes to index fine and the counts/position/velocity all look like they should even when it flips out.  Doesn't lose track of where it is.


I'm going to try connecting it like an open-loop stepper tonight - connect stepgen pos-fb to pid.b.feedback and joint motor-pos-fb.  That should help me see if my issue is with the PID or not.

Just to try to straighten out this thing in my head, I've cobbled up a chart which shows the connections.  Also where I'm fuzzy on various units.

Feel free to point any mistakes I've made as the chart is what I have in hal... not necessarily what Andy intended.

 

More detailed version below.  Does not have the caxis.comp internal logic which returns the axis to previous position when the spindle is stopped.

I've added the various pin/parameter values I've been trialing.  Maybe someone can see where there's a scaling issue or other improperly connected item.
 
 

I think pid output should be angular velocity - derivative of position with respect to time.
The rest is scaling factor  

@pawal77,

Thank you for the comment and consideration.  Unfortunately I'm having a hard time translating your comment/suggestion in to something concrete I can or should change in the above configuration.

Do you have a specific suggestion for a specific component or value I can test?  Something like "instead of connecting pinN to pinY, connect pinZ to pinY and set XYZ value to 1234"