Following error - Rotary Axis

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07 May 2022 21:39 - 07 May 2022 21:40 #242268 by Slaybaw
I'm getting a following error on Joint 4 (A Axis) when running the following section of gcode on my fixed gantry machine + rotary axis.

I've read through myriad of threads and I can't figure out how to fix it!  Any help would be greatly appreciated.

INI and HAL files attached.

Gcode:
I get a following error on the line that starts with G1 A-720.
G93
G1 A0.00 F21.8
G1 Z13.37 A-29.65 F345.1
G1 Z12.50 A-70.17 F234.8
G1 Z11.00 A0.00 F135.6
G1 A-360.00 F26.4
G1 Z10.43 A-393.88 F384.3
G1 Z10.00 A-419.54 F472.0
G1 Z9.00 A-360.00 F203.4
G1 A-720.00 F33.6
G0 Z29.04
G94
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Last edit: 07 May 2022 21:40 by Slaybaw.

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08 May 2022 01:47 #242284 by Slaybaw
Few more details that may be important - this is a machine with open loop steppers...from other threads I've read...2 things cause following error message:

1) Stepgen velocity and stepgen accel not having enough "headroom" over the axis valuse
2) The base thread rate not actually being able to make all the requested pulses.

But I think I'm good on this front? My Base_Thread = 50000ns, which should allow for 10000 steps/sec....well above what my ini files specify.

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08 May 2022 14:28 #242303 by PCW
Replied by PCW on topic Following error - Rotary Axis
You should not have a base thread at all with a Mesa configuration...

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08 May 2022 18:49 - 08 May 2022 19:44 #242316 by Slaybaw
Right - yep, agree. After doing some pretty good searching over the last couple days, I found that BASE_PERIOD does nothing on Mesa configs. If you look at the HAL config, nothing is tied to the base thread anyway, so I don't think it had any effect.

Anyway, I remove the BASE_PERIOD from the .ini today, and tried again, and I still get a following error on Joint 4 at the same place in the G-code file.

Anything else I can try and scope to try and figure this out?  Do my FERROR and MIN_FERROR values look good in the .ini?  I can't even figure out where those values play in as I can't find those params referenced in the HAL file.

Updated INI and HAL files attached.

This is what halscope shows right when the following error occurs:
 
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Last edit: 08 May 2022 19:44 by Slaybaw. Reason: Add'l clarity added.

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09 May 2022 19:07 #242403 by Slaybaw
Updating here for posterity...I guess it really was as simple as an update to the STEPGEN_MAXVEL and STEPGEN_MAXACCEL values.

This fixed the issue immediately.

Before:
STEPGEN_MAXVEL = 450
STEPGEN_MAXACCEL = 1250

After:
STEPGEN_MAXVEL = 600
STEPGEN_MAXACCEL = 1500

 
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09 May 2022 19:22 - 09 May 2022 19:23 #242405 by PCW
Replied by PCW on topic Following error - Rotary Axis
The original values in the ini file should be OK
(stepgen velocity and accel values are 25% > than
the joint/axis limits)

Can you plot the joint velocity along with the following
error (with the original ini file values) to see
what's gone wrong?
Last edit: 09 May 2022 19:23 by PCW.

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09 May 2022 19:39 #242406 by Slaybaw
Thanks for the note - I am interested in troubleshooting more just to learn more...

I'll do some more testing this evening and report back.

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10 May 2022 01:04 #242446 by Slaybaw
Here's a plot with joint.4.vel-cmd as well...that was the only signal I could find that was joint velocity.

 
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10 May 2022 01:12 - 10 May 2022 01:12 #242447 by Slaybaw
Same plot, but with:
STEPGEN_MAXVEL = 600
STEPGEN_MAXACCEL = 1500

 
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Last edit: 10 May 2022 01:12 by Slaybaw.

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10 May 2022 01:56 - 10 May 2022 02:00 #242453 by PCW
Replied by PCW on topic Following error - Rotary Axis
If you look at the slope of the velocity,
the acceleration on the fast velocity downslope
exceeds 1500 deg/s^2, causing the increasing
following error because the stepgen is not allowed
to accelerate beyond 1500 deg/s^2.

So this seems like a trajectory planner or ini setup issue.
Last edit: 10 May 2022 02:00 by PCW.
The following user(s) said Thank You: Slaybaw

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