Following error - Rotary Axis

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10 May 2022 11:42 #242480 by Slaybaw
Ah I see, thanks.

Does this warrant any further investigation? Or should I just leave it with the higher STEPGEN_MAXACCEL value of 1500 and move on with life?

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10 May 2022 13:49 - 10 May 2022 13:53 #242490 by PCW
Replied by PCW on topic Following error - Rotary Axis
If the joint and axis MAX_ACCELERATION in the ini file are still 1000
it seem like a trajectory planner bug unless there's something funny about
angular axis I don't understand.

What version of LinuxCNC is this?

If your motors don't stall, you can just increase the stepgen maxaccel value
and move on, but what the actual acceleration bound is remains  a mystery...
Last edit: 10 May 2022 13:53 by PCW.

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10 May 2022 13:56 - 10 May 2022 17:23 #242491 by Slaybaw
Yes the joint and axis accelerations are 1000.

LinuxCNC 2.8.2.
Last edit: 10 May 2022 17:23 by Slaybaw.

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10 May 2022 23:55 #242541 by andypugh

G1 Z9.00 A-360.00 F203.4

I think that the line provoking the error might actually be this one. 

You are moving the Z axis 1mm, from Z10 to Z9 at 203mm/sec. So this program line will execute in 0.0049 seconds. 
At the same time you are asking to move the A axis from -419 to -360, a difference of 59 degrees, in the same 0,0049 seconds. ie an angular feed rate of 11977 deg/sec...

linuxcnc.org/docs/html/gcode/machining-c...r.html#sub:feed-rate

The answer is to use inverse time feed mode. But it's not a very neat answer. 

If you google for "linuxcnc rapid rotary" you should find an input filter that converts G-code to G93 mode for you. 

 

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11 May 2022 00:43 - 11 May 2022 01:17 #242546 by Slaybaw
Take another look at the G-code I pasted: The first line is G93. i.e. all the lines I had posted are in inverse time mode. Final line is G94 switching things back to Unit/Minute mode.

I think it's commanding the axis to go from -419 to -360 in 60/203.4 = .29 seconds...~= 200 deg/sec.

The subsequent line takes it from -360 to A-720 F33.6...or -360 deg in 60/33.6 = 1.785 sec...~=201 deg/sec.

I'm using DeskProto Multi-Axis edition to create the G-code.  It has an inverse time option that I'm utilizing.
Last edit: 11 May 2022 01:17 by Slaybaw.

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11 May 2022 12:07 #242624 by andypugh
Sorry, this is a question I answer almost in auto-pilot.

I will try to remember to try the code out in a simulator and see if the same exceeding-of-limits is seen.

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11 May 2022 16:00 #242653 by Slaybaw
No worries!

Curious to see if you see anything interesting in a simulator. Appreciate your time!

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11 May 2022 18:41 #242661 by andypugh
It can be reproduced in a simulator, I have raised an issue in the tracker.

github.com/LinuxCNC/linuxcnc/issues/1738

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11 May 2022 21:00 #242676 by Slaybaw
Oh cool, I found a bug!

Thanks for confirming, Andy.

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12 May 2022 19:19 #242810 by Todd Zuercher
Quick, step on it, before it scurries away! (sorry couldn't resist.)
The following user(s) said Thank You: tommylight

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