Linear Quadrature Encoder Calibration Error
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@btmclain we've seen this once before. The cause was identified as high backlash in the drive chain between the motor and the axis. In the version 3.6.0-rc.1+3 binaries at https://www.dropbox.com/scl/fo/geqmn8gbn97n6b587mkbk/AJ2hBIqO-L57_QpR_uqHJ9c?rlkey=fw37wycbp2gil8rvxhe7aopy7&dl=0 I've increased the amount of backlash allowed when using a linear composite encoder, so that version might work for you. To use it you will need to update your whole system to firmware 3.6. If you are running in SBC mode then update to 3.6.0-rc.1 first, then you can install the 3.6.0-rc.1+3 binary on the 1HCL.
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@dc42 Thank you for the reply!
We went through the steps that you recommended and tried the binaries but still are facing the same error. We have noticed that there is a jerk at the beginning of the quadrature calibration that may be causing us to skip steps. We do not see this jerky motion during normal operation or during the magnetic encoder calibration. Do you have any idea of what could be causing this? Our driver configurations are all listed above.
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Have you tried the calibration steps manually?
once you have the magnetic encoder calibrated once you should not have to calibrate it again unless you change the mounting or magnet.
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@ironhydroxide Is there a way to manually perform the calibration for the linear encoder? It is my understanding that we cannot use the system until both encoders have been calibrated. Thank you for the reply!
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@btmclain By "manually" i mean not in a homing macro, but by sending the gcode manually either in the DWC console or connected SBC.
But after rereading your first post, I assume that's what you've done.I think your issue may lie in the initial configuration of the encoder. the C parameter should be the number of cycles from the quadrature encoder per motor revolution.
I don't see anywhere you specify the motion relationship between motor and linear encoder, the linear encoder you specify has a 5um/pulse output, (20um/cycle)
With your C value of 1000 that works out to a movement of 20mm/motor rotation. is that correct?Are you doing a small motor movement in open loop mode before attempting calibrations?
When playing with my setup I was able to somehow get the system to move in closed loop with only a magnetic encoder calibration, then I was able to confirm the linear encoder cycles/rotation value (i had to iterate a few times as the documentation says Pulses per revolution, I believe it should say cycles/revolution instead as that is what I ended up at to get the correct movement) Once I had the C value in the ballpark I was able to get the system to calibrate the Quadrature encoder (M569.6 V1) successfully.
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@btmclain there should not be a jerk at the star of encoder calibration. Please post a video showing exactly what you mean.
If you configure the system to use just the magnetic encoder, does your system behave correctly, and is motion smooth?
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@ironhydroxide Thank you for the reply. Our system is currently setup to do 5mm/rev of travel. Yes, we have been doing some small motor movements before beginning the calibration. We tried your suggestion of implementing cycles/rev instead of counts/rev for the C parameter but unfortunately no luck.
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@dc42 We have recorded a video showing both calibration routines but I am unable to post a link because of my reputation. Do you have another option for getting the video link to you?
The motion is fine and smooth for operation during the magnetic cycle. You can hear a loud jerk at the beginning of the linear encoder calibration cycle, quickly followed by the calibration failing.
Thank you!
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@btmclain said in Linear Quadrature Encoder Calibration Error:
We have recorded a video showing both calibration routines but I am unable to post a link because of my reputation.
I've upvoted a couple of your posts, so you should be able to post it. It's a forum anti spam measure.
Ian
TronXY X5S with Duet 3 MB6HC and Roto toolboard : Cartesian bed-slinger with Duet 3 Mini 5+ WiFi and 1LC : RRP Fisher Delta v1 with Duet 2 Maestro : Polargraph with Duet 2 WiFi
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@droftarts Excellent thank you!
Here is the video. It first runs through the magnetic encoder calibration which sounds smooth. You can hear the jerk at the beginning of the linear encoder calibration.
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@btmclain I see you have standstill current at 0% (M917 X0), have you tried commenting out this line, or increasing the standstill current value?
on my system when I add the M917 X0 I also get this clunk. Removing it and I have no clunk when tuning.
