Encoder Indexing

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26 Mar 2021 01:00 #203659 by Hamel2020
Encoder Indexing was created by Hamel2020
1. PID was done to ensure smooth start/stop values as per the attachment
2. The servo mode was Torque mode.
3. I think I have indexing and FERROR problems, because :
When I restart the servo drive I have two possibilities:
- Either the encoder read zero of less than 1mm and then start changing the output until reach the zero .
- OR start with a different output far away from Zero , in that case the servo motor lose the location completely and never move correctly , and in that case I have to restart the driver ( may be 2-4) times until I get the encoder within a range less than 1mm , then I being able to move it .
Question [01] : Isn’t indexing problem ? if yes how can solve it ?
4. As per the attached images, when I use CMD say[G0 X500] the motor rotate until reach 498(or near) then stop rotation while the encoder continue increase the output unit reach 499.998 then stop I used FERROR : 20 Min_FERROR 10 which is too much but once I reduce is I got joint following error
Question [02] : Isn’t FEEROR problem ? if yes how can solve it ?

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26 Mar 2021 02:56 #203664 by PCW
Replied by PCW on topic Encoder Indexing
Is the encoder signal coming from the drive or from an actual encoder on the motor?

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26 Mar 2021 03:50 #203667 by Hamel2020
Replied by Hamel2020 on topic Encoder Indexing
Encoder feedback --> to drive --> to 7i77 Mesa

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26 Mar 2021 14:50 #203721 by PCW
Replied by PCW on topic Encoder Indexing
Hmm sounds like the drive is outputting many counts at startup

Does the drive have absolute encoders?

Maybe there is an option to disable this behavior

Normally LinuxCNC will clear the encoder counters at start-up
so the encoder position will start at 0

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26 Mar 2021 19:08 #203740 by Hamel2020
Replied by Hamel2020 on topic Encoder Indexing
the servo motor motor has incremental encoder .
there is an option to reset the fault ...as the attached sheet ... and the driver has P2 cable connection to mesa card , and P4 which is the feedback from servo motor .
attached P2 & P1 pinout .
Attachments:

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26 Mar 2021 19:42 #203743 by PCW
Replied by PCW on topic Encoder Indexing
You might try plotting the encoder position with halscope from
when LinuxCNC starts to when the drives are enabled to try and track
down what is happening

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27 Mar 2021 19:17 #203822 by Hamel2020
Replied by Hamel2020 on topic Encoder Indexing
Here is the HALSCOPE
Attachments:

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27 Mar 2021 22:01 - 27 Mar 2021 22:05 #203844 by PCW
Replied by PCW on topic Encoder Indexing
That does no show any startup errors but does show you have
too much FF1. You need to tune FF1 or calculate it if you know
the full joint speed at 10V

Notice the error pedestal? that will be negative with too much FF1
and positive with too little (with a positive velocity = increasing position
as you show in your plot)
Last edit: 27 Mar 2021 22:05 by PCW.

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