Ethercat random jitter fix

Interesting.
My computer is an ancient IPC from 2006. Except for the SSD, everything is original hardware.
The network card, however, has an Intel chip and is Beckhoff certified.

infosys.beckhoff.com/index.php?content=..../9309844363.html&id=

Perhaps that's a clue.

What are the clues supposed to point us to?
I have igc i210 advertised as supported by igh and Beckhoff.
There maybe a lot of reasons why your setup works for you, but there is only one cause for the jitter noise I was experiencing, there maybe other unrelated noises on other hardware, but the one I identified is fixed in my fork of the code.
What will figuring out why you don't have the issue get us? Did you run extensive testing with restarts looking at the halscope to prove you don't have the issue?

Sorry,

It was just a thought. And no, I haven't had any jitter problems so far, despite endless restarts. I've often even had to restart the servos mid-operation (homing failure).
I'm absolutely certain that your driver is working and resolving the jitter issues.
But what if the hardware isn't compatible or is causing problems...?
I just wanted to throw that out there.

Sorry.

grandixximo wrote:

The linuxcnc-ethercat current release does not respect the ethercat standard, it has time phasing issues, this is demonstrably true.
Anyone lucky enough to not experience any issue has:

Not used pos-cmd mode.

 

what do you think with not to use pos cmd mode ? do you have an unreliable experiences with them?

@andrax
No need to apologize, just trying to understand where you were going with it.
With my fork I don't have any jitter noise when things are set as they should. Finding the issue was no easy feat, before looking at linuxcnc ethercat, hardware wise I tested with  different servos, different CPUs, different network chips, software wise, different ethercat versions, different kernels, different linuxcnc versions. Ruled out basically everything else, I knew it had to be linuxcnc-ethercat, and after putting in the time to find the issue, I am sure I found it, while before it was random, I can now reproduce it at will, and I can turn off the jitter at will, I can place the phasing in and out of the jitter with the sync0shift setting, this is correct and expected within the ethercat standard, even twincat has a default Sync0shift of 30% cycle time, and you should expect issue somewhere between 0 and 30% what issues will depend on hardware, but the standard does not want your Sync0shift in that range for a good reason, and the hardware is not supposed to work properly when you don't follow the standard, and the original code was NOT following the standard, maybe accidentally on some hardware it was ok, even a broken clock is right twice per day...

@Endian
I only use pos-cmd mode, i think velocity and torque mode can get better performance, give you more control, but require more tweaking, and I think (but not sure) any slight issue like the jitter of this topic might be absorbed by a finely tuned PID for the job.
While pos-cmd rely on PID of the servo, it's normally a general one, which will work for most applications, in my case it's very strict and quick, that's why the motor vibrates, it's trying to respect position very strictly, which usually is a good thing...
 

If there are still users with the jitter noise, and they are using my fork, please increase your Sync0shift, check your latency, try with both synctorefclock true and false, post halscope readings of the various relevant pins, and your XML ini and hal files.
Whatever is left must be software of hardware tuning issues, there maybe some network chips or some CPUs with very bad latency, that my phasing can't fix, I know it works well on my hardware, but it needs to be seen if I need to create some more Hal pins or not, some hard code values which could help with tuning the phasing process, some users might want to tune these, but I'm not sure it's worth it, if your latency is decent, the current hard coded values will work well.