Gmoccapy SCARA EtherCAT drive - joint error

Hello,
I am not sure my topic is in correct category, please move to correct one if it is not.
My testing system is:
- Debian bookworm, kernel 6.1.0-22-rt-amd64
- LinuxCNC: 2.9.2; EtherCAT:  Igh EtherCAT 1.6.0
I test SCARA in step:
- Using sim.gmoccapy.non-trival-kinematics.scara to record position X,Y,Z in 2 positions.
  In simulation, it runs well.
- Create macro position_1 and position_2
- Apply same to real system: it has error of joint as attach photos.
Can you explain why and how to avoid this issue ?.
Thank you.

Have you tried substantially increasing the FERROR and MIN_FERROR values in your ini file?
Since you are using an EtherCAT drive the following error should be handled in the drive already.

Hello Aciera,

Before your advice, I did not have FERROR & MIN_FERROR.
After I added both of above setting, the issue still happens.
I tried (FERROR; MIN_FERROR) options: (1;0.1) ; (0.1; 0.01) ; (0.01; 0.001)

Yes, I think EtherCAT drives handle joint error, but it makes motor shocking so strong & stop suddenly without finishing targeted  position.

I attach my INI file for your reference.
 

 

After I added both of above setting, the issue still happens.

FERROR and MIN_FERROR entries need to be in the [JOINT_n] section not in the [AXIS_l] section:
linuxcnc.org/docs/html/config/ini-config.html

I tried (FERROR; MIN_FERROR) options: (1;0.1) ; (0.1; 0.01) ; (0.01; 0.001)

I would suggest something like (100,100). I presume you are running your drives in position mode and the loop is closed in the drive, if so LinuxCNC really has no part in monitoring following errors at all and setting the values very high will effectively eliminate following error checking in LinuxCNC.

Yes, I think EtherCAT drives handle joint error, but it makes motor shocking so strong & stop suddenly without finishing targeted  position. 

If you get drive faults because of following error then you likely need to lower acceleration/velocity values. Also note that if your SCARA pose is close to a singular point  the kinematic model will likely fail and cause large or even infinite angular velocities which will then cause the drives to fault.

When I have this problem with the Mesa card, I increase these parameters:
STEPGEN_MAXVEL
STEPGEN_MAXACCEL
I have no experience with Ethercat, so I don't know if this information will help you.

What is your max servo driver acceleration?
What is your max servo driver velocity?

What is your max acceleration joint in INI file?
What is your max velocity joint in INI file speed?

The maximum acceleration and maximum speed of the physical hardware should be greater than the maximum acceleration and maximum speed of the LCNC.

Do you have yerk set in the servo drivers? 3rd derivation of position. LCNC can't do this, so that could also be a source of problems.

Do you use velocity control or position control?

Hi Aciera,
I tried (FERROR; MIN_FERROR) = (10;1) first, it runs well. I will try 1-2 days more.
After that I will test your advice of high value (100, 100). Just want to test all scenario for understanding.

Hi zz912,
I have not revised STEPGEN_MAXVEL/MAXACCEL, and not check info of drivers, just let it as default.
I will do it in next step

Thanks all of you a lot.

Hi,

I'm trying to get my Scara to work with Ethercat too. However, so far in 3 months the only progress has been in finding the slave on the Raspberry Pi4 terminal.

How do I configure the LinuxCNC software from scratch so that the Scara robot can run with Ethercat? Could you give me some guidance?

Hello bertoldo,
I have no experience with Raspberry Pi. I do with Laptop + Debian 12 RT kernel + LinuxCNC
Here is my files for SCARA with Gmoccapy demo.
You just need to revise EtherCAT "xml" file to meet your real motor servo controller.
Hope you find it helpful.
Tks.
 
 
 

So, I still haven't been able to move forward.
I haven't been able to properly understand how Linux CNC works... so I'm following the tutorials here but without a knowledge base, that's what's holding me back now.
Would you be interested in doing some consulting to help me? Because I have to hand it in at college and I can't do it.

I can move the servo motors manually and see their position. However, I don't want to have to go to home because the encoders are absolute. The image of the side screen doesn't appear on mine either... I don't know where I can adjust the ratio because I have a reducer. I also couldn't move it automatically once.