how to synchronize two servomotors

Jasper 3 wrote: when I run my motors in openloop modus than it works great. But than I have no possibility to synchronize my servomotors.

I don't think that is the case at all. Many people are using open loop stepper motors on gantry systems. Even though your motors are servos, in position mode they should work identically.

If the motors are fighting each other then it sounds like some sort of homing/squaring problem.

If the drives are running in position mode, Then they WILL have internal loops that must also be tuned before you can do anything with tuning them in Linuxcnc. Was that done?
Usually that has to be done using the drive manufacturer's own drive configuration software. (Often using a Windows PC.) Doing that could be a complicated trick on a duel motor gantry.

hey,
thanks that makes sense. I know they have an internal loop, otherwise they wouldn't work in openloop mode. On my X and Z axis erverything works well. (There the internal loop is ok - i think) And I can run my servomotors in a closed loop in Linux. Tuning the X and Z axis was no problem.

So now I tried to run my Y-Axis with one motor connected via timingbelt to both ballscrews. In closed loop it doesn't work (always oscillates and tuning was not really possible) But in openloop it works great and it's not possible that the motor turns off. It get's a bit warm because one motor alone is a bit weak for that load.

When I have both motors on the Y-Axis with no timingbelt:
My Y-axis runs in Openloop modus for about 2 minuts well. Than one servo turns off.

If the motors are fighting each other then it sounds like some sort of homing/squaring problem.

mh makes sense but there is nothing to hear. Maybe they aren't working against each other. It could be possible that only one motor is truly working and the other one just runs behind the Motor.

When I close the Loop in Linux nothing works maybe because the internal loop isn't tuned well enough.

I'm sure I have to tune they driver with the Leadshine software.

so you suggest tuning the Y-Axis drivers via leadshinesoftware and then try again with linux?

Jasper 3 wrote: Maybe they aren't working against each other. It could be possible that only one motor is truly working and the other one just runs behind the Motor.

I think you need to be sure about this. Can you measure the motor currents (if they are equal and opposite then they are probably fighting each other).
If there is a belt reduction, can you feel the belt tension?

Are you 100% sure all of your motor and drive connections are correct? Nothing is crossed, So that Linuxcnc Y1 command signals and encoder feed back are connected to the drive for Y1 and that is connected to the motor power and encoders for the Y1 motor. And the same for Y2, If any of those things are confused between Y1 and Y2, wildly disastrous things could happen, and tuning would be impossible. (This really does kind of sound to me like one of the command signals or encoder feedback signals might be crossed between Y1 and Y2.)

You should be able to run the Y1 and Y2 open loop, using the PID. You simply don't connect the encoder feedbacks to the PID loop feedbacks. Instead connect the PID feedbacks to the sudo feedbacks from the hardware stepgenerators. (using P=1000 and FF1=1 (all other PID settings set to 0). If you can get that to work. Then you could try reconnecting only one of the encoder feedbacks and tuining only that one side. If you can get that to work acceptibly, then you could try adding the feedback from the 2nd motor.

hey,
when the motors are both connectet without timingbelt they defenetly work against each other.
only in openloop when they are connectet via belt it could be possible. I will test it tomorrow.
Do you mean there is a possibility to get it working?

hey
today I tried a lot but unfortunally nothing worked. Before I can try your suggestion Todd I have to tune my Driver with the leadshine software.
After I run Linuxcnc a while I get this message. Than I restart linuxcnc and everything is great again. Any suggestions what I can do?

Look like you have lost communication with the 7I76 card

The combination of joint following errors and sserial errors suggests there may
be a problem with 7I76s 5V since that affects step/dir outputs and sserial communications

Which version of LinuxCNC?

Does dmesg give you a Smart Serial version number?

I power the 7i76 via FPGA card. so you suggest to connect an external voltage?

I run the 2.8 prerealese but also had this problem under version 2.7.8
I'm not sure what you mean "Does dmesg give you a Smart Serial version number?" can you tell me where I have to look at?