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Position lost with CanOpen controlling Schneider drive

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We're controlling four LXM28AU07M3X (Lexium 28) Schneider drive at the same time.  For years, with only one drive, we got no problem. But now, when "Switching On" the drive, we sometimes loose the current position. We end up with a small negative value (we think it's the portion of a motor turn the encoder reads).

We tried with Schneider, with no success.

Anyone here can send us an example of code to start the drive, trough CanOpen?

Anyone had similar issues?

We wonder if a filter on the power lines will fix it. We'll try it next week.

Here is our code, if anyone wonder.

Thank you all

scie automatique 328.vlp

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  • MVP 2023

Clarifying.....you previously had only one drive and this all worked without an issue.  Now you have 4 and you have this problem on switching on any of the four?  OR......

One drive only out of 4 that have always been working together is affected, and this problem has recently appeared?

cheers, Aus

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uhThanx for your reply, Aus :)

on other projects, we were working with only one drive. 

For the current project, we have 4 drives. We use the same code (with different bits et node numbers for each drive, obvioulsy) and 2 drives loose their position 40% of the times when we switch them on. So, it aint all the time, it's intermittent. We haven't been able to see a pattern (like tring to switch them on while they're moving). 

Theese drive never worked well together. But on previous projects, we were using the same bloc of code, the same hardware (but only one drive) 

Thanx for thinking about it! 

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One of the reasons why your CANopen  network can't starts your drivers is the inability to simultaneously transfer data to drivers during drivers startup,
because drivers startup duration can not be accurately determined.
I do not know how the settings are made in the driver, but you definitely need to make changes to the 7-01 parameter.
It is also possible to change the startup option of the zero point search at the time of activation of 6-01 and to set the correct way to find the zero point.

Please see ch. Homing data set for absolute movements in driver user manual.


I create a sequential data transfer queue in CANopen  network, which ensures guaranteed delivery of data to the driver.

This is especially important for the transfer SDO that you used in homing process.

This is because the driver handles the SDO command much slower than the PDO command.

Consequently,  your driver does not have time to get the correct data about the zero position at first turn on,

or in the process of command transfer the driver loses part of the commands due to their too fast transmission SDO from the PLC.

The solution to the problem - program the transmission in such a way that the next SDO instruction is transmitted when the previous transmission is guaranteed.


Please note SDO in progress bit must be used for switch SDO queue.
You use this bit in program net but no queue is present for sdo transmision.



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About the home reset, this button is simply a patch for this problem, so when the position was lost, and the drive still saying the home was good, se coule manually reset every home with this button. 

Node 12 isnt there because it wasnt convinient for our specific project. 

Overall, we rarely user this button. 

Thank you kratmel for your input :) 

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Maybe you need to switch off automatic homing in drive and perform homing by software step by step for each drive

like in CNC machine where next axis is homed when previos is in home position.

In this case you guarantee that system is know zero positions and you can test it in automatic mode.

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