Change of Master Encoder Position Value After Edit and Download on RSLogix 5000

I am using RSLogix 5000 with a Kinetix 6000 servo system and I sometime see the value of the Master Encoder change after a very simple program offline edit and download. (Like changing a NO contact to NC contact)

Hardware
Master encoder - Sick SRM25-7-H10S-GA or SRM50-BC02-M02-S
(HIPERFACE MULTI-TURN ABSOLUTE) Connected in the AUX FEEDBACK connection.

Servo Drive - Kinetic 6000 IAM 2094-BC02-M02 (there are 2-12 servo drive is the systems)

I stop the machine on Master Position 0.000.
I edit the NC contact to NO offline, download and the Master Position sometimes changes to something else.
I made sure that my offline program and online program are the same before the edit. The machine is ESTOPed and does not move between the edit and download.

If I do this 10 times as a test, I see the master position change 2 out of 10 times but not with any consistency.

All motors and the master have been homed properly.
No other issues seem to appear after the edit and download.
I have seen this occur on RSL5000 ver 16, 17, 19 and 20

If you have seen this problem and know how to prevent or fix the problem I would appreciate and assistance you can provide.

As of now I just write down the master position before the edit, edit and download, then I go back and Home the master at the position I wrote down.

Are you uploading the tags and saving the project before you do the offline edits? Any particular reason why you aren't making these changes online?

FluxCap said:

Are you uploading the tags and saving the project before you do the offline edits? Any particular reason why you aren't making these changes online?

Click to expand...

Thanks for the reply.

Yes, I am saving everything from the processor to my laptop and then editing.

I do most of my edits online but some require me to edit offline, like adding new tags. (I know newer versions let me do this.) I do not see this issue if I edit online.

The first time I saw this I had saved the program and tags from the processor, went offline to add a new tag and some very simple logic for the customer's line interface. I downloaded the program and noticed the Master position had changed even though the machine had not moved.

When you do get the occurrences when the encoder values change by how much do they change? Example say your encoder is in units of degrees does it change from a homed position of 0 to say 20 when you go from offline to online after the changes or is it a very small change like from a value of 0 to 0.25,0.69?

What kind of an Encoder is it? I'm assuming its an absolute Encoder each position is unique so it should remember its current position when you go offline and then online or even a power cycle. Now i have seen an issue with other absolute encoders not serving their purpose pretty much acting like an Incremental encoder where it does not remember its last know position and keep it, but this was not an Allen Bradley system, but i highly doubt that's the case because you said it happens roughly twice out of every ten times.

Suggestions (You may have already done this)

1. Make sure you are working with the same project in Online vs Offline

2. Test a power cycle if possible to make sure the encoder is not losing its position value.

3. Double check your Encoder wiring, and make sure they are properly terminated.

4. Maybe its noise that causing the issue, encoder cable maybe close to an high voltage AC source

Hope this helps.

dbh6 said:

When you do get the occurrences when the encoder values change by how much do they change? Example say your encoder is in units of degrees does it change from a homed position of 0 to say 20 when you go from offline to online after the changes or is it a very small change like from a value of 0 to 0.25,0.69?

What kind of an Encoder is it? I'm assuming its an absolute Encoder each position is unique so it should remember its current position when you go offline and then online or even a power cycle. Now i have seen an issue with other absolute encoders not serving their purpose pretty much acting like an Incremental encoder where it does not remember its last know position and keep it, but this was not an Allen Bradley system, but i highly doubt that's the case because you said it happens roughly twice out of every ten times.

Suggestions (You may have already done this)

1. Make sure you are working with the same project in Online vs Offline

2. Test a power cycle if possible to make sure the encoder is not losing its position value.

3. Double check your Encoder wiring, and make sure they are properly terminated.

4. Maybe its noise that causing the issue, encoder cable maybe close to an high voltage AC source

Hope this helps.

Click to expand...

Thanks for your reply. Any ideas are worth evaluating because I have tried everything I can think of to find what causes this and how to solve it.

Scaling is in Inches 0-12 on one machine and Degrees 0-360 on others. This happens on multiple machines done by different engineers. The panels are wired slightly different based on customer required components and methods.

If I stop the machine on zero do the offline edits and download I have seen the master change to a 160.??? degrees, not a minor change but about half a machine cycle. Other time it will be a different number.

It is a multi-turn absolute encoder. I have never seen it have an issues with remembering where it is through power cycles.

No issues with positional information or relationships with slave axes.

When I do the offline edit and downloads the machine is ESTOPPED so no motors running most solenoids off so very little noise generators inside the cabinet.

Hi

Did you try to download with the power off on the drives or did you try to power the drives down after the download and see what they return after you power them back up .
Is this an external encoder and if so want make is it

Donnchadh

It would be a good idea to post the code.

It sounds to me like something is doing an MAH or MRP to the encoder axis position at first pass, although if that were the case, you wouldn't expect the new position values to be random.

Donnchadh said:

Hi

Did you try to download with the power off on the drives or did you try to power the drives down after the download and see what they return after you power them back up .
Is this an external encoder and if so want make is it

Donnchadh

Click to expand...

3-phase power is off of the drives when I download but control power is on. Machine is E-STOPPED, setting on mechanical zero.

External encoder Sick brand, see OP (original post) for part numbers.

bmacattack33 said:

It would be a good idea to post the code.

It sounds to me like something is doing an MAH or MRP to the encoder axis position at first pass, although if that were the case, you wouldn't expect the new position values to be random.

Click to expand...

I have one MAH command for the master encoder. It is only used when a pushbutton is pressed on the HMI. If it were code related I would expect the master position to change every time I downloaded or stopped then started the processor, but it does not. Also, the value for homing the master is always 0.0 so when I do a MAH the master position is set to 0.0.

I have no MRP commands in my program.

Hi

Could you also remove the control power after you have downloaded and let the drive power down, then power it back up again just something I would like you to try.

Donnchadh