Motion Instruction Enable flag stuck on

Has anybody seen anything like this? I was called out to a customer site tonight because their motion axis (Kinetix 6000 with ControlLogix PLC) hit the hard overtravel. They got the axis moved off the overtravel sensor, but when they tried to restart, the servo would not enable. When I came in, I could enable the servo with a motion direct command, but when they would stop and restart, the servo would disable but not re-enable. I added a test bit to manually trigger the MSO instruction in the code, but that didn't work. I finally noticed that the enable bit of the MSO instruction stayed on even when the input conditions were false. So I manually reset the enable bit, and things started working.



Only time I've seen behavior like that before is when the motion instruction tag was used multiple times instead of just once, but that wasn't the case as far as I could tell.

Not in commissioned code.

What version?

Any chance of viewing the Code?

v20.01
Program is protected under a nondisclosure, so I can't share it. Anything particular you would look for?

I had the exact same problem, the MSO would sometimes stay enabled. What I found was that they were using the wrong type of instruction to stop the drive. I don't have access to the program right now, but once I changed the MSO to something else (can't recall) it was much happier:beerchug:

That sounds like the same problem. Too bad you can't remember the instruction used, that would be helpful!

I had a look at the backups, and the actual instructions I had to change was a MDF to MSF. I think it was to do with how it is switched off.
Just see if there is another instruction that could be used to switch off the motion

Maybe,

I checked the program, and only MSF is being used to turn off the axis. I wonder though if it's related to the hard overtravel, since that when it happened? The hard overtravel fault action is Stop Motion. I wonder if that has the same effect as the MDF instruction.

osmanmom - what are you showing us? Is that an example of what to do, or what not to do?

I've seen similar things with various motion instructions. I think if you try to execute an MSO when the drive is in a state that doesn't allow it to turn on, the instruction gets enabled, but can never complete (or get the .DN bit true). I believe it might need to see that .DN bit to release the enable.

I believe the state of the rung only triggers the enable bit, it does not keep it on or turn it off.

I often see code that has logic to unlatch the .EN bit and other motion instruction bits.

the attach what i saw in few programs,

if you refer to manual (MOTION-RM002D-EN-P - September 2014 page 43)

the program use both instructions MSF and MASD ( for shut off/down)

then use MASR and MFAR to clear everything to make/reset MSO back to normal

I saw things like this quite often back in V17......part of the reason I won't use Logix for motion. Yaskawa is much better for motion.

OK, thanks. I'll pass this along to the customer. The machine is two years old, and the first time this has happened. Since they know how to fix it if it occurs, I don't know if they'll want to pay me to make changes, especially since I don't know exactly how to fix it. Resetting the enable bit seems like the most sure-fire way. I've had to do stuff like that before, but usually in third-party add-on instructions.

Thanks!