Powerflex 527 motor overshoot.

[PiperJohn]

Yes sir.
Although It'd be more fun if i didn't have other head scratchers to contend with.

There are two stations doing exact same thing, Drive A220 and A225. A 225 has more overshooting but both problematic.

Alarm gives generic message saying Mechanical anomaly or overheat. No faults on the Drive itself. Alarm (113) is coming from S01200 tag A225_Errore (bool) which is in S10211 MOV_Guide(A225_moveguide............,A225_Errore,.........) Where is that coming from?

To confuse matters, There's also a tag A225_Error (not Errore)

I have swapped A220,A225 drives and overshoot problems did not follow Drive.

IP for A225 is 192.168.1.36
Mechanically it's been completely looked over by myself and Machine guys.

Thanks for digging into the mystery with me.

 

[kalabdel]

Yes sir.
Although It'd be more fun if i didn't have other head scratchers to contend with.

There are two stations doing exact same thing, Drive A220 and A225. A 225 has more overshooting but both problematic.

Alarm gives generic message saying Mechanical anomaly or overheat. No faults on the Drive itself. Alarm (113) is coming from S01200 tag A225_Errore (bool) which is in S10211 MOV_Guide(A225_moveguide............,A225_Errore,.........) Where is that coming from?

To confuse matters, There's also a tag A225_Error (not Errore)

I have swapped A220,A225 drives and overshoot problems did not follow Drive.

IP for A225 is 192.168.1.36
Mechanically it's been completely looked over by myself and Machine guys.

Thanks for digging into the mystery with me.

Based on my litre understanding of AB motion control, the drives are configured as morion group axes and whatever error you are getting are read from the drive. The drive gets a target destination, I think on mm and does it's own positioning and generates error if stops outside of the considered limits. So the questions is, of it is getting the same target and works properly what happens that it drifts off or suddenly goes too far. Very important to determine if it drifts a little by little or all of a sudden. Drifting to means indicates cumulative calculation error. Sudden change is a difficult one.
The steps I would take is to first determine if the target is manipulated on code before being sent to the drive and of it happens everyove or only once, when it entered in HMI, and them saved and reused. Then I would look for and encoder value adjustments in any of the code.

 

[Keystone]

I had a similar incident lately, had a cart moving on a rail using a motion axis card and drive. The cart started to be off location by about 1/2", I asked if there were mechanical issues since NOTHING changed electrically. It had been working for 8yrs this way. All of a sudden it was not positioning it correctly. I was assured the break is holding good and not moving it was "going to the wrong place".
We looking into the motion code and found the PLC programmer did somethings that are highly unrecommended. After changed some of the motion code to make it better it still had problems but they were a little better.
After some more head banging I ask the mechanic to take off the break to make sure it was not hanging or binding. It was not the break - the gearbox developed a LOT of backlash and the cart could drift the 1/2" on the backlash (there is a slight grade on the rail).
Too many times we have tried fixing mechanical problems with electrical solution (jury rigging), or we keep fighting "electrical" issue that are actually mechanical because we did not look close enough at the moving parts.
Even if it is not the "best" system but has been running for "years" take some extra time and check for slop, backlash in the system.
It seems ALL problems are electrical until proven other wise. (even if you see a broken shaft laying in the machine).

 

[kalabdel]

See page 237 (Why Does My Axis Overshoot Its Target Speed?) in this manual.


And page 106 in this manual :
Risk of Velocity and/or End Position Overshoot
If you change move parameters dynamically by any method, that is by changing move dynamics [Motion Change Dynamics
(MCD)] instruction or by starting a new instruction before the last one has completed, be aware of the risk of velocity and/or
end position overshoot.

 

[PiperJohn]

Yes, I get that I need to be very careful about messing with motion dynamics. I know little on the subject, but enough to be dangerous.

I may slow it down a little as it's rather a fast stroke.

It doesn't drift that I can see. It always seems to hold it's position.
As I said, it seems to be getting worse which leads me believe Keystone is absolutely right in that its mechanical in nature. Program was not changed and ran problem free for a long time.
I've been dragged down the "It's electrical" rabbit hole more than I'd like to admit.

Yes, error bit (A225_Errore bool) likely is coming from the Drive, but I'd expect a gsv from the module.
It's all IP communication to the drive other than the home switch.
If the Drive is faulting why isn't the fault set in the drive?

I had also swapped gearboxes and encoders. No changes. Same overshoot.

I think i need to convince the mechanics to take another closer look at it.

Thanks

 

[kalabdel]

Yes, I get that I need to be very careful about messing with motion dynamics. I know little on the subject, but enough to be dangerous.

I may slow it down a little as it's rather a fast stroke.

It doesn't drift that I can see. It always seems to hold it's position.
As I said, it seems to be getting worse which leads me believe Keystone is absolutely right in that its mechanical in nature. Program was not changed and ran problem free for a long time.
I've been dragged down the "It's electrical" rabbit hole more than I'd like to admit.

Yes, error bit (A225_Errore bool) likely is coming from the Drive, but I'd expect a gsv from the module.
It's all IP communication to the drive other than the home switch.
If the Drive is faulting why isn't the fault set in the drive?

I had also swapped gearboxes and encoders. No changes. Same overshoot.

I think i need to convince the mechanics to take another closer look at it.

Thanks

A couple of nuances that are important to understand, drive position error is likely to "not* generate a fault in the drive, that is something the program would track, and it does to a small degree but it lacks detail. So as far as I know the drive will not fault on this error.
The link about dynamics is specific to instruction calls, that is, motion instructions are asynchronous and need to finish before being called again. One instruction is to go to target A and before it gets there you send another instruction to target B, that is what they referred to. Calls to those type of instructions need to be tied to one or more of their status bits.



Their manuals are quite good and I quite enjoyed browsing a few of them. The drives and motion control are also quite impressive. Have a look and see if they lead you closer.

 

[PiperJohn]

Thanks Kal,
I'm looking forward to reading that manual when I can carve out some free time.
Yes, I know there wasn't active faults on the Drive but what about in its fault history?

This cutter cycles at beginning of the cycle, after a few seconds it returns. No fancy commands just adv and ret posions. So probably not a case where code is trying to recall motion out of order, right? Then again I have seen logic do strange things although usually after someone changed the program. I hope I can get some more understanding from that link.

Thank you for letting me ramble and ask dumb questions because it's part of my learning process.

Tomorrow I'm going in guns blazing and getting the repair guys take a serious look at it.

Regards
John

 

[kalabdel]

drive position error is likely to "not* generate a fault in the drive, ......... So as far as I know the drive will not fault on this error.

That is incorrect. Faults, including positioning faults, will be stored and in the drive and can be reviewed.



See this manual, page 73 and 75.


And this manual pages 123-128 for troubleshooting faults conditions.


Attached are pages of both manuals.



Please be sure to let us know when you eventually solve it, be it mechanical or otherwise. It

 

[PiperJohn]

I see in the manual where it says faults are stored in the Fault Log.

I don't see how to access this Log on a Powerflex527?

Update; Our mechanics tightened a belt tensioner pully and it's been running fault free for about 4 hours.

Fingers crossed.

 

[PiperJohn]

Looking good!
Day 2 and still No drive faults.

I appreciate everyone's help.