Kinetix 7000 Is Running Without Drive Enable

mjp123gp

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Mar 2012
Location
Savannah, GA
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We have a Kinteix 7000 that is used in a winding application. About a month ago we started having issues where the drive will get a stop command and will come to a complete stop, then it will slowly start ramping back up and running at a slow speed. It doesn't do this everytime. It has only happened maybe 10 times in the past few weeks. We have been running trends trying to capture some data when this events happen and what we are seeing is the logic is giving the stop command, the command velocity goes to zero along with the actual velocity. The DriveEnableStatus bit along with the ServoActionStatus bit both go low but the actual velocity will still creep back up. If I understand this correctly, the MSF command should be what would normaly cause the DriveEnableStatus bit to go low. I have also heard that a drive fault will also cause this to go low but unfortunately I wasn't trending any fault statuses at the time it last happened. It has since been added and we're waiting on the next event.

Just a little more info about when this issue started that may or may not be related- We had the vendor that designed the machine in here doing some programming around the same time this started happening so the first thought was that it was something they did that caused the issue but now, seeing it run after losing the DriveEnableStatus, i'm not so sure. The initial problem we had with this axis was instability of this motor with a lot of vibration. They were not able to tune it out so the motor and drive were both replaced. After replacing both, we still had the same problem. Their fix was to use SSV commands to change the drive gains depending on the speed it was running. From looking at the logic, I don't see where this would cause the issue but i'm not exactly sure what all is affected behind the scenes when doing these SSV's.

Any ideas on what might cause this or suggestions on other data point I should trend to help capture more important data?

Thanks in advance.

EDIT: Just wanted to add a little more info. This drive is controlled over SERCOS. It does not use hardwire enable. Since the last trend capture I have also added a new trend to watch torque feedback, Sercos ring faults, axis faults, and drive faults. I can try to upload the trend log file when I get back to the office in the morning. Not sure what the file size limit is here but I think the files is around 3-4mb.
 
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What's the command velocity doing when it creeps back up? Are you running position loop, velocity loop or torque loop? What's the structure of your MAS instruction? Is it stop ALL or some specific motion? Is the axis involved in a MAG (Gearing) with another axis?

Next time it happens can you be online, and go into the motion direct commands and issue a MAS ALL and see if it stops. Sounds to me like you could have a compound move axis going on. Maybe a MAJ with a MAM, and the MAS is only being applied to the MAM, such that the MAJ is still active. Or an MAG is still active.
 
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What's the command velocity doing when it creeps back up? Are you running position loop, velocity loop or torque loop? What's the structure of your MAS instruction? Is it stop ALL or some specific motion? Is the axis involved in a MAG (Gearing) with another axis?

Next time it happens can you be online, and go into the motion direct commands and issue a MAS ALL and see if it stops. Sounds to me like you could have a compound move axis going on. Maybe a MAJ with a MAM, and the MAS is only being applied to the MAM, such that the MAJ is still active. Or an MAG is still active.

We didn't have command velocity on the last trends we were running when this happened. It has since been added. That axis is running in velocity loop and is using a MAG to gear to a master virtual axis. The axis we are having issues with does not have a MAS instruction tied to it, it follows the master then is issued a MSF when the axes should be disabled. The strange thing is that the axis that has the problem is geared to the master along with several other axes that are not moving. There are also a few axes that are geared to the axis with the problem and they are not moving. I plan on spending some time with it Monday and hopefully I can get some more data. The problem is so intermittent that it's hard to catch. As soon as we plan to sit with it for a while, the problem goes away. We do have a dedicated PC setup to run continuous trends now so hopefully we can get more data next time. Do you have any suggested data points that would be useful to monitor in the trends? Right now we have the following:
MotionStatus
CommandVelocity
ActualVelocity
TorqueFeedback
MSO Command
MSF Command
DriveEnableStatus
Machine Run command
Machine Stop Command
DriveStatus
 
Check your MAG instruction for the misbehaving axis....Is the Master Reference set to "Command" or "Actual"? I always use Command as I don't want my slave axis to move unless I'm telling the Master to move. Depending on your application and how well your master is tuned in its position loop would dictate whether you could use "Command" if you are using "Actual".

But, since your Axis movement is dependent upon the Master, I would be also trending the Master command position, actual position, command velocity and actual velocity. And I don't see you trending commanded and actual position on the slave axis either...that might be helpful.
 
Check your MAG instruction for the misbehaving axis....Is the Master Reference set to "Command" or "Actual"? I always use Command as I don't want my slave axis to move unless I'm telling the Master to move. Depending on your application and how well your master is tuned in its position loop would dictate whether you could use "Command" if you are using "Actual".

But, since your Axis movement is dependent upon the Master, I would be also trending the Master command position, actual position, command velocity and actual velocity. And I don't see you trending commanded and actual position on the slave axis either...that might be helpful.

It is geared to the Command of the master. I just looked back at the trend log and the troubled axis doesn't appear to getting the MSF command. However the DriveEnableStatus bit is going low and staying low. What else would cause the enable bit to go low? Is there any condition that would let the drive continue to follow a reference after the enable bit was low. Isn't this bit feedback from the drive saying its not enabled?
 
Does the motor have a brake? Could it be being pulled by external forces? Could the brake be too weak for the external forces?

It does not have a brake. That was one of the initial thoughts is that that another axis could be pulling it. However we are winding very thin paper that would most likely have a web break before moving another axis. And since the initial problem started they have seen it run with no product at all in the machine so we are positive that isn't the case now.
 
Not sure of that status bit....I've done hundreds of kinetix axes and never used it. I also don't use MSF to turn off an axis...if you do that it's free wheeling and no longer holding position. Usually after an MSO I'm only using MAS to stop an axis but leave it enabled to hold position. In most of my applications only a safe stop releases a drive...never an MSF.
 
Thanks for the help. I will get more data when I get back onsite Monday. A screen shot of the last trend we have is attached. It does have the master axis velocity on it but I think we need to trend the command instead of the actual since this is a virtual axis.

UWR Trend.jpg
 

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