RMC150 Target not Following Command

[SawmillElectricians]

We are controlling bunks on a Headrig Carriage with and RMC 150 with a Allen Bradley Studio 5000 V36. Problem we are having is very intermittent, sometimes it will not happen for 3-4 days and sometimes it will happen few times a day. What happens is we issue a command for the knees and the target will continue past the command. The knees will follow the target and get beyond its limits. For example the last one we had.
Command 19.4"
Target 4"
Actual 5" (blocking valve comes on)

I am brand new to the RMC so not sure on where to go from here. Hoping I could get some insight

Thanks in advance

[Paul_Huumala]

Hello,

Does this sound like the issue you are seeing?

The Open Loop to Closed Loop Problem

A fairly common support question is “Sometimes when I issue a move command to an axis, it goes the opposite direction first, before heading in the right direction. What is happening with my axis?” This is a symptom of sending a closed loop command to an axis that is currently in open loop. Why does this happen? The answer is noisy feedback. The conditions where this problem usually occur are: the axis is stopped, the feedback signal is noisy, and the Actual Acceleration value is low. When a …

If you axis is in open-loop before you issue the command, I expect this is the problem you are seeing.

[SawmillElectricians]

Thanks for the quick response! I don’t think this is the problem because it is always in closed loop. I will add velocity to my trend though. I have attached a trend from Studio 5000 to maybe give a better visual of the problem.
Blue is Command
Red is Target
Green is Actual
They are all at 24" and then we get command to move to 19.4". The target continues to decrease and the actual follows. The Voltage out from the RMC is white and it is sending approx -5V.
I

[Paul_Huumala]

Would it be possible for you to capture an RMCTools trend of this issue?

[SawmillElectricians]

We have a trend running and are hoping to and as soon as we get one I will post it! The problem is how intermittent it is. We are in a sawmill running two shifts and although our guys are very familiar with Rockwell Software we do not have any knowledge with the RMC (learning slowly). So hopefully we get one while I am here.

I just can not wrap my head around why the target does not follow the command. What I know is that it is an absolute move and we are in closed loop. When it does occur it’s when the operator jogs the knees forward and releases the push button. The command stays where it is but the target continues to 0 and the knee follows it.

Thanks!

[SawmillElectricians]

We had it happen! I will be sending the Trend and the Event log to the support email shortly

[ndzied1]

@SawmillElectricians

Command 19.4"
Target 4"
Actual 5" (blocking valve comes on)

In your first post you mention that the blocking valve comes on.

• Is something else commanding the blocking valve closed?
• Is the wiring to the blocking valve vibrating loose sometimes?
• Or is the axis faulting out on a saturation fault and that is why the blocking valve is closing?

[SawmillElectricians]

The problem has been solved! Problem was caused by the Acceleration and Deceleration being too low in the Move Absolute command.
Thanks to Jacob and Paul for the help!