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Old May 15th, 2019, 03:11 PM   #1
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Troubleshooting Excessive Velocity Error/PhysicalAxisFault

Hi All,
I have a 2097-V31PR0-LM Kinetix 350 and a TLY-A110T-Hxx2 servo. It is a new setup and I've commissioned the drive: Scaling, hookup tests, polarity, Autotune, which all worked fine. The hookup tests I did were "Motor and Feedback", "Motor Feedback" and "Marker".

The only logic in the PLC are 2 residual MSG instructions which I used to Disable the EnableInputChecking and the OvertravelChecking.

As soon as I give an MSO from the motion direct commands, the servo starts spinning and after about a second the drive faults and gives F55, Physical Axis Fault, Excessive Velocity Error. Where is the command coming from, telling it to spin as soon as the MSO is given?

This may be unrelated, but when I was first setting up the drive I was able to give an MSO without the servo running away or the drive faulting. Then, I changed the application type from Basic to Point-to-Point, and the Load ratio from 0 to 1, did another autotune and then opened the manual tune window. From that point on, even though I've changed the settings back to what they originally were, an MSO command has always caused the same fault.

Any ideas?
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Old May 15th, 2019, 03:34 PM   #2
James Mcquade
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Just a guess on my part, what if you power down the entire drive, wait 30 seconds, then power back up?

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Old May 15th, 2019, 04:22 PM   #3
Ken Roach
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Double-check, then triple-check, then check one more time each of the encoder connections and the motor output connections.

A "runaway" axis that happens right after the Motion Servo On (MSO) command turns on the position control loop is almost always a single-phased motor (one loose motor output wire) or an encoder feedback wiring problem.

When a problem like that is present during initial tuning, you can get garbage autotune results, so the procedure is usually "disconnect everything, reconnect everything, repeat tuning".

If you can spin the servo shaft by hand, that's a good way to check the feedback wiring to see if you can read the Current Position and get results that are consistent with the configuration of the encoder.
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Old May 16th, 2019, 08:40 AM   #4
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Unfortunately, power cycling the drive did not fix it. I've double-checked and triple-checked all the wiring and everything is wired as the manual says to wire it.

The thing that confuses me is that the hookup tests work without a problem. The motor and feedback test accurately moves the motor the commanded 360 degrees. And the Motor Feedback test accurately identifies the polarity.

What else can I check?
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Old May 16th, 2019, 09:38 AM   #5

tarik1978 is offline
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As Ken siad the issue is an incorrect motor connections to the drive
check this technote:Excessive velocity error on Kinetix 350 after successful hookup and autotune.
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Old May 16th, 2019, 10:27 PM   #6

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My guess: check if you have a motor feedback parameter called Startup Method and try changing it.
Another option is deleting the axis and creating it again
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Old June 20th, 2019, 03:12 PM   #7
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Well, unfortunately this was never fully resolved. Here is what we found: Deleting the axis and starting from scratch did seem to stop the runaway problem. However, after adding a new axis and autotuning, the unloaded shaft still (about 1/2 the time) would drift and correct itself. It would bounce back and forth through an angle of about 30deg.

When I rotated the shaft by hand, it would easily allow me to rotate it, and it would "cog" every 40 or 50 deg and sometimes not servo back to its original position.

However, this was not repeatable, and it often would servo.
One behavior that was repeatable, was that if we commanded it to jog forward it would sort of jump or cog in 50-60deg intervals. This could be smoothed out by increasing the system damping in the Manual Tuning parameters.

Rockwell tech support agreed with the previous posts, that it was behaving like it was single phasing, or not commutating.
We tried new drive, and saw the same exact behavior. For now, we aren't going to replace the motor or cables, because it seems to be managed by increasing the system damping (for example from 1.0 to 0.7).

Thanks to everyone for your help.
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