KinetixServoDrive Losing Home position

[gbradley]

Kinetix 2097-V34PR6

A few weeks back the drive lost its HOME position
I got an E27 FaultCode: Absolute move attempt without system homed.
I went about re setting the Home (I use the Immediate home)
It's been running for a week or so, but this morning it did the same thing.
I don’t think that there is a battery inside.
Is there a Capacitor that holds the Data?
OK, I Know that the drive is near the end of its lifecycle.

 

[JBooth]

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/2097-um001_-en-p.pdf

Page 114: Absolute homing is the only method that retains homing data/status after a power cycle. Data is written to non-volatile memory, so no battery or capacitor, but it is limited to 1 million writes.

 

[Ken Roach]

Is this a 2097-V34PR6 (Kinetix 300) or a 2097-V34PR6-LM (Kinetix 350) ?

The Kinetix 300 and 350 could use absolute encoders with Tamagawa and Hiperface protocols, which used a small 3.6V battery housed in the "low profile" connector hood. I think the associated motors were TLY style, or a TLAR linear actuator.

I'd feel better if there was a "Feedback Battery Low" or "Bad Battery" fault in there too, since the servo does monitor the voltage of that battery; I think the fault level is somewhere around 2.75 volts.

I admit I don't know if an ordinary feedback loss would result in an absolute position loss and require a Home function before you could go back to doing Absolute moves. You could test that by literally unplugging the feedback cable at the motor, to simulate a broken conductor or signal interference/loss.

 

[gbradley]

Kinetix 300

 

[gbradley]

The Kinetix 300 drive is controlling an MPL servo motor (MPL-A4560F-MJ72AA)
It shut down again today.
I am going to look at the Encoder connections to make sure that they are not loose or something.

 

[Ken Roach]

Thank you for that detail !

MPL-A4560F-MJ72AA

The "M" in the seventh position of the part number indicates a high-resolution multi-turn absolute encoder. For MPL motors, the Technical Details document says that is a "1024 sin/cos, absolute multi-turn encoder (Hiperface protocol)".

The document goes on to say:

"Multi-turn encoder provides high-resolution absolute position feedback within 4096 turns. The electromechanical design does not require a battery."

So this isn't a battery backup or NVRAM problem.

Without getting too deep into it, this classic HIPERFACE signal encoder is designed to give a high-resolution single-turn position using 4 conductors (SIN+/SIN-/COS+/COS-) as well as an RS485 half-duplex connection to transmit the turn number (DATA+/DATA-). The typical 8-conductor cables also include V+/COM.

HIPERFACE has largely been replaced with HIPERFACE DSL, which is literally two conductors with a super-fast RS485 protocol. A-B makes a converter that allows you to use older MPL's with modern Kinetix servo controllers that have just the DSL feedback connection.

It makes sense to me that an encoder signal loss means that the absolute position is lost too, so the drive can't perform an absolute move because it doesn't know where it is.

"What will cause the motor and drive to re-sync the absolute position other than doing a Home action" is an interesting question, but probably not as relevant as "what's wrong with the cable, connectors, encoder, or signal".

 

[gbradley]

Yes,
I am using a modified version of the Sample Code program that you directed to me to years ago.
SMC_ENETIP_ML1400_K300_2AXIS_V1_0.rss

MotionView seetings are set to Drive Mode EtherNet/IP External Reference

It has been running for years and years with some drive swaps and motor swaps here and there. I think this press has ~29 million cycles on it.
This part where it is losing it's home VALUE and getting an E27 fault is a relatively new Phenomenon.

 

[Ken Roach]

29 million shakes and jiggles are certainly prime suspects in a worn, fractured, or frayed wire or connector component.

My next troubleshooting step would be to disconnect the feedback cable to intentionally cause a feedback signal fault, then try an Absolute move. If the Absolute move fails with a "a home is required first" fault, then it's very likely that the root problem is the encoder, cable, or connector.

 

[gbradley]

I replaced the Green Cable 2090-CFBM7DF-CEAA03 because it is a possible culprit considering the E07 error
So far so good.