Troubleshooting help: number of ethercat devices changed

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David Feil-Seifer

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Jun 28, 2018, 2:33:47 PM6/28/18
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I'm hoping for a little help debugging a problem I'm having with my PR2.

When teleop-ing the robot with the joystick, if I rapidly change directions using the controller, I sometimes (often) get this problem where the breakers trip and all the motors disable. The problem can be fixed by turning off the E-STOP and turning it back on, but I get the more than occasional breaker disable and it's pretty annoying.

At the moment the motors halt, pr2_dashboard shows the following errors:

Motors halted (device error); Number of EtherCAT devices changed; Dropped packets in last 10 seconds

EtherCAT Device (fl_caster_l_wheel_motor): Too many dropped packets; Could not collect WG0X diagnostics; Timestamp jumped; Could not collect diagnostics

EtherCAT Device (fl_caster_r_wheel_motor): Too many dropped packets; Could not collect WG0X diagnostics; Timestamp jumped; Could not collect diagnostics

EtherCAT Device (fl_caster_rotation_motor): Too many dropped packets; Could not collect WG0X diagnostics; Timestamp jumped; Could not collect diagnostics

EtherCAT Master: Motors halted (device error); Number of EtherCAT devices changed; Dropped packets in last 10 seconds


Has anyone seen a problem like this before?

Any help would be appreciated,
Dave



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David Feil-Seifer, Ph.D.
Assistant Professor, Computer Science and Engineering
University of Nevada, Reno, 89557

Lundberg, Cody Lee

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Jun 28, 2018, 2:40:29 PM6/28/18
to David Feil-Seifer, PR2_Users

Hello all,

 

I often get the same problem, even during pr2_2dnav. I also use the E-STOP to correct the problem each individual time.

I do believe I also had a dropped packet warning or error. I can send the full message from dashboard later if you are interested.

I believe this started after the Clearpath Indigo upgrade. It may have occurred a few rare times before the upgrade.

 

Thanks,

Cody Lundberg

Research Engineer I

University of Texas at Arlington Research Institute (UTARI)

7300 Jack Newell Blvd. S.

Fort Worth, TX 76118

Co...@uta.edu

www.uta.edu/utari

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David Feil-Seifer

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Jun 28, 2018, 2:43:48 PM6/28/18
to co...@uta.edu, PR2_Users
I am also running the indigo upgrade, that's a good clue. Might it be that the upgrade (which uses a low-latency kernel rather than a real-time kernel) might be causing delays making the motors think that they've got some problem?

-Dave

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Lundberg, Cody Lee

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Jun 28, 2018, 2:46:42 PM6/28/18
to David Feil-Seifer, PR2_Users

Dave,

 

That would make sense. When using pr2_2dnav the robot navigation is far less smooth than it was before the upgrade. It jerks and comes to a stop in the middle of moving in a line then jerks forward again as if the packets are not arriving consistently.

 

Cody Lundberg

Research Engineer I

University of Texas at Arlington Research Institute (UTARI)

7300 Jack Newell Blvd. S.

Fort Worth, TX 76118

Co...@uta.edu

www.uta.edu/utari

 

Gustavo Goretkin

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Jul 3, 2018, 10:08:08 AM7/3/18
to Lundberg, Cody Lee, David Feil-Seifer, PR2_Users
This is similar to a failure that's been discussed in this group: br_caster_l_wheel_motor Safety Lockout: UNDERVOLTAGE

The caster has some kind of slip ring, to allow continuous rotation, and it seems like this part is prone to failure. You will likely need to replace the caster (or this particular part)


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David Feil-Seifer, Ph.D.
Assistant Professor, Computer Science and Engineering

University of Nevada, Reno, 89557

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Yuki Furuta

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Jul 3, 2018, 10:12:15 AM7/3/18
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Hi All,

I'm Yuki Furuta, a student at JSK Lab in Univ. Tokyo, Japan who is maintaining our PR2s.
I recently got the same problem with our PR2 and it was because the slipring of the base module went wrong.

- TL;DR
I replacing the slipring of the caster and the problem never happens now.

- Long log of struggle
In my case, we found that the fault causes on only the one caster.
And I further investigated which devices are the actual causes of this error by replacing ethernet cables, MCBs, etherCAT hubs on the path, and also swapping the ports with other cables but still no luck.

Then I found that the `RX Error Port` property of the errored motor device on the caster is quite higher than those of other casters.
On the fl_caster (front left) the topology of each device is:
ethercat hub -> (port 0) fl_caster_r_wheel_motor (port 1) -> (port 0) fl_caster_l_wheel_motor (port 1) -> (port 0) fl_caster_rotation_motor (port 1)
and looking `RX Error Port` and `Forwarded RX Error` properties of each devices, I came to think that there was the actual cause between the port 0 of the fl_caster_r_wheel_motor and ethercat hub.
That is why I suspect the slipring is broken.

I then found that the product name of the slipring is LPC-0205-0402(JP06-015-01) from JINPAT Electronics Co.,Ltd in China and we bought some pieces from them.
(The contact was:
Tel:   +86-755 8204 2235 
Fax:  +86-755 2151 7849
Skype:  jinpatslipring
Email : sales02@slipring.cn
Website: www.jinpatslipring.com )

And after replacing with the new one, it worked without any problem now.

I briefly documented how to replace the slipring.

Any other materials is also logged in our github issue:

I hope it helps you!
 
Greetings from Japan,
⌘ Yuki Furuta
University of Tokyo  

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David Feil-Seifer, Ph.D.
Assistant Professor, Computer Science and Engineering

University of Nevada, Reno, 89557

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