Reducing CAN network noise

[jwakeman]

Originally Posted by Mike Copioli

When using the 2CAN are you observing CAN errors in the web dash?

It did not show any errors in the web dash. But if I connected to one of the Jaguars with BDC-Comm after the glitch occurred I could see "Comm errors" in the extended status thingy of the BDC-Comm utility. I did notice that the packet counts in the web dash that are normally counting up very quickly would slow down or stop during the glitch.

Originally Posted by Mike Copioli

Also how many jags are you running?

Started with four. During my troubleshooting I went to using two. So during the 4 tests I listed I was using two Jaguars.

Originally Posted by Mike Copioli

Could you please describe what you mean by "glitches" all jags or only one or two? Have you tested using only one or two jags on the bus? If so what was the result.

I think all the jags would glitch. At least two of the four when i was running 4 and both when I was running two.

Glitch: With the 4 jag setup I was running a PID loop that was setting a current reference on the jags every 20 ms. When the glitch occured they would momentarily stop providing power to the motors. I could see the LED's on the jag also momentarily change color during the glitch. So if two were steady red they would go to amber I think (hard to tell since it was such a short time) momentarily. Also the definition of a glitch includes the behavior with the packet count in web dash and the Comm faults showing up in BDC-Comm as desribed above.

When I went to troubleshooting mode (the 4 tests with 2 Jags on the bus) I would set the current reference once in my code and then while(1){Wait()}. When the glitch occurred the motors would stop completely. So in the setup with the PID loop the glitch was only momentary because the PID loop would immediately set the current reference again. But in the troubleshooting tests I only set the current reference once so after the glitch occurred the motors stopped until the test was restarted.

I also ran some tests where I was calling GetFaults() and GetPowerCycled() periodically. They never showed any faults or power cycles when the glitches occurred. I did not call these functions during my 4 tests because I didn't want to put any extra traffic on the network and they had shown nothing in prior tests anyway.

Originally Posted by Mike Copioli

Your problem sounds more like poor connectivity/termination. Try reducing the number of Jags on the bus, then adding additional jags until the problem reproduces.

We are building our 'production' version of the robot now. We are going to do our best to be diligent in wiring/terminating/etc. I'm hoping I won't be able to reproduce the problem on this robot!!