971's Control System

[NotInControl]

Just off the bat, immediately after watching your release video the Mammoth became my favorite robot this season.

With the performance to boot. As a control engineer, it is very interesting to see all the cool things you guys do.

I did have a couple of questions of my own I am hoping someone on 971 can answer.

I think the most obvious first question is:

1. What are some of the main reasons your team choose to use the Begalebone to read through all the sensors vs using the cRIO?

2. Does the cRIO do any processing? If so, what? (aside from the compressor)

3. How do you handle graceful shut down of the bone? Or do you not care? In particular, do you take any measures to protect the filesystem on an unplanned shutdown because you are writing to the filesystem as well (I assume this because it was mentioned the bone writes a log file)?

4. What is the communication protocol used between the beaglebone and the cRIO?

5. Do you have vision processing on the beaglebone as well?

6. Do I understand correctly that all of your PID loops are on the beaglebone and not run on the cRIO?

7. What language do you run on the bone? what language do you run on the cRIO?

8. What linux distro are you running on the bone?


We used a beaglebone white this year for our vision processing only. All other sensor data (3 encoders, 1 pot, 2 limit switches, and 2 analog IR sensors were all connected to the cRIO.) This gave us 20fps with 100ms lag, well within our requirements of vision detection.

We have a custom fault tolerant TCP link between the bone and cRIO such that if the link ever goes down, it is displayed on our custom dashboard, and the robot continues to operate without a camera. If the link comes up, the server and clients reset, and comms are re-established automatically.

This system worked flawlessly through our 3 in-season competitions. We had problem at our first off-season event event 2 weekends ago. The filesystem on the SD card started to become corrupt and would crash upon startup. This is because we mount the filesystem r/w and do nothing to prevent ungracefull shutdowns. The quick fix was buy a new SD card, and put a clean img on there and then it worked like a champ.

I have planned countermeasures to prevent this failure from happening in the future, I would just like to know your experience with these devices as well.

Thanks in advanced,
Kevin