2013 Lessons Learned for a Vision Co-Processor

[Jerry Ballard]

Thanks Joe for the formatting tip.

Here are a few more lessons learned related to your questions:

7) Stable and reliable power is required: During competition, the system voltage can vary significantly (below 10V) due to the varying demands of the other powered components. If input voltage dropped that much the PandaBoard would drop power and reboot (not good). So we used the MiniBox DC-DC converter (http://www.mini-box.com/DCDC-USB?sc=8&category=981) to solve this problem. The only issue (we believe) we had in competition with power was probably due to a loose power connection into the PandaBoard.

8) Hard Stop and Rebuild during competition: During the build season, we made the decision not to find a graceful method to shutdown the system during competition. Instead we let the system hard stop when the power was shutdown and then did a reboot and fsck'ed (file system checked) between matches. Also, we maintained multiple copies of the complete OS on memory cards and often did card swaps between short match times. Swaping OS memory cards allowed for some simple diagnostics of target tracking and provided redundancy in case of severe system crash.

9) Diagnostic photos are good: During the matches, we captured and saved frames from the camera once a second (sometimes less) to help us determine how the targeting system was doing. It turned out that these images were very useful to the pilot/copilot of the robot to quickly replay the previous match. Visual cueing from these images helped the students recall better what happened during the match (from the robot's point of view). I've attached an example image below. The blue circle is the aim point of the shooter, cross-hairs identify targets in range, the red dot is the predicted frisbee hit, and the green circle is the target selected.

10) Raspberry Pi didn't work for us: We spent a lot of time trying to get the RPi to run the targeting code. But as written, our code wasn't able to achieve the fps speed needed. We had set a goal of 15 fps as a minimum. The most we could squeeze out of the RPi was 10 fps. We all love the RPi but in this case we weren't able to get the required speed.