Quote:
Originally Posted by Mike Schreiber
I was the initial inspector on this robot. We did the isolated frame check and it passed with no issue. Wiring looked pretty clean actually.
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As Mike said, the team had passed initial frame isolation check. They "dropped coms" earlier in the day, and after a few minutes, I went personally to check on them.
They said they had already found the issue, a loose Anderson connection on the battery as well as cleaned up the VRM input which had a possible whisker.
I verified those and was about to leave, but asked the team if this was the first time. They replied they had other drops at other events. I did a frame isolation check and found the positive side grounded to the frame. The team had LEDs, and it was one of the first items I asked about. The team told me they were disconnected*.
We then dug through the various areas and found a different item that would clear the frame isolation. Once cleared, I returned to the field. couple hours later, the fire occurred. I do not have first hand details of how the fire was handled as I was covering the other field, and a large group of people were gathered around, and I thought it was some robot with a typical sensor wire or PWM that had been pinched and smoked.
After the fire was out, the issue was diagnosed as a power cable that had previously fed the LEDs. It had a barrel connector that was disconnected earlier.
We suspect that the positive side frame grounding was intermittent and the barrel connector likely was exposed negative. This lead to the power cable catching fire when both sides grounded to the frame. It was relatively thin wire, so a short caused it to catch fire relatively quickly.
The team did an amazing job of keeping a positive attitude. They had a student lead the rebuild, and she did an amazing job of keeping students on task. One of the new Michigan LRIs working the event stayed with them to ensure it was rebuilt properly. After initial teardown, we inspected the remaining components and had the team not only change out most of the electronics, but most of the pneumatics as well. We were quite fortunate no one was injured, and the team only missed 1 match.
I know a report was sent in about the fire incident, and I plan to talk some more with other LRIs about possible ways of improving and/or mitigating future incidents.
*I missed asking the team exactly how they "disconnected" the LEDs. I did not see the barrel connector, and assumed the disconnection was done properly. I will be adding a more thorough line of questioning when "something is disconnected".