FireCheetah returns to Abington

Posted by Erica on Apr 18, 2013 in Making |

Saturday was the Abington firefighting competition. I had entered this contest last year with very little time to prepare, and was looking forward to trying again. I made considerable progress (as blogged here over the past few months), and showed up with a robot that was stronger and simpler. Most importantly, it was smarter.

Tests had gone very well at home. Audio start, full navigation of the maze, blowing out the candle, and the crowd-pleasing return to start all functioned reliably. So our drive to Philadelphia Friday night was relaxed and I slept well. The kids had a robot also, a LEGO Mindstorms creation named Dark Lord who used a sponge to extinguish the candle. (Dark Lord is white in color so I don’t understand the name.)

On Saturday I showed up as early as possible to calibrate, get ready, and talk with the other roboticists. First step, attach the battery and power on the robot. Except…it wasn’t powering on. Battery was fully charged, as was the spare, and neither worked. After some increasingly frantic work with the voltmeter, I realized that one of the wires on my main power switch had snapped. The switch had worked well for over a year. Fortunately I had a soldering iron and extra wire with me; unfortunately, I did not have a third-hand. Paul Boxmeyer of Lycoming Robotics was kind enough to loan me a clamp but it was still very difficult to attach a wire to a small switch without shorting the terminals. Not fun. Eventually though, I fixed it. And then discovered that the other wire had snapped.

I did fix the switch, but this consumed a tremendous amount of time. Next step, calibrate the sensors. IR was basically the same as at home since I had white walls in my maze. The candle, however, was another matter. When I came in Paul took a look at my robot and expressed surprise that I didn’t have an adjustable potentiometer. That was a prescient remark. I found that I had trouble seeing the candle in the maze room, no doubt due to all the fluorescent lights. Still, boosting the threshold level in software allowed me to see my practice candles from the necessary distance.

I finally had time to do a practice run. The official candles were much thinner than mine, but I succeeded in the quick single-room test and hoped for the best. Alas, it was not to be. In the first official run, the robot went smoothly to the room, looked for the candle, and left it burning there. It simply couldn’t see it. Later Paul explained to me why my circuit had failed; I would have been better off with only one photodiode rather than four in parallel. They really act like transistors. And a pot would have allowed for better tuning.

For the second run, I knew I would miss the candle, so I asked the judges to put the candle in the fourth room so that I could show off the navigation. My proudest moment was watching the robot pirouette through the first three rooms. Its movement was so beautiful. The carpets were far thinner than I had remembered and the robot barely seemed to notice them; the ones I had at home were much more difficult. On the fourth room — I discovered that my home maze construction had an error. I was 4″ off spec, and Saturday’s maze was another 3″ off. With that, the robot was too far over and scraped a wall, forcing a turn. The recovery code kicked in and kept FireCheetah moving, but with misinformation of its location the robot could not do anything useful. This run was quite frustrating. If I’d had the time to do one full practice run, I would have seen the problem and fixed it with a simple edit. But the switch chose a bad moment to fail.

This year I had more time to watch the competition itself, and it was quite enjoyable. You really empathized with these little creatures and wanted them to succeed. Some were more interesting than others. As I feared, the no-carpet option meant that a lot of robots went for dead reckoning, and that is a bit dull in my humble opinion. Others bumbled around in a charming way. Many of them had trouble, as I did, finding the candle. Or in putting it out. Once again I am convinced that a fan is the way to go. So many sponges, balloons, and other exotic methods failed to work. Almost all other robots there were kits: Vex, LEGO, Boebot, and Paul’s students used his standard base. One woman came up to me later and said she thought my robot was the cutest, which was quite nice of her. They do begin to feel like pets after a while.

The kids’ robot did very well, which was no surprise. Oh the reliability of remote control! They had some competition this year with another girl who also had a LEGO robot. Since their division was untimed, everyone got a trophy anyway. Paul won the Senior Division, along with several other awards for innovation including the multi-robot division where he was unchallenged. One of his students won the Junior Division as well. Note, she used a fan. The other students used sponges, most of which failed.

Steve Rhoads and Foster Schucker from the Vex robotics club were there also, and this time we successfully exchanged contact information. They are cheerful guys and I enjoyed seeing their new Arduino-based robot. They are trying to use Arduino while still retaining kit-level reliability — no home soldering here — and it’s an interesting challenge. They have found a very nice IR grid sensor and I look forward to seeing that at work. Best of all, they are planning to hold some firefighting competitions this summer. I am happy to hear this because I would like to succeed next time, without waiting an entire year, and cross it off the list.

Obviously, I need a better way to detect the candle. Paul suggested that my circuit could work with some tweaks, and that’s probably true, but fiddling with pots is not what I want to do. Since I don’t have the same type of lighting at home to test with I want something more reliable, and that means spending more money on a better sensor. One option is the UV Tron, at least for detection. At the moment I am considering the MLX90620 thermopile. Interfacing with it is something of a software challenge, and it could provide continuous directional feedback as the robot approaches the candle.

Preparing for a competition is very intense and after it is over there is always a letdown. What to do next? In firefighting, I could go well beyond the thermistor; it would be very easy now to shrink the robot significantly, always good when navigating a maze. I still have a ton of I/O from my Mega clone, and could add more sensors. This would allow better obstacle detection. My second run failed due to a wrong number that was hard-coded. I didn’t have many of them, but there were a few. A great robot would not need any of that, it could center itself as it approached a new hallway. Heck, it would be possible to slap an Asus (Kinect clone) on the robot, it fits the size limitation. An exotic candle extinguisher (with a fan as backup!) gets extra points. Or maybe it would be fun to make a walking robot — something completely different.

Beyond firefighting, there are a number of challenges at RoboGames that look fun. The space elevator robot or table bot would all be very new. I like the creative aspect of these and they are less pass/fail than firefighting — which is another contest option at RoboGames.

I’ve ended up with some nice C++ code for any differential drive robot. It’s already on Github but I need to separate it out from the firefighting class to make it of general use. There is a local robotics hackathon on Sunday so maybe I will have it ready by then. The link will be announced here when it’s done.

Here is a video of the one successful run I did in the official maze. Go FireCheetah!

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