Yesterday Jordi and his wife drove up with the BlimpBot to Monterey, where I was attending the TED conference, so I could demo it. This was a pretty high-stakes demo, since not only would there be 2,000 of the most influential people in the technology, entertainment and design (TED) worlds watching, but they included Al Gore in the FRONT ROW, Google's Sergey Brin and Larry Page and movie stars such as John Cusack and Cameron Diaz.

The bot worked great in the hotel room, and then we took it the the auditorium during a break to test it on the main stage. Yikes. We were getting IR interference from everything, from LCD screens to the bright stage lights, and our reception range dropped to something around three feet. Even worse, the air currents were overcoming the blimp's ability to fight them. So we gave up on the idea of a fixed IR beacon on the ground, and I decided to hold it in my hand to keep it near the blimp. Even then, the motors couldn't fight the currents well enough.

So we rushed back to our staging area (my hotel room) and Jordi updated the firmware to give more power to the motors even at the cost of battery life (this demo only had to run three minutes) . We tested it again in the hotel room, it worked fine, and then it was time to go.

When we got to auditorium and waited in the wings to go on, it was clear that something bad had happened in the firmware update. The vertical motor wasn't coming on at all sometimes and it wasn't clear why. Then Jordi realized that in changing the power settings, he'd also changed the timing of the loops, and we weren't resetting the motor controllers at the right time, which meant that the chance of them working when needed was random (and low). We'd just been lucky in the hotel room, but clearly weren't now. Still, I crossed my fingers and went on, carrying the blimp.

Disaster! It turns out that one big thing had changed since our test run in the auditorium: 600 people had arrived. All that body heat had raised the temperature of the room, kicking in the air conditioning, which came out of huge ducts right over the stage. Basically I was under a raging waterfall of cold air, and the poor blimp sank right to the floor, its little vertical thruster completely overcome.

  • Lesson 1: Little blimps need still air
  • Lesson 2: If you can't find still air, you need WAY more powerful thrusters (which means more battery power, which means more weight, which probably means a bigger blimp)
  • Lesson 3: Don't update your firmware five minutes before you're going to fly an autonomous robot ten feet away from a former Vice President of the United States.
  • Lesson 4: Hey, it's a tech demo on stage, and they *always* go wrong--don't let it throw you. So I didn't. I just stood there holding the blimp, as you can see in the picture above, and went on with my talk and slides as planned. Points made, time limit met, applause gained. I looked a bit awkward, I'm sure (although hopefully not always as unhappy as I look above), but at least I got the sympathy vote! Now on to San Diego for Etech on Tuesday, where we get to do it again for an hour in front of the smartest geeks in the world. So much for the sympathy vote ;-) Jordi's hard at work fixing the firmware problems, so fingers crossed...
[Photo credit: Red Maxwell]

Views: 1208

Comment by Howard Gordon on March 1, 2008 at 9:58am
Sounds like you made a good recovery.

With regard to lesson #2, it's useful to think about the aerodynamic forces that are likely to come into play in any particular environment, and it seems that some additional consideration needs to be given to the shape of the airframe as well as the placement of the motors.
Comment by Peter Klemperer on March 1, 2008 at 10:17am
I hear you. Once I had to do a demo of a piece of custom computer hardware and it worked great until the dry run.

Fortunately, we had brought in a big group of grad students to heckle us and we held it in the same room that we were holding the event the next day. Sure thing, the temp in the room jumped 15-20 degrees and the machine overheated and tripped it's power supply safeties. I went to wally-world and picked up two 3 dollar dorm fans and duck taped them to the hardware. It worked, and I even got to make a joke about it during the demo. I had my advisor stand behind the box to give me a secret signal in case it overheated so that I wouldn't give a functional demo if it did. Fun times.

Best of luck at Etech, hope you get a better run at it. Maybe they can shut off the airconditioning there for a few minutes during the talk?
Comment by Jack Crossfire on March 1, 2008 at 5:21pm
CEO's have definitely been elevated to pharoah status in our age, but it's not a big loss. Remember doing a video software demo for Larry Augustin 8 years ago. Now no-one even remembers who he is.
Comment by Gareth Farrington on March 1, 2008 at 6:42pm
Bad luck guys, A/C sucks. I hope the presentation was well received.

Lesson 3 is a big one. No matter how tempting, don't mess with the software right before its deployed/used/demoed. You will get bit in the 4$$.

Can we see the presentation or the sides?

3D Robotics
Comment by Chris Anderson on March 1, 2008 at 6:58pm
Sure. The presentation is here (my voiceover is in the notes field):
Comment by Patrick Egan on March 2, 2008 at 8:59pm
Yep, blimps turn into kites in the slightest wind. Are you guys going to go for the outside demo at Etech?

3D Robotics
Comment by Chris Anderson on March 2, 2008 at 9:36pm
Er, no. These are meant for controlled-condition indoor aerial robotics contests. Demos at conferences are actually a lot tougher conditions than they would experience in their planned use.
Comment by Michael Evans on March 2, 2008 at 11:52pm
wait was this in Monterey CA??!!! dang didnt even know about it and its in my home town!
Comment by Patrick Egan on March 3, 2008 at 12:23am
Well, at least you gave it the old college try. :-)
Comment by Ryansway on March 3, 2008 at 2:21am
That's tough luck, hopefully the people you set out to impress understand that not everyone has the budget to afford thorough testing, and that a device that's fundamentally dependent on it's operating climate had a good chance of being affected by the conditions typical of an auditorium filled with people.


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