Category Archives: Balancing
Yes, I finally put the finishing touches on my mini, balancing robot that does color tracking. His name is Flexo. Yes…after Benders smarter brother. I used Flexo extensively for testing cone tracking techniques for our RoboMagellan contest entry
Here is Bob showing Flexo’s cone tracking technique:
Flexo has sonar onboard, so we can send him into a crowd, and he will find someone wearing red and follow them around without running into them. We took Flexo with us to Seattle for the 2004 SRS Robothon, and he was a big hit. Every time we powered him up, he drew a good sized crowd, and almost always, he found someone wearing red to make friends with.Sure enough, birds of a feather flock together, he ran into his big, balancing, distant cousin, a Segway, and it’s owner was kind enough to let me get a photo of the Segway, and Flexo, balancing together.
Flexo took the “Best Engineered Robot” award at the 2004 Robothon. Here is a snapshot of Flexo with his award ribbons, and Odyssey, our Robo-Magellan Robot, which took 2nd place in the Robo-Magellan competition.
Next steps for Flexo, are better navigation techniques for roaming around, and a better camera/vision system for doing more than just following the color red.
We finally added the complete board stack to the mini-ISIS, to make mini-ISIS go autonomous! We mounted a pan-tilt camera head, so it can chase some toys like my tabletop challenge robot. It has a separate CPU board controlling the higher level functions. We have been dreaming about doing this for awhile, but we really only started the whole process about 2 weeks ago. One of the producers from Tech TV’s, The Screen Savers, ran into us at the Robolympics, and was asking “So what are you guys working on that we haven’t seen yet??” And we said, well, we’re working on mounting a camera on top of the robot, and his reply was “Thats cool! Can you have it done next week for the show?!?” A week later, it’s working, and ready for it’s debut on TV.
There were several major problems to be solved to make mini-bender autonomous with a camera on top.
- Mount a pan-tilt head on the robot
- Update the camera software and hardware from Tracker-bot, so that it was smoother, and could track faster.
- Build and tune a velocity-control algorithm so the robot could automatically adjust its tilt angle to achieve a constant wheel velocity.
- Write software to take the box tracking information, and convert that into the appropriate wheel geometry to steer and drive the robot toward the target.
Here are some video clips of the initial tests of some of each of these development components. Again, as with all my videos, these are all Windows Media Player 9.0 format:
|Pan-Tilt Camera Test (4.9 meg)- Video of the initial tests of the camera head, tracking the little red box from tracker-bot.|
|Driving Test (1.6 meg)- Early test of driving forward with constant velocity. The algorithm is still a little clunky and needs some tuning at this point, but it does make it across the kitchen, despite crashing into the noisy dishwasher|
|Steering Test (1 meg)- I needed to make sure that the robot could steer itself properly, and still maintain constant forward velocity.|
|Target Tracking (3.2 meg)- I took the robot to the club meeting only hours after finishing it. I mounted a little red target on the end of a stick, that the robot could follow around. Here is one of it’s first demonstrations at the Home Brew Robotics Club.|
|Children Tracking (2.4 meg)- A new member of the club showed up to the meeting, and little did he know that his red shirt would attract self-balancing robots|
The first rework of the PCB is done. We wanted to make another balancing robot, using off-the-shelf motors that wouldn’t set us back lots of $$$. As you might remember, Bender and ISIS are using surplus motors, which we can’t hope to find again, unless we get really lucky. We found some smaller motors that were only $15 new, and that had tail shafts to allow the mounting of a small optical encoder for motor feedback. So, we had to scale down the mechanical design to one that the motors could accommodate.
Although we built two of these, they are both not yet perfect. Bobs was the first to be up and running. It still needs a little bit of software work to make it more stable, but initial tests are encouraging. Once I had it balancing, Bob took it home, and mounted a much larger battery pack on it than I had used in the initial tests. When he showed up with it at the latest robot club meeting, I was really surprised to see how the extra mass helped the balancing stability. Lately we have also been experimenting with gyro mounting locations, and it appears to be much more stable with the gyro/accelerometer board mounted down low on the robot, rather than up high, which is something that was not an obvious thing to do.
Here are some video clips of mini-Bender. These clips are in Windows Media Player 9.0 format:
|Mini-Bender #1 - Here he is, balancing on the kitchen floor, looking pretty stable.|
|Mini-Bender #2 - I have the radio control unit hooked up, and am taking him for a spin around the kitchen floor. It’s a bit difficult to drive and film at the same time, but at least I don’t run into anything|
Most of the balancing robots in North America, (that actually work properly and can stay balanced indefinitely), showed up at the Seattle Robothon for a Balancing Robot Symposium. It was inspirational to meet fellow balancing robot builders such as Dave Anderson, and Larry Barello. Here is a shot of all the robots balancing together, like birds of a feather. From left to right, the Legway, nBot, Gyrobot, Isis, and Bender.
Dave Anderson shot lots of video of nBot and bender balancing together, and belly bucking. Hopefully his website will soon be updated with some fun clips. I learned a ton from seeing the other robots in-action, and sharing ideas with the other builders.
Here are Bender and Isis all strapped into the back seat of the rental car for the trip over to the Seattle Center for the Robothon. They survived the trip on the airplane quite nicely, thanks to lots of packing foam and a couple of big boxes, although I am sure the TSA didn’t like them.
Overall, we had lots of fun at the Robothon. Hats off to the Seattle Robotics Society for a well planned and executed event!
Here is the smaller test platform, balancing out in the back yard. Look MA! Only two wheels!
It has the PCB mounted on it, and has been made a bit taller to get the center of mass up nice and high.
It took quite A-LOT of work to get it to balance the first time. Lots of trial and error. I shot some videos along the way.
Baby’s First Steps (2.2 meg) – First time it got to balancing was late on a Friday night. The balancing algorithm is still a little shaky, but it is standing on it’s own two wheels!
Backyard Balance (3.6 meg)- Here it is, much smoother now, on the nice, uneven surface of the brick patio, smoothly balancing.
Kitchen Rampage (4.2 meg) – I finally got the remote control algorithms working. Now I can drive it around R/C. Here it is, tearing around the kitchen floor. My driving is not too good, but it doesn’t fall down! Even when I crash it into a kitchen cabinet. My house is getting more and more robot damage.
Robot Expo (3.8 meg) – Here is some footage of it balancing at the SF Robotics Society of America Robot Expo & Games. It balanced for about 6 hours straight, and only fell over once when I accidentally drove it into my leg going full speed. This was its longest balancing endurance yet. It is amazing how good the battery life on a balancing robot is, since the motor is only delivering small corrections it draws very little current.
Bob recently got his balancing robot working too. Here is a shot of the two of them balancing together at a recent robot club meeting.
Bender Gets a Head:
Bender has a head! Thanks to the great design skills of Bob Allen. The head can pan and tilt. It adds some interesting additional complexity to the balancing problems to compensate for head movement, but it won’t be that complicated to do…just a little more code!