scooty, the balancing test platform
Scooty came into existence from a desire to build a full-blown, ridable balancing scooter. It seemed like the perfect combination of electronic / programming / mechanical engineering as a developement project. After much (much) reading on the subject, and some sensible persuasion, a model-sized version was built first. And that is Scooty.
At this point Scooty does one thing, and that is balance. But it does a commendable job of it, which is no small feat. If you’d like some great background info on how this is done, check out here, and here.
There’s a few things that make Scooty a little different from the pack. For starters, with the large motors, it was possible to drive the wheels directly from the motor shafts. Even with a curb weight of almost 12lbs (5.4kg), the motors do a good job of recovering from jolts. And, it eliminates the gear-lash that would come from the added gearbox, which is a good thing when trying to balance. Of course, this adds abuse to the motors, so I wouldn’t recommend it (unless your motors were also salvaged from the scrap-heap). Another was the realization that by rotating the gyro board to vertical, it also allows for filtering the gyro’s x-axis for yaw correction, keeping the bot moving in a straight line. By grabbing on the top of the bot and turning, it’s possible to feel the motors “fighting back” against the rotation, eventually returning to it’s starting point.
With the addition of the LCD screen and three push-buttons on the starter kit, it was possible to build a menu system, where many of the parameters could be adjusted “live”. This offers an excellent method for testing out different values and seeing the results without a trip back to the bench.
scooty parts list
- Microchip pic32 starter kit microcontroller board
- Microchip pic32 i/o expansion board
- Sparkfun 5dof inertia measurement unit combo board
- Salvaged pair of 18v electric dc motors from an Ikea stand/sit office desk
- DimentionEngineering Sabertooth 2×10 motor controller
- Banebots wheel encoders
- Banebots wheels
- Sparkfun LCD (with serial backpack)
- Maxbotix ultrasonic range finder
- Pair of Phidgets 20Amp current sensors
- Pair of 18v NiMH battery packs salvaged from some old cash registers
Scooty has become a great starting point for a larger, ridable version, and there have been many lessons learned - at a fraction of the cost. And, I can hope, some saved road-rash as well!