ChArLeS from Cambridge, MA, wrote in with his self-balancing scooter.
SEGFAULT is a balancing vehicle with a 100% hardware stability controller. Not a single line of code runs to keep the vehicle upright.
An analog complementary filter implemented with operational amplifiers combines the outputs of an accelerometer and rate gyroscope and passes it to a proportional-integral (PI) compensator. The output of the PI compensator has a steering offset differentially added to it. The resulting analog voltage is the input to two custom 24 volt, 30 amp locked-antiphase H-bridge drivers (Class D amplifiers), which control the two 27:1 geared, 500 watt drive motors.
The vehicle frame is waterjet-cut aluminum and diamond-plate aluminum, and features a tiltable handlebar for steering input. Lastly, the P, I, and K controller gains are accessible and tunable by the user through a set of knobs on the handlebars.