Omni wheels are fascinating mechanisms, typically consisting of a driven wheel with a number of freely-rolling cylinders arranged around its circumference. When several are configured properly, they can exhibit very interesting motion, but a single wheel is normally not that interesting by itself. That rule, however, changes entirely with the OmBURo — Omnidirectional Balancing Unicycle Robot — which uses an omni wheel with powered rollers.
OmBURo employs a pair of servo motors: one for driving the main wheel in the longitudinal direction, the other for actuating the rollers laterally through an ingenious gearing system. The rollers are linked together via flexible shafts, allowing four small helical gears to transmit torque to each, and only turn when there is a speed difference between the two servos.
The robot is controlled by an Arduino Mega, with the help of an IMU and encoders for each of the motors to balance and move as a two-dimensional inverted pendulum. Power is provided by a 14.4V LiPo battery, making it entirely self-contained.
OmBURo was designed a mobility unit for use in tight spaces shared with humans. As seen in the video below, the device can follow a triangular or circular path under remote control, and can even balance on a non-level surface. Impressively, the demo also shows it “ballet dancing,” where a human spins it around and is able to recover without missing a beat. Check out its entire research paper for more details on this amazing project!