I wanted to design a robot that
contained only a single
moving part, and that could travel
in any direction instantaneously.
The result was
a generalization of those
rolling ball robots that
have a little wheeled vehicle inside:
As the vehicle tries to ride
up the inside of the ball, the weight
shifts inside (to keep the vehicle
near the bottom), and the ball rolls.
In the case of the TumbleBot, the outer sphere is made of metal, and the inner core contains six electromagnets. The core assembly tries to climb up inside the sphere by turning on selected electromagnets. This causes the center of gravity to shift, and the ball rolls.
By turning on different electromagnets, the TumbleBot can shift direction instantly (as in the simulation at right).