Robotic unicycle

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The problem of creating a robotic unicycle, a self-powered unicycle that balances itself in three dimensions, is an interesting problem in robotics and control theory.

To first order, a robotic unicycle can be considered as a control problem similar to that of a two-dimensional inverted pendulum with a unicycle cart at its base: however, there are many higher-order effects involved in modelling the full system. Rotation of the drive wheel itself can provide control in only one dimension (ie. forwards and backwards): control in other dimensions generally requires other actuators, such as auxiliary pendulums, reaction wheels, or control moment gyroscopes attached to the main unicycle pendulum.

The theoretical work on the unicycle problem is complemented by work on the construction of actual mechanically ridden unicycles.

A number of vehicles are almost robotic unicycles:

• The Segway is a vehicle which is capable of automatically balancing itself in the forwards-and-backwards direction, but has two parallel wheels rather than being capable of balancing from side to side.

• In 2003, Bombardier announced a conceptual design for such a device used as a sport vehicle, the EMBRIO. It is unclear whether Bombardier ever intends to create a working prototype of this vehicle.

[edit] References

• S. V. Ulyanov et al. Soft computing for the intelligent robust control of a robotic unicycle with a new physical measure for mechanical controllability. Soft Computing Volume 2 Issue 2 (1998) pp 73-88.
• Zenkov, DV, AM Bloch, and JE Marsden [2001] The Lyapunov-Malkin Theorem and Stabilization of the Unicycle with Rider. Systems and Control Letters, Volume 45, Number 4, 5 April 2002 , pp. 293-302(10) (postscript format available here)
• Zenkov, DV, AM Bloch, NE Leonard and JE Marsden, Matching and Stabilization of Low-dimensional Nonholonomic Systems. Proc. CDC, 39, (2000), 1289-1295. (pdf format available here)
• Sheng, Zaiquan; Yamafuji, Kazuo: Realization of a Human Riding a Unicycle by a Robot. Proceedings of the 1995 IEEE International Conference on Robotics and Automation, Vol. 2 (c1995), pp 1319 - 1326
• A. Schoonwinkel, "Design and test of a computer stabilized unicycle," Ph.D. dissertation, Stanford University, California, 1987.
• Johnson, R.C. Unicycles and bifurcations, American J. of Physics, volume 66, no.7, 589-92

[edit] See also

• Inverted pendulum
• Inertia wheel pendulum
• Control moment gyroscope
• Fenton Crackshell, a Disney character depicted wearing a robotic unicycle suit

[edit] External links

• Bombardier Recreation Products EMBRIO one-wheeled recreational vehicle concept design
• The loonycycle, which superficially resembles a simple robotic unicycle, but uses side-thrusting fans for lateral balance
• Rosie the Robot - a Question of Balance Ken Perlin's page on robotic unicycles, with designs and java applet examples.
• Pixar - Red's Dream, a short CGI movie depicting a unicycle riding itself
• The Unibot: a working robotic unicycle built for a university engineering project (with movies)
• Lego Unicycle (RCX): with very simple software (movie and links to controller software)