The theoretical work on the unicycle problem is complemented by work on the construction of actual mechanically ridden unicycles.
- 1 Control theory of the self-balancing unicycle
- 2 Early work
- 3 Human-ridable self-balancing unicycles
- 4 Similar-looking vehicles that are not true unicycles
- 5 Fictional self-balancing unicycles
- 6 See also
- 7 References
- 8 Further reading
- 9 External links
Control theory of the self-balancing unicycle
To first order, a self-balancing unicycle can be considered as a non-linear control system 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 (i.e., 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.
A number of academic papers have been published that either investigate the problem theoretically, or document laboratory-scale prototypes. A number of student and amateur engineering projects have implemented similar designs. Self-riding self-balancing unicycles are necessarily two-axis balancing devices.
Human-ridable self-balancing unicycles
Single-axis self-balancing ridable unicycles
A number of self-balancing unicycles have been created which are self-balancing only in the forwards-backwards direction, and still need a human being to balance them from side to side. Trevor Blackwell's Eunicycle is an example of a human-ridable single-axis self-balancing unicycle. Focus Designs advertises a similar commercial device. Inventist markets a stand-up, seatless version called the Solowheel. The R.I.O.T. Wheel is a ridable single-axis self-balancing unicycle with an unusually low centre of gravity, with its rider in front of, rather than on top of its single wheel, balanced by a counterweight within the wheel.
True two-axis self-balancing ridable unicycles
A two-axis self-balancing unicycle balances itself both forward and backward, and also 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.
- Aleksander Polutnik's Enicycle (2006) is probably the first two-axis balancing human-ridable unicycle.
- In 2009, RYNO Motors of Portland, Oregon created a one-wheeled electric motorcycle called the Micro-Cycle. According to the company, a commercial version is scheduled to begin shipping in April 2014.
Similar-looking vehicles that are not true unicycles
A number of vehicles are almost self-balancing unicycles:
- The Segway is a vehicle which is capable of automatically balancing itself in the forwards-and-backwards direction, but is a dicycle with two parallel wheels rather than being capable of balancing from side to side.
- In 2006, researchers at Carnegie Mellon University developed a 2-dimensional inverted pendulum that balances on a ball rather than a wheel.
- two-wheeled self-balancing (mobile) robots 
- The Uno, a vehicle that superficially resembles a self-balancing unicycle but is actually a dicycle with its two wheels very close together
- The Honda U3-X looks like a self-balancing unicycle, but balances on a powered Omni wheel rather than on a single wheel
Fictional self-balancing unicycles
- A self-balancing unicycle was described in 1969 in The Man From R.O.B.O.T., a short story by science fiction author Harry Harrison.
- Fenton Crackshell, a Disney character, is depicted wearing a robotic unicycle suit.
- Demolishor, a Decepticon from the 2009 Transformers sequel, whose robot mode is a gigantic robotic unicycle.
- the "tumblebugs" in The Roads Must Roll
- the protagonist in the Flash browser game, Little Wheel.
- Thor, fictional inventor of the wheel and the comb, of B.C. (comic strip).
- Slide 3 Slide 3 (2013-04-17). "Self-Balancing Unicycle | Focus Designs, Inc. | The SBU is the coolest light electric vehicle on the market. The gyro-stabilized SBU contains full-frontal nerdity!". Focusdesigns.com. Retrieved 2013-04-26.
- Inventist Solowheel
- "Introduction". Enicycle.com. Retrieved 2013-04-26.
- http://rynomotors.com/ Micro-Cycle — archived RYNO Motors 'blog page
- About RYNO Motors page.
- Carnegie Mellon Press Release, August 6, 2006 – "Ballbot"
- ANALOG — Science Fiction/Science Fact, Vol. LXXXIII, No. 5, July 1969, pp. 120-151. Illustrations by Peter Skirka.
- "Little Wheel - game at". Fastgames.com. Retrieved 2013-04-26.
- 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  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
|Wikimedia Commons has media related to Solowheel.|
- Bombardier Recreation Products EMBRIO one-wheeled recreational vehicle concept design
-  China version solowheel
- 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.
- The Unibot: a working robotic unicycle built for a university engineering project (with movies)
- Robotic Unicycle: Ongoing project
- Micycle (reports, papers, photographs and movies)
- "Unicycle riding robot unveiled". BBC News. 24 September 2008. Retrieved 2008-11-24.