# Self-balancing unicycle

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

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

## 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.

## Early work

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.[1] Inventist markets a stand-up, seatless version called the Solowheel.[2] 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.[3]
• In 2009, RYNO Motors of Portland, Oregon created a one-wheeled electric motorcycle called the Micro-Cycle.[4] According to the company, a commercial version is scheduled to begin shipping in April 2014.[5]

## Similar-looking vehicles that are not true unicycles

A number of vehicles are almost self-balancing unicycles:

## References

1. ^ 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.
2. ^ Inventist Solowheel
3. ^ "Introduction". Enicycle.com. Retrieved 2013-04-26.
4. ^ http://rynomotors.com/ Micro-Cycle — archived RYNO Motors 'blog page
5. ^ About RYNO Motors page.
6. ^ Carnegie Mellon Press Release, August 6, 2006 – "Ballbot"
7. ^ [1]
8. ^ [2]
9. ^ [3]
10. ^ [4]
11. ^ ANALOG — Science Fiction/Science Fact, Vol. LXXXIII, No. 5, July 1969, pp. 120-151. Illustrations by Peter Skirka.
12. ^ "Little Wheel - game at". Fastgames.com. Retrieved 2013-04-26.