Robotic unicycle
Encyclopedia
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.
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 gyroscope
s attached to the main unicycle pendulum.
is an example of a human-ridable single-axis self-balancing unicycle. Focus Designs and Inventist advertises a similar commercial device. 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.
Unicycle
A unicycle is a human-powered, single-track vehicle with one wheel. Unicycles resemble bicycles, but are less complex.-History:One theory of the advent of the unicycle stems from the popularity of the penny-farthing during the late 19th century...
that balances itself in three dimensions, is an interesting problem in robotics
Robotics
Robotics is the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots...
and control theory
Control theory
Control theory is an interdisciplinary branch of engineering and mathematics that deals with the behavior of dynamical systems. The desired output of a system is called the reference...
.
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 pendulumInverted pendulum
An inverted pendulum is a pendulum which has its mass above its pivot point. It is often implemented with the pivot point mounted on a cart that can move horizontally and may be called a cart and pole...
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 gyroscope
Control moment gyroscope
A control momentum gyroscope is an attitude control device generally used in spacecraft attitude control systems. A CMG consists of a spinning rotor and one or more motorized gimbals that tilt the rotor’s angular momentum. As the rotor tilts, the changing angular momentum causes a gyroscopic...
s 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.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 EunicycleEunicycle
A Eunicycle is a computer controlled, partially self-balancing, motorized unicycle invented by Trevor Blackwell. It uses a computer control system similar to the one used by the Segway HT that servos its wheel to balance itself by keeping the contact point of the wheel below the center of mass of...
is an example of a human-ridable single-axis self-balancing unicycle. Focus Designs and Inventist advertises a similar commercial device. 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 forwards and backwards and also side to side. Aleksander Polutnik's Enicycle is probably the first two-axis balancing human-ridable unicycle.- In 2003, BombardierBombardier Recreational ProductsBombardier Recreational Products or BRP is a Canadian company that traces its roots back to the year 1942 when Joseph-Armand Bombardier founded L'Auto-Neige Bombardier Limitée in Valcourt in the Eastern Townships, Quebec.In 2003, Bombardier Inc...
announced a conceptual design for such a device used as a sport vehicleVehicleA vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
, the EMBRIO. It is unclear whether Bombardier ever intends to create a working prototype of this vehicle.
- In 2011, Ryno Motors created a one-wheeled electric motorcycle called the Micro-Cycle.
Similar-looking vehicles that are not true unicycles
A number of vehicles are almost self-balancing unicycles:- The SegwaySegway PTThe Segway PT is a two-wheeled, self-balancing transportation machine invented by Dean Kamen. It is produced by Segway Inc. of New Hampshire, USA. The name "Segway" is a homophone of "segue" while "PT" denotes personal transporter....
is a vehicle which is capable of automatically balancing itself in the forwards-and-backwards direction, but is a dicycleDicycleA dicycle is a vehicle with two wheels side by side, unlike single-track vehicles such as motorcycles and bicycles, which have one wheel followed by another....
with two parallel wheels rather than being capable of balancing from side to side. - In 2006, Carnegie Mellon developed a 2-dimensional inverted pendulum that balances on a ball rather than a wheel.
- The Uno, a vehicle that superficially resembles a self-balancing unicycle but is actually a dicycleDicycleA dicycle is a vehicle with two wheels side by side, unlike single-track vehicles such as motorcycles and bicycles, which have one wheel followed by another....
with its two wheels very close together - The Honda U3-XHonda U3-XThe Honda U3-X is a self-balancing one-wheeled electric vehiclesimilar to the Segway PT.Honda developed the U3-X with technology originally developed for ASIMO the bipedal human robot project. Honda states that the "U" stands for unicycle and for universal. It weighs and travels at , a similar...
looks like a self-balancing unicycle, but balances on a powered Omni wheelOmni wheelOmni wheels or poly wheels, similar to Mecanum wheels, are wheels with small discs around the circumference which are perpendicular to the rolling direction. The effect is that the wheel will roll with full force, but will also slide laterally with great ease...
rather than on a single wheel
Fictional self-balancing unicycles
- Fenton Crackshell, a Disney character, is depicted wearing a robotic unicycle suit.
- Demolishor, a DecepticonDecepticonThe Decepticons are usually depicted as the antagonists in the fictional universes of the Transformers stoyline and related comics and cartoons, and the enemies of the Autobots and the University of California Davis Aggies...
from the 2009 Transformers sequelTransformers: Revenge of the FallenTransformers: Revenge of the Fallen is a 2009 American science fiction-action film directed by Michael Bay and produced by Steven Spielberg. It is the sequel to the 2007 film Transformers and the second installment in the live-action Transformers series...
, whose robot mode is a gigantic robotic unicycle. - the "tumblebugs" in The Roads Must RollThe Roads Must Roll"The Roads Must Roll" is a 1940 science fiction short story by Robert A. Heinlein. In the late 1960s, it was awarded a retrospective Nebula Award by the Science Fiction Writers of America and published in The Science Fiction Hall of Fame, Volume One, 1929-1964 in 1970.The story is set in the near...
- the protagonist in the Flash browser gameBrowser gameA browser game is a computer game that is played over the Internet using a web browser. Browser games can be created and run using standard web technologies or browser plug-ins. Browser games include all video game genres and can be single-player or multiplayer...
, Little Wheel. - Thor, fictional inventor of the wheel and the comb, of B.C. (comic strip)B.C. (comic strip)B.C. is a daily American comic strip created by cartoonist Johnny Hart. Set in prehistoric times, it features a group of cavemen and anthropomorphic animals from various geologic eras...
.
See also
- Inverted pendulumInverted pendulumAn inverted pendulum is a pendulum which has its mass above its pivot point. It is often implemented with the pivot point mounted on a cart that can move horizontally and may be called a cart and pole...
- Inertia wheel pendulumInertia wheel pendulumAn inertia wheel pendulum or gyroscopic pendulum is a pendulum with an inertia wheel attached. It can be used as a pedagogical problem in control theory.- References :* Mark W. Spong, Peter Corke, Rogelio Lozano. ....
- Control moment gyroscopeControl moment gyroscopeA control momentum gyroscope is an attitude control device generally used in spacecraft attitude control systems. A CMG consists of a spinning rotor and one or more motorized gimbals that tilt the rotor’s angular momentum. As the rotor tilts, the changing angular momentum causes a gyroscopic...
Further reading
- 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
External links
- The Enicycle, a true 2-axis self-balancing unicycle
- Gizmodo article: Self-Balancing eniCycle is Like a Segway for the Circus
- Honda unveils U3-X – a battery-powered unicycle
- The R.I.O.T Wheel
- Le Monorue
- Hack A Day: Motorized unicycles
- Hack A Day: Commercial self-balancing unicycle
- 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)
- Home made unicycle: Radio controlled unicycle robot (with movies)
- Lego Unicycle (RCX): with very simple software (movie and links to controller software)
- Robotic Unicycle: Ongoing project
- Micycle (reports, papers, photographs and movies)