Omni wheels or poly wheels, similar to Mecanum wheel

Mecanum wheel

The Mecanum wheel is one design for a wheel which can move in any direction. It is sometimes called the Ilon wheel after its Swedish inventor, Bengt Ilon, who came up with the idea in 1973 when he was an engineer with the Swedish company Mecanum AB....

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Wheel

A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s with small discs around the circumference

Circumference

The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

 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. These wheels are often employed in holonomic drive systems.

A platform employing three omni wheels in a triangular configuration is generally called Kiwi Drive. The Killough platform is similar; so named after Stephen Killough's work with omnidirectional platforms at Oak Ridge National Laboratory

Oak Ridge National Laboratory

Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...

. Killough's 1994 design used pairs of wheels mounted in cages at right angles to each other and thereby achieved holonomic movement without using true omni wheels.

They are often used in small robots. In leagues such as Robocup

RoboCup

RoboCup is an international robotics competition founded in 1997. The aim is to develop autonomous soccer robots with the intention of promoting research and education in the field of artificial intelligence...

, many robots use these wheels to have the ability to move in all directions. Omni wheels are also sometimes employed as powered casters for differential drive robots to make turning faster. However, this design is not commonly used as it leads to fishtailing

Fishtailing

Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...

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Omniwheels combined with conventional wheels provide interesting
performance properties, such as on a six wheel vehicle
employing two conventional wheels on a center axle and four omniwheels
on front and rear axles http://allardengineering.com/omniwheel.html.

Although omniwheels are capable of movement in many directions, they are not true omni-directional wheels, a classification reserved for spherical wheels such as ball transfer unit

Ball transfer unit

Ball transfer units are omni-directional load-bearing spherical balls mounted inside a restraining fixture. They are identical in principle to a ball computer mouse upside-down, or a trackball, except there is an array of them side-by-side. Typically the design involves a single large ball...

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External links

• PPRK - A commercial holonomic drive system developed by Carnegie Mellon University utilizing poly wheels.
• Airtrax - A series of commercial vehicles utilizing Mecanum wheel
  Mecanum wheel
  The Mecanum wheel is one design for a wheel which can move in any direction. It is sometimes called the Ilon wheel after its Swedish inventor, Bengt Ilon, who came up with the idea in 1973 when he was an engineer with the Swedish company Mecanum AB....
  
  s with poly wheels to provide omni-directional vehicle motion.