http://www.airtrax.com/company/history.shtml
From United States Patent Office:
Omni-directional vehicles capable of controlled motion in any direction have long been recognized as having many useful applications. A number of designs of omni-directional vehicles have been disclosed. Most omni-directional vehicle designs are similar in that they use wheels that feature a number of rollers positioned about the periphery of the wheel; the rollers permit the wheels to support motion in directions at an angle to the wheel's plane of rotation. Omni-directional vehicles using such omni-directional wheels can move in any direction by rotating the wheels and rollers in an appropriate combination. Each omni-directional wheel's rotation is mechanically driven and servo controlled in a coordinated fashion to cause the vehicle to follow a desired path as previously disclosed by Ilon in U.S. Pat. No. 4,598,782. Three, four, or more omni-directional wheels are connected to a suitable chassis, suspension, wheel drives, and controls to form an omni-directional vehicle. Hereinafter, all uses of the words "roller" and "rollers" refer to the type of rollers used on or designed for omni-directional wheels for omni-directional vehicles.
Omni-directional wheels can be grouped into two general classifications. The first class of wheels is comprised of a rigid hub that supports a number of free spinning rollers around its periphery. The hub is rigidly coupled to an axle that, along with other omni-directional wheels and axles, supports the vehicle. The rollers are mounted at an oblique angle to the wheel's axle and are free to rotate about their own axles. Omni-directional wheel roller mounting angles of ninety degrees have been disclosed by Blumrich in U.S. Pat. No. 3,789,947. The omni-directional wheel disclosed by Blumrich was mechanically driven to produce motion parallel to the axis of rotation of the wheel. Omni-directional wheel designs with a ninety-degree roller mounting angle and free-spinning rollers have been disclosed by Bradbury in U.S. Pat. No. 4,223,753; Hiscock in U.S. Pat. No. 4,335,899; Smith in U.S. Pat. No. 4,715,460; and Guile in U.S. Pat. Nos. D318,219 and D318,791. Omni-directional wheels with rollers mounted obliquely at roller mounting angles of approximately forty-five degrees with respect to the wheel shaft have been disclosed by Ilon in U.S. Pat. No. 3,876,255 and Amico in U.S. Pat. No. 5,701,966. U.S. Pat. Nos. 3,876,255 and 5,701,966 are hereby incorporated by reference in their entirety.
The second class of omni-directional wheels differ from the above described omni-directional wheel design concepts in that the rotational axes of the free spinning rollers intersect with the wheel's axis of rotation. Wheels of this class have been disclosed by Bradbury in U.S. Pat. No. 4,223,753, and by Pin, et al, in U.S. Pat. No. 5,374,879. In wheels of this class, two or more spherical rollers are mounted in fixed positions so as to constrain the vehicle's motion in the direction of wheel rotation, while being unconstrained in a direction that is orthogonal to the wheel's axis.
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