A HOGfoot Wheel is a robotic appendage design that enables agile rolling-based locomotion and, in conjunction with legs, walking, running, and climbing. A device equipped with this sort of wheel can roll along on a suitable surface, then pick up its legs and convert the wheels into various other forms of locomotive device such as a foot or a clawed pad as required.
The HOGfoot is an evolutionary offshoot of the HOG wheel, or Hemispherical Omnidirectional Gimbaled wheel. The HOG wheel has a hemispherical rolling surface, the equivalent of the rim on a cylindrical wheel. The hemisphere rotates about an axis like a spinning ball, and the gimbal mechanism can alter the vector of the axis, redirecting the full torque of the drive motor in a fraction of a second. By changing the angle of incidence of the hemisphere’s axis relative to the surface being rolled upon, effectively the circumference of the wheel (and consequently the gear ratio) is infinitely variable within a finite range. If the axis is perpendicular to the surface, the effective wheel circumference is zero.
Two or more HOG wheels used in conjunction enable omnidirectional rolling locomotion.
The HOGfoot wheel can take various forms. The above images depict an example that has four adhesive footpads and a claw that are stored inside the body of the wheel when not in use. Other variations include telescoping tentacles, footpads stored on the outside of the cylinder, folding up against it; and a large inflatable myomaterial footpad, advantageous for soft ground.
Text by John Edds
Initially published on 10 January 2014.
Video of a Hogwheel in action