Patent ID: 7363994

Claim:
A wheeled structure, comprising: a body having at least first and second side portions and having a profile in a center plane, the profile comprising a top-of-body profile; first and second sets of wheel elements rotatably attached to the first and second side portions, respectively; a tail element pivotally coupled to a portion of the body, the tail element being pivotally coupled to the body via an articulation element and substantially conforming to and substantially within the top-of-body profile when in a stowed position; and a drive module coupled to the tail element to control the movement of the tail element between a first, stowed position and a second position where said tail element can make selective contact with a ground plane, wherein the drive module is operable to control, in a continuously variable manner, the angle and position of the tail element relative to the body, so that the tail element can assist in enabling the wheeled structure to traverse steep or difficult terrain; wherein the first and second sets of wheel elements each comprise at least front and rear wheels; and wherein the tail, when in the stowed position, is disposed substantially entirely within a wheeled structure profile defined by a plane substantially tangent to a topmost point of the front and rear wheels and within a perimeter defined by the front and rear wheels.