Patent ID: 7597160

Claim:
A four wheel drive system for a bilaterally symmetrical vehicle having pairs of front and rear wheels, respectively, comprising (a) a first drive system for independently rotating each of the front wheels in forward and reverse directions about a horizontal axis to propel the vehicle; (b) a second drive system for independently rotating each of the rear wheels about a horizontal axis at similar speeds in the same direction to propel the vehicle; (c) said rear wheels further being connected with said vehicle for rotation about vertical axes, respectively, beyond 180 degrees; (d) a third drive system independently rotating the rear wheels about vertical axes to steer the vehicle; and (e) a controller connected with said first, second and third drive systems for controlling the operation thereof to steer and propel the vehicle, said controller operating said first drive system to simultaneously rotate said front wheels in opposite directions when executing a sharp turn approaching a turning radius of zero.