In an electrical drive system, an electric differential comprises a first rotor for driving a first drive wheel, a second rotor for driving a second drive wheel, the first and second rotors capable of independent relative rotation, and a common stator for driving the first and second rotors. The common...http://www.google.com/patents/US6914410?utm_source=gb-gplus-sharePatent US6914410 - Electric differential traction-control drive system
