The assistive torque generated by a motor or the torque transmitted by a clutch when the speed of travel of a motor vehicle is increased beyond a prescribed value while a steering torque is being applied, is reduced with time from a predetermined value. The assistive torque generated by the motor or...http://www.google.ca/patents/US4651840?utm_source=gb-gplus-sharePatent US4651840 - Motor-driven power steering system
