A programmable variable degree of tactile feedback for the operation of a manipulator by a pair of motors, one connected to the load and one to the control. Computer controlled four quadrant regulators for each motor are used to drive the load motor shaft to the same position as the control motor shaft...http://www.google.co.uk/patents/US5103404?utm_source=gb-gplus-sharePatent US5103404 - Feedback for a manipulator
