A sensory feedback method for a handwriting robot with D.O.F. redundancy

In order to enhance dexterity of a robot hand, it is said that the robot should be designed to have a redundant number of degrees-of-freedom(D.O.F.). However, in redundant robotic systems, the inverse kinematics from task-description space to joint space becomes ill-posed. Therefore the problem of determination of joint motions becomes difficult. In order to avoid this ill-posedness, many methods have been proposed, most of which introduce an additional input term calculated from minimization of some intentionally introduced artificial index of performance. This paper treats a 4-D.O.F. redundant handwriting robot by using a novel and simple control method and resolving the problem of such ill-posedness based on sensory feedback in task-coordinates. The effectiveness of the proposed control method is demonstrated through computer simulation and a preliminary experiment.