Control of a Handwriting Robot with DOF Redundancy Based on Feedback in Task Coordinates

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(DOF). 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 some intentionally artificial index of performance. This paper treats a 4-DOF redundant handwriting robot by using a novel and simple control method for resolving the problem of such illposedness based on feedback in task-coordinates. The effectiveness of the proposed control method is demonstrated through computer simulation.