Abstract
In order to enhance dexterity in execution of robot tasks a surplus number of DOFs (Degrees of Freedom) is necessary for design of robotic mechanisms. In case of such redundant robots, it is said that a problem of inverse kinematics becomes ill-posed and therefore an extra performance index is indispensable to determine uniquely the inverse mapping from task space to joint space. This paper treats a problem of reaching tasks under the effect of gravity by a redundant robot arm or hand and shows that such ill-posedness of DOF redundancy can be resolved in a natural way by using a simpler task-space feedback with adequate dampings at joints and gravity compensation and without introducing any extra performance index. An application of the proposed method to control of hand-writing robots is also discussed.
