Strategies for Increasing the Tracking Region of an Eye-in-Hand System by Singularity and Joint Limit Avoidance

An eye-in-hand system visually tracking objects can fail when the manipulator encounters a kinematic singularity or a joint limit. A solution to this problem is presented in which objects are visually tracked while the manipulator simultaneously avoids kinematic singularities and manipulator joint limits by moving in directions along which the tracking task space is unconstrained or redundant. A manipulability measure is introduced into the visual tracking objective function, providing an elegant and robust technique for deriving a control law that visually tracks objects while accounting for the configuration of the manipulator. Two different tracking strategies, one using a standard visual tracking strategy and the other using the newly proposed strategy, are experimentally compared on an actual hand/eye system. The experimental results demonstrate the effectiveness of the new method by showing that the tracking region of a manipulator tracking objects with planar motion can be greatly increased.