Visual servoing of a redundant manipulator using shape moments

This paper is concerned with real-time visual servoing of a redundant manipulator using shape moments. The forward kinematics of the PowerCube manipulator with seven degrees of freedom (DOF) has been derived. The visual servoing is carried out with camera placed at the end-effector which is also known as eye-in-hand configuration. Image plane features such as centroid, area and orientation are considered to derive the image interaction matrix (image Jacobian) that maps image plane pixel velocities to the end-effector Cartesian velocities. The proposed image based visual servoing (IBVS) method uses the moments invariant of an elliptical object and can position the end-effector to grasp the object with z-axis orientation of the end of effector. Actual experiments have been carried out on the PowerCube manipulator from Amtec Robotics to show that kinematic and image Jacobians derived are accurate.