From the McGill pepper-mill carrier to the Kindai ATARIGI Carrier: A novel two limbs six-dof parallel robot with kinematic and actuation redundancy

Abstract

ATARIGI, a novel two limbs six-dof parallel robot, redundantly driven by eight actuators, is proposed in this paper. By the special arrangement of the mechanism, ATARIGI simultaneously has kinematic redundancy and actuation redundancy. Kinematic redundancy enables singularity avoidance and collision avoidance, that contribute to expanding the workspace. Actuation redundancy generates an internal force that eliminates backlash at the joints, thus increasing the positioning accuracy. Mechanical design of ATARIGI is extended from the McGill Pepper-Mill Carrier, a two limbs parallel Schönflies-motion generator. Inverse displacement analysis and Jacobian analysis of ATARIGI are derived. For utilization of the actuation redundancy and the kinematic redundancy, the null space of each Jacobian matrix is derived by means of computer algebra. The null spaces are simplified in closed form, which eases the control. Numerical tests demonstrate the collision-avoidance between limbs, while keeping the position and orientation of the gripper using the kinematic redundancy.