SLIM: A Symmetric, Low-Inertia Manipulator for Constrained, Contact-Rich Spaces

Operation in constrained and cluttered spaces poses a challenge for robotic manipulators, in part due to their bulky link geometry and kinematic limitations in comparison to human hands and arms. To address these limitations, we introduce SLIM, a custom end-effector consisting of a bidirectional hand and an integrated 2-axis wrist. With an opposing thumb that tucks alongside the palm and fingers that bend in both directions, the hand is shaped like an articulated paddle for reaching through gaps and maneuvering in clutter. Series elastic actuation decouples finger inertia from motor inertia, enabling use of small, highly-geared motors for forceful grasps while maintaining a low effective end-point mass. The thumb is mounted on a prismatic axis that adjusts grasp width for large or small objects. We illustrate advantages of the design over conventional solutions with a computed increase in grasp acquisition region, decrease in swept volume when reorienting objects, and reduced end-point mass. SLIM's thin form factor enables faster and more successful teleoperated task completion in constrained environments compared to a conventional parallel-jaw gripper. Additionally, its bidirectional fingers allow demonstrators to complete a sequential picking task more efficiently than with an anthropomorphic hand.