M Gripper: Extending the Dexterity of a Simple, Underactuated Gripper

In the development of robotic hands, researchers have sought to increase inherent functionality without incurring greater complexity and cost. In this paper, we extend the manipulation capabilities of a simple gripper through a novel, underactuated design that produces several distinctive modes of operation. The proposed asymmetric hand design, the Multi-Modal (M) Gripper, consists of a modular thumb with varying degrees of passive compliance and a dexterous, tendon-driven forefinger that can produce either underactuated or fully-actuated behaviors. With only two actuators and basic open-loop control, the hand is able to adaptively grasp objects of varying geometries, pinch-grasp smaller items, and perform some degree of in-hand manipulation via rolling and controlled sliding. We also detail the properties of this hand morphology that make it well-suited for future work in medical applications, haptic exploration, and studies on controlled stick-slip manipulation tasks.