Grasping mechanisms must both create and subsequently hold grasps that permit safe and effective object manipulation. Traditional mechanisms address the different functional requirements of grasp creation and grasp holding using a single morphology, but have yet to achieve the simultaneous strength, gentleness, and versatility needed for many applications. We present “loop closure grasping,” a method of robotic grasping that addresses these different functional requirements through topological transformations between open-loop and closed-loop morphologies. Topologically open-loop mechanisms enable versatile grasp creation via unencumbered tip movement around the object, but lack the simultaneous strength and compliance needed for holding heavy yet fragile objects. Closed-loop mechanisms (e.g., slings) can bear heavy loads in a passive cradled state with effectively infinite bending compliance, but present challenges for grasp creation because the object must somehow enter the loop. Loop closure grasping circumvents the tradeoffs of single-morphology designs by transforming the mechanism’s topology from open-loop to closed-loop between the grasp creation and holding stages. We formalize these morphologies for grasping, formulate the loop closure grasping method, and present a design architecture and implementation using soft growing inflated beams, winches, and clamps. Finally, we demonstrate grasps involving historically challenging objects, environments, and configurations.
Paper: Loop closure grasping: Topological transformations enable strong, gentle, and versatile grasps
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Some hardware photos