SCAL for Pinch-Lifting: Complementary Rotational and Linear Prototypes for Environment-Adaptive Grasping

2025-10-26

AI Summary

To address the challenge of stable pinch grasping for thin, low-profile, or geometrically weak objects, this paper proposes an environment-adaptive grasping mechanism based on Slot-Constrained Adaptive Linkages (SCAL). Two complementary finger designs—SCAL-R (active enveloping) and SCAL-L (passive unfolding)—directly convert surface-following motion into lifting action while preserving fingertip orientation, enabling low-deformation, minimally sensed grasping. A geometry-aware closed-form fingertip force model is derived to support structural optimization and manipulation planning. The gripper, fabricated via 3D-printed PLA, integrates rotational-drive folding with linear-drive opening/closing, and incorporates sliding retention, ramp negotiation, and wide-range adaptability. Experiments demonstrate robust pinch-and-lift performance across diverse targets—including small parts, boxes, cans, and tape rolls—with minimal parameter tuning, validating the feasibility of highly reliable single-DOF-dominated grasping.

Technology Category

• Intelligent Robots: Manipulation
• Computer Vision: Low Level & Physics-based Vision
• Planning, Routing, and Scheduling: Replanning and Plan Repair

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

This paper presents environment-adaptive pinch-lifting built on a slot-constrained adaptive linkage (SCAL) and instantiated in two complementary fingers: SCAL-R, a rotational-drive design with an active fingertip that folds inward after contact to form an envelope, and SCAL-L, a linear-drive design that passively opens on contact to span wide or weak-feature objects. Both fingers convert surface following into an upward lifting branch while maintaining fingertip orientation, enabling thin or low-profile targets to be raised from supports with minimal sensing and control. Two-finger grippers are fabricated via PLA-based 3D printing. Experiments evaluate (i) contact-preserving sliding and pinch-lifting on tabletops, (ii) ramp negotiation followed by lift, and (iii) handling of bulky objects via active enveloping (SCAL-R) or contact-triggered passive opening (SCAL-L). Across dozens of trials on small parts, boxes, jars, and tape rolls, both designs achieve consistent grasps with limited tuning. A quasi-static analysis provides closed-form fingertip-force models for linear parallel pinching and two-point enveloping, offering geometry-aware guidance for design and operation. Overall, the results indicate complementary operating regimes and a practical path to robust, environment-adaptive grasping with simple actuation.

Problem

• Develops environment-adaptive pinch-lifting mechanism for robotic grasping
• Creates complementary rotational and linear finger designs for diverse objects
• Enables robust grasping with minimal sensing and simple actuation

Innovation

• Slot-constrained adaptive linkage enables environment-adaptive pinch-lifting
• Complementary rotational and linear fingers maintain orientation during lifting
• Geometry-aware force models guide robust grasping with simple actuation