Dexterous Three-Finger Gripper based on Offset Trimmed Helicoids (OTHs)

2025-03-01

AI Summary

Traditional soft grippers suffer from high actuation forces, limited workspace, non-adjustable curvature, and poor dynamic manipulation capability when handling highly deformable rigid-elastic materials (e.g., TPU). To address these limitations, this work proposes a novel three-finger dexterous gripper based on an offset truncated helicoid (OTH) geometry. Its key innovation is a tunable deformation center design integrated with a dual-helical tendon-driven mechanism, enabling decoupled in-plane bending and out-of-plane lateral motion, continuous curvature variation along the finger length, and six-degree-of-freedom dexterous manipulation. Tip stiffness is customizable via mounting position selection. Leveraging TPU-based elastic energy storage and compliance-aware modeling optimization, the gripper achieves high-speed dynamic screwing at 60 r/s within 15 ms and accomplishes complex in-hand tasks such as precise rod spinning—significantly enhancing adaptability to diverse objects and dynamic task performance.

Technology Category

• Intelligent Robots: Manipulation
• Computer Vision: Low Level & Physics-based Vision
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

This study presents an innovative offset-trimmed helicoids (OTH) structure, featuring a tunable deformation center that emulates the flexibility of human fingers. This design significantly reduces the actuation force needed for larger elastic deformations, particularly when dealing with harder materials like thermoplastic polyurethane (TPU). The incorporation of two helically routed tendons within the finger enables both in-plane bending and lateral out-of-plane transitions, effectively expanding its workspace and allowing for variable curvature along its length. Compliance analysis indicates that the compliance at the fingertip can be fine-tuned by adjusting the mounting placement of the fingers. This customization enhances the gripper's adaptability to a diverse range of objects. By leveraging TPU's substantial elastic energy storage capacity, the gripper is capable of dynamically rotating objects at high speeds, achieving approximately 60 in just 15 milliseconds. The three-finger gripper, with its high dexterity across six degrees of freedom, has demonstrated the capability to successfully perform intricate tasks. One such example is the adept spinning of a rod within the gripper's grasp.

Problem

• Develops a dexterous three-finger gripper with tunable deformation center.
• Reduces actuation force for elastic deformations with harder materials.
• Enables high-speed dynamic rotation and intricate task performance.

Innovation

• Offset-trimmed helicoids structure for finger flexibility
• Helically routed tendons enable complex finger movements
• TPU material allows high-speed dynamic object rotation