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Under-actuated Robotic Gripper with Multiple Grasping Modes Inspired by Human Finger

Jihao Li, Tingbo Liao, Hassen Nigatu, Haotian Guo, Guodong Lu, Huixu Dong

TL;DR

Under-actuated grippers offer simple, low-cost manipulation but suffer from limited versatility. This work introduces a three-finger gripper with retractable phalanges driven by a single motor, enabling $5$ grasping modes via a reconfiguration mechanism that uses worm-gear and rack transmissions. The main contributions are the novel retractable-contact mechanism for adaptive grasping, the compact single-motor drive producing both grasping and reconfiguration, and experimental validation across slender, thin, and large objects. The design expands the practical reach of under-actuated grippers for diverse manipulation tasks while reducing actuation complexity.

Abstract

Under-actuated robot grippers as a pervasive tool of robots have become a considerable research focus. Despite their simplicity of mechanical design and control strategy, they suffer from poor versatility and weak adaptability, making widespread applications limited. To better relieve relevant research gaps, we present a novel 3-finger linkage-based gripper that realizes retractable and reconfigurable multi-mode grasps driven by a single motor. Firstly, inspired by the changes that occurred in the contact surface with a human finger moving, we artfully design a slider-slide rail mechanism as the phalanx to achieve retraction of each finger, allowing for better performance in the enveloping grasping mode. Secondly, a reconfigurable structure is constructed to broaden the grasping range of objects' dimensions for the proposed gripper. By adjusting the configuration and gesture of each finger, the gripper can achieve five grasping modes. Thirdly, the proposed gripper is just actuated by a single motor, yet it can be capable of grasping and reconfiguring simultaneously. Finally, various experiments on grasps of slender, thin, and large-volume objects are implemented to evaluate the performance of the proposed gripper in practical scenarios, which demonstrates the excellent grasping capabilities of the gripper.

Under-actuated Robotic Gripper with Multiple Grasping Modes Inspired by Human Finger

TL;DR

Under-actuated grippers offer simple, low-cost manipulation but suffer from limited versatility. This work introduces a three-finger gripper with retractable phalanges driven by a single motor, enabling grasping modes via a reconfiguration mechanism that uses worm-gear and rack transmissions. The main contributions are the novel retractable-contact mechanism for adaptive grasping, the compact single-motor drive producing both grasping and reconfiguration, and experimental validation across slender, thin, and large objects. The design expands the practical reach of under-actuated grippers for diverse manipulation tasks while reducing actuation complexity.

Abstract

Under-actuated robot grippers as a pervasive tool of robots have become a considerable research focus. Despite their simplicity of mechanical design and control strategy, they suffer from poor versatility and weak adaptability, making widespread applications limited. To better relieve relevant research gaps, we present a novel 3-finger linkage-based gripper that realizes retractable and reconfigurable multi-mode grasps driven by a single motor. Firstly, inspired by the changes that occurred in the contact surface with a human finger moving, we artfully design a slider-slide rail mechanism as the phalanx to achieve retraction of each finger, allowing for better performance in the enveloping grasping mode. Secondly, a reconfigurable structure is constructed to broaden the grasping range of objects' dimensions for the proposed gripper. By adjusting the configuration and gesture of each finger, the gripper can achieve five grasping modes. Thirdly, the proposed gripper is just actuated by a single motor, yet it can be capable of grasping and reconfiguring simultaneously. Finally, various experiments on grasps of slender, thin, and large-volume objects are implemented to evaluate the performance of the proposed gripper in practical scenarios, which demonstrates the excellent grasping capabilities of the gripper.
Paper Structure (10 sections, 7 equations, 12 figures, 4 tables)

This paper contains 10 sections, 7 equations, 12 figures, 4 tables.

Table of Contents

  1. INTRODUCTION
  2. METHODOLOGY
  3. Kinematic Analysis of the Under-actuated Finger
  4. Design of the Under-actuated Finger
  5. Design of the Reconfiguration Mechanism
  6. Description of Multi-grasping Mode
  7. EXPERIMENTS
  8. Grasps at Different Grasping Modes
  9. Grasp Objects with Regular Shapes and Daily Necessities
  10. CONCLUSIONS

Figures (12)

  • Figure 1: The prototype of presented gripper (A, B), grasp slender and thin objects through the human finger (C) and the presented gripper (D).
  • Figure 2: A general three-phalanx finger consists of the metacarpophalangeal (MCP) joint, proximal interphalangeal (PIP) joint and distal interphalangeal (DIP) joint (A); A full-actuated three-phalanx finger (B); An under-actuated three-phalanx finger (C); The prototype of the proposed three-phalanx finger in this work (D). The parallel grasping mode (D-1) and the enveloping grasping mode (D-2/D-3). The thick dotted line represents the driven linkage, and the dotted line indicates that the linkage is retractable.
  • Figure 3: Kinematics model of the proximal phalanx and middle phalanx.
  • Figure 4: Initial state (A); Parallel grasp (B) and Enveloping grasp (C, D); Maximum flexion state (E); The retractable ability of the distal phalanx (F).
  • Figure 5: Part connected to the slider (A-1). Part connected to the slide rail (A-2). Retractable linkage at its original length (B-1). Retractable linkage after being compressed (B-2).
  • ...and 7 more figures