Hoecken-D Hand: A Novel Robotic Hand for Linear Parallel Pinching and Self-Adaptive Grasping

TL;DR

The Hoecken-D Hand addresses the need for robust, adaptable grasping in unstructured environments using a compact, low-cost underactuated design. By marrying a modified Hoecken linkage for near-linear fingertip motion with a differential linkage that passively transitions to enveloping upon contact, the device achieves two complementary grasp modes under a potentially single linear actuator drive; kinematic and force analyses yield closed-form relations that illuminate how geometry and spring preload govern performance. A PLA 3D-printed prototype demonstrates a ~200 mm pinching span and reliable operation across diverse objects, with notable improvements in thin-object handling through passive enveloping and high success rates for mid-range objects. The work offers a practical, mechanically intelligent solution with clear pathways toward actuator synchronization, stiffness optimization, and formal benchmarking for unstructured manipulation tasks.

Abstract

This paper presents the Hoecken-D Hand, an underactuated robotic gripper that combines a modified Hoecken linkage with a differential spring mechanism to achieve both linear parallel pinching and a mid-stroke transition to adaptive envelope. The original Hoecken linkage is reconfigured by replacing one member with differential links, preserving straight-line guidance while enabling contact-triggered reconfiguration without additional actuators. A double-parallelogram arrangement maintains fingertip parallelism during conventional pinching, whereas the differential mechanism allows one finger to wrap inward upon encountering an obstacle, improving stability on irregular or thin objects. The mechanism can be driven by a single linear actuator, minimizing complexity and cost; in our prototype, each finger is driven by its own linear actuator for simplicity. We perform kinematic modeling and force analysis to characterize grasp performance, including simulated grasping forces and spring-opening behavior under varying geometric parameters. The design was prototyped using PLA-based 3D printing, achieving a linear pinching span of approximately 200 mm. Preliminary tests demonstrate reliable grasping in both modes across a wide range of object geometries, highlighting the Hoecken-D Hand as a compact, adaptable, and cost-effective solution for manipulation in unstructured environments.

Figures (13)

• Figure 1: 3D-printed prototype of the proposed Hoecken-D hand for linear pinching and self-adaptive grasping.
• Figure 2: Motion Analysis of the Hoecken Linkage.
• Figure 3: Horizontal parallel pinching motion.
• Figure 4: Enveloping grasp transition via differential linkage.
• Figure 5: Configuration of the Hoecken-D Hand.