Hybrid Rigid-Soft Robotic Gripper with Shape Adaptation, Uniform Force Distribution, and Self-Locking Capabilities

2026-07-16

AI Summary

This study addresses the longstanding challenge in agricultural robotics wherein conventional grippers struggle to simultaneously achieve compliance, uniform contact pressure, high payload capacity, and energy efficiency. To overcome these limitations, this work proposes a hybrid soft-rigid gripper that integrates low-cost membrane-based pneumatic soft actuators with a 3D-printed dual ratchet-and-pawl mechanism. By asymmetrically assembling the dual ratchets, the design enhances angular resolution during joint locking and, for the first time in soft grippers, unifies high-load capability, minimal energy consumption, and damage-free surface interaction. Combining pneumatic actuation with a passive mechanical self-locking mechanism, the gripper achieves a maximum payload of 4200 g, exhibits a contact force variation ratio of only 1.75–35.29%—substantially lower than the 56.77–66.44% observed in rigid counterparts—and reduces energy consumption per grasp to 42.6 J, representing a 50.05% improvement in efficiency.

Abstract

Conventional robotic grippers face a significant challenge in agricultural automation: the trade-off between compliant, adaptive grasping, pressure balancing among all joints, and high load capacity, often at the cost of high energy consumption. This paper presents a novel hybrid rigid-soft gripper that integrated low-cost, membrane-based pneumatic actuators with 3D-printed dual ratchet-pawl mechanisms to simultaneously achieve shape adaptation, uniform force distribution, and energy-free self-locking. The dual-ratchet structure assembled in an offset configuration significantly increased the angular resolution of the joint locking mechanism. Key experimental results demonstrated the gripper's superior performance: a remarkable maximum load capacity of 4200 g, far exceeding that of conventional soft grippers (45-210 g); more uniform force distribution across object sizes (1.75-35.29% difference ratio) compared to a rigid gripper (56.77-66.44%), with peak contact forces remaining below surface damage thresholds; and a 50.05% reduction in total energy consumption to 42.6 J per grasp cycle, achieved by eliminating the need for continuous pneumatic pressure through the self-locking mechanism, compared to 85.28 J for a conventional soft gripper. The combination of additive manufacturing for ratchets and commercially available materials for pneumatic chambers ensured a low-cost and easily fabricated design. These findings validated that the proposed gripper successfully bridged the gap between soft compliance and rigid reliability, offering a robust and efficient solution for scalable agricultural harvesting and manipulation tasks.

Problem

• robotic gripper
• shape adaptation
• force distribution
• energy consumption
• agricultural automation

Innovation

• hybrid rigid-soft gripper
• shape adaptation
• self-locking mechanism
• uniform force distribution
• energy-efficient actuation