In context
In early 2025, research on bistable mechanisms in robotics was gaining attention for their rapid response and energy storage capabilities, yet most existing bistable grippers were limited to a single operational mode. This constrained their flexibility in diverse industrial tasks, prompting exploration into multimodal designs that could adapt to various objects and functions.
What was reported
Researchers from Nanjing University of Information Science and Technology and Harbin Institute of Technology proposed a rigid-flexible coupling multimodal gripper based on an adjustable bistable mechanism. The gripper features an elastic band gripping surface that passively conforms to object shapes, supported by a finger skeleton of rigid links forming the bistable mechanism, which stores energy via elastic rings. An active cord with a clutch allows energy regulation of the elastic band.
By coordinating the bistable mechanism and the active cord, the gripper achieves three operational modes: triggered jump closure, controlled grasping, and object ejection. An analytical model of the trigger force was developed, and design parameters such as stiffness and free length of elastic elements were optimized through simulation and experiments.
Prototype tests showed the trigger force could be adjusted from 0.1 to 1.1 N when switching from initial to triggered state. In ejection mode, a cylinder of 30 mm diameter and 10 g mass was horizontally ejected up to 3.35 m. The adjustable range of trigger force was 0.12–0.98 N via linkage adjustment and 0.28–0.98 N via rope length adjustment, with trigger times ranging from 2–10 s and 1–10 s, respectively.
Why it mattered
This work addresses the limitation of single-mode bistable grippers by introducing adjustable energy barriers, enabling versatile operations such as rapid grasping and ejection. The multimodal capability could enhance flexibility in automated handling systems, allowing a single gripper to perform tasks that previously required multiple end-effectors, potentially improving efficiency and reducing changeover time in manufacturing lines.
By coordinating the control of the bistable mechanism and the active rope to regulate the energy of the gripper, different operating modes can be implemented, such as triggered jump closure, controlled grasping and object ejection.
Source: 《机器人》期刊 (robot.sia.cn) · Published 2025-01-15 · “基于可调双稳态机构的刚柔耦合多模态抓手”