In context
Soft robots offer flexibility but often lack load capacity. Variable-stiffness techniques, especially jamming-based methods, have become key to enhancing their rigidity. By early 2025, researchers were combining different jamming mechanisms to overcome the limitations of single-mode approaches.
What was reported
Researchers at Anhui University of Technology designed a soft driver combining pneumatic network actuation with a fiber-particle jamming structure. The driver features three 75° sector air chambers wrapped with fiber to limit expansion, and a jamming layer with an outer silicone cavity, middle fiber layer, and inner particle chamber. Vacuum pressure compresses the silicone, which presses fibers onto particles, increasing friction and stiffness.
A theoretical model based on Hertzian contact and virtual work predicted stiffness as a function of pressure, fiber radius, and particle radius. Experiments showed a maximum stiffness of 0.1825 N/mm at -80 kPa with fiber radius 1.25 mm and particle radius 0.3 mm, a stiffness ratio of 2.08 versus no vacuum.
Comparative tests showed the hybrid structure improved variable-stiffness performance by 88.05% over pure fiber jamming and 26.73% over pure particle jamming. Stability tests, measured by relative standard deviation over 50 cycles, showed a 67.43% improvement over pure particle mode.
“Compared with the particle jamming and fiber jamming based soft drivers, the stiffness, variable-stiffness performance and stability of the fiber-particle jamming based variable-stiffness soft driver are all highly improved.”
Why it mattered
This hybrid jamming approach addresses the trade-off between stiffness range and stability, offering a more robust solution for soft grippers and manipulators in industrial settings where both adaptability and load capacity are needed.
Source: 《机器人》期刊 (robot.sia.cn) · Published 2025-03-15 · “基于纤维－颗粒干扰的变刚度软体驱动器的设计与实验”