In context
Soft robotics had long struggled with slow speeds and low load capacities due to material limitations. By 2024, researchers were exploring bistable mechanisms—structures that snap between two stable states—to store and release energy, mimicking natural systems like Venus flytraps. This work aimed to apply that principle to legged soft robots, a key step toward practical applications in inspection and handling.
What was reported
Engineers at Nanjing University of Science and Technology designed a bistable soft actuator combining rigid links, a Pneu-Net soft actuator, and pre-tensioned springs. The springs store energy, and when driven by compressed air, the actuator rapidly snaps between two stable states, with jump times of 60–100 ms and end output forces 2–4 times higher than a conventional soft actuator under the same conditions.
Using this actuator as the robot's feet, they built a turtle-inspired quadruped with servo-controlled leg lifting. Two gaits—walking and rowing—were analyzed via simulation and tested on a prototype. The robot achieved an average creeping speed of 158.62 mm/s (1.11 body lengths/s) and a peak instantaneous speed of 396.62 mm/s (2.83 body lengths/s), while carrying a 400 g load—1.08 times its own mass.
The actuator's energy model, based on the Yeoh hyperelastic material model, was validated against experiments, showing good agreement. The design eliminates the need for continuous driving to maintain posture, reducing energy consumption.
Why it mattered
This work demonstrated that bistable mechanisms can significantly enhance the speed and load capacity of soft legged robots, addressing a critical bottleneck. The approach could enable soft robots to handle heavier payloads and move faster, expanding their use in industrial settings where gentle handling and adaptability are required.
“The prototype can creep 125 mm or turn 15° in one motion cycle, with an average creeping speed of 158.62 mm/s (1.11 times body length/s) and a peak instantaneous speed of 396.62 mm/s (2.83 times body length/s).”
Source: 《机器人》期刊 (robot.sia.cn) · Published 2024-05-08 · “一种基于双稳态驱动器的气动软体四足机器人”