The sponge makes the robot device a soft touch
Robotic sponge. Image credit: Tianqi Yue
This easy-to-build sponge distraction device could help rigid robots handle delicate items with care by emulating the nuanced touch, or variable stiffness, of humans.
The robots can hop, jump, and perform somersaults, but they are too clumsy to hold eggs easily. Variable stiffness devices are a potential solution for contact compliance in hard robots to reduce damage, or to increase the load capacity of soft robots.
This study, published at the 2023 IEEE International Conference on Robotics and Automation (ICRA), shows that variable stiffness can be achieved with a silicone sponge.
Main author Tian Qiyue from Bristol Department of Mathematical Engineering explains: “Stiffness, also known as softness, is important in contact scenarios.
“Robotic arms are too stiff that they can’t make a soft, human-like grip on soft objects, such as eggs.
“What makes humans different from robotic arms is that we have soft tissue covering the stiff bones, which acts as a natural mitigation mechanism.
“In this paper, we successfully developed software with variable stiffness, to be attached to the end of a robotic arm to make robot-object contact safe.”
Robot sponge in action. Video Credit: Tianqi Yue.
Silicone sponges are cheap and easy to make. It is a porous elastomer like cleaning sponge used in everyday tasks.
By squeezing the sponge, it stiffens so that it can be converted into a variable stiffness device.
The device can be used in industrial robots in a variety of scenarios including gripping jelly, eggs and other fragile substances. It can also be used in service robots to make human-robot interactions safer.
Mr Yue added: “We have successfully used sponges to create a cheap and agile yet effective device that can help the robot make gentle contact with objects. Great potential comes from low cost and light weight.
“We believe these silicon-sponge based variable stiffness devices will provide new solutions in industry and healthcare, for example, tunable stiffness requirements in robotic polishing and ultrasound imaging.”
The team will now work on getting the device to achieve variable stiffness in multiple directions, including rotation.
Paper: “Silicon-sponge-Based Rigidity Devices” by Tianqi Yue at the IEEE International Conference on Robotics and Automation (ICRA) 2023.
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