Soft, pneumatic actuators may not be an expression that comes up in everyday conversation, but you have probably benefited from their usefulness. The devices use compressed air to power movement, and with sensing capabilities, they have proven to be a critical backbone in a variety of applications, such as assistive wearables, robotics and rehabilitation technologies.
But there’s a bit of a bottleneck in making the small dynamic devices that have advantages like high response rates and power-to-input ratios. They require a manual design and manufacturing pipeline, which translates into a lot of trial and error to actually test and see if the designs will work.
Scientists at MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL) devised a scalable pipeline to computationally design and fabricate soft pneumatic actuators called “PneuAct”.
PneuAct uses a machine knitting process, not unlike knitting with your grandma’s plastic needles, but this machine works autonomously. A human designer simply specifies the stitch and sensor design patterns in software to program how the actuator will move, and it can then be simulated before printing. The fabric piece is fabricated by the knitting machine, which can be attached to a cheap, ready-made silicone rubber tube to complete the actuator.
The knitted actuator integrates conductive yarn for sensing, allowing the actuators to “feel” what they are touching. The team made several prototypes of a supportive glove, a soft hand, an interactive robot and a pneumatic quadruped. Their prototypes, which resemble banana fingers due to the use of yellow fabric, include an auxiliary glove, a soft hand, an interactive robot and a pneumatic quadrupedal robot.
While there has been a lot of movement over the years in the hardware development of soft pneumatic actuators — a 2019 collaborative robot prototype used such actuators to reproduce human grip in its hands — the design tools have not improved as quickly. Old processes mostly used polymers and casting, but the scientists used a combination of elastic and tactile stitches (with conductive yarn) that allows programming the bending of the actuators when inflated, and the ability to capture real-world feedback. to take.
For example, the team used the actuators to build a robot that sensed when specifically touched by human hands and responded to that touch.
The team’s glove can be worn by a human to complement the movement of the finger muscles, minimizing the amount of muscle activity required to perform tasks and movements. This can have a lot of potential for people with injuries, limited mobility or other trauma to the fingers. The method can also be used to create an exoskeleton (portable robotic units controlled by a computer that complement human movement and restore locomotion and movement); for example, the authors created a sleeve that can help wearers bend their elbow, knee, or other body parts.
“The use of digital machine knitting, a common manufacturing method in today’s textile industry, allows for ‘printing’ a design in one go, making it much more scalable,” said Yiyue Luo, MIT CSAIL Ph.D. student and lead author of a new paper on the research. “Soft pneumatic actuators are intrinsically compliant and flexible, and when combined with intelligent materials they have become the backbone of many robots and assistive technologies – and rapid fabrication with our design tool can hopefully increase convenience and ubiquity.”
One type of sensing the team used was ‘resistive pressure sensing’, where the actuator ‘directs’ pressure. When manufacturing a robot gripper, for example when it grips something, the pressure sensor will detect how much force is applied to the object and then will try to see if the gripper is successful or not. The other type is ‘capacitive sensing’, where the sensor receives some information about the materials the actuator comes into contact with.
While the actuator is sturdy – no wires were broken in any of their experiments, one limitation of the system is that they were limited to tubular actuators because it’s very easy to buy off the shelf. A logical next step is to explore actuators with different shapes, to avoid being limited by that one structure. Another extension the scientists will explore is the extension of the tool with a task-driven, optimization-based design, where users can specify target poses and optimal stitch patterns that can be synthesized automatically.
“Our software tool is fast and easy to use, accurately previewing users’ designs so they can virtually iterate quickly while only having to fabricate once. But this process still requires some trial and error from people. Can a computer reason on how to physically program textiles into actuators to enable rich, sensor-driven behavior? That’s the next frontier,” said Andrew Spielberg, a postdoctoral fellow in Materials Science and Mechanical Engineering at Harvard University, another author of the paper.
The paper was published through the CHI Conference on Human Factors in Computing Systems†
Technology accelerates thermal activation for soft robotics
Yiyue Luo et al, Digital fabrication of pneumatic actuators with integrated sensing by machine knitting, CHI Conference on Human Factors in Computing Systems (2022). DOI: 10.1145/3491102.3517577
Provided by MIT Computer Science & Artificial Intelligence Lab
Quote: Soft supportive robot wearables get a boost from the rapid design tool (2022, May 3), retrieved May 3, 2022 from https://techxplore.com/news/2022-05-soft-robotic-wearables-boost-rapid.html
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