The new heavyweight champions of robotics will be lighter, smaller, and disconnected from a power source.
Researchers at Arizona State University are developing bioinspired robotic “muscles” that will enable robots to operate in boiling water, survive abrasive surfaces, bypass impediments that keep their motorized counterparts benched, and still lift up to 100 times their own weight.
“Essentially, we developed a novel artificial muscle that mimics real muscles,” Eric Weissman said. “While bioinspired muscles previously existed, we have made them more versatile, more lightweight and more powerful.”
Today’s quadruped robots, for example, are significantly limited in mobility because they are usually motor-based and tend to be very heavy and less flexible.
Weissman’s helical anisotropically reinforced polymer (HARP) actuators, on the other hand, mimic natural muscle contraction and expansion. These actuators are flexible, very lightweight and quiet for use in soft robotics — providing muscle that can lift far more proportionally than electrical-driven counterparts of the same weight.
Here is an exclusive Tech Briefs interview, edited for length and clarity, with Lead Author Weissman, Doctoral Student, ASU’s Robotic Actuators and Dynamics Lab, and Lab Director Jiefeng Sun, Co-Author, Assistant Professor at the School for Engineering of Matter, Transport, and Energy in the Ira A. Fulton Schools of Engineering at ASU.
Tech Briefs: What was the biggest technical challenge you faced while developing these heart actuators?
Weissman: The biggest technical challenge? I would say manufacturing reliability, just because these muscles had existed before, not these exact ones, but similar muscles had previously existed. But there wasn’t really good documentation on producing these types of muscles reliably and getting them to work reliably. So, we spent a lot of time iterating on the nitty-gritty stuff that doesn’t make it into the papers — e.g., how to fabricate them, how to fabricate them quickly, how to connect them to pressure sources, and for that to be a reliable connection that we can use in robotics.
Tech Briefs: Can you please explain in simple terms how they work?
Weissman: Yeah, so explaining it without visual diagrams is kind of challenging. Essentially, we take a tube and we put a nylon cord through the center of it, and this nylon cord kind of acts as the backbone. When we coil the muscles later on, this core is going to hold the shape of that coil.
Then, to actually get them to actuate, what we do is on the outside of that tube, we wrap another helical coil. That one is also typically made out of nylon. And so how do we explain this? As you can imagine, you take a tube and you wrap a coil on the outside. If you were to inflate that tube, the only thing that that coil can do is untwist, right? So, by inflating it, we have to untwist this coil, which causes the entire tube to untwist.
When you take that tube, that untwist, and then you coil that again into a spring-like shape, into a helical shape, that untwist gets converted into linear contraction. I know that was not necessarily in simple terms.
Tech Briefs: Do you have any set plans for further research, work, etc.? If not, what are your next steps?
Weissman: As far as the muscles go, I think we want to continue to improve their reliability and manufacturability. Additionally, we discussed looking at using hydraulics to actuate the muscles. Very briefly, in the paper that we published, we discussed using hydraulics and we showed a couple of examples of using hydraulics. We think that further exploration down that line will increase the force output of these muscles pretty significantly. So, I know we want to look at that.
Sun: I guess the vision is to further increase its force capability. It's better than the state-of-the-art [technology], but still far from as good as biological muscles. For example, it needs more force. We currently can only build a small-sized automated robot, and that robot — even though it's a first of its kind — is still not able to carry heavy loads and run very fast.
Our vision is that we increase what we call power density — basically making it stronger and gaining more muscle strength. Then, with the compact size, we can make the robot more agile. For example, some people, they look slim or compact, but they are really strong, right? Their muscle is, I would say, dense or maybe more powerful.
Tech Briefs: Do you have any advice for researchers aiming to bring their ideas to fruition?
Weissman: Yes, two main points. The first one is a quote from Thomas Edison, who said, “Invention is 10 percent inspiration, 90 percent perspiration. Meaning there's just a lot of hard work; research is never a linear path. You never really have a good idea of what timelines are going to look like. It's a lot about sticking with an idea and pushing through a lot of the small technical challenges that are going to take a long time. That's the first piece of advice.
The second one is fail quickly because there's no linear timeline. You're going to fail. You're going to mess up. You're going to try ideas that just don't work because no one's tried these before. So, if you can fail quickly, then you can move on to the next idea quicker.
