Why Robots That Bend Are Better

• These are soft robots. Their structural components are built, not out of metal or wood, but flexible materials like plastic tubing. But how do they work? And why would you want a soft robot in the first place? This video was sponsored by KiwiCo. Check out their robots at the end of the show.

(machine blowing)

So I came up to Stanford to meet Zach Hammond and his soft robot.

Zach Hammond: How's it going?

Interviewer: All right, you want to tip it? So is the idea that the robot could walk this way?

Zach Hammond: Totally, yeah. So you can kind of chain these rolls together to kind of roll around in any environment. They call this punctuated rolling locomotion. Wherein it's kind of stuck on a face until it tips over and now it's on a new face and it can then continue to move its center of gravity. Once that center of gravity exits the support polygon or the base, then it tips over one of the edges of the face.

• This is a different soft robot made out of flexible tubing. It was designed to mimic the way a turtle walks, where diagonally opposite legs move together. It's powered entirely by compressed air and perhaps most impressive, it requires no electronics. All of the circuitry is pneumatic and this means the robot can be used in places like mines, where electronics could spark explosions, or in the strong magnetic fields around MRI machines. But why would you want a soft robot in the first place?

Zach Hammond: One of the things that I like to do is just to take the robot and kind of like beat it up a little bit and show how it's compliant and compressive.

Interviewer: Nope, because they're safer.

Zach Hammond: If you'd like to take a whack at it, you know, feel free.

Interviewer: But I don't think this is your work, I don't want to break it, obviously.

Zach Hammond: No, feel free, go for it.

• For operation around humans, there's not much damage a soft robot can do to you.

Interviewer: I can stand on these?

Zach Hammond: Yep.

Interviewer: This is a pretty crazy compliant robot.

Zach Hammond: Because the fundamental structure of this robot is compliant, there's only some maximum force that it could ever exert on me. So it's inherently safe to be operating around people.

Interviewer: Could we make it fall and have me be inside it?

Zach Hammond: Yeah. Yeah, we could do that for sure. Just watch your head.

Interviewer: Yep, if I go over here.

Zach Hammond: If you're there, yeah, we can do that.

Interviewer: All right, let's try it. Here it comes. Well, that's not bad at all. Is it?

Zach Hammond: I can try another shape. That's supposed to open up one of the faces, so you can jump out of it quickly.

Interviewer: Okay.

Zach Hammond: I haven't tested it in a little while, so...

Interviewer: Sure.

Zach Hammond: I don't know how it's gonna go, but let's try this. There you go that's the face right there to your right and you can exit the trust from that face.

Interviewer: Boom.

Zach Hammond: Perfect.

Interviewer: Just that easy. Did you build this by yourself?

Zach Hammond: Me and one other grad student built this entire thing ourselves, basically.

Interviewer: And how long did it take?

Zach Hammond: We did it in about a month, I want to say, like actually constructing everything.

Interviewer: And was it tricky? I mean, were you sewing that stuff?

Zach Hammond: Yep, we sewed this all ourselves.

• The main structural members of this robot are fabric tubes inflated with air.

Zach Hammond: Yeah, so these red tubes are a nylon fabric and then internally, there is a polyethylene tube that provides the air tightness.

• The tubes are inflated to about six PSI above atmospheric. So it's almost one and a half atmospheres. Each tube passes through pairs of rollers connected to a motor. The rollers pinch the tube, so it bends kind of like a pinched straw.

Zach Hammond: Add the rods and then we have this like high friction material wrapped around the rods. And then that coupled with the fact that we have this pressurized tube that's kind of pushing the membrane of the tube into the rollers, prevents us from slipping.

• By driving the motor, it changes the length of the tubes.

Zach Hammond: Kind of like when a clown creates a twist in a balloon and then folds that balloon into a balloon animal. The difference between what the clown does and what we do is that there's some passage of air between adjacent segments of the tube. So that as the robot drives around, we're not pressurizing the segments of the tube.

• This robot is made of four inflated tubes, each one connected to a pair of motors, forming triangular sides.

Zach Hammond: We also think that they kind of look like sausage links when put together, which is why we've named these robots after different sausages. So this one's called Polish, that one over there is Chorizo, There's a Linguica and a kielbasa over there somewhere.

Interviewer: So what shape is the overall thing? It's an octahedron?

Zach Hammond: Yeah, we call it an octahedron because if you drew lines between these kind of kinematic joints here, it would create an octahedral shape.

• Driving the motors together allows the robot to dramatically change shape. It can get very tall or short and squat. But since the tubes themselves don't change in length, the overall perimeter of the robot, the length of all the edges combined doesn't change. So the robot is considered isoparametric.

Interviewer: How do you feel when you watch those Boston Dynamics videos?

Zach Hammond: Oh, I love those videos, they're so cool.

Interviewer: The Boston Dynamics robots are kind of terrifying.

Zach Hammond: Mm-hmm.

Interviewer: I guess, and the idea with soft robots, it's to like convince people that robots are good and soft and kind, and friendly and fake?

Zach Hammond: That's definitely true, yeah. There are some things that you can do to rigid systems to make them feel like compliant systems based on how you're controlling the motors. But yeah, they're definitely, you know, heavy, expensive and can be dangerous if they're not used correctly.

• The hard robots we're used to are strong and precise. Their actions are accurate and repeatable, but they are also heavy and they can't really change their volume as dramatically, but this robot is still capable of carrying a heavy load.

Zach Hammond: So I have a GUI in MATLAB.

Interviewer: Oh nice.

Zach Hammond: That enables me to just put in the positions that I want the robots to move in inches and then send them out. There's another other functionality of some like stored configurations to send to the robots.

• Soft robots also have the advantage of shape changing. They can become tall to go over obstacles or short to fit under obstructions.

Zach Hammond: So if there is some rock that it didn't see or that it wanted to roll over. It could simply do that and the compliance of the tubes would simply just bend around that disturbance.

Interviewer: Do you imagine robots like this doing work in space?

Zach Hammond: Oh yeah, definitely.

• So one of the nice things about these types of structures is that they can shrink down their volume very drastically. And because volume on rockets is such an expensive premium, being able to have a robot that can pack down small for transport is very valuable. So NASA was at one point looking into trust robots for exactly that reason. And they've contacted us since we've made this robot to explore different ideas for space exploration projects.

• So one of the things that they're thinking about doing is deploying robots underneath a sheet of ice. So they're gonna drill through this sheet of ice and then deposit a robot through what is a kind of a small diameter hole. And so if you can have a robot that can change its volume very drastically or be disassembled and then reassembled to form like a much larger structure. Then you can have large robots that are able to fit through these tight spaces and be deployed in kind of difficult to access areas.

Interviewer: Is this a little bit like an octopus? Is that how you could think of it?

Zach Hammond: There is some connection there because they use their shape-changing ability and their compliance to squeeze through tight passageways, and then also to wrap their body around objects. So, for example, they can open jars with their tentacles, and one of the things that we want to use this robot for is grasping and manipulating objects.

Interviewer: So this robot is even capable of picking objects up off the ground.

Zach Hammond: We'll try that and see if we can grab it. Because of the compliance of the tubes, it has a natural ability to grasp and manipulate objects because as it does so, the tubes bend ever so slightly, which increases the contact area and distributes evenly the forces that are exerted on the object.

Interviewer: So, I mean, is the biggest risk if it pops?

Zach Hammond: Yeah, that's a big risk. I mean, you obviously need the compressed air for your structure and so if you have a leak. Oh. Then you don't have a robot, right?

Interviewer: It's a pretty big drawback of soft robots.

Zach Hammond: You know, some things that you could do to mitigate that would be to have onboard a small compressor, which isn't there to provide power to the robot, but would help you maintain pressure if there were any small leaks.

Interviewer: When you tell someone you're working on a robot and they see this, does it defy expectations?

Zach Hammond: Totally. They have no idea what it is I'm talking about until I show them like a video or a picture. I think most people's conception of soft robots was really expanded by the movie Big Hero 6. And I think they did a great job in kind of showcasing what a soft robot can do and why they're useful, and kind of just popularizing the notion. It's really great to have compliance built into any mechanical system, especially as we want robots to work closer and closer with humans. So I think we'll definitely see more soft robots in the future.

• Hey, this video was sponsored by KiwiCo and since I was up in the Bay Area, I got to visit KiwiCo headquarters which was mostly empty because COVID, but I met with a few designers who make the awesome projects that come in KiwiCo crates.

Zach Hammond: There you go.

Interviewer: Oh boy.

• And I'm not gonna lie, it kind of seems like the best job. I was in awe of some of the ideas they have brought to life.

Zach Hammond: Dude, that's cool. Look at that.

• You know, KiwiCo offers eight subscription lines for kids of all ages and everything you need comes right in the box, so that means no running out to the store. Each crate not only gets kids making and having fun, but also learning about STEAM concepts. KiwiCo believes that kids are often better at thinking big and as a father of three kids, I know that to be true. If I can get them learning little things every day that can all add up to a big perspective change in how they see the world.

• So for viewers of this video, KiwiCo is offering 50% off your first month of any crate. Just go to kiwico.com/veritasium50 I will put that link down in the description. So I want to thank KiwiCo for sponsoring Veritasium and I want to thank you for watching.