Stretch 3 Brings Us Closer to Realistic Home Robots

A lot has happened in robotics over the last year. Everyone is wondering how AI will transform robotics, and everyone else is wondering whether humanoids are going to blow it or not, and the rest of us are busy trying not to get completely run over as things shake out however they’re going to shake out.

Meanwhile, over at Hello Robot, they’ve been focused on making their Stretch robot do useful things while also being affordable and reliable and affordable and expandable and affordable and community-friendly and affordable. Which are some really hard and important problems that can sometimes get overwhelmed by flashier things.

Today, Hello Robot is announcing Stretch 3, which provides a suite of upgrades to what they (quite accurately) call “the world’s only lightweight, capable, developer-friendly mobile manipulator.” And impressively, they’ve managed to do it without forgetting about that whole “affordable” part.

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Hello Robot

Stretch 3 looks about the same as the previous versions, but there are important upgrades that are worth highlighting. The most impactful: Stretch 3 now comes with the dexterous wrist kit that used to be an add-on, and it now also includes an Intel Realsense D405 camera mounted right behind the gripper, which is a huge help for both autonomy and remote teleoperation—a useful new feature shipping with Stretch 3 that’s based on research out of Maya Cakmak’s lab at the University of Washington, in Seattle. This is an example of turning innovation from the community of Stretch users into product features, a product-development approach that seems to be working well for Hello Robot.

“We’ve really been learning from our community,” says Hello Robot cofounder and CEO Aaron Edsinger. “In the past year, we’ve seen a real uptick in publications, and it feels like we’re getting to this critical-mass moment with Stretch. So with Stretch 3, it’s about implementing features that our community has been asking us for.”

“When we launched, we didn’t have a dexterous wrist at the end as standard, because we were trying to start with truly the minimum viable product,” says Hello Robot cofounder and CTO Charlie Kemp. “And what we found is that almost every order was adding the dexterous wrist, and by actually having it come in standard, we’ve been able to devote more attention to it and make it a much more robust and capable system.”

Kemp says that having Stretch do everything right out of the box (with Hello Robot support) makes a big difference for their research customers. “Making it easier for people to try things—we’ve learned to really value that, because the more steps that people have to go through to experience it, the less likely they are to build on it.” In a research context, this is important because what you’re really talking about is time: The more time people spend just trying to make the robot function, the less time they’ll spend getting the robot to do useful things.

Hello Robot

At this point, you may be thinking of Stretch as a research platform. Or you may be thinking of Stretch as a robot for people with disabilities, if you read our November 2023 cover story about Stretch and Henry and Jane Evans. And the robot is definitely both of those things. But Hello Robot stresses that these specific markets are not their end goal—they see Stretch as a generalist mobile manipulator with a future in the home, as suggested by this Stretch 3 promo video:

Hello Robot

Dishes, laundry, bubble cannons: All of these are critical to the functionality of any normal household. “Stretch is an inclusive robot,” says Kemp. “It’s not just for older adults or people with disabilities. We want a robot that can be beneficial for everyone. Our vision, and what we believe will really happen, whether it’s us or someone else, is that there is going to be a versatile, general-purpose home robot. Right now, clearly, our market is not yet consumers in the home. But that’s where we want to go.”

Robots in the home have been promised for decades, and with the notable exception of the Roomba, there has not been a lot of success. The idea of a robot that could handle dishes or laundry is tempting, but is it near-term or medium-term realistic? Edsinger, who has been at this whole robots thing for a very long time, is an optimist about this, and about the role that Stretch will play. “There are so many places where you can see the progress happening—in sensing, in manipulation,” Edsinger says. “I can imagine those things coming together now in a way that I could not have 5 to 10 years ago, when it seemed so incredibly hard.”

“We’re very pragmatic about what is possible. And I think that we do believe that things are changing faster than we anticipated—10 years ago, I had a pretty clear linear path in mind for robotics, but it’s hard to really imagine where we’ll be in terms of robot capabilities 10 years from now.” —Aaron Edsinger, Hello Robot

I’d say that it’s still incredibly hard, but Edsinger is right that a lot of the pieces do seem to be coming together. Arguably, the hardware is the biggest challenge here, because working in a home puts heavy constraints on what kind of hardware you’re able to use. You’re not likely to see a humanoid in a home anytime soon, because they’d actually be dangerous, and even a quadruped is likely to be more trouble than it’s worth in a home environment. Hello Robot is conscious of this, and that’s been one of the main drivers of the design of Stretch.

“I think the portability of Stretch is really worth highlighting because there’s just so much value in that which is maybe not obvious,” Edsinger tells us. Being able to just pick up and move a mobile manipulator is not normal. Stretch’s weight (24.5 kilograms) is almost trivial to work with, in sharp contrast with virtually every other mobile robot with an arm: Stretch fits into places that humans fit into, and manages to have a similar workspace as well, and its bottom-heavy design makes it safe for humans to be around. It can’t climb stairs, but it can be carried upstairs, which is a bigger deal than it may seem. It’ll fit in the back of a car, too. Stretch is built to explore the world—not just some facsimile of the world in a research lab.

“NYU students have been taking Stretch into tens of homes around New York,” says Edsinger. “They carried one up a four-story walk-up. This enables real in-home data collection. And this is where home robots will start to happen—when you can have hundreds of these out there in homes collecting data for machine learning.”

“That’s where the opportunity is,” adds Kemp. “It’s that engagement with the world about where to apply the technology beneficially. And if you’re in a lab, you’re not going to find it.”

We’ve seen some compelling examples of this recently, with Mobile ALOHA. These are robots learning to be autonomous by having humans teleoperate them through common household skills. But the system isn’t particularly portable, and it costs nearly US $32,000 in parts alone. Don’t get me wrong: I love the research. It’s just going to be difficult to scale, and in order to collect enough data to effectively tackle the world, scale is critical. Stretch is much easier to scale, because you can just straight up buy one.

Or two! You may have noticed that some of the Stretch 3 videos have two robots in them, collaborating with each other. This is not yet autonomous, but with two robots, a single human (or a pair of humans) can teleoperate them as if they were effectively a single two-armed robot:

Hello Robot

Essentially, what you’ve got here is a two-armed robot that (very intentionally) has nothing to do with humanoids. As Kemp explains: “We’re trying to help our community and the world see that there is a different path from the human model. We humans tend to think of the preexisting solution: People have two arms, so we think, well, I’m going to need to have two arms on my robot or it’s going to have all these issues.” Kemp points out that robots like Stretch have shown that really quite a lot of things can be done with only one arm, but two arms can still be helpful for a substantial subset of common tasks. “The challenge for us, which I had just never been able to find a solution for, was how you get two arms into a portable, compact, affordable lightweight mobile manipulator. You can’t!”

But with two Stretches, you have not only two arms but also two shoulders that you can put wherever you want. Washing a dish? You’ll probably want two arms close together for collaborative manipulation. Making a bed? Put the two arms far apart to handle both sides of a sheet at once. It’s a sort of distributed on-demand bimanual manipulation, which certainly adds a little bit of complexity but also solves a bunch of problems when it comes to practical in-home manipulation. Oh—and if those teleop tools look like modified kitchen tongs, that’s because they’re modified kitchen tongs.

Of course, buying two Stretch robots is twice as expensive as buying a single Stretch robot, and even though Stretch 3’s cost of just under $25,000 is very inexpensive for a mobile manipulator and very affordable in a research or education context, we’re still pretty far from something that most people would be able to afford for themselves. Hello Robot says that producing robots at scale is the answer here, which I’m sure is true, but it can be a difficult thing for a small company to achieve.

Moving slowly toward scale is at least partly intentional, Kemp tells us. “We’re still in the process of discovering Stretch’s true form—what the robot really should be. If we tried to scale to make lots and lots of robots at a much lower cost before we fundamentally understood what the needs and challenges were going to be, I think it would be a mistake. And there are many gravestones out there for various home-robotics companies, some of which I truly loved. We don’t want to become one of those.”

This is not to say that Hello Robot isn’t actively trying to make Stretch more affordable, and Edsinger suggests that the next iteration of the robot will be more focused on that. But—and this is super important—Kemp tells us that Stretch has been, is, and will continue to be sustainable for Hello Robot: “We actually charge what we should be charging to be able to have a sustainable business.” In other words, Hello Robot is not relying on some nebulous scale-defined future to transition into a business model that can develop, sell, and support robots. They can do that right now while keeping the lights on. “Our sales have enough margin to make our business work,” says Kemp. “That’s part of our discipline.”

Stretch 3 is available now for $24,950, which is just about the same as the cost of Stretch 2 with the optional add-ons included. There are lots and lots of other new features that we couldn’t squeeze into this article, including FCC certification, a more durable arm, and off-board GPU support. You’ll find a handy list of all the upgrades here.