On a sunny morning in June, I walked to work with a quadruped robot beside me. I’ve never gotten more attention from strangers.

A bunch of people snapped pictures of my robot dog. Several people asked me questions. Was it mine? (Yes.) Did I build it? (No.) Was it being used for surveillance? (No.)

Biological dogs kept a safe distance from my mechanical companion. Some growled or barked at it.

Children were fascinated. I paused and had it do tricks for several of them: “shake hands,” do a handstand, or leap into the air.

I live in a leafy Washington, DC, neighborhood called Mount Pleasant. The neighborhood lives up to its name, so my morning commute is mostly downhill. My robot companion, manufactured by the Chinese company Unitree, walked the two miles to my office near the White House with battery capacity to spare.

I recharged the battery during the workday, but it still struggled on the afternoon walk home. We were now mostly walking uphill, and the temperature had risen to 87°F (30°C). The robot’s steps seemed increasingly labored as the path got steeper.

As I entered my own neighborhood, I glanced at two indicators in the corner of my phone screen. One showed that the robot’s battery was at 5 percent—dangerously close to empty. The other showed the internal temperature was 84°C (183°F).

We were within sight of my front door when the robot suddenly collapsed. I’m not sure if it ran out of power or overheated, but either way it didn’t shut down gracefully—it rolled onto its back with its legs in the air.

My robot dog after it collapsed steps from my home. The light on its “face” was blinking red, and the lidar sensor on its “nose” was still spinning. Credit: Timothy B. Lee

Several people have asked me what my robot is useful for, and the honest answer is not much.

Unitree quadrupeds are widely used for academic research, and they are sometimes used for entertainment. But there don’t seem to be a ton of practical applications.

Wheeled robots are faster and more energy-efficient, making them better for deliveries. Flying drones are a better choice for a lot of surveying and inspection work. My robot has no arms or hands, making it mostly useless around the house.

But my robot did have one big thing going for it: It was astonishingly cheap.

I paid $4,017. That’s more money than I’ve ever spent to review a product. But it’s also far less than I would have had to pay for this type of robot a few years ago. And it’s cheap enough that people may find uses for it that wouldn’t have made sense at higher prices.

Sometimes what changes the world isn’t the invention of a new technology; it’s figuring out how to make it affordable enough for a mass market. Xerox built the first personal computer with a graphical user interface, but companies like Apple, IBM, and Microsoft made the technology mainstream. Perhaps Unitree will play a similar role for quadruped robots—though, as I’ll discuss later, Unitree’s robots now face legal restrictions in the United States.

Unitree has also used quadruped robots as a stepping stone to another market that could be much more important—humanoids. Unitree launched its first humanoid robot in 2023. Leveraging its experience making cheap quadrupeds, Unitree is able to sell humanoid robots for as little as $13,500.

That’s still way out of my price range, which is why I bought a robot dog instead. But it’s dramatically cheaper than any humanoid you could buy a few years ago. And the low cost has made Unitree a global leader in humanoid robots.

Financial markets are bullish. Unitree debuted on the Shanghai stock market on August 19. On its first day of trading, shares shot up more than fivefold. It has lost some altitude since then, but at Monday’s closing price, the company was still valued at $34 billion—more than triple its valuation before the IPO.

How Unitree democratized legged robotics

Prof. Xuesu Xiao standing in front of four Unitree quadruped robots in his lab in Arlington, Virginia. Credit: Timothy B. Lee

Earlier in June, I visited Professor Xuesu Xiao, a roboticist at George Mason University.

“Ten years ago, only a very small set of research groups were working on quadruped locomotion because they were the only people on the planet who could build a quadruped,” Xiao told me. “Then Unitree came onto the market. And it basically democratized the entire world of quadruped locomotion research.”

Xiao gave me a tour of his lab, which had four Unitree quadrupeds. Each cost around $15,000. The lab also had a quadruped robot called Spot. It was made by Boston Dynamics—widely seen as the industry leader before Unitree came along. But Spot is expensive, starting around $75,000.

Unitree founder Wang Xingxing developed a crude quadruped robot called XDog for his master’s thesis at Shanghai University.

“Marc Raibert from Boston Dynamics is my idol,” Wang told IEEE Spectrum in March 2016. “Their papers helped me to design XDog.”

Early Boston Dynamics prototypes—with names like BigDog and WildCat—had gasoline engines and hydraulic actuators. This made them too large, noisy, and polluting for practical use.

In that 2016 interview, Wang said that his goal was to “make quadruped robots simpler and smaller, so that they can help ordinary people with things like carrying objects or as companions.”

Boston Dynamics officially unveiled an electric quadruped called Spot in June 2016. But Spot didn’t become commercially available until 2020.

That created an opening for Unitree, which Wang founded in May 2016. The company’s first quadruped products—Laikago in 2017 and AlienGo in 2019—were powered by electric motors. Designed for research labs, they cost tens of thousands of dollars.

In 2021, Unitree launched the Go1 line, which started at $2,700 for the “Air” model. In 2023, Unitree unveiled the Go2, which was even cheaper—$1,600 for the Air and $2,800 for the more capable Pro.

Today, Unitree’s cheapest robot—the Go2 Air—is more than 97 percent cheaper than Spot. But this is not an apples-to-apples comparison; Spot is larger than Unitree’s Go2 line and can carry heavier payloads.

Still, the fact remains that Unitree made quadruped robots affordable to many people who could never afford Spot—including me! My wife never would have let me spend $75,000 or even $15,000 on a robot dog. But I convinced her to let me spend $4,017 (after tariffs and shipping costs) on a Go2 Pro.

Why are Unitree robots so cheap?

Last year, the firm Simplexity tore a Go2 robot dog apart and made a video showing what they found.

Simplexity took a Unitree Go2 Air robot apart to understand its components, including the 12 identical motors that keep costs down while giving the legs a “really dynamic range of motion.” Credit: Simplexity

Each of the robot’s four legs is powered by three motors. There’s a motor in the shoulder that controls the angle of the legs and a motor driving each of the two leg segments. “With three motors, you get a really dynamic range of motion,” said Luis Elenes, a mechanical engineer at Simplexity.

“They use all the same motors throughout,” Elenes added. “All four shoulders are identical in arrangement. There’s tons of benefit to that. There’s reduced cost, there’s reduced part count. The more you can reuse motors and reuse parts, the simpler your design gets, and the more robust overall your design will be.”

Jakub Bartoszek, an expert on motors and legged robots at the startup MAB Robotics, argues that Unitree also saved money by using low-quality components. The motors in Unitree robots—many of which are made in-house—tend to wear out more quickly than those in some other robot brands, he told me. But the cost savings make the robots affordable to more people.

Unitree seems to have designed its robots for easy repairs when they wear out.

“They want these legs to be serviceable in the field,” Elenes said. Thanks to the simple way the robot’s legs are attached to its body, “you can swap out a leg pretty easily. I would guess it would take you less than a minute.”

Unitree also gets significant support from the Chinese government, including tax credits and large-scale purchases by public institutions. It’s hard to quantify the scale of this support because the Chinese system blurs the line between public and private, military and civilian. But a supportive policy environment clearly helped Unitree to scale up its manufacturing operations and thereby drive down the cost of each robot.

How powerful motors enable cheap actuators

My 5-year-old daughter enjoys steering my Unitree robot. Credit: Bethany Lee

Unitree has another counterintuitive cost-saving strategy: using large and powerful motors. More powerful motors aren’t inherently cheaper, of course. But they allow Unitree to save money on another component called the reducer that can be even more expensive

Suppose you have a lever where one side is five times longer than the other. If you push the long side down by five inches, the short side goes up by just one inch. But force is magnified: 10 pounds on the long side becomes 50 pounds on the short side.

Many robots use gear systems called reducers that serve the same function; they convert the fast, relatively weak movement of an electric motor into a slower but stronger movement of a robot’s body parts.

Traditional industrial robots require extreme precision, so they tend to have large reduction ratios.

A page on the Boston Dynamics website, for example, indicates that two of the motors in Spot’s legs are paired with reducers that have gear ratios of 51 to 1. In other words, the motor would need to do 51 full rotations in order to produce one full rotation of a leg joint.

This enables Spot’s movements to be very precise while magnifying the power of Spot’s motors. But it also has some disadvantages. One is cost. Reducers with 51:1 ratios are complex and—as a result—tend to be significantly more expensive than reducers with lower ratios.

Another is rigidity. When a robot’s arm encounters physical resistance, it should yield gracefully—a property called backdriveability. It’s also helpful if a robot can sense this kind of physical resistance electrically. Robots with higher gear ratios perform badly on both these fronts; their limbs feel stiffer and they are less sensitive to physical resistance.

In contrast, Unitree uses large motors combined with a simple 6.33-to-1 gearbox. This makes its robots more nimble and dynamic while reducing costs. The simpler design is also easier to simulate, making Unitree robots easier to train.

Unitree’s decision to use a lower gear ratio is part of an industry-wide trend. High gear ratios made sense for industrial robots that were programmed to perform simple, repetitive motions. In contrast, many modern robots perform complex actions in unpredictable environments. This requires sophisticated control software that can respond flexibly to changing conditions. The software is constantly making small corrections anyway, so it can compensate for less precise hardware.

The humanoid pivot

My Unitree robot doing a handstand. Credit: Bethany Lee

One of the most impressive and crowd-pleasing capabilities of my Go2 Pro robot dog is handstands. The robot can balance on either its front or hind legs indefinitely, and can even move forward, backward, or side to side while doing so.

So it was natural for Unitree to expand into humanoids. Unitree first debuted a humanoid called the H1 in 2023. The next year, Unitree unveiled a cheaper and more capable robot called the G1.

I got to see one when I visited Xiao’s lab in June. He paid around $50,000 for a research-grade EDU version. The consumer version starts at $13,500. This is shockingly cheap given the robot’s capabilities.

A Unitree G1 humanoid robot in the Xiao robotics lab. Credit: Timothy B. Lee

A humanoid robot is more than a quadruped standing on its hind legs. My Go2 quadruped robot has three motors per leg, for a total of 12. The cheapest G1 humanoid has five motors in each arm, six in each leg, and one in the torso, for a total of 23. The leg motors in a humanoid robot also need to be more powerful, since it’s more work to balance on two legs than to stand on four.

Still, I suspect that Unitree’s experience with quadrupeds gave it a leg up on humanoids. By the early 2020s, Unitree had been shipping quadruped robots for several years. The company had deep expertise in actuator design and an extensive network of suppliers.

According to filings connected to Unitree’s August stock offering, the company’s quadruped revenue tripled between 2024 and 2025—from RMB 230 million ($34 million) to RMB 697 million ($104 million). The comparable figures for Unitree’s humanoids were RMB 107 million ($16 million) and RMB 867 million ($129 million)—an eightfold increase.

Humanoids accounted for 51 percent of Unitree’s revenue in 2025. I expect this figure to be even higher for 2026.

Unitree could have a durable advantage

Me with my Unitree robot outside the Understanding AI office. Credit: Nat Purser

“We are witnessing the birth of another Chinese hardware giant,” wrote a team at SemiAnalysis in June. “Three years ago, Unitree was a quadruped company. By last year, they parlayed quadruped dominance into creating and leading the humanoid market.”

The SemiAnalysis authors draw a parallel to DJI, the Chinese company that dominates the global drone market.

“DJI’s Phantom 1 shipped January 2013 at $679, and was not a fully-fledged product at the time,” the SemiAnalysis team writes. “It had no built-in camera, no gimbal (stabilizer), ten minutes of flight, no live video feed, but it was roughly half the cost of the build-it-yourself drone.”

Like DJI in 2013, Unitree’s robots today have a lot of rough edges. Certainly mine does.

The app to control the robot is buggy. Features Unitree showcased in its launch video—like climbing stairs and following a human owner—don’t work well in real life. If I turn the robot on with its legs slightly out of place, they will often thrash around wildly and the robot will wind up on its back.

Then there was the time my robot collapsed just feet from my house. A more polished product might have detected the low battery (or high temperature) and shut itself down gracefully.

But for bleeding-edge technologies, this kind of polish may not be very important. Far more important is getting costs down.

“DJI chose to inhouse the most expensive and technically difficult component first: the flight controller,” SemiAnalysis writes. “Later on, DJI brought inhouse the gimbals, motors, and ESCs.”

DJI figured out how to make these components more cheaply than they could be purchased from external suppliers, which in turn allowed it to undercut other drone makers. And that expanded the market for DJI’s drones.

Before DJI came along, “professional aerial photography was the domain of helicopters and Hollywood second-unit teams, but now, small businesses could perform this on their own. As such, whole new markets were unlocked for DJI, like real estate listings, wedding videos, local news, agricultural surveying.”

There’s a flywheel here: The more units a company sells, the better deals it can negotiate with suppliers and the more money it can spend optimizing its manufacturing process. Larger sales volumes also allow a company to bring more components in-house. This allows the company to push costs even lower, which will mean more sales and even more money to invest in improving the production process.

Over a few years, this flywheel helped DJI to dominate the global drone market. SemiAnalysis argues that Unitree is on track to do the same thing for legged robots.

According to SemiAnalysis, Unitree has developed its own motors, gearboxes, lidar sensors, and cameras. “Unitree’s self-produced motors can run as low as 30-40% of equivalent Western motors,” SemiAnalysis reports. “They now make some of the cheapest humanoid gearboxes in the world.”

This could enable Unitree to take over the global market for quadruped and humanoid robots in much the same way that DJI took over the global drone market.

Of course that’s not guaranteed to happen. Unitree has a number of Chinese rivals. Unitree is the global leader in quadrupeds, but a Chinese rival, AgiBot, has sold more humanoid robots than Unitree in recent months. There are also many smaller robot companies in China that could challenge Unitree and AgiBot in the coming years.

But Unitree does not face much competition in the United States or the West more generally. Boston Dynamics sells excellent robots, but they tend to be significantly more expensive. There are a number of American startups aiming to build humanoid robots, including Tesla, Figure, and 1X, but consumers cannot buy a robot from any of these companies today.

That has alarmed some American policymakers. In June, a bipartisan group in the House introduced a bill to restrict importation of Chinese robots. The official press release for the legislation mentioned Unitree by name. Then in July, the FCC imposed broad new regulations on foreign-made robots that are likely to impact Unitree and other Chinese companies.

However, the robot market is global. Even if Chinese companies get locked out of the US market, Unitree or one of its Chinese rivals could still come to dominate the global market for humanoid robots.

There’s an obvious parallel here to electric vehicles, where Chinese companies like BYD are effectively banned from the US but are making rapid gains in the rest of the world. There’s a risk that a ban on Chinese robots could have a similar impact: rather than hampering the growth of companies like Unitree, it could make the US a robotics backwater.

Tim Lee was on staff at Ars from 2017 to 2021. He recently launched a new newsletter, Understanding AI. It explores how AI works and how it’s changing our world. You can subscribe to his newsletter here.

Read full article

Comments

Iranian-backed Houthi rebels in Yemen have captured a strategic island in the Bab el-Mandeb Strait. The move threatens Saudi oil exports through a key commercial lane. And Saudi Arabia said it shut down a major oil pipeline as a precaution after it came under attack.

(Image credit: STR)

Patriot Platform wants to build a group of working-class voters to influence political parties on the right.

Games may be life with all the hard bits removed, but they provide a way to study why people make the choices they make. Traditional games are usually played against a static background: the rewards per outcome are constant. That limits their relevance to behavior because, in real life, the rewards and consequences of strategic choices are ever changing. Now, researchers have used a mathematical model to study a series of games that include evolving strategies and randomly varying returns.

A bit of history

Perhaps the most famous game-theory contest is the prisoner’s dilemma. In the prisoner’s dilemma, a pair of thieves have been captured and are being separately interrogated by the police. If both clam up, they will be punished for a lesser crime. If one prisoner makes a deal (defects) then that prisoner gets to go free and the other gets a heavier sentence. If both make a deal, they both get an in-between punishment.

The person running the game can start it with different rewards for cooperating and defecting to explore how the optimum strategy varies with reward and risk, which the players can figure out by varying the strategies across multiple rounds. Depending on the balance between the reward for staying silent (cooperating) and betrayal, the game stabilizes with everyone betraying everyone. In this simple situation, everyone loses.

Similar dynamics can be found in games of chicken, rock-paper-scissors, and more. The evolution of strategies can lead to stable populations, bistable populations (where the population flips between two stable strategies), or limit cycles, where the population shifts continuously among multiple strategies.

There is also a rich history of changing a game as it is played. Usually, these are within-game variations. For instance, you can set a limit on the amount of reward available, so strategies evolve to take into account increasingly limited resources as the number of rounds goes up. In other words, most of this older work studied situations where the player’s behavior in the current round changed the resources or rewards available for the next round.

Your influence is limited

In real life, though, we are driven by external factors that are not under our control. The rabbit does not control the rain that floods its burrow or the drought that kills its food. The game changes each round because the risks and rewards of each strategy change over time. The researchers recognized that incorporating these dynamics into a mathematical model might reveal new behaviors. And they were not wrong.

Τhe prisoner’s dilemma as described above has only a single stable point (everyone loses). The model quickly converges to that point, where all players adopt the same strategy within a few rounds. But the new work found that if the rewards change with time (even by a small amount), then a second stable point emerges from the model, allowing both cooperators and defectors to coexist. Under even greater variation, the defector point becomes unstable, meaning that only cooperators exist.

In chicken, the model’s results are a bit scarier: With no change in rewards, the stable point is that everyone swerves and we all survive. Add in just a bit of variation, and a population that does not swerve emerges. Add in more noise, and a bistable flipping between survival and crashing emerges. (Given that chicken was basically the Cold War strategy, I’m even more amazed we all survived to face our next existential challenge.)

For rock-paper-scissors, an even more complex dynamic emerges. In terms of stable and unstable points, regular rock-paper-scissors has no stable points—the strategy never settles into everyone choosing rock, for instance. Instead, everyone keeps flipping continuously among the three options. If the rewards change randomly per round, however, new stable and unstable points emerge. Depending on the case, this can cause the game to more quickly evolve to the flipping strategy or develop a limit cycle. Limit cycles emerge if the rewards are uneven (for instance, rock versus scissors gives the winner a greater payoff than paper versus rock). In this case, the population continuously cycles, with the probability of choosing rock versus paper versus scissors evolving predictably and stably over time.

The conclusion from all this game theorizing is that, even though the behavioral tendencies of the players may influence the game, a varying game environment can have a huge effect on the optimal strategy.

Life revealed through simple rules

If we take the prisoner’s dilemma as the classic game theory tool, it yields a depressing conclusion: Cooperation is a losing strategy. Yet even under the conditions set by the prisoner’s dilemma, we observe cooperation. Why? Because there are external influences on the reward—the prisoner who defects and is released may well be retaliated against under slightly different circumstances, and not under others. Therefore, a more complex mix of strategies is likely to emerge.

However, it was still surprising to see that a relatively small amount of variation in the reward structure could lead to such strong changes in behavior.

Game-theory models are also often used to try and understand economic behavior. I’ve always been skeptical (perhaps overly skeptical) of the insights drawn from these games, and I think this paper makes it explicit why I distrust these models. But the results here also point a way forward, where the richer dynamics that we observe in real life are replicated in games that are still quite simple.

Physical Review Letters, 2026, DOI: 10.1103/3yby-qq2n

Read full article

Comments

Saudi Arabia’s oil exports are plummeting as oil prices surpass $100 a barrel.

After 10 years of design and development, the appliance maker Breville has just released a $300 toaster that the company believes will revolutionize the category. The Eye Q Auto Toaster, now hitting stores in the U.S., rethinks the core process behind making a piece of toast. Instead of applying heat for a set amount of time, Breville’s Eye Q toaster uses optical sensors and advanced algorithms to see when bread has been toasted just the right amount.

For Breville, an Australia-based company that has been making kitchen appliances for almost a century, this proved to be an unexpectedly complicated paradigm change. “We don’t mind a challenge, but if somebody had said to me it’s going to take 10 years to develop a toaster at the beginning of this project, I would have thought, you’re crazy, we shouldn’t do it,” says Tom Groundes-Peace, Breville’s senior global category manager and head of research.

But the company couldn’t stop thinking about the inherent shortcomings of traditional toasters. “Every toaster in the world up until this point has just used time as its proxy for toasting,” Groundes-Peace says. Timing a toast only works, however, if what you’re toasting is always the same. According to Breville’s research, many homes toast multiple kinds of breads in a given week or day, from white to wheat to bagels to sourdough. “Different bread, different amounts of time,” Groundes-Peace says.

The look test

Toasting may be the bare minimum of culinary acts, but Breville’s product designers have been working for decades to make even this simplest of kitchen tasks easier for people. The company introduced the “A bit more” button in 2007, which puts undertoasted bread back in the heat for another 30 seconds. In 2016 it created a toast type selector, with preset toasting times for different breads.

But even these advancements in toasting couldn’t match the ultimate test for toastedness. “How do you check that your toast is done? You look at it and you go, is that brown enough, or do I want to toast it a little bit more?” Groundes-Peace says. Breville wanted to bring that look test into the toaster itself.

So, a decade ago, the company set out to create a toaster with its own set of eyes.

How the Breville Eye Q toaster works

The Eye Q toaster has two optical sensors built inside its shell. Tucked between one side of the toaster and the heating element, two small sensors peek through tiny rectangular holes at the bread as it sits at the bottom of the toasting cavity. Green lights flash 10 times a second through those holes, bouncing light and infrared wavelengths off the bread and back to the sensors, which measure the rate of color change in the bread. The toaster has seven built-in darkness settings, and the sensor data feeds into specially developed algorithms that know when the amount of color change is enough.

Thousands of data points may seem like overkill for toast, but Groundes-Peace says the difference between a perfectly toasted slice of bread and a burnt one can be measured in moments. “If you don’t catch it quick enough, if you’re not reading the data quick enough, you miss the target and it burns,” he says.

Using a borrowed Eye Q Auto Toaster that Breville had mailed to me, I toasted a spectrum of breads and bagels, from a pale sourdough to a seeded multigrain to a grainy bagel. Trying the lightest, middle, and darkest settings, the various breads came out browned but not burnt. The interface is simple, with only a few setting buttons and a large start/stop button. The one slight upturn in the learning curve is remembering to use the correct slot for a single-piece toast session, because the sensors are situated on one side of the toaster. The only overtoast I experienced was when a thick bagel got jammed on its way to the bottom of the toaster, apparently misaligning with the sensor view and staying down long enough to get thoroughly singed. Even easy toast can sometimes be hard.

A decade in the works

Getting to this point was a roller coaster. Breville decided early on that optical sensing was the ideal way to build a new kind of toaster, but couldn’t find the hardware to do it. “There’s lots of optical sensors in the world. There were no sensors in the world to detect bread color change. Like, that’s not a thing,” Groundes-Peace says.

Breville’s engineers had to work directly with manufacturers to develop a sensor that could do the very specific job of tracking the tiny changes in the shade of a slice of sourdough or pumpernickel. “We also said to the sensor manufacturers, oh yeah, by the way, we’re also going to put it in a super-hot environment and toast it 10,000 times,” Groundes-Peace says. “That sounds ridiculous and impossible.”

They finally got the sensor they needed. Breville’s industrial designers slotted it into a case as close to the size of a typical toaster as possible, and by about 2021, the company was almost ready to send it off for mass production.

But with sensors and circuit boards, and the heatshields needed to protect the tech, the resulting toaster was bigger and heavier than the company really wanted. “The problem with that is it takes too long to heat up, too long to toast. It was too expensive, and it wasn’t delivering great toast outcomes,” Groundes-Peace says. “We were about to press the go button on making 10,000 of these. And then we just said, look, guys, it’s not there.”

The project went back to the drawing board, with set goals of cutting costs by 40%. An expensive dial interface was cut, and replaced with a minimal array of simple buttons. Breville pushed suppliers to streamline and trim costs. Materials within the toaster were brought down to the minimum without sacrificing its ability to toast.

Planting a flag

Now, after a decade, the final product is out. “There’s a big army of people behind this,” Groundes-Peace says. “Collectively, I think there’s a sense of pride.”

All that time developing the Eye Q toaster is an investment in the company’s future. “We believe sensing toasters are the way to go. So we will be leaning into that in future product development,” Groundes-Peace says. That could result in a wider range of optical sensor toasters, including some at lower price points.

For now, Breville is hoping this new approach to toasting will help it make the Eye Q Auto Toaster the new standard in this part of the kitchen appliance marketplace. “If there’s such a thing as a flagship toaster, this is it,” Groundes-Peace says.