Humanoid Robots Rise. Now, Can They Walk?

Watch out, Asimo, these new humanoids are on your tail

5 min read

Erico Guizzo is IEEE Spectrum’s digital innovation director.

Humanoid Robots Rise. Now, Can They Walk?

Watch out, Asimo, there are some new humanoids on your tail! Photo: Honda

Japan has long held world dominance when it comes to full-body walking humanoid robots. There's the pioneering Waseda robots, the impressive HRP series, the diminutive but nimble Sony Qrio and Toyota Partner robots, and of course, the country's most famous emissary: the charismatic, child-size, astronaut-like Honda Asimo, which ambles, runs, and climbs stairs with (almost) perfect precision. Until recently, only South Korea -- with its Hubo and Mahru robots -- had demonstrated humanoids with legs as impressive as those of their Japanese counterparts.

Now other countries are trying to catch up. Below I describe four humanoids that may give the Asian humanoids a run for their money. Or as one editor here put it, these robots may kick your Asimo.

But first, a digression. Every time I encounter a roboticist building legged humanoids, I ask the same question, Why do we need legged humanoids? Wheels appear to be easier and cheaper to implement and provide great maneuverability -- so why legs?

The answer they give me is two-fold: First, they argue that robots with human-shaped bodies are more apt to navigate human environments. So if we want robots to operate in our homes and offices, where there are stairs, uneven surfaces, and shaggy rugs, we need legs. The second part of the answer is that by building walking humanoids we can better understand how humans walk, balance, and move our bodies to do things like pirouette on a toe or perform incredible kicks.

After hearing their answer, my next question to the humanoid builder is, And why is it so hard to create full-body walking humanoids? Researchers have been working on this for over three decades and it seems we're still taking, well, baby steps. When can we expect a quantum leap in humanoid legged locomotion?

The answer is too complex -- and too interesting -- to summarize here; I will have to write another post on this topic. For now, let's just say there is a preferred walking control scheme, but some researchers are betting on competing approaches, and that although dc motors are the preferred actuators, some groups are seeking alternatives such as compact, powerful linear actuators.

Okay, so here are the four humanoids. Let me emphasize we're showing here only full-body adult-size humanoids. Yes, there are small humanoids capable of walking, of course, like the Nao; there are also robot legs that can run at full speed -- but that lack an upper body; and there are full-body humanoids that still have to show they can take a step. So the robots below are the ones we think could take on Asimo in robot race, or soccer match.

Did we leave out a robot you think should be here? Let us know in the comments section below.

Pal Robotics, Barcelona

Reem-B was designed to assist humans with everyday tasks, says Davide Faconti, founder of Pal Robotics. The 1.47-meter-high robot, unveiled two years ago, can walk at a relatively slow speed of 1.5 kilometers per hour, but thanks to powerful actuators in its legs and arms, Reem-B "is probably the strongest humanoid in the world," says Faconti, boasting that his robot can carry a 12-kilogram payload—say, a big watermelon. Try that, Asimo.

Photo: PAL Robotics

Watch Reem-B walking. The video is a bit old. I'd love to know if Pal has continued to improve the robot's mobility and see what it can do today.

Institute of Robotics and Mechatronics at the German Aerospace Center (DLR), Oberpfaffenhofen-Wessling, Germany

Justin is by far one of the most impressive humanoids unveiled in recent years. Its lightweight, strangely shaped arms are amazingly dexterous, and the German researchers are consistently pushing the envelope in terms of hardware and software design. At every major robotics conference you can expect to see Justin showing off a new trick.

Photos: Institute of Robotics and Mechatronics/DLR

The thing is, Justin, at this point, is not actually a full-body humanoid. It's currently an upper body with head, torso, and two arms that can be mounted on a fixed base or a four-wheeled mobile platform [see photo above].

The reason we're including it here is because DLR researchers have demonstrated early this year a pair of legs that we suspect may become Justin's lower body.

The legs use the same powerful yet lightweight motors employed in Justin's arms. The idea was to explore joint torque-based control concepts for biped balancing and walking, according to Christian Ott, the lead researcher working on the legs.

If Justin's lower body turns out to be as nimble as its upper body, this robot will be able to do things we have never seen a robot doing before.

Watch the DLR legs in action:

Virginia Tech's Robotics & Mechanisms Laboratory, Blacksburg, Va.

Photo: Virginia Tech

We wrote about CHARLI before. CHARLI is the first untethered, autonomous, full-size walking humanoid robot built in the United States, according to Virginia Tech roboticist Dennis Hong. Hong loves creating acronyms for his robots. CHARLI stands for Cognitive Humanoid Autonomous Robot with Learning Intelligence.

There are actually two CHARLI models. One, smaller, called CHARLI-L uses motors and a linkage system of pulleys and springs to generate movement. Hong and his team are now building a heavier version, CHARLI-H, to be equipped with custom-made linear actuators. See CHARLI-H's future leg on the photo, right.

Hong is secretive about these new actuators, saying only they will help mimic how human limbs move. (They rely on compliance, or "springiness," at the joints instead of stiff position control like most other humanoid robots use, Hong says.)

I look forward to seeing CHARLI-H play the humanoid league in RoboCup! Will it kick like Roberto Carlos?

Watch CHARLI-L taking somewhat timid steps, but steps nonetheless!

University of Tehran's Advanced Vehicles Center, Tehran

Finally, we're including here the Iranian robot Surena 2, unveiled a few months ago, just because it was such a surprising development. After the first reports surfaced, some people were skeptical the robot was more than an Asimo-looking plastic shell. But finally, video proved the humanoid was indeed a humanoid.

The 1.45-meter-high robot was developed to help researchers explore aspects of bipedal locomotion, Tehran University professor Aghil Yousefi-Koma told IEEE Spectrum. His team is working on a feedback control system that yields a much more humanlike motion.

Surena might be a slow walker, but it has its tricks: It can bow, stand on one leg, and according to some news reports, dance. Dance-off, Asimo?

Photo: Alireza Sotakbar/ISNA/AP

Surena 2 shows off its skills:

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