5 ms·

Humanoid Robot Actuators

169 points by ofrzeta 6mo ago

num42 6mo ago
Check out opensource actuator for robots. Opentorque actuator https://www.gabrael.io/new-page https://www.gabrael.io/new-page https://github.com/G-Levine/OpenTorque-Actuator https://github.com/G-Levine/OpenTorque-Actuator
- regularfry 6mo ago
  In the context of the torques in the article, a nylon sun gear in the gearbox feels optimistic.
aardvarkdriver 6mo ago
Why the AI "engineering expert"? Seems to take some credibility away from what otherwise could be an interesting and informative read.
- barbegal 6mo ago
  Yeah I couldn't get past so many issues in the AI generated illustrations. Not useful at all when they are completely wrong.
  - Tanxsinxlnx 6mo ago
    right
  - moffkalast 6mo ago
    Even the video is generated. The whole thing is just slop upon slop, I'm amazed that it got to the top of the front page here. I suppose it's a genuinely impressive amount of fakery all integrated together.
Miles_Stone 6mo ago
[flagged]
modeless 6mo ago
AI was clearly heavily used in the making of this article, and I almost dismissed it as slop. But after reading it I think there's enough correct information here for it to be useful as a general overview of the problems in the space.
- ramon156 6mo ago
  They should've left out figure 6. it adds very little and the screws are wrong.
- raphman 6mo ago
  I believe that bad/wrong explanations are actually much worse than no explanations. Many figures seem to be either missing key information (e.g. Fig. 5: the elliptical deformation is not shown - a human artist would have created a very different figure to explain the concept) or plain wrong (Fig. 6: the threaded rollers have the wrong orientation, Fig. 7: the ball is much too large for the bearing and the whole figure seems nonsensical at first glance). And if the author did not spot these obvious problems with the figures, they either have no clue, accept sloppy work, or didn't even read the article they generated. That article is not really good advertising for the company's products. (That the link behind the author's name leads to their Wikipedia article which seems to be a revised copy of the CV on their website is interesting, too.)
Animats 6mo ago
The power of money. I spent some time on legged locomotion back in the 1990s. It was clear then that you wanted torque control, and I did some work on the theory for that, trying to solve it from first principles, not machine learning. Got some nice theory and a patent out. But the parts just weren't there to build such things. As the article points out, the key to this is motor back-drivability. The final drive has to survive shock loads, and it has to dump forces into the motor, where the magnetic fields can take it. As I've quoted before, "you cannot strip the teeth of a magnetic field", a comment from early General Electric locomotive sales. (Locomotives are Diesel-electric, not Diesel with a clutch and shifting gearbox, because the clutch required is huge. Yes, it's been tried.) That's something few areas of engineering cared about, with the exception of aircraft flight control systems with mechanical backup. Pneumatic actuators looked promising, but proportional dynamic valves were big, heavy, and about $1000 each. Linear motors (not ball screws) looked like the coming thing back then, as 10:1 power/weight ratio had been achieved. But that technology never got much further, and Aura, the biggest player, collapsed in a financial scandal. Series elastic actuators were (and still are) a race between the spring compressing and the ball screw motor starting up. Hydraulics were too clunky; Boston Dynamics built a 400 pound mule, but the Diesel power pack never worked. Direct drive pancake motors were used by some SCARA industrial robots, but those were too big for leg joints. I thought someone would crack the direct drive problem eventually, but nobody ever did. We're still stuck with some gear reduction. Some of the exotic ideas for muscles mentioned in this article go back that far. The McKinney muscle is old, and not too useful. There was some interest in electrorheological fluids, fluids whose mechanical properties change when an electric field is applied. That didn't become useful either. Shape-memory alloys were a dead end; liquid cooling can overcome the slowness problem, but not the inefficiency problem. Everybody went back to good old electric motors, although they became 3-phase AC instead of DC. It helped that the drone industry made 3-phase motors and their controllers small, cheap, and powerful. Academic robotics groups were tiny. MIT and Stanford had less than a dozen people each. Progress required hundreds of millions of dollars for all that custom engineering and R&D. The level of effort just wasn't there. Nor would throwing money at the problem prior to machine learning have led to useful products. It's impressive what's been accomplished in the last five years. It took a lot of money.
- 6mo ago
ReptileMan 6mo ago
Except we don't need 100% bipedal robots. Wheels are perfectly ok for majority of city work and factory floor. Put the robot on rollerskates break the wheels for the occasional stair.
- fragmede 6mo ago
  I don't know about your city, but my city, while covered in smooth surfaces, still has a lot of interactions between those surfaces. Most of the roads have a curb between the sidewalk and the road, though the ADA means there's curb cuts and ramps. I don't know that I'd agree that they're "perfectly okay". Traversing over a 20 cm/8 inch obstacle constantly seems to make wheels less than perfect.
elil17 6mo ago
I simply do not understand why you would ever prefer a fully humanoid robot as opposed to a humanoid torso on some other locomotion system.
- rob74 6mo ago
  Isaac Asimov already explained that better than I could (https://www.reddit.com/r/asimov/comments/pm84ud/why_robots_are_humanoid/ https://www.reddit.com/r/asimov/comments/pm84ud/why_robots_a...): > Besides that, our entire technology is based on the human form. An automobile, for instance, has its controls so made as to be grasped and manipulated most easily by human hands and feet of a certain size and shape, attached to the body by limbs of a certain length and joints of a certain type. Even such simple objects as chairs and tables or knives and forks are designed to meet the requirements of human measurements and manner of working. It is easier to have robots imitate the human shape than to redesign radically the very philosophy of our tools.
  - elil17 6mo ago
    Right, but: 1. Asimov wrote that because he needed robots to be indistinguishable from humans for plot reasons. 2. We do 99% of our tool use with our arms and hands. We are already very good at building robot arms. We are getting better at robot hands. We can build robot legs, but they're very expensive and they pose a major safety risk for the robot itself and surrounding humans (because the robot can fall if there is a failure). For most applications, why not just put biomimetic hands and arms on a rolling base? Of course, all this humanoid robotics research is still useful because if you can build a fully humanoid robot you can trivially build a torso-on-rolling-base robot. I sort of suspect that most of the humanoid robotics companies already know that the vast majority of their sales will be in that category.
    - rob74 6mo ago
      You can still have a humanoid robot that looks very different from an actual human (and most robots from Asimov's novels were of that kind, although one of the main characters wasn't - https://en.wikipedia.org/wiki/R._Daneel_Olivaw https://en.wikipedia.org/wiki/R._Daneel_Olivaw). Ok, so maybe a robot with wheels could solve most tasks, but it would still be severely limited: couldn't climb stairs (which would make it unsuitable as a domestic robot in a house or multi-storey flat), couldn't drive a car, truck or any other vehicle designed for humans etc.
ramon156 6mo ago
I cannot un-see these left border hints, it's driving me crazy.
gpugreg 6mo ago
This is AI slop and the article contains some of the worst illustrations I have ever seen. Most do not make any sense mechanically. Here are the worst ones: - The "orbiting threaded rollers" in figure 6 are not meshing with anything (not that they could, since they are orientated in the wrong direction). - The ball of the ball screw in figure 7 deforms the screw and the roller screw "meshes" with a flat surface. - The guy on the pogo stick in figure 14 is jumping himself rather than putting his feet on the stands of the pogo stick. - In figure 16, a key penetrates the elastomer skin of the optical tactile sensor, destroying it. - The gears in figure 20 touch perpendicularly.
- ofrzeta 6mo ago
  > - The ball of the ball screw in figure 7 deforms the screw and the roller screw "meshes" with a flat surface. Really, it is hilarious. This will teach me a lesson or two.
- ofrzeta 6mo ago
  Is it? Now I feel bad for having posted it. I mean, I know some stuff but not enough to judge over all the content in this article. It's unfortunate but from glancing over I thought it was a comprehensive and useful resource. I guess I will just give up on the Internet or something like that.
  - sailingparrot 6mo ago
    « Rotary Actuators (The "Reflected Inertia" Trap) », « Quasi-Direct Drive (QDD) — The "Cheetah" Approach « The pattern ‘something — The « metaphor » <qualifier> ‘ screams Gemini. Gemini seem completely unable to generate a section title that doesn’t follow this annoying pattern.
  - ModernMech 6mo ago
    You just need some AI literacy, this document is very plainly AI generated. You don’t need to be an expert in the content to see that. First time you see an em dash your AI sense should be tingling. Then you see random bolded words alarm bells should be going off. Next you notice 70% of the headlines follow the pattern “The X: Y” and that seals it.
itrunsdoomguy 6mo ago
Do they run Doom?
RaSoJo 6mo ago
How can we trust this article or the company if the writer/so-called chief engineer decides to hide himself behind an AI avatar? From what I can understand this is the Robbie Dickson in question: https://www.huffpost.com/entry/lessons-from-a-serial-ent_b_9230012 https://www.huffpost.com/entry/lessons-from-a-serial-ent_b_9... Nobody has a problem with companies using AI to edit articles, create images. But when even the writer is an AI persona, the trust factor gets destroyed.
- olig15 6mo ago
  I think at very least, the diagrams are AI generated too. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/strain-wave-gear-components-exploded-diagram.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/strai... The middle component has teeth on the inside half way round, should be smooth on the inside. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/inverted-planetary-roller-screw-linear-actuator-mechanism.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/inver... 4 of the 5 orbiting threaded rollers are perpendicular to the screw thread, so wont do anything. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/ball-screw-vs-roller-screw-hertzian-contact-stress.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/ball-... Ball doesnt fit in the screw thread, just 'squashed' to make it fit?. Screw thread isnt consistent. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/stiffness-bandwidth-tradeoff-graph.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/stiff... Classic 3 interlocked gears. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/optical-tactile-sensor-gelsight-diagram.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/optic... Has the elastomer been ripped when the key was inserted? > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/biological-gap-robot-actuator-vs-artificial-muscle.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/biolo... Another gearbox that doesnt do anything... The rest of the website seems filled with just as much slop too...
  - Mars008 6mo ago
    I wouldn't be surprised if article is actually AI generated summary from several sources.Guided by human. It's a new phenomena. Recently got a book on agentic AI which looks like OpenAI docs with added generated water.
Loic 6mo ago
Asking: As gpugreg remarked[0], this is AI slop to the point that it is impossible to trust anything from this article/blog post. As such, I flagged the submission. - I wonder, is it possible to give a reason to the flag? - Is flagging the submission without comments the right way to go? For me, it is important that slowly but surely it goes through that AI slop is not what is accepted here on HN. Yes to have whatever LLM helping with grammar, spelling, etc. but the content should not be the output of a one shot "write me a blog post about humanoid robot actuators" prompt. [0]: https://news.ycombinator.com/item?id=48005917 https://news.ycombinator.com/item?id=48005917
- epaga 6mo ago
  I also flagged it when I realized the video claimed to be someone it wasn't. Unacceptable in my mind.
vova_hn2 6mo ago
Probably a dumb question, because I know nothing about robotics, but: > The "Zero RPM" Problem > When a robot bends its knees to stand, the motor must constantly fight gravity. There is no skeletal structure to lock against. To an electric motor, holding a static load—known as stall torque—is the most punishing state possible. Why not just add some kind of brake that can fully or partially lock the joint?
- AntiUSAbah 6mo ago
  You need to keep balancing fast enough. I don't think a break would give you this agility.
- thrownthatway 6mo ago
  Complexity, weight, failure modes, wear, maintenance, support burden of legacy parts. Also the brake components are never in the same plane as the drive components, so now you have additional forces to engineer for.
  - korse 6mo ago
    It's just weight. If you remove the human scale constraint, you can use hydraulics and easily lock out all your joints with reasonable complexity and maintenance demands. If you're unfamiliar, just look up the history of electrohydrostatic actuators and see where they're at now. https://www.moog.com/products/actuators-servoactuators/actuation-technologies/electrohydrostatic.html https://www.moog.com/products/actuators-servoactuators/actua...
- blueblisters 6mo ago
  Brakes are being added to actuators but they're more useful for static holds / locking than dynamic balancing. Standing even in humans is a dynamic balancing activity.
  - regularfry 6mo ago
    It is, but you don't have to do it at every joint all the time. If you lock your knees your front and back thigh muscles don't have to work on balancing in that axis at all.
spwa4 6mo ago
TLDR: we don't have the actuators required to make humanoid locomotion work reliably. Also: something every human actually kind of knows. You need to take impacts on muscles, not on mechanical connections. Even if we had the actuators required, you also need perfect control. The only way actuators can work this well is if they properly predict the impacts so that the power of the motor ("the magnetic field") can absorb nearly all the impact. If you try to take the impacts even on human bones (that are very solid and self-repairing) they will break surprisingly quickly. My opinion is that the need for high reduction is only because we can't have high voltage on the motors. If we either had very small distances between the magnets and electrical wires (think micrometers), or we have voltages in the 100s to 1000s of volts, we don't have to make this poisoned choice. (in a way, VERY small distances between magnets and wires is how human and animal muscles do it. But they go all the way down to sub-10 nanometers)
- regularfry 6mo ago
  Naively it feels like the improvements to resistive losses ought to be so dramatic from this that we must already be at some sort of equilibrium position. Double the voltage and divide the resistive losses by 4 - that's neither a trivial gain nor seemingly difficult to achieve? We're not talking kVs here.
jFriedensreich 6mo ago
Its completely impossible to trust an article when half the diagrams have serious issues and headlines are worst slop indicators. I am sure the author is knowledgeable and spend some time on this. But please please, with butter, please, either spend the last 10% to get rid of these issues or just don't publish it! Keep it in your ai research gallery or if you want to publish that gallery as ai research?
scotty79 6mo ago
I really like the idea of using two series elastic actuators in parallel on the same joint. This way motors acting in opposite direction can pre-tension the springs making the leg stiffer or softer. And if a lot of strength is needed they can act in the same direction summing their forces. It should be fairly straightforward to control dynamically so you can use pretty much any motor and gearbox.
- Animats 6mo ago
  That's an idea that predates series elastic actuators. It's been used in tendon robots, where there are two winding drums pulling on two cables, with a spring between the end of each cable and the load. The cables oppose each other. Tighten up both, and the joint becomes stiff. Loosen up both, and the joint becomes flexible. Like muscles. CWRU robotics liked this idea. Lightweight robot arms and painting robots have used it. Snake robots often work that way. Robot hands are often tendon driven. Tendon robots are not popular for industrial use. The tendon cables wear out. Robots which do the same thing over and over wear their tendons at the same points. Not good in factory settings. A useful model of a muscle is a spring and damper in parallel, like an auto suspension. The spring's neutral point, the spring's spring constant, and the damper's damping constant are all controllable. An actuator built that way can provide both force and position control, and can absorb shock loads. This is roughly how biological muscles behave. The most practical actuator like that is a double-ended air cylinder. Each end has two proportional valves, to let air in from the air supply and to let air out to exhaust. Such devices can be tuned from stiff to rigid, held at any position, and can absorb shock loads, which just compress the air trapped in the cylinder. Festo, the German automation equipment manufacturer, is a leading promoter of that approach.[1] They've popularized precision pneumatic control with a computer managing the valves. Works great in factories where you can plug into a compressed air line. Festo has lots of videos online, if you like looking at pneumatic actuators. A series elastic actuator is a different concept. It's a stiff spring on the end of a stiff screw-type linear actuator. Shock loads compress the spring, a sensor at the spring detects this, and the linear actuator is commanded to quickly spin up the motor and unload the spring. Force can be measured from the length of the spring. It's a way to fake a real force actuator with a cheap positional one. This was a popular idea in research robotics, because it's something that can be put together from off the shelf components. It's a useful research tool. But it's not a very good actuator for large loads. There's a race between the applied load squeezing the spring and the motor spinning up to take off the load before the spring bottoms out. It's only useful for a limited load range. If the spring is too stiff, you still take a high shock load at the gear train. If the spring is too soft, the spring bottoms out before the motor can catch up. You can buy series elastic actuators from academic and hobbyist suppliers [2], but they're rarely seen in factories. There's been much robot actuator progress in the last decade. Not miracles, just money and good specialized mechanical engineering. [1] https://www.youtube.com/watch?v=GedJiaz_E1I https://www.youtube.com/watch?v=GedJiaz_E1I [2] https://www.hebirobotics.com/actuators https://www.hebirobotics.com/actuators
scotty79 6mo ago
AI that drew the diagram couldn't get it's neurons around how planetary screws in linear actuator should work. Here's an actual schematic: https://ae-pic-a1.aliexpress-media.com/kf/Sd3fe9841e4ed4871b86da2693f3f4293Q.jpg_720x720q75.jpg_.avif https://ae-pic-a1.aliexpress-media.com/kf/Sd3fe9841e4ed4871b... Why these screws are used instead of just threads? Because rolling friction is lower than sliding friction. You can use less or more of them trading friction for shock resistance.
amelius 6mo ago
What are the SOTA algorithms for making them walk/move? I see a lot of videos lately, mostly from China, and I'm curious what everybody is using.
amelius 6mo ago
Those running blades used e.g. in the paralympics can make locomotion more efficient.
- regularfry 6mo ago
  Similar principle taken to more of an extreme: https://is.mpg.de/publications/bb01 https://is.mpg.de/publications/bb01 I really want to build one of those, they look great fun. (specifically in context of the article I want to see what happens if you lower the CG. Harder balance problem, but might reduce some of the instantaneous torques)
giannicmptr1000 6mo ago
This is a direction worth focusing on. Inspiring work.
korse 6mo ago
Does anyone know of a non-slop summary of the same material? Despite the AI diagrams and symbols, the material is more than directionally accurate.
Unable0841 6mo ago
Through the first 10 figures I looked at, there was literally A SINGLE ONE that didn't have obvious functional errors. This was not written by someone who read or understood the material. This is slop

169 points by ofrzeta 6mo ago

num42 6mo ago

Check out opensource actuator for robots. Opentorque actuator https://www.gabrael.io/new-page https://www.gabrael.io/new-page https://github.com/G-Levine/OpenTorque-Actuator https://github.com/G-Levine/OpenTorque-Actuator

regularfry 6mo ago
In the context of the torques in the article, a nylon sun gear in the gearbox feels optimistic.

aardvarkdriver 6mo ago

Why the AI "engineering expert"? Seems to take some credibility away from what otherwise could be an interesting and informative read.

barbegal 6mo ago
Yeah I couldn't get past so many issues in the AI generated illustrations. Not useful at all when they are completely wrong.
- Tanxsinxlnx 6mo ago
  right
- moffkalast 6mo ago
  Even the video is generated. The whole thing is just slop upon slop, I'm amazed that it got to the top of the front page here. I suppose it's a genuinely impressive amount of fakery all integrated together.

Miles_Stone 6mo ago

[flagged]

modeless 6mo ago

AI was clearly heavily used in the making of this article, and I almost dismissed it as slop. But after reading it I think there's enough correct information here for it to be useful as a general overview of the problems in the space.

ramon156 6mo ago
They should've left out figure 6. it adds very little and the screws are wrong.
raphman 6mo ago
I believe that bad/wrong explanations are actually much worse than no explanations. Many figures seem to be either missing key information (e.g. Fig. 5: the elliptical deformation is not shown - a human artist would have created a very different figure to explain the concept) or plain wrong (Fig. 6: the threaded rollers have the wrong orientation, Fig. 7: the ball is much too large for the bearing and the whole figure seems nonsensical at first glance). And if the author did not spot these obvious problems with the figures, they either have no clue, accept sloppy work, or didn't even read the article they generated. That article is not really good advertising for the company's products. (That the link behind the author's name leads to their Wikipedia article which seems to be a revised copy of the CV on their website is interesting, too.)

Animats 6mo ago

The power of money. I spent some time on legged locomotion back in the 1990s. It was clear then that you wanted torque control, and I did some work on the theory for that, trying to solve it from first principles, not machine learning. Got some nice theory and a patent out. But the parts just weren't there to build such things. As the article points out, the key to this is motor back-drivability. The final drive has to survive shock loads, and it has to dump forces into the motor, where the magnetic fields can take it. As I've quoted before, "you cannot strip the teeth of a magnetic field", a comment from early General Electric locomotive sales. (Locomotives are Diesel-electric, not Diesel with a clutch and shifting gearbox, because the clutch required is huge. Yes, it's been tried.) That's something few areas of engineering cared about, with the exception of aircraft flight control systems with mechanical backup. Pneumatic actuators looked promising, but proportional dynamic valves were big, heavy, and about $1000 each. Linear motors (not ball screws) looked like the coming thing back then, as 10:1 power/weight ratio had been achieved. But that technology never got much further, and Aura, the biggest player, collapsed in a financial scandal. Series elastic actuators were (and still are) a race between the spring compressing and the ball screw motor starting up. Hydraulics were too clunky; Boston Dynamics built a 400 pound mule, but the Diesel power pack never worked. Direct drive pancake motors were used by some SCARA industrial robots, but those were too big for leg joints. I thought someone would crack the direct drive problem eventually, but nobody ever did. We're still stuck with some gear reduction. Some of the exotic ideas for muscles mentioned in this article go back that far. The McKinney muscle is old, and not too useful. There was some interest in electrorheological fluids, fluids whose mechanical properties change when an electric field is applied. That didn't become useful either. Shape-memory alloys were a dead end; liquid cooling can overcome the slowness problem, but not the inefficiency problem. Everybody went back to good old electric motors, although they became 3-phase AC instead of DC. It helped that the drone industry made 3-phase motors and their controllers small, cheap, and powerful. Academic robotics groups were tiny. MIT and Stanford had less than a dozen people each. Progress required hundreds of millions of dollars for all that custom engineering and R&D. The level of effort just wasn't there. Nor would throwing money at the problem prior to machine learning have led to useful products. It's impressive what's been accomplished in the last five years. It took a lot of money.

6mo ago

ReptileMan 6mo ago

Except we don't need 100% bipedal robots. Wheels are perfectly ok for majority of city work and factory floor. Put the robot on rollerskates break the wheels for the occasional stair.

fragmede 6mo ago
I don't know about your city, but my city, while covered in smooth surfaces, still has a lot of interactions between those surfaces. Most of the roads have a curb between the sidewalk and the road, though the ADA means there's curb cuts and ramps. I don't know that I'd agree that they're "perfectly okay". Traversing over a 20 cm/8 inch obstacle constantly seems to make wheels less than perfect.

elil17 6mo ago

I simply do not understand why you would ever prefer a fully humanoid robot as opposed to a humanoid torso on some other locomotion system.

rob74 6mo ago
Isaac Asimov already explained that better than I could (https://www.reddit.com/r/asimov/comments/pm84ud/why_robots_are_humanoid/ https://www.reddit.com/r/asimov/comments/pm84ud/why_robots_a...): > Besides that, our entire technology is based on the human form. An automobile, for instance, has its controls so made as to be grasped and manipulated most easily by human hands and feet of a certain size and shape, attached to the body by limbs of a certain length and joints of a certain type. Even such simple objects as chairs and tables or knives and forks are designed to meet the requirements of human measurements and manner of working. It is easier to have robots imitate the human shape than to redesign radically the very philosophy of our tools.
- elil17 6mo ago
  Right, but: 1. Asimov wrote that because he needed robots to be indistinguishable from humans for plot reasons. 2. We do 99% of our tool use with our arms and hands. We are already very good at building robot arms. We are getting better at robot hands. We can build robot legs, but they're very expensive and they pose a major safety risk for the robot itself and surrounding humans (because the robot can fall if there is a failure). For most applications, why not just put biomimetic hands and arms on a rolling base? Of course, all this humanoid robotics research is still useful because if you can build a fully humanoid robot you can trivially build a torso-on-rolling-base robot. I sort of suspect that most of the humanoid robotics companies already know that the vast majority of their sales will be in that category.
  - rob74 6mo ago
    You can still have a humanoid robot that looks very different from an actual human (and most robots from Asimov's novels were of that kind, although one of the main characters wasn't - https://en.wikipedia.org/wiki/R._Daneel_Olivaw https://en.wikipedia.org/wiki/R._Daneel_Olivaw). Ok, so maybe a robot with wheels could solve most tasks, but it would still be severely limited: couldn't climb stairs (which would make it unsuitable as a domestic robot in a house or multi-storey flat), couldn't drive a car, truck or any other vehicle designed for humans etc.

ramon156 6mo ago

I cannot un-see these left border hints, it's driving me crazy.

gpugreg 6mo ago

This is AI slop and the article contains some of the worst illustrations I have ever seen. Most do not make any sense mechanically. Here are the worst ones: - The "orbiting threaded rollers" in figure 6 are not meshing with anything (not that they could, since they are orientated in the wrong direction). - The ball of the ball screw in figure 7 deforms the screw and the roller screw "meshes" with a flat surface. - The guy on the pogo stick in figure 14 is jumping himself rather than putting his feet on the stands of the pogo stick. - In figure 16, a key penetrates the elastomer skin of the optical tactile sensor, destroying it. - The gears in figure 20 touch perpendicularly.

ofrzeta 6mo ago
> - The ball of the ball screw in figure 7 deforms the screw and the roller screw "meshes" with a flat surface. Really, it is hilarious. This will teach me a lesson or two.
ofrzeta 6mo ago
Is it? Now I feel bad for having posted it. I mean, I know some stuff but not enough to judge over all the content in this article. It's unfortunate but from glancing over I thought it was a comprehensive and useful resource. I guess I will just give up on the Internet or something like that.
- sailingparrot 6mo ago
  « Rotary Actuators (The "Reflected Inertia" Trap) », « Quasi-Direct Drive (QDD) — The "Cheetah" Approach « The pattern ‘something — The « metaphor » <qualifier> ‘ screams Gemini. Gemini seem completely unable to generate a section title that doesn’t follow this annoying pattern.
- ModernMech 6mo ago
  You just need some AI literacy, this document is very plainly AI generated. You don’t need to be an expert in the content to see that. First time you see an em dash your AI sense should be tingling. Then you see random bolded words alarm bells should be going off. Next you notice 70% of the headlines follow the pattern “The X: Y” and that seals it.

itrunsdoomguy 6mo ago

Do they run Doom?

RaSoJo 6mo ago

How can we trust this article or the company if the writer/so-called chief engineer decides to hide himself behind an AI avatar? From what I can understand this is the Robbie Dickson in question: https://www.huffpost.com/entry/lessons-from-a-serial-ent_b_9230012 https://www.huffpost.com/entry/lessons-from-a-serial-ent_b_9... Nobody has a problem with companies using AI to edit articles, create images. But when even the writer is an AI persona, the trust factor gets destroyed.

olig15 6mo ago
I think at very least, the diagrams are AI generated too. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/strain-wave-gear-components-exploded-diagram.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/strai... The middle component has teeth on the inside half way round, should be smooth on the inside. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/inverted-planetary-roller-screw-linear-actuator-mechanism.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/inver... 4 of the 5 orbiting threaded rollers are perpendicular to the screw thread, so wont do anything. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/ball-screw-vs-roller-screw-hertzian-contact-stress.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/ball-... Ball doesnt fit in the screw thread, just 'squashed' to make it fit?. Screw thread isnt consistent. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/stiffness-bandwidth-tradeoff-graph.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/stiff... Classic 3 interlocked gears. > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/optical-tactile-sensor-gelsight-diagram.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/optic... Has the elastomer been ripped when the key was inserted? > https://cdn.shopify.com/s/files/1/0554/0567/4694/files/biological-gap-robot-actuator-vs-artificial-muscle.png https://cdn.shopify.com/s/files/1/0554/0567/4694/files/biolo... Another gearbox that doesnt do anything... The rest of the website seems filled with just as much slop too...
- Mars008 6mo ago
  I wouldn't be surprised if article is actually AI generated summary from several sources.Guided by human. It's a new phenomena. Recently got a book on agentic AI which looks like OpenAI docs with added generated water.

Loic 6mo ago

Asking: As gpugreg remarked[0], this is AI slop to the point that it is impossible to trust anything from this article/blog post. As such, I flagged the submission. - I wonder, is it possible to give a reason to the flag? - Is flagging the submission without comments the right way to go? For me, it is important that slowly but surely it goes through that AI slop is not what is accepted here on HN. Yes to have whatever LLM helping with grammar, spelling, etc. but the content should not be the output of a one shot "write me a blog post about humanoid robot actuators" prompt. [0]: https://news.ycombinator.com/item?id=48005917 https://news.ycombinator.com/item?id=48005917

epaga 6mo ago
I also flagged it when I realized the video claimed to be someone it wasn't. Unacceptable in my mind.

vova_hn2 6mo ago

Probably a dumb question, because I know nothing about robotics, but: > The "Zero RPM" Problem > When a robot bends its knees to stand, the motor must constantly fight gravity. There is no skeletal structure to lock against. To an electric motor, holding a static load—known as stall torque—is the most punishing state possible. Why not just add some kind of brake that can fully or partially lock the joint?

AntiUSAbah 6mo ago
You need to keep balancing fast enough. I don't think a break would give you this agility.
thrownthatway 6mo ago
Complexity, weight, failure modes, wear, maintenance, support burden of legacy parts. Also the brake components are never in the same plane as the drive components, so now you have additional forces to engineer for.
- korse 6mo ago
  It's just weight. If you remove the human scale constraint, you can use hydraulics and easily lock out all your joints with reasonable complexity and maintenance demands. If you're unfamiliar, just look up the history of electrohydrostatic actuators and see where they're at now. https://www.moog.com/products/actuators-servoactuators/actuation-technologies/electrohydrostatic.html https://www.moog.com/products/actuators-servoactuators/actua...
blueblisters 6mo ago
Brakes are being added to actuators but they're more useful for static holds / locking than dynamic balancing. Standing even in humans is a dynamic balancing activity.
- regularfry 6mo ago
  It is, but you don't have to do it at every joint all the time. If you lock your knees your front and back thigh muscles don't have to work on balancing in that axis at all.

spwa4 6mo ago

TLDR: we don't have the actuators required to make humanoid locomotion work reliably. Also: something every human actually kind of knows. You need to take impacts on muscles, not on mechanical connections. Even if we had the actuators required, you also need perfect control. The only way actuators can work this well is if they properly predict the impacts so that the power of the motor ("the magnetic field") can absorb nearly all the impact. If you try to take the impacts even on human bones (that are very solid and self-repairing) they will break surprisingly quickly. My opinion is that the need for high reduction is only because we can't have high voltage on the motors. If we either had very small distances between the magnets and electrical wires (think micrometers), or we have voltages in the 100s to 1000s of volts, we don't have to make this poisoned choice. (in a way, VERY small distances between magnets and wires is how human and animal muscles do it. But they go all the way down to sub-10 nanometers)

regularfry 6mo ago
Naively it feels like the improvements to resistive losses ought to be so dramatic from this that we must already be at some sort of equilibrium position. Double the voltage and divide the resistive losses by 4 - that's neither a trivial gain nor seemingly difficult to achieve? We're not talking kVs here.

jFriedensreich 6mo ago

Its completely impossible to trust an article when half the diagrams have serious issues and headlines are worst slop indicators. I am sure the author is knowledgeable and spend some time on this. But please please, with butter, please, either spend the last 10% to get rid of these issues or just don't publish it! Keep it in your ai research gallery or if you want to publish that gallery as ai research?

scotty79 6mo ago

I really like the idea of using two series elastic actuators in parallel on the same joint. This way motors acting in opposite direction can pre-tension the springs making the leg stiffer or softer. And if a lot of strength is needed they can act in the same direction summing their forces. It should be fairly straightforward to control dynamically so you can use pretty much any motor and gearbox.

Animats 6mo ago
That's an idea that predates series elastic actuators. It's been used in tendon robots, where there are two winding drums pulling on two cables, with a spring between the end of each cable and the load. The cables oppose each other. Tighten up both, and the joint becomes stiff. Loosen up both, and the joint becomes flexible. Like muscles. CWRU robotics liked this idea. Lightweight robot arms and painting robots have used it. Snake robots often work that way. Robot hands are often tendon driven. Tendon robots are not popular for industrial use. The tendon cables wear out. Robots which do the same thing over and over wear their tendons at the same points. Not good in factory settings. A useful model of a muscle is a spring and damper in parallel, like an auto suspension. The spring's neutral point, the spring's spring constant, and the damper's damping constant are all controllable. An actuator built that way can provide both force and position control, and can absorb shock loads. This is roughly how biological muscles behave. The most practical actuator like that is a double-ended air cylinder. Each end has two proportional valves, to let air in from the air supply and to let air out to exhaust. Such devices can be tuned from stiff to rigid, held at any position, and can absorb shock loads, which just compress the air trapped in the cylinder. Festo, the German automation equipment manufacturer, is a leading promoter of that approach.[1] They've popularized precision pneumatic control with a computer managing the valves. Works great in factories where you can plug into a compressed air line. Festo has lots of videos online, if you like looking at pneumatic actuators. A series elastic actuator is a different concept. It's a stiff spring on the end of a stiff screw-type linear actuator. Shock loads compress the spring, a sensor at the spring detects this, and the linear actuator is commanded to quickly spin up the motor and unload the spring. Force can be measured from the length of the spring. It's a way to fake a real force actuator with a cheap positional one. This was a popular idea in research robotics, because it's something that can be put together from off the shelf components. It's a useful research tool. But it's not a very good actuator for large loads. There's a race between the applied load squeezing the spring and the motor spinning up to take off the load before the spring bottoms out. It's only useful for a limited load range. If the spring is too stiff, you still take a high shock load at the gear train. If the spring is too soft, the spring bottoms out before the motor can catch up. You can buy series elastic actuators from academic and hobbyist suppliers [2], but they're rarely seen in factories. There's been much robot actuator progress in the last decade. Not miracles, just money and good specialized mechanical engineering. [1] https://www.youtube.com/watch?v=GedJiaz_E1I https://www.youtube.com/watch?v=GedJiaz_E1I [2] https://www.hebirobotics.com/actuators https://www.hebirobotics.com/actuators

scotty79 6mo ago

AI that drew the diagram couldn't get it's neurons around how planetary screws in linear actuator should work. Here's an actual schematic: https://ae-pic-a1.aliexpress-media.com/kf/Sd3fe9841e4ed4871b86da2693f3f4293Q.jpg_720x720q75.jpg_.avif https://ae-pic-a1.aliexpress-media.com/kf/Sd3fe9841e4ed4871b... Why these screws are used instead of just threads? Because rolling friction is lower than sliding friction. You can use less or more of them trading friction for shock resistance.

amelius 6mo ago

What are the SOTA algorithms for making them walk/move? I see a lot of videos lately, mostly from China, and I'm curious what everybody is using.

amelius 6mo ago

Those running blades used e.g. in the paralympics can make locomotion more efficient.

regularfry 6mo ago
Similar principle taken to more of an extreme: https://is.mpg.de/publications/bb01 https://is.mpg.de/publications/bb01 I really want to build one of those, they look great fun. (specifically in context of the article I want to see what happens if you lower the CG. Harder balance problem, but might reduce some of the instantaneous torques)

giannicmptr1000 6mo ago

This is a direction worth focusing on. Inspiring work.

korse 6mo ago

Does anyone know of a non-slop summary of the same material? Despite the AI diagrams and symbols, the material is more than directionally accurate.

Unable0841 6mo ago

Through the first 10 figures I looked at, there was literally A SINGLE ONE that didn't have obvious functional errors. This was not written by someone who read or understood the material. This is slop