joreilly

I can't give an answer which would pass a proper roboticist without them wrinkling their nose, but my guess is that rotary actuators are more simple and space efficient to implement, and can generate the necessary high torques for these systems.

When using a linear actuator, you need to offset it from the joint so that it generates torque (that's part of the reason we have kneecaps, actually; it increases the distance between the centre of rotation of our knee and where our leg muscles are actually pulling from, increasing the output torque). This involves more mechanical complexity in the design compared to rotary actuators, which can just be slapped onto the joint directly. That offset also takes up space, so your system is now less compact.

None of the heavier legged robots I know of use direct drive actuators; ANYmal uses Series Elastic Actuators, MIT Cheetah and (maybe) Boston Dynamics Spot use Quasi-Direct Drive actuators with a low gear ratio gearbox (sub-10:1, I believe), RealHyQ uses hydraulic actuators. Electric actuators simply can't output the amount of torque these systems need to carry themselves around, so they need some form of gearing. The linked actuators you shared are direct driven, so they would need some gearing on their output. I had trouble finding anything about gearing direct drive linear actuators, which leads me to believe it's not really a thing, because if you need high loads, you'll jump to geared linear actuators, which are really just rotary actuators with a belt or rack and pinion!

Aside from the mechanical challenges associated with using a linear actuator setup, it's (to my knowledge) not necessarily better to follow biology when it comes to robots. Wheeled robots can move faster on flat terrain than any animal, so legs aren't ideal when you have access to gas-powered engines or electric actuators. Airplanes with turbines can carry much heavier loads than birds because flapping wings just doesn't scale up to the weight of a jumbo jet with luggage and passengers. Legged robots are actually more energy efficient when they don't try mimicking an animal's gait because they don't have organic muscles arranged in the same way. Any finally, rotary actuators are a better choice than linear actuators (for now) because we don't have hyper-compact, super torque-dense linear actuators that can match our muscles.

This isn't to say that biologically inspired designs can't be better, and there's a lot of research into finding ways of replicating the natural properties of certain materials, such as the strength of silk or hardness of the shells of some crustaceans. But in the end, with the technology we have, rotary actuators provide better torque density, and a more compact and simple design than linear actuators.

[1]: I didn't cite anything here because of time constraints, but it's an amalgamation of half-forgotten knowledge from some research I've done on the topic of legged robots

Eh, robots are tools, and like most, they'll be used and abused. ANYmal and Boston Dynamics Spot are currently being used for automated site inspections, and most of the top spots for the recent DARPA subterranean challenge were legged robots [1]. Of course, you also have companies like Ghost Robotics which are weaponising their platform [2]. Should we have not made airplanes because someone would eventually put bombs on them?

I'm sure there's a lot more philosophical depth to the topic, and perhaps my quick dismissal of your criticism is equally unproductive as your comment, but I see a use-case for these (frankly super cool) robots in every day society/workplaces.

[1]: https://www.subtchallenge.com/results.html [2]: https://www.engadget.com/robot-dog-gun-ghost-robotics-sword-...

In this case, "Dynamic" is likely referring to the fact that the robot is dynamic, not the company Boston Dynamics. In fact, Dynamics is literally just the study of forces and their effect on motion, so I feel like it would be a stretch for them to try and own a term used in every undergraduate mechanics class [1].

[1]: https://en.wikipedia.org/wiki/Dynamics_%28mechanics%29

I'm not sure any of the big legged robots are using direct drive actuation yet; MIT Cheetah and Cheetah mini use quasi-direct drives with a sub-10:1 gear ratio for super high proprioceptive sensing. ANYmal actually uses series-elastic actuators, since they allow the actuator to operate at a higher speed and lower output torque, thus making them more efficient than a quasi-direct drive setup found in other quadrupeds [1]. They also allow for some energy reuse, since they can release energy stored by compressing the spring. The downside is, like you said, reduced control bandwidth, since the spring element will behave optimally under a given set of conditions and, going outside that operating range, will either be more stiff or less than is ideal.

That said, for the kind of work ANYmal is currently being deployed on (site inspection mainly, I believe), they're hardly doing hyper-dynamic movements, so I think selecting SEAs over quasi-direct drive was a fairly judicious choice. Just like it makes more sense to have quasi-direct drives in a highly dynamic robot like the MIT Cheetah; it depends on the use case.

[1]: https://www.researchgate.net/figure/Comparison-of-EV-electri...

I've written a similar guide that goes into a bit more detail, such as setting up S3-compatible object storage as the primary storage, using a custom domain name, etc.:

https://joshuaoreilly.com/Blog/nextcloud_linode.html

I've enjoyed using Nextcloud so far. Download and upload speeds seem better than my previous cloud provider, despite using the cheapest node available. Having my Notes, Calendar, and Deck all available on the same platform is nice too. It's great having a cloud that isn't chock full of dark patterns; the only thing I've found similar so far with Nextcloud is the server branding at the bottom, which, as you detailed, can be removed.

From the article:

> In her suit, Viola acknowledged writing most of the posts. But she denied being behind the anti-Muslim screed. That was critical to Sorokin’s decision to allow the libel and defamation part of Viola’s suit to proceed. The former professor “has plausibly alleged that Benton may have been negligent in his failure to verify that she was the author,” the judge wrote.

If she can prove that it wasn't her/Benton can't prove that it was her (I'm not familiar with the legal system, so I don't know which it would be), then there would indeed be an untrue statement. As for damage; why does anyone dredge up another's darker side, if not to damage them in some way? I can't think of another motive for doing so.

Parroting jimkleiber, I like the distinction between advertising in public and private spaces, although I suppose it would be a matter of being adamant that anywhere that isn't in a private building, isn't private space.

> There's not that much physical world advertising in my part of Europe (e.g. almost no road side banners at all), but I still despise how we've sold bus stops and metro walls to the highest bidder

I lived in Germany for a few months and was shocked to see advertisements for cigarettes on the sides of the local buses. I suppose this will be changing in 2022, so a good first step [0].

[0]: https://www.thelocal.de/20200918/germany-set-to-ban-cigarett...

> Reminds me of how one day, I think in SF, I was trying to go around without reading things and just realized there are so many things shouting at me with words, especially billboards and other forms of public advertising. I would love to even have a city here in the US experiment with something like this.

I'm in the exact same position, I'd love to see a large-scale experiment to determine the economic and psychological impact of removing public advertising, or at least reducing it to a more "comfortable" level, whatever that may be. The Canadian government experimented a bit with universal basic income in the 70s, and more again recently with COVID, so perhaps they'd be willing to give this a shot as well.

> I would, too, especially as a consumer, and yet, as a producer, I wonder how annoyed I would be without ads. Maybe there's a balance, and I believe needs to be have more consumer voice, and less producer voice.

Another concern/shortcoming I forgot to address above is what companies will do to get their products out there; will advertising take a more subtle, perverse tone if they're not allowed billboards and banner ads? Perhaps a middle-ground will stop a more covert extreme from appearing. Perhaps I'm falling for the middle ground fallacy.

Performing the same though-exercise, I find myself with a different conclusion; I despise physical advertising. I hate driving down the high-way and seeing a massive billboard for who-even-cares interrupting the fields and forests. I don't want to have products pushed at me while walking around downtown. São Paulo removed all billboards/branding/advertising with their Clean City Law [0] in 2007 and the difference before and after is massive. It immediately looked so much more clean and beautiful (at least for the parts of the city they photographed, probably some selection bias here). Assuming that billboards and advertising are somehow putting money into the government's pockets, I would gladly raise my taxes to eradicate public advertising permanently. Bringing the analogy back to digital advertising, I'd be happy to pay some sort of monthly fee to "The Internet" to receive access to it and never see an ad or be tracked again, perhaps similar to what Coil [1] is attempting, but somehow at full-internet scale. Naturally, how this could be implemented is far beyond me, as are the economics behind advertising, so I suppose I'm doing little more than wistful thinking.

If I had to compromise, I would agree that more agency and less intrusive ads and tracking are a start.

[0]: https://99percentinvisible.org/article/clean-city-law-secret...

[1]: https://coil.com/

I added a link to my website in my profile, my email is on there. Cheers!

I'm building a quadruped robot a-la Boston Dynamics/MIT Cheetah. I'm not really happy with the state of legged robots in terms of affordability and performance. I've found there are two classes of robots; robots in the first sacrifice mobility for the sake of driving cost down, either limiting the legs to move in a single plane, or using lower cost, but extremely slow servo motors [1][2][3][4]. Robots in the second class don't compromise the performance of the robot, but cost at the very least $6000 [5][6][7]. I'm working on using an underactuated leg (3 degrees of freedom, but only 2 actuators instead of the typically used 3) to bring the cost down, as actuators are the largest cost center for these robots. It should also (hypothetically) have better performance than other robots which use 2 actuators per leg but constrain them to a single plane.

[1]: https://hackaday.io/project/171456-diy-hobby-servos-quadrupe...

[2]: https://stanfordstudentrobotics.org/pupper

[3]: https://open-dynamic-robot-initiative.github.io/

[4]: https://stanfordstudentrobotics.org/doggo

[5]: https://hackaday.io/project/176487-k3lso-quadruped

[6]: https://build-its.blogspot.com/2019/12/the-mini-cheetah-robo...

[7]: https://shop.bostondynamics.com/spot?cclcl=en_US&pid=aDl6g00...

I'm a relatively new user to HN. I've greatly appreciated how much more civil the conversations tend to be when compared to reddit. I have noticed, however, that news submissions, especially those which do not inherently have a technological aspect to them, tend to digress into what I can only assume are strongly held, but not adequately supported, opinions on the topic. These are then met by a flurry of flags. Further, submissions such as this one seem to directly contradict the HN guidelines, as it is arguably [1]:

> Off-Topic: Most stories about politics, or crime, or sports, unless they're evidence of some interesting new phenomenon. Videos of pratfalls or disasters, or cute animal pictures. If they'd cover it on TV news, it's probably off-topic.

On one hand, this type of submission is not a new phenomenon and has been submitted to HN multiple times. If you search for Hong Kong arrests on HN, you get dozens of results; for example, [2][3][4][5], etc. On the other hand, I understand why people who feel strongly about this topic want to submit content pertaining to it past an initial submission some months ago.

[1]: https://news.ycombinator.com/newsguidelines.html

[2]: https://news.ycombinator.com/item?id=25654143

[3]: https://news.ycombinator.com/item?id=20846681

[4]: https://news.ycombinator.com/item?id=23698247

[5]: https://news.ycombinator.com/item?id=25654803

I'm assuming you're referring to how softly he tip-toes around events like the Tiananmen Square Protests or the massive famine during the Great Leap Forward? If so, I certainly agree with you and many of the Goodreads reviewers in that his approach could be considered overly diplomatic. If anything, I think knowing the weaknesses of the book in advance is advantageous for weighing what Kissinger says throughout. If not, I'm curious to know your thoughts. My knowledge on China is limited to discussions with family friends who have some experience through their work, and this book, so I would not be surprised to know that I am severely lacking.

Thanks for the recommendation! I feel as though On China sacrificed detail to allow for greater scope, and it left me wanting for more information on certain periods.

If anyone is looking for a relatively digestible book on China, I can wholeheartedly recommend On China by Henry Kissinger [1]. While he does tend to meander at some points, it gives a solid introduction to China's recent history (arrival of the British, the civil war, up to around 2010) and interactions with the United States throughout. At least, to someone who initially had very little knowledge on the topic.

[1]: https://www.goodreads.com/book/show/9328314-on-china

I'm not well versed in CPU design; how does a 3.1Ghz peak clock A14X outperform a 4.8GHz peak clock i9 [1]? The only thing that immediately comes to mind is a massive hypothetical instructions-per-clock advantage.

[1]: https://www.apple.com/shop/buy-mac/macbook-pro/16-inch-space...