[HN Gopher] Active ball joint mechanism with 3 DoF based on sphe...
___________________________________________________________________
Active ball joint mechanism with 3 DoF based on spherical gear
meshings (2021)
Author : nabla9
Score : 131 points
Date : 2022-12-28 12:30 UTC (10 hours ago)
(HTM) web link (ieeexplore.ieee.org)
(TXT) w3m dump (ieeexplore.ieee.org)
| luma wrote:
| Here's a video of this linkage in action:
| https://youtu.be/AHUv9Zda_48
| jcims wrote:
| Some incredible explanatory animations.
| etrautmann wrote:
| Anyone know what CAD software was used to make these
| animations?
| luma wrote:
| I'm curious as well, the "flat" shader being used is
| gorgeous.
| hwillis wrote:
| Probably 90% chance its either fusion 360 or solidworks
| luma wrote:
| Together Autodesk and Dassault account for less than 40%
| of the market: https://www.cadalyst.com/cad/pandemic-
| transforms-cad-industr...
|
| That number also includes CATIA from Dassault and
| Inventor and AutoCAD and all the other stuff from
| AutoDesk. Solidworks and F360 themselves are likely less
| than 20% of the overall market.
|
| f360 and Solidworks are common in the maker
| communities/youtube/etc as they both offer free/cheap
| licenses to get started, so that's what you're mostly
| likely to encounter unless you actually work in the
| field.
| ge96 wrote:
| at 2:01 that differential pinion... trying to figure out how
| that would work... it looks like it's locked in place yet it
| spins.
|
| edit: oh maybe it's some kind of worm gear/helical gear to
| translate 90 deg or maybe weird bevel gear
| henearkr wrote:
| Edited. Thought the name in the linked article ("ABENICS") was a
| reference to the former PM (yikes), but instead it is probably a
| reference to the author of the article himself.
|
| Still weird to call a technology by one own's name... usually we
| let other people do it for us. Especially in Japan, where
| humbleness is valued. Thus I am still a bit suspicious.
|
| I would still welcome an alternative name, more descriptive.
|
| Edit: "spherical gear" is the name used elsewhere, and it fits
| nicely!
| RobotToaster wrote:
| The fact that it's in capitals makes me think it's an acronym
| of some kind? Active Ball Effector?
|
| Or since it's always written next to "active ball mechanism" it
| could be Active Ball mEchaNICS?
| jabbany wrote:
| Umm, you do realize that the first author's surname is also
| Abe? And that in general it's a common-ish surname...
| henearkr wrote:
| Ok. I edited my comment accordingly. Thanks.
| HPsquared wrote:
| Perhaps someone else in the group coined the name?
| henearkr wrote:
| Doesn't make sense if the Abe person is part of the group who
| developped it (at least, according to the way Japanese people
| think of groups of persons). Unless he's dead.
| pimlottc wrote:
| It's a product they're looking to commercialize. Naming
| products after yourself is nearly as old as time.
| formerly_proven wrote:
| Might be a pun on both one of the author's name and abenomics.
| _a_a_a_ wrote:
| Can't see teh video but I think I've seen this before - very neat
| but there seems to be a couple of conditions where a kind of lock
| up (gimbal lock?) could occur.
| Animats wrote:
| That's very clever. I've seen videos of this before. It's a
| robotic actuator.
|
| Notice that it's overconstrained. The ball has 3 degrees of
| freedom, but is driven by 4 motors, which must maintain some
| invariant relationship. It's kind of like a mechanical
| implementation of a quaternion.
| dtgriscom wrote:
| Good point. I wonder how they manage the inevitable mis-match
| of the motor positions? Seems like it would be easy to get the
| system into a high-tension state, with motors fighting each
| other.
| calvinmorrison wrote:
| This seems so trivial I can't help but think there's prior art?
| jacquesm wrote:
| Trivial??
| [deleted]
| samwillis wrote:
| This is far from trivial, there is significant control needed
| to keep the gears in sync and track the relative position of
| the main spherical gear.
| calvinmorrison wrote:
| Significant like more than someone can do with a 3d printer
| and two stepper motors? I don't know... I just feel like this
| would have been solved.
|
| Looks like an old mouse, except it has a motor instead of a
| sensor
| bqmjjx0kac wrote:
| A mouse ball has two degrees of freedom, but this spherical
| joint has three.
| calvinmorrison wrote:
| and here's a very similar article from 2008..
|
| "A new kind of spherical gear and its application in a
| robot's wrist joint"
| jacquesm wrote:
| It's not even close.
| addaon wrote:
| This 2008 paper seems to describe the mechanical and
| manufacturing side of a 2DOF spherical joint, not a
| fully-realized actuated 3DOF spherical joint.
| keepquestioning wrote:
| Can this be used in 3d printing?
| xpe wrote:
| To clarify: you are wondering if this has applications to make
| better 3D printers?
| keepquestioning wrote:
| yes
| jwagenet wrote:
| I could see this being used for a 5 axis fdm printer to
| replace a traditional 2 axis gimbal. I'm not sure where the
| value would be except for highly specialized applications
| where you are ok with fdm, but want to avoid traditional
| layer building (think making a sphere 'smooth')
| leeoniya wrote:
| reminds me of the Triple Gear:
| https://www.youtube.com/watch?v=I9IBQVHFeQs
| jacquesm wrote:
| There appears to be an improved version that they have in the
| works:
|
| https://link.springer.com/chapter/10.1007/978-3-031-08140-8_...
| carabiner wrote:
| Previously: https://news.ycombinator.com/item?id=28556208
| mhb wrote:
| Among others: https://hn.algolia.com/?q=spherical+gear
| henearkr wrote:
| Here we are! "spherical gear" (used in your link) is a waaayy
| better name than "abenics" (used in the link of the present HN
| submission)...
| hinkley wrote:
| This solution seems to have a lot of "gimbal lock" positions so
| I'm not sure 3 degrees is really accurate. The gears are so large
| that you lose 120deg of rotation along one axis. 2.6 DoF is
| probably more accurate.
| xpe wrote:
| What are some ways the robotics field / industry quantifies
| degrees of freedom?
| hinkley wrote:
| The six degrees I'm aware of are translation through three
| dimensions and rotation along each axis. Assembling a car
| takes a lot of those for some fiddly bits for the interior
| and under the car.
|
| Some configurations of this device can rotate 180deg on one
| and about 240deg on another. One configuration, the one that
| gets the most screen time, is worse than that, which is what
| got me wondering in the first place.
| jacquesm wrote:
| That's a beautiful write-up. At the end under 'media' there are
| two videos linked.
| lizardactivist wrote:
| Just looking through the paper makes my head spin. The Japanese
| are undoubtedly the most skilled engineers in the world.
| keepquestioning wrote:
| Japanese and also German.
|
| Old-school, driven by craft, not obsessed about clicks and
| profit. Just incredible utility to society and civilization.
|
| Thank god for these countries.
| rng_civ wrote:
| > Old-school, driven by craft, not obsessed about clicks and
| profit.
|
| While this has been the prevailing sentiment for Germany, I
| wouldn't be so sure after the Volkswagen emission fiasco. At
| least Volkswagen seems pretty eager to work around QA laws...
| xpe wrote:
| Japan and Germany have also demonstrated terrifying war-
| making capability and willingness not so long ago. This is
| consistent with part of your comment ("old-school, driven by
| craft") but problematic w.r.t. "utility to society and
| civilization", given the goals of authoritarian regimes,
| under both a secular demagogue and a supreme divine ruler.
| The U.S., through IBM, sold Nazi Germany tabulating machines,
| which made atrocities more "efficient".
|
| My point is not to assign blame or simply comment on
| geopolitics. Rather, I just want to raise awareness that
| technology and craft exist in a broader context, easily
| misappropriated and distorted.
|
| I hope the technologists of today (us) are the leaders of the
| future. We should not abdicate key decisions about technology
| to others. We must get involved with investment, ethics,
| safety, and regulatory decisions.
| 082349872349872 wrote:
| > _We should not abdicate key decisions about technology to
| others._
|
| cf Hesse, _The Glass Bead Game_
| xpe wrote:
| There is an opinion piece in The Atlantic highlighting how
| important hands-on building (i.e. manufacturing) is for long-
| term innovation.
|
| https://www.theatlantic.com/magazine/archive/2023/01/science.
| ..
|
| """The U.S. remains the world's R&D factory, but when it
| comes to building, we're plainly going backwards."""
|
| """For many decades, the American government has focused
| overwhelmingly on discovery rather than deployment."""
|
| """And then, around 1980, we basically stopped building,"
| Jesse Jenkins, who researches energy policy at Princeton,
| told me. In the past 40 years, he said, the U.S. has applied
| several different brakes to our capacity to build what's
| already been invented. Under Ronald Reagan, the legacy of
| successful public-private partnerships was ignored in favor
| of the simplistic diagnosis that the government was to blame
| for every major problem. In the '70s, liberals encouraged the
| government to pass new environmental regulations to halt
| pollution and prevent builders from running roughshod over
| low-income neighborhoods. And then middle-class Americans
| used these new rules to slow down the construction of new
| housing, clean-energy projects--just about everything. These
| reactions were partly understandable; for example, air and
| water pollution in the '70s were deadly crises. But "when you
| combine these big shifts, you basically stop building
| anything," Jenkins said."""
|
| Note: If you skim the above article, be aware that "Bush"
| refers to Vannevar Bush (not George #41 or George #43) in
| several places.
| williadc wrote:
| May I have your permission to use this as an example of a
| logical fallacy?
| jacquesm wrote:
| If you're only going to post once a month or so make it
| count.
| xpe wrote:
| > If you're only going to post once a month or so make it
| count.
|
| I agree in a sense. Life is short. Our online comments
| probably will last longer than us. What do we want to put
| out into the world?
|
| We can use comments to learn, or we can respond
| uncharitably. The former is more worthwhile in most cases.
|
| [1] inclusive-or
| downvotetruth wrote:
| > inclusive-or
|
| ior & eXclusive: eor
| lizardactivist wrote:
| No.
| xpe wrote:
| >> Just looking through the paper makes my head spin. The
| Japanese are undoubtedly the most skilled engineers in the
| world.
|
| > May I have your permission to use this as an example of a
| logical fallacy?
|
| _If_ the comment was "Just looking through the paper makes my
| head spin; therefore, the Japanese are undoubtedly the most
| skilled engineers in the world." then it would be a logical
| fallacy.
|
| As written, one has to make an _uncharitable_ assumption in
| order to classify it as a fallacy.
|
| A _charitable_ reading is that the author has other
| experience suggesting the ascendancy of Japanese engineers.
| Such a mindset would open the door to interesting
| conversation, such as "What else have you seen that impresses
| you about Japanese engineering?" That might lead to everyone
| learning more, and, heck, even being inspired. Try this next
| time, please?
| Ord3rChaos wrote:
| I saw this last year, really cool demo. Stronger materials are
| needed to make this useful and that looks like a nightmare to
| manufacture at scale. Also mechanical advantage seems to be a
| major tradeoff.
|
| There is a reason biology tugs on ropes and lets reaction
| surfaces slide around instead.
| hwillis wrote:
| > There is a reason biology tugs on ropes and lets reaction
| surfaces slide around instead.
|
| And that reason is that it's very difficult to have a rolling
| joint or muscle because you can't get blood into it. It's
| largely fundamentally inaccessible to an organism that must
| grow itself. There are massive advantages that are unexplored
| by evolution.
|
| Even further, gears are inherently asymmetric, meaning they are
| even harder to evolve. Nevertheless nature DOES use gears[1]
| when it can.
|
| > You can shape the surfaces the way you want for the movement
| you need.
|
| You can actually do the same with gears and screws:
| https://www.youtube.com/watch?v=100is1XpXcE
|
| [1]: https://www.smithsonianmag.com/science-nature/this-insect-
| ha...
| rolph wrote:
| its actually like a hydraulic cushion , with a self renewable
| matrix between the bones. we are close to mimicking tissue
| renewal with some of the recent materials advances.
|
| https://en.wikipedia.org/wiki/Shoulder_joint
|
| https://en.wikipedia.org/wiki/Self-healing_material
| busyant wrote:
| > Also mechanical advantage seems to be a major tradeoff. There
| is a reason biology tugs on ropes and lets reaction surfaces
| slide around instead.
|
| I'm not sure I understand. Do you think that there's a
| biological benefit to ropes and sliding (compared to this)? Or
| is it simply that ropes/sliding are easier to evolve? You
| probably know this, but (in case others are unaware) there are
| rotary "engines" in biology (e.g., bacterial flagellum and F0F1
| ATPase), but, obviously, they are not quite like this spherical
| gear.
| scotty79 wrote:
| Imagine two sliding surfaces held agains each other and
| pulled by ropes.
|
| You can shape the surfaces the way you want for the movement
| you need. Make them as big or small depending on how much
| compressive load you need to transfer. You can place as many
| ropes, controlled ropes or just stretch ropes to have as much
| flexibily, control and ability to survive tension as you
| need.
|
| You can do all of this with pretty crappy materials and high
| tolerances.
|
| When compared to that, gears that transfer all of the load
| through individual small teeth that must be made from
| incredible materials and struggle if you need multiple
| degrees of freedom there's really no competition.
|
| Unless you need to deal with fast spinning things or simple
| 1dof fixed axis rotations gears are terrible technology and
| they rarely ever evolved not because they are hard but
| because they have huge weeknesses and barely any advantages.
|
| The only gears that ever evolved that I know of are used for
| syncing movement.
| ethbr0 wrote:
| Also, "ropes" have the benefit of driving wide ranges of
| rotation while requiring relatively small muscle
| contraction distance, by attaching close to a joint's pivot
| point, which meshes well with muscle fiber physical
| characteristics and limits.
|
| E.g. a 135deg forearm range driven by a 4-5cm tri/bicep
| contraction
| guyomes wrote:
| Example of 1D gear used in planthopper used for syncing the
| movement of the legs [1]. Even there the gears are only
| used for young planthoppers, and adults use another syncing
| mechanism after their skin molts away.
|
| [1]: https://www.smithsonianmag.com/science-nature/this-
| insect-ha...
| irjustin wrote:
| I believe the parent comment is talking about scale at human
| sized.
| miketery wrote:
| What is meant by "reaction surfaces slide"? Is this referring
| to joints?
___________________________________________________________________
(page generated 2022-12-28 23:01 UTC)