Active ball joint mechanism with 3 DoF based on spherical gear meshings (2021)

Anyone know what CAD software was used to make these animations?

I believe the parent comment is talking about scale at human sized.

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.

Isn't that the only known instance of meshing gears in nature?

Agreed that there are plenty of geometries that would be very hard to evolve but are very useful. Wheels are another example.

The paper mentions that the rough surface of sintered powdered metal 3D printing won’t work (presumably way to much sliding friction). It also suggests the possibility of using that printing technique and surface machining it after printing.

I once designed a mirror array to track the sun and reflect the image on a solar panel to get more concentrated power (solars cells = expensive, mirrors = cheap). Obviously there are all kinds of limits to that but the interesting part in the current context was the drive: it started off with two motors per mirror and in successive iterations that went to one motor per row of mirrors and one motor per column to one for all the rows and one for all the columns and finally a single motor for all of the mirrors. It was mostly my lack of understanding about the way the sun and the earth interact over time at the beginning of the project that caused me to choose the most naive solution, but as understanding increased I saw more and more ways to optimize the whole thing ending up with a set of gears that resemble the relationship between the two bodies pretty much in the same way that a planetarium would do, with the angles of the mirrors as the function of the time of day and the position of the earth in its orbit around the sun as well as the axis of tilt.

That whole process took about a year and it looks to me as though this project is on a similar path of optimization, though it likely won't go much further than 3 motors, 4 gears assuming they can find a way to put the twist motor inside the spherical gear, which would come with its own challenges (supplying power, feedback).

Even moreso as the "pitch" of each monopole gear is controlled by a worm gear. So I think if you don't implement the controller very carefully, you could get situations where both worm gears work against each other.

Named after Old Abe, the Japanese scientist.

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 180° on one and about 240° 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.

I’ve been noodling on this while doing shores today. I think the main thing is not degrees of freedom here, but degrees of freedom around a fixed point. There are four servos in this thing, and about nine gears. You can rotate a probe through a full three degrees of freedom with three servos and six gears, but you also need the X Y and Z coordinates if you want to spin an object without moving it.

I think one more motor would give you full 3 degrees of freedom by allowing you to move the braces out of the path of movement. But I also suspect that one more of these motor assemblies would get you close to five degrees, and four of them total would get you six, with some wiring troubles to deal with. In the end you’d have an arm with just a “shoulder” and a wrist, which could be pretty interesting.

I aLso wonder if you could invert the gear and the cog, with motors inside the sphere.

Ok. I edited my comment accordingly. Thanks.

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.

yes

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.

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.

> 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...