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Hackaday Links: October 23, 2022

There were strange doings this week as Dallas-Forth Worth Airport in Texas experienced two consecutive days of GPS outages. The problem first cropped up on the 17th, as the Federal Aviation Administration sent out an automated notice that GPS reception was “unreliable” within 40 nautical miles of DFW, an area that includes at least ten other airports. One runway at DFW, runway 35R, was actually closed for a while because of the anomaly. According to GPSjam.org — because of course someone built a global mapping app to track GPS coverage — the outage only got worse the next day, both spreading geographically and worsening in some areas. Some have noted that the area of the outage abuts Fort Hood, one of the largest military installations in the country, but there doesn’t appear to be any connection to military operations. The outage ended abruptly at around 11:00 PM local time on the 19th, and there’s still no word about what caused it. Loss of GPS isn’t exactly a “game over” problem for modern aviation, but it certainly is a problem, and at the very least it points out how easy the system is to break, either accidentally or intentionally.

In other air travel news, almost as quickly as Lufthansa appeared to ban the use of Apple AirTags in checked baggage, the airline reversed course on the decision. The original decision was supposed to have been based on “an abundance of caution” regarding the potential for disaster from its low-power transmitters, or should a stowed AirTag’s CR2032 battery explode. But as it turns out, the Luftfahrt-Bundesamt, the German civil aviation authority, agreed with the company’s further assessment that the tags pose little risk, green-lighting their return to the cargo compartment. What luck! The original ban totally didn’t have anything to do with the fact that passengers were shaming Lufthansa online by tracking their bags with AirTags while the company claimed they couldn’t locate them, and the sudden reversal is unrelated to the bad taste this left in passengers’ mouths. Of course, the reversal only opened the door to more adventures in AirTag luggage tracking, so that’s fun.

Energy prices are much on everyone’s mind these days, but the scale of the problem is somewhat a matter of perspective. Take, for instance, the European Organization for Nuclear Research (CERN), which runs a little thing known as the Large Hadron Collider, a 27-kilometer-long machine that smashes atoms together to delve into the mysteries of physics. In an average year, CERN uses 1.3 terawatt-hours of electricity to run the LHC and its associated equipment. Technically, this is what’s known as a hell of a lot of electricity, and given the current energy issues in Europe, CERN has agreed to shut down the LHC a bit early this year, shutting down in late November instead of the usual mid-December halt. What’s more, CERN has agreed to reduce usage by 20% next year, which will increase scientific competition for beamtime on the LHC. There’s only so much CERN can do to reduce the LHC’s usage, though — the cryogenic plant to cool the superconducting magnets draws a whopping 27 megawatts, and has to be kept going to prevent the magnets from quenching.

And finally, as if the COVID-19 pandemic hasn’t been weird enough, the fact that it has left in its wake survivors whose sense of smell is compromised is alarming. Our daily ritual during the height of the pandemic was to open up a jar of peanut butter and take a whiff, figuring that even the slightest attenuation of the smell would serve as an early warning system for symptom onset. Thankfully, the alarm hasn’t been tripped, but we know more than a few people who now suffer from what appears to be permanent anosmia. It’s no joke — losing one’s sense of smell can be downright dangerous; think “gas leak” or “spoiled food.” So it was with interest that we spied an article about a neuroprosthetic nose that might one day let the nasally challenged smell again. The idea is to use an array of chemical sensors to stimulate an array of electrodes implanted near the olfactory bulb. It’s an interesting idea, and the article provides a lot of fascinating details on how the olfactory sense actually works.

Forearm Muscle Contraction Sensor Is Useful Component For Open Source Prosthetics

Being able to actuate parts of a prosthetic limb can make it much more useful. To help in this goal for partial arm or hand amputees, [TURFPTAx] has developed a sensor for detecting forearm muscle contractions. 

The sensor itself is cost-effective and simple to build.

The build is part of the Open Prosthetics project, which aims to offer open designs for various types of prosthetic devices. It apes common commercial designs using a simple electromechanical system.

The build relies on magnets mounted on twelve pistons that move when the muscles contract under the skin. The pistons are sprung to allow them to follow the expansion and contractions of the muscles, and the motion of the magnets is detected by hall effect sensors. The system is bulkier than some other solutions, but has the benefit of clean output and the ability to detect the movement of several distinct muscle groups. The data is all collected by an ESP32 which is then sent wirelessly to a computer for measurement, with [TURFPTAx] using the PyGame library to plot the sensor data.

[TURFPTAx] notes that the output of the sensors would be perfect to input into a machine learning system. Video after the break.

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3D Printing Delivers “Glass” Eyes In Record Time

Obviously, losing an eye would be bad for your vision. But if you think about it, it is also a detriment to your appearance. You might not need a prosthetic eye, and you can certainly rock an eye patch, but a lot of people with this problem get an artificial or “glass” eye. These glass eyes are hand-painted disks that fit into the eye socket. However, a British man now has a new kind of eye prosthesis that is 3D printed, a technology that can potentially cut waiting time for patients in half.

The existing process is lengthy because it requires taking a mold of the eye socket and manually matching the remaining eye with the new artificial eye. With the 3D printed technology, scans of the eye socket and the other eye make this process much simpler.

Moorfields Eye Hospital, the source of the eye, says that a conventional eye takes about six weeks, but the new ones take no more than three weeks. The patient only needs to spend about a half-hour doing the scans before the wait starts. We presume it can be made for less cost, as well.

Medicine is embracing 3D printing and we’ve seen a 3D ear. We are waiting for our personal exoskeleton. Some of the medical 3D printing we’ve seen is for the birds.

Tiny ball magnets implanted in muscles could provide much better control over prosthetics.

Magnets Could Give Prosthetic Control A Leg Up

Today, prostheses and exoskeletons are controlled using electromyography. In other words, by recording the electrical activity in muscles as they contract. It’s neither intuitive nor human-like, and it really only shows the brain’s intent, not the reality of what the muscle is doing.

Researchers at MIT’s Media Lab have figured out a way to use magnets for much more precise control, and they’re calling it magnetomicrometry (MM). By implanting pairs of tiny ball magnets and tracking their movement with magnetic sensors, each muscle can be measured individually and far more accurately than with electromyography.

After embedding pairs of 3mm diameter ball magnets into the calves of turkeys, the researchers were able to detect muscle movement in three milliseconds, and to the precision of thirty-seven microns, which is about the width of a human hair. They hope to try MM on humans within the next couple of years. It would be a great solution overall if it works out, because compared with the electromyography method, MM is cheaper, less invasive, and potentially permanent. Couple MM with a new type of amputation surgery called AMI that provides a fuller range of motion, less pain overall, and finer control of prosthetics, and the future of prostheses and rehabilitation looks really exciting. Be sure to check out the video after the break.

There’s more than one way to control prostheses, such as deep learning and somatosensory stimulation.

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Deep Learning Enables Intuitive Prosthetic Control

Prosthetic limbs have been slow to evolve from simple motionless replicas of human body parts to moving, active devices. A major part of this is that controlling the many joints of a prosthetic is no easy task. However, researchers have worked to simplify this task, by capturing nerve signals and allowing deep learning routines to figure the rest out.

The prosthetic arm under test actually carries a NVIDIA Jetson Nano onboard to run the AI nerve signal decoder algorithm.

Reported in a pre-published paper, researchers used implanted electrodes to capture signals from the median and ulnar nerves in the forearm of Shawn Findley, who had lost a hand to a machine shop accident 17 years prior. An AI decoder was then trained to decipher signals from the electrodes using an NVIDIA Titan X GPU.

With this done, the decoder model could then be run on a significantly more lightweight system consisting of an NVIDIA Jetson Nano, which is small enough to mount on a prosthetic itself. This allowed Findley to control a prosthetic hand by thought, without needing to be attached to any external equipment. The system also allowed for intuitive control of Far Cry 5, which sounds like a fun time as well.

The research is exciting, and yet another step towards full-function prosthetics becoming a reality. The key to the technology is that models can be trained on powerful hardware, but run on much lower-end single-board computers, avoiding the need for prosthetic users to carry around bulky hardware to make the nerve interface work. If it can be combined with a non-invasive nerve interface, expect this technology to explode in use around the world.

[Thanks to Brian Caulfield for the tip!]

Console Controller Mod Gets Amputee Back In The Game

No matter how it happens, losing one or more fingers is going to change one’s life in thousands of ways. We’re a manipulative species, very much accustomed to interacting with the world through the amazing appendages at the ends of our arms. Finding ways around the problems that result from amputations is serious business, of course, even when it’s just modifying a game console controller for use with a prosthetic hand.

We’ve gotten to know [Ian Davis] quite well around these parts, at least from his videos and Instagram posts. [Ian]’s hard to miss — he’s in the “Missing Parts Club” as he puts it, consisting of those who’ve lost all or part of a limb, which he has addressed through his completely mechanical partial-hand prosthetic. As amazing as the mechanical linkages of that prosthetic are, he hasn’t regained full function, at least not to the degree required to fully use a modern game console controller, so he put a couple of servos and a Trinket to work to help.

An array of three buttons lies within easy reach of [Ian]’s OEM thumb. Button presses there are translated into servo movements that depress the original bumper buttons, which are especially unfriendly to his after-market anatomy. Everything rides in an SLA-printed case that’s glued atop the Playstation controller. [Ian] went through several design iterations and even played with the idea of supporting rapid fire at one point before settling on the final design shown in the video below.

It may not make him competitive again, but the system does let him get back in the game. And he’s quite open about his goal of getting his designs seen by people in a position to make them widely available to other amputees. Here’s hoping this helps.

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Plastic Prosthetics For Rubber Duckies

Will someone please think of the rubber duckies?!

For decades they’ve been reduced to a laughing stock: a caricature of waterfowl. Left without a leg to stand on, their only option is to float around in the tub. And they don’t even do that well, lacking the feet that Mother Nature gave them, they capsize when confronted with the slightest ripple. But no more!

Arise!

Due to the wonders of 3D printing, and painstaking design work by [Jan] from the Rubber Ducky Research Center, now you can print your own rubber ducky feet. We have the technology! Your ducks are no longer constrained to a life in the tub, but can roam free as nature intended. The video (embedded below) will certainly tug at your heartstrings.

OK, it’s a quick print and it made my son laugh.

The base and legs probably don’t fit your duck as-is, but it’s a simple matter to scale them up or down while slicing. (Picture me with calipers on the underside of a rubber ducky.) The legs were a tight press-fit into the body, so you might consider slimming them down a tiny bit when doing the scaling, but this probably depends on your printer tolerances.

It looks snazzy in gold-fleck PETG, and would probably work equally well for some more elaborate rubber duckies as well.

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