Определение Аварии по MEMS Акселерометру
В настоящее время акселерометры встраивают куда только можно: в часы, автомобили, самокаты, LapTop-ы и прочее. В данном тексте изложена концепция распознавания аварии по данным с MEMS акселерометра. В этом тексте Вы узнаете зачем программисту микроконтроллеров надо знать дифференциальную геометрию .
https://habr.com/ru/articles/916386/
#crash_detection #crash_detection_by_accelerometer #accident_alert #mems #дифференциальная_геометрия #accelerometer
All I did was open github's webpage then search "i2c accelerometer".
What is my crime?
Обзор Акселерометра LIS3DH
В этом тексте я написал о своем опыте работы с акселерометром LIS3DH . Это трёх-осевой цифровой 16-битный MEMS акселерометр с перегрузкой 16g и управлением по I2C. Тут я написал с какой стороны следует подходить к ASIC акселерометрам.
https://habr.com/ru/articles/851180/
#LIS3DHTR #акселерометр #accelerometer #lis3dh #ADC #i2c #uartcli #asic #8308 #метрология
Our paper "Similarities of motion patterns in skateboarding and hydrofoil pumping" has been accepted by iWOAR2024! 🎉
@ACM
#skateboarding #surfing #accelerometer #imu #machinelearning
PicoQuake: a USB vibration sensor https://blog.adafruit.com/2024/06/03/picoquake-a-usb-vibration-sensor/ #accelerometer #earthquake #projects #sensors #sensor #usb
Time for Tessellation #quilt prototype tile layout below. This is an exploded #tessellation, and so far, it's my favorite, because it shows more of the quilt top. #hackerboxes control tile goes in the center.
I am going to do the anchor points for the control tile now. I'm using a historical sail eyelet model and built-in stitches on the #sewing machine to achieve the reinforced holes. Need a good thread to suspend the control tile and provide strain relief for the flexible wire that will route through these holes. Something neutral is what I am looking for.
The control tile will be able to move, therefore utilizing the #accelerometer to change the pattern of the circle of fifths #music #theory theme.
What a cool nerdy explanation video from @breakingtaps of Micro-electro-mechanical devices- #mems devices - in this case #gyroscope and #accelerometer in your phone. So cool.
In a past life, I worked in the commercialization office of a university, selling rights to our patents. A good chunk of them were MEMS devices - and it was always delightful to learn about these microscopic innovations.
#nebulatv:
https://nebula.tv/videos/breakingtaps-how-your-phone-knows-up-from-down/
YouTube:
https://youtu.be/9X4frIQo7x0
The ingenious micro mechanisms inside your phone
https://www.youtube.com/watch?v=9X4frIQo7x0
This video shows how accelerometers and gyroscopes work.
We analyse #DBS-evoked responses and relate them to objective quantitative parameters of movement extracted from #accelerometer recordings in a cohort of 22 patients with PD (3/5)
This video about MEMS IMUs by @breakingtaps is amazing!
Stunning electron microscope images and a really well done hands on explanation of how these intricate devices work!
(Amazing SEM image of an MPU6050 shown in the video!)
https://www.youtube.com/watch?v=9X4frIQo7x0
#mems #gyroscope #accelerometer #imu #sem #microscopy
How _does_ your phone track its relative position/orientation in space? Tiny little accelerometers and gyroscopes!
I dissected an IMU so we could trace it out in detail, play with printed models, analyze high speed footage and look at pretty SEM images
https://www.youtube.com/watch?v=9X4frIQo7x0
Cheers to all the folks I badgered with questions! ♥ The gyros in particular were a bit of a challenge to figure out, since they don't operate quite like a "textbook" MEMs gyro (or rather, they are more sophisticated in their sensing)
#mems #gyroscope #accelerometer #3dprinting #decapping #imu #sem #microscopy
We're taking a look at IMUs!
I decapped and scanned a 6-axis accelerometer/gyro chip, traced it, printed demonstration models, and filmed some high speed footage of how they work.
Video is live now on Nebula, will be up on YT this weekend!
https://nebula.tv/videos/breakingtaps-how-your-phone-knows-up-from-down
#mems #decapping #decap #accelerometer #gyroscope #3dprinting
Behold! A Macro Micro Electromechanical System! Only the most precise plastic sensors from Breaking Taps Macrofab Foundry!
(Vacuum hot-filament ionization gauge for scale, I guess 😅)
3ax accelerometer/gyro chip. Composite of 3 different chips that I decapped. Didn't get a complete view of top right unfortunately.
I thought the bottom was accel at first, but thinking they are gyros now? Dual mass vibrating kind? Lack of combs on the top devices is throwing me, just a few plates that I can see.
There are "pits" or cutouts under two of the three devices under the bottom, which is contributing to my feeling they are gyros (to help allow coriolis distortion)
#mems #decapping #gyroscope #accelerometer #sem #electronmicroscopy
Just get stuck on a #youtube and about #nucefic I noticed how it went right to the end where it tells you what it's about by just rotating my phone. #YouTube has learned how to detect when you're pissed off by looking at the #accelerometer on your #phone. Anyway, my question is, can #pihole block YouTube ads too? Also have you noticed #adremoved when you don't even have an ad removing app?
Anyway, I don't think #youtube realizes how fed up we all are with ads.
Accelerometer/gyroscope MEMS are just so damn cool. 😍
I think this'll turn into a really interesting video! 🤞
#mems #sem #microscopy #electronmicroscopy #accelerometer #gyroscope
TapType: AI-Assisted Hand Motion Tracking Using Only Accelerometers
The team from the Sensing, Interaction & Perception Lab at ETH Zürich, Switzerland have come up with TapType, an interesting text input method that relies purely on a pair of wrist-worn devices, that sense acceleration values when the wearer types on any old surface. By feeding the acceleration values from a pair of sensors on each wrist into a Bayesian inference classification type neural network which in turn feeds a traditional probabilistic language model (predictive text, to you and I) the resulting text can be input at up to 19 WPM with 0.6% average error. Expert TapTypers report speeds of up to 25 WPM, which could be quite usable.
Details are a little scarce (it is a research project, after all) but the actual hardware seems simple enough, based around the Dialog DA14695 which is a nice Cortex M33 based Bluetooth Low Energy SoC. This is an interesting device in its own right, containing a "sensor node controller" block, that is capable of handling sensor devices connected to its interfaces, independant from the main CPU. The sensor device used is the Bosch BMA456 3-axis accelerometer, which is notable for its low power consumption of a mere 150 μA.
User's can "type" on any convenient surface.
The wristband units themselves appear to be a combination of a main PCB hosting the BLE chip and supporting circuit, connected to a flex PCB with a pair of the accelerometer devices at each end. The assembly was then slipped into a flexible wristband, likely constructed from 3D printed TPU, but we're just guessing really, as the progression from the first embedded platform to the wearable prototype is unclear.
What is clear is that the wristband itself is just a dumb data-streaming device, and all the clever processing is performed on the connected device. Training of the system (and subsequent selection of the most accurate classifier architecture) was performed by recording volunteers "typing" on an A3 sized keyboard image, with finger movements tracked with a motion tracking camera, whilst recording the acceleration data streams from both wrists. There are a few more details in the published paper for those interested in digging into this research a little deeper.
The eagle-eyed may remember something similar from last year, from the same team, which correlated bone-conduction sensing with VR type hand tracking to generate input events inside a VR environment.
#machinelearning #wearablehacks #accelerometer #ai #bayesianclassifier #bluetoothlowenergy #predictivetext #textinput
This Golf Club Uses Machine Learning to Perfect Your Swing
Golf can be a frustrating game to learn: it takes countless hours of practice to get anywhere near the perfect swing. While some might be lucky enough to have a pro handy every time they're on the driving range or putting green, most of us will have to get by with watching the ball's motion and using that to figure out what we're doing wrong.
Luckily, technology is here to help: [Nick Bild]'s Golf Ace is a putter that uses machine learning to analyze your swing. An accelerometer mounted on the shaft senses the exact motion of the club and uses a machine learning algorithm to see how closely it matches a professional's swing. An LED mounted on the club's head turns green if your stroke was good, and red if it wasn't. All of this is driven by an Arduino Nano 33 IoT and powered by a lithium-ion battery.
The Golf Ace doesn't tell you what part of your swing to improve, so you'd still need some external instruction to help you get closer to the ideal form; [Nick]'s suggestion is to bundle an instructor's swing data with a book or video that explains the important points. That certainly looks like a reasonable approach to us, and we can also imagine a similar setup to be used on woods and irons, although that would require a more robust mounting system.
In any case, the Golf Ace could very well be a useful addition to the many gadgets that try to improve your game. But in case you still end up frustrated, you might want to try this automated robotic golf club.
Quantum Atomic Interferometer For Precision Motion Sensing
The current state of the art of embedded motion sensing is based around micro-electromechanical systems (MEMS) devices. These miracles of microfabrication use tiny silicon structures, configured to detect acceleration and rotational position in three dimensions. Accumulate these accelerations and rotations, and you've got a device that can find its orientation and track movement without any external waypoints.
Why do we care about dead reckoning anyway? Surely GPS and related positioning systems are good enough? Above ground GPS is usually good enough, but underwater and underground this simply won't work. Even heading indoors has a dramatic effect on the GPS signal strength, so yes, we need another way for some applications.
Right now, the current state of the art in portable sensors are MEMS devices, and you can get them for the cost of a hamburger. But if you want the ultimate in accuracy, you'll want a quantum atomic interferometer. What that is, and how it will be possible to make one small enough to be useful, is half of the story. But first, let's talk MEMS.
Fusion of The Sensors
Given an initial position and accumulated accelerations in 3D, it is possible to track position, for a short while at least. According to this (outdated) Cambridge University report on Inertial navigation systems, with a MEMS-based inertial tracking system, positional error can exceed 150 meters in under a minute, because the errors don't average out, they accumulate.
Improvements can be made by fusing data from other sensors into the navigation model. It all depends on where you are; here on earth such additional data inputs could be taken from a magnetometer, and also an altimeter. It has been shown that adding the magnetometer data alone can reduce that 150 meter error to only 5 meters. The study is a few years old, but we expect it to be about right, as progress with MEMS technology has not improved all that much.
Want to see how good or bad inertial navigation is in real life? A fantastic device for doing all this complicated multi-sensor fusion stuff is the Bosch BNO055, for which Adafruit have helpfully popped on a module. You just might want to brush up on quaternions before you do, mind.
All these measurements will exhibit an error, which will have some particular statistical distribution. One technique to mitigate this error is by using Kalman filtering, which is used heavily by inertial navigation systems. A Kalman filter enables a better understanding of the unknowns in a model, and essentially adjusts itself over time, to allow more influence from measurement points with the least uncertainty. The result is hopefully a better positional fix and an idea of which way you're currently pointing. But, you still can't get away with it for long, the error is still there, and it will still accumulate given enough time. Current research seems to suggest an error figure of about 5% of total distance travelled, best case. Longer term, sub-meter inertial navigation is the goal, and we aren't there yet.
MEMS Sensors: Sources of Error
A MEMS Gyro uses a resonating mass inside an isolated frame
The MEMS gyro is a dynamic device, in that it consists of a tiny vibrating structure that detects angular rotation rate by leveraging the coriolis effect. A mechanical shift is induced orthogonal to the vibration direction, which is sensed as a small change in capacitance.
Gyro sensors typically exhibit two main kinds of error; a rate bias and an angle random walk error, the latter is due to thermo-mechanical white noise and flicker noise in the signal chain electronics. The random walk error grows with time, which is what contributes mostly to the overall absolute orientation error. The rate bias however can be measured long-term and largely cancelled out. There are some other so-called calibration effects that affect stability and will also contribute error terms that are harder to compensate for.
A MEMS accelerometer is much simpler
The MEMS accelerometer has a more static structure, and is essentially a sprung element which deflects in one axis to due to acceleration. This mechanical shift is also picked up as a tiny change in capacitance. Again, we have the same two main sources of error; acceleration bias error and velocity random walk error. The bias error now is more complicated, because on this planet we have gravity, and in order to cancel out the bias error, we need to know the orientation of the sensor. Luckily with a multi-sensor fusion system, the orientation can be measured and this bias can be compensated. The velocity random walk error is again due to thermo-mechanical effects and accumulates with time. Also, as with the gyro, there are additional error factors that add to problem.
Other sensors used for inertial navigation systems will all have their own sources of error, and add to the complexity of the problem. There are optical gyros available, for example the ring laser gyro, and more esoteric devices, but these are not necessarily easy to make really small. For example, the ring laser gyro is less accurate the smaller you make it due to the limit in the maximum beam path length. This is why current research is taking a very different approach to this type of sensing; namely the atom interferometer.
Atom Interferometry
Back in 1924 French physicist Louis de Broglie proposed that matter behaves like a wave, with a wavelength equal to the Planck constant divided by its momentum. This meant that just like light, matter waves can be diffracted and produce interference patterns. In this case matter waves are manipulated with lasers, which leads us into the fun part. Remember though, that unlike light, atoms are massive and such, gravity has an influence, as we shall see.
Six intersecting orthogonal laser beams and a pair of anti-Helmholtz coil from a magneto-optical trap
Most atom interferometer experiments seem to operate similarly, in that they all depend upon a high vacuum pressure vessel, and utilise a magneto-optical trap to cool and slow down a stream of rubidium atoms produced from some source. This device uses six intersecting, circularly polarised laser beams, aimed at the centre of the device, with a pair of anti-Helmholtz coils at the top and bottom.
A Helmholtz coil is configured to generate a uniform magnetic field, using a single pair of coils, with current flowing in the same direction. The anti-Helmholtz coil (aka Maxwell gradient coil) simply flips one of the coils over, to produce a magnetic field gradient, with a field zero at the centre. Exactly what we need to trap those pesky little atoms.
The photons from the containment lasers give the atoms a little kick in momentum, and due to the Zeeman effect, the specially-shaped magnetic field ensures that atoms are more likely to get pushed back towards the optical null in the centre of the trap. On average the atoms in the trap centre slow down enough to reach temperatures of a few micro -kelvin. Which is jolly chilly.
The next bit is where things get a bit freaky. The trap is turned off, and immediately each of the suitably frigid atoms is hit with a specially prepared laser pulse, formed by a pair of opposing lasers, either Raman or Bragg transitions are effected, depending on the properties of the laser pulses. The atoms are forced into a quantum superposition of being both hit and not hit by the pulse. This causes the atoms to change momentum and state. (And not, simultaneously, it's superposition of states, right?) The atom cloud diverges and depending on the motion of the cell, interferes with itself as it expands out from trap centre.
When a low power laser illuminates the atom cloud, the superposition collapses and the interference pattern is observed on a suitably placed CCD. By decoding this pattern it is possible to infer angular velocity as well as acceleration, with incredible accuracy that will open up new applications both on earth and beyond. NASA are interested for one. For more detail on atom interferometry, checkout this introduction from Berkeley Physics.
Practicality
All of this is of little use as a navigation device if you can't get it out of the lab and shrink it down in size, make it reliable and make it cheap. Sounds easy, right? Let's look at the requirements for an atomic gyroscope: you need a pressure vessel with optically pure windows, usually sapphire, that can maintain a pressure of less than 10-7 torr with very low contamination. You also need the lasers themselves, with associated filters and control electronics. All of those things can be miniaturized, even down to chip size, but maintaining that vacuum is a big challenge. The usual way to get down to such low vacuum pressure is with a turbomolecular pump, in combination by an ion pump. Making these smaller has proved problematic.
A Passive Pumped Vacuum Package
Now there is a possibility of removing the need for that complex and bulky vacuum system. A team from Sandia National Laboratories and the University of Oklahoma, have developed a technique for achieving the ultra-high vacuum (UHV) needed for inertial guidance atomic gyroscope applications, without the need for turbo pumps, ion pumps or any pumps at all. OK, that last bit isn't strictly true, as they needed to get the vacuum to the desired level first and the standard techniques were needed for that, but once the initial conditions were achieved, the pressure vessel could be sealed off permanently, and the pumps removed.
Typical Zirconium sintered getter via saesgetters.com
The system relies on chemisorption using sintered porous getters, which are a kind of non-evaporable getter (NEG). These simple passive devices are formed from a sintered porous structure of zirconium powder and other materials, wrapped around an electrical heating element. When manufactured they are exposed to air, forming a passivating coating and protecting them from contamination. When installed in a vacuum chamber, the getter is activated by heating it up during the pump-down process. This diffuses the passivation layer into the bulk of the structure and provides an activated surface ready for adsorbing any contaminants during pump-down and afterwards when the chamber is sealed off. Getters are pretty common in many household vacuum vessel devices, from incandescent light bulbs, to radio valves, but the getters used here are a little bit more specialised than those of old, and capable of grabbing more atoms over a longer period and keep them contained.
The whole point here is that in order to have a small pure group of super cool rubidium atoms to poke with lasers, you first need to not have any other atoms kicking around, getting in the way. Such getters are super important for grabbing rogue atoms and maintaining this purity.
Outgassing is a problem with ultra-high vacuum devices. Contaminant gasses present in the structure of the housing diffuse out into the pressure vessel, contaminating the vacuum. Another related issue is that of permeation from the outside of the vessel. NEG devices work on chemical principles, so any helium that manages to diffuse into the vacuum from outside the enclosure will not react with the getter, and will contaminate the vacuum. Both of these problems were minimised by careful selection of materials. The frame was made from pure titanium, which had a low hydrogen content, with the windows made from sapphire, which apparently has no measurable helium permeability. These two materials have closely matched thermal expansion coefficients, which helps to maintain the vacuum seal and reduce stress on the structure as the temperature drops.
The team found that once pumped-down and sealed the 'passively pumped' vessel could maintain the 10e-9 torr vacuum pressure needed for over 200 days, and that means if all the other components could be successfully miniaturised, there is now a path to producing the first small and therefore portable MOT, and with it an atom interferometer capable of inertial guidance applications. Of course, since the application here is essentially an accelerometer, it can be used as a super-sensitive gravimeter which would be useful for ground surveying for sectors such as oil and mineral exploration as well as for geological research.
#engineering #featured #originalart #science #accelerometer #atomicinterferometer #getter #gyrometer #laser #optical #quantumaccelerometer #rubidium #vacuum
