I don't have time to watch the video but I was curious why MEMS gyros were shaped thus. Apparently it is to maximize sensitivity through the Coriolis force.
A few things about MEMS devices I have not been able to figure out is:
1. Is the sensing/moving structure actually disconnected from the rest of the device?
2. If so, how does it not get stuck to a side?
3. If it isn't disconnected, doesn't the friction from the connection cause an offset in the reading?
4. How do they etch the structure so that it is disconnected from the layer below?
1. Not entirely, it has two degrees of freedom. Think of it like a bridge.
2. The opposing springs are normally in equilibrium, so in the absence of forces the center mass moves back to position zero.
3. Think of it like a bridge. The points of contact and support are to the sides and stationary, while the spring mass system is suspended in air or in a vacuum.
4. Is simple enough if you start with two disconnected layers of materials, and then etch the top layer. You could also start with a layer of something like photoresist spincoated on the bottom layer, except for the adhesion points...
An interesting real-life scenario was the possibility of helium atoms being able to get inside the MEMS clock of some smartphones and cause the phone to stop working until enough helium can escape.
I believe the answer to your question is that the structure is "connected" to form a solid piece of material, but like any real material it isn't perfectly rigid. So it can vibrate, kind of like a tuning fork, and the thinner parts can act as springs. See the diagrams here: https://pmc.ncbi.nlm.nih.gov/articles/PMC9571586/
If you wanted to use such a device as a simple oscillator, you just set it vibrating and measure the oscillation frequency. Since the material isn't perfectly elastic, the vibrations will eventually be damped and die out (I guess this is what you mean by "friction"), so you use a feedback mechanism to keep the oscillation going.
A gyroscope works the same way, except that you use feedback to maintain an oscillation in one axis, and measure how much of that oscillation couples to a different axis. Whatever effect the damping has on the final measurement, I would assume it can be easily calibrated out.
I don't really know how they physically manufacture these devices without damaging the tiny, delicate structures. It's kind of mindblowing that they're so incredibly cheap.
I wonder why it's still here after all these years? It seems both useless and harmful, one of those features whose lifecycle consists of someone rolling it out because of some idea they had and then removing it three hours later after having to fix multiple headlines because they didn't think it through.
A lot of clickbait titles start with "How..." and removing it was an attempt to make titles more neutral. Unfortunately it sometimes has nonsensical results.
Mistakes happen, but in a video about gyroscopes it's hard to forgive mistaking position and orientation. That's the kind of thing that warrants a delete and re-upload.
Later in the video it correctly uses ‘movement in space’ (showing changing (x,y,z)) and ‘orientation’ separately when talking about use of accels and gyros respectively. The ‘position’ in the introduction is glossing over this before getting into details. You could argue with the presentation decision, but it’s not ignorance.
The video talks about accels in a few places, and how they are required for pose estimates.
This is not wrong at the pop sci level of the video.
Your phone undoubtedly has a gyroscope, accelerometer, and magnetometer all in a single IMU IC. Data from this IMU can be used to create a position cloud.
Add in some other sensor data to help collapse the position cloud, and your phone absolutely knows its position in space. Incidentally part of why IMU have magnetometers is that it’s basically one more sensor data to help collapse position clouds from just the orientation and acceleration data.
I think the only leap is how precise your phone would be with only gyroscopes generating orientation and acceleration data. But it sort of hints at this with the first rocket design using this data.
They are correctly using position. The dead reckoning a phone does over its accelerometers absolutely yields a position. It would of course drift quickly, but it would know its position relative to where it was was a while ago.
It's basically what VR headsets and controllers do, sans their periodic error correction from cameras or lighthouses.
>The dead reckoning a phone does over its accelerometers absolutely yields a position
Accelerometers yes, gyroscopes no. The video covers accelerometers later but hasn't introduced them yet, and the "your phone knows its position" line has a visual of an IC labelled "MEMS gryoscope".
I work very hard to downvote or block as much as I reasonably can. But I think the writing is on the wall.
Maybe YouTube will cater to those who don't know/care about AI generated content. Given that they make money on the spread between showing ads and views that are not monetized (I assume there is some lower threshold such that yt doesn't have to pay anything?). Those viewers might be a higher tier of ad consumer; one that is easier fooled and manipulated.
It's only going to get harder to detect AI voice. Sometimes they can talk for 15m before one syllable is mispronounced. I'm sure they are working on adding breath sounds and inflection.
Or if it gets bad enough, they will charge for a tier that requires human verification from the creators, perhaps.
If I'm doing research, I don't mind if it's AI but it should be clearly labelled and de-selectable.
Except it's not really gyroscopes, but gyrometers. The literature is very sloppy with this, but gyroscopes give you an angle, while gyrometers give you an angular velocity.
Using a gyroscope, you can look at it an hour after starting it, and understand how your orientation changed. Using a gyrometers, you need to continuously integrate the result (including the measurement error) to get your orientation: it's far less precise and tends to drift. Both laser and mems gyrometers suffer from this.
Besides this, the video is full of slop and likely AI-narrated. Someone mentioned the bacteria bit, I can also mention the weird-looking PCB image, where traces do not connect correctly to the chip.
I see several comments critical of this video. As someone whose only exposure to gyroscopes was the classic string-driven all-metal toy[0] when I was a kid, is this video helpful for getting a better understanding of how modern ones work, or should I just stick to the wikipedia page on gyrometers?
It does a passable job of presenting the ideas be mind miniature inertial measurement units we find on our phones, but the details are completely wrong, so do not read too much into them.
For instance, decreasing distance increases capacitance (thankfully, imagine the capacitive parasitics Voyager 2 would induce into all of our electronics otherwise... I'm taking a ridiculous example, but the claim is ridiculous too). On the very same diagram, it shows two capacitor values changing, but those would be connected in parallel, so you would get a constant value at the end: the structure as presented is wrong, though it has the correct idea: inertia in a mass-spring system, readout (usually) via capacitance change.
So yeah it works, but if you don't know these devices already, you can't really tell what is accurate. The Wikipedia article is more accurate.
38 comments
[ 0.19 ms ] story [ 3.8 ms ] threadhttps://en.wikipedia.org/wiki/Vibrating_structure_gyroscope
Their curious geometry reminds me of computer-designed antenna.
https://en.wikipedia.org/wiki/Evolved_antenna
2. The opposing springs are normally in equilibrium, so in the absence of forces the center mass moves back to position zero.
3. Think of it like a bridge. The points of contact and support are to the sides and stationary, while the spring mass system is suspended in air or in a vacuum.
4. Is simple enough if you start with two disconnected layers of materials, and then etch the top layer. You could also start with a layer of something like photoresist spincoated on the bottom layer, except for the adhesion points...
An interesting real-life scenario was the possibility of helium atoms being able to get inside the MEMS clock of some smartphones and cause the phone to stop working until enough helium can escape.
If you wanted to use such a device as a simple oscillator, you just set it vibrating and measure the oscillation frequency. Since the material isn't perfectly elastic, the vibrations will eventually be damped and die out (I guess this is what you mean by "friction"), so you use a feedback mechanism to keep the oscillation going.
A gyroscope works the same way, except that you use feedback to maintain an oscillation in one axis, and measure how much of that oscillation couples to a different axis. Whatever effect the damping has on the final measurement, I would assume it can be easily calibrated out.
I don't really know how they physically manufacture these devices without damaging the tiny, delicate structures. It's kind of mindblowing that they're so incredibly cheap.
God, I so hate the auto-title "fixing" feature on HN.
What is it even supposed to do?
https://www.ifixit.com/News/11986/iphones-are-allergic-to-he...
It's an ESP32 with:
- microphone and speaker
- wifi
- bluetooth
- screen
- two buttons
- IMU with six dimensions
all for under $35.
You can see a video of me using it to control a web based mini plane simulator https://x.com/alexpotato/status/2109782226841870352?s=20
Wild how cheap this kind of stuff has gotten.
Mistakes happen, but in a video about gyroscopes it's hard to forgive mistaking position and orientation. That's the kind of thing that warrants a delete and re-upload.
The video talks about accels in a few places, and how they are required for pose estimates.
This is not wrong at the pop sci level of the video.
Your phone undoubtedly has a gyroscope, accelerometer, and magnetometer all in a single IMU IC. Data from this IMU can be used to create a position cloud.
Add in some other sensor data to help collapse the position cloud, and your phone absolutely knows its position in space. Incidentally part of why IMU have magnetometers is that it’s basically one more sensor data to help collapse position clouds from just the orientation and acceleration data.
I think the only leap is how precise your phone would be with only gyroscopes generating orientation and acceleration data. But it sort of hints at this with the first rocket design using this data.
It's basically what VR headsets and controllers do, sans their periodic error correction from cameras or lighthouses.
Accelerometers yes, gyroscopes no. The video covers accelerometers later but hasn't introduced them yet, and the "your phone knows its position" line has a visual of an IC labelled "MEMS gryoscope".
Maybe YouTube will cater to those who don't know/care about AI generated content. Given that they make money on the spread between showing ads and views that are not monetized (I assume there is some lower threshold such that yt doesn't have to pay anything?). Those viewers might be a higher tier of ad consumer; one that is easier fooled and manipulated.
It's only going to get harder to detect AI voice. Sometimes they can talk for 15m before one syllable is mispronounced. I'm sure they are working on adding breath sounds and inflection.
Or if it gets bad enough, they will charge for a tier that requires human verification from the creators, perhaps.
If I'm doing research, I don't mind if it's AI but it should be clearly labelled and de-selectable.
Using a gyroscope, you can look at it an hour after starting it, and understand how your orientation changed. Using a gyrometers, you need to continuously integrate the result (including the measurement error) to get your orientation: it's far less precise and tends to drift. Both laser and mems gyrometers suffer from this.
Besides this, the video is full of slop and likely AI-narrated. Someone mentioned the bacteria bit, I can also mention the weird-looking PCB image, where traces do not connect correctly to the chip.
[0]: https://www.istockphoto.com/photo/toy-gyroscope-gm172188163-...
For instance, decreasing distance increases capacitance (thankfully, imagine the capacitive parasitics Voyager 2 would induce into all of our electronics otherwise... I'm taking a ridiculous example, but the claim is ridiculous too). On the very same diagram, it shows two capacitor values changing, but those would be connected in parallel, so you would get a constant value at the end: the structure as presented is wrong, though it has the correct idea: inertia in a mass-spring system, readout (usually) via capacitance change.
So yeah it works, but if you don't know these devices already, you can't really tell what is accurate. The Wikipedia article is more accurate.