Microscopic pictures of the iPhone's MEMS gyro


Our MEMS gyros work the same way. Gorgeous.


(From iFixit, via Adafruit)




Views: 1878

Comment by Chris McNair on June 30, 2010 at 5:48pm
WOW!
Comment by Dustin Romero on June 30, 2010 at 6:42pm
does it actually spin? or does it measure capacitance?
Comment by Nima K on June 30, 2010 at 8:05pm
If I recall correctly, you measure angular velocity by having a cantilever beam in vibration on a single plane (vertical for example). Once the cantilever beam is rotated in the axis of the beam, a component of vibration will present itself in the perpendicular plane and by measuring this component you can measure the angular rate. This lateral vibration is the result of the coriolis effect of the rotation on the vibrating mass.

I think there's multiple types of vibration based gyroscopes and I'm only describing (from memory) one of them. It'd be interesting to get information on other types.
Comment by will y. on June 30, 2010 at 8:09pm
IMO the future of gyros is in laser based systems. It sounds like it's impervious to vibration and mechanical failure. http://en.wikipedia.org/wiki/Sagnac_effect Very cool, using interferometry to find rotation.
Comment by Greg Fletcher on June 30, 2010 at 9:21pm
Here's how they work as far as I know. Fallow my thought experiment. You are sitting in a chair looking forward (Y axis). The chair is not on the floor. It rotates around the Y axis. You're holding a flexible rod with a mass at the end pointing in the Y axis. The mass is oscillating vertically, powered by top and bottom magnets that run at the natural resonant frequency of the vibrating mass. The vibrating energy is in the vertical plane so if your chair rolls the mass will want to vib in the same plane, but the carbon fiber rod is twisting to force the vib/plane to rotate. Now, there are lateral position sensors top & bottom. These sense the twisting of the cantilever by sensing the top to bottom differential. That is how rotation rate is sensed. Only they do it on a micro scale at very hi frequencies, using electrostatic effects at micro scale. I think they use a tuned charge pump oscillator to excite the mass at resonance. Maybe PLL feedback? All the actual sensing is by variable capacitance. The mass is one plate of a capacitor moving in relation to the fixed plates (at least 4). Analog filtering and 'what ever' turn this into the output voltage. Whew! Either I'm a PHD from MIT or I did a lot of research on this subject. I report, You decide :)
Comment by Greg Fletcher on June 30, 2010 at 9:42pm
That first picture looks like the device is broken. Check the upper right thingy. This is a failure analysis pic. The really cool thing are the machines that make this possible. Multimillion dollar machines in very costly buildings with extra thick foundations in certain areas. Electron beam etching. Getting really really small. Like an electron microscope in reverse. Very expensive stuff that needs to be regularly topped of with liquid nitrogen. Extremely cool stuff (lowers thermal noise on the backscatter detectors).

Admin
Comment by Morli on July 1, 2010 at 12:22am
Greg,
you mean the second picture( I can see top right has a leak)? If not, can you highlight the broken area and post the pic again pls.

Admin
Comment by Morli on July 1, 2010 at 12:23am
ok got it , it is the first pic :)
Comment by Ken McEwan on July 1, 2010 at 4:25am
Using SEMs(Scanning Electron Microscopes) to do failure analysis on electronic devices. We used SEMs to examine GaaS FETs after thermal cycling and exposure to gamma radiation. It's amazing to see what happens to see what happens to semiconductors when stressed thermally and with radiation.

While no one was looking, we also looked at bugs, dust, skin cells, pollen etc....

Very cool pictures.

Developer
Comment by Sandro Benigno on July 1, 2010 at 7:27am
The last photo shows the first time that a system bug was shooted so close. This is a digital flea. :P

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