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membrane displacement with AC actuation/excitation
Posted Dec 10, 2013, 5:30 a.m. EST MEMS & Nanotechnology, MEMS & Piezoelectric Devices Version 4.3 2 Replies
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I have a MEMS structure which is comparable to a parallel plate capacitor: The top membrane/plate is fixed at both end and free to bend up and down, while the bottom membrane/plate is fixed (not moving). Top plate is considered as terminal and bottom plate is ground. So when there's potential difference, the top plate will be displaced/bend towards the bottom plate.
The idea is to use AC actuation instead of DC, in order to avoid the charging effect. Plus, the frequency should be set beyond the natural frequency, so that we can get a constant/stable (not oscillating) top plate displacement. This has been confirmed experimentally. In the simulation however, if the frequency is set beyond the first natural frequency of the structure, the membrane start to bent upwards. Even with AC, the electrostatic force between these two plate should be the same, and the plate should move to each other. So it is "weird" for the top membrane to move away from the bottom plate (as far as I know). Does anyone knows why it is like this? I have spent more than a month to figure this out, but with no success.
The physics used are: electric current & solid mechanics. Study is done in frequency domain. This was also done with DC actuation, and the results are comparable to experimental values. So i suspect my AC-simulation might be wrong somewhere.
Many thanks in advance for your helps!! =)
Hello Mustaqim Iskhandar
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If yes, there's no error. The result is simply shown with the "wrong" phase.
You can go to Results > Data Set > Solution > Solution at angle. And you can increase the displayed value by 180°.
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