ANGULAR VELOCITY IN HARMONIC ANALYSIS

[FRANCESCA PISTORIO]

Hi everyone!

I would like to perform a harmonic analysis on a MEMS gyroscope structure to obtain the frequency response function. In brief, the structure is excited in the x-direction by a harmonic force and when there is an angular rate around the z-direction, the structure starts to move along the y-direction. I attach an image of my very simple structure.

I have performed an initial harmonic analysis with no angular velocity and I had no problem. My results match very well the analytical ones.

The problem starts when I try to apply a constant angular velocity on the structure and perform the harmonic analysis. I summarize the steps which I followed (I am using APDL at the moment but I can use also Workbench):

1) I built the model (the central rectangular plate is meshed with shell181 elements, while the beams suspension system is meshed with beam188 elements);

2) I activate the Coriolis effect using a stationary reference frame;

3) I apply on the central plate the constant angular velocity around the z-axis, using the CMOMEGA command (CMOMEGA, NAME-OF-THE-CENTRAL-PLATE-SELECTION,,,VALUE-OF-VELOCITY);

4) I perform a full harmonic analysis, applying the harmonic force along the x-direction.

My results are completely wrong and they are the same as the case of no velocity applied. I doubt this is related to having applied a constant angular rate.

Any advice?

Thanks for your time.

Best regards,

Francesca

[FRANCESCA PISTORIO]

 

 

Inviato da Posta per Windows 10

 

Da: FRANCESCA PISTORIO
Inviato: venerdì 28 agosto 2020 16:05
A: Ansys
Oggetto: ANGULAR VELOCITY IN HARMONIC ANALYSIS

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[Serkan Guler]

Dear Francesca,

In the harmonic analysis, you can not use angular velocity. If you want to drive the structure with constant velocity or varying velocity, you should carry out transient response analysis then obtain time responses of the structure. Taking the FFT transform of the time-dependent results you can obtain the FRF of the structure. In the linear harmonic analysis, you drive the structure (at any node) by implementing harmonic force you can obtain FRF of the structure. Hope all of these will help you.

Good luck,

Serkan

[Francesca Pistorio]

Dear Serkar,

sorry for my late reply. My simulation now works.

 

Thank you for your precious suggestion. It helped me a lot.

 

Kind regards,

 

Francesca

 

 

 

Inviato da Posta per Windows 10

 

Da: Serkan Guler
Inviato: venerdì 28 agosto 2020 20:39
A: an...@googlegroups.com
Oggetto: Re: ANGULAR VELOCITY IN HARMONIC ANALYSIS

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[Serkan Guler]

Dear Frencesca,

Great to hear your simulation runs.

Best wishes,

Serkan

To view this discussion on the web visit https://groups.google.com/d/msgid/ansys/90772AF8-9CCA-498A-88F5-E27E1242A36B%40hxcore.ol.