Very Fast MEMS Gyro Simulation
Posted by Josephus van Kuijk on Tue, Sep 08, 2009 @ 02:07 PM
If you are working on the
next generation gyroscope design take a look at this article presented by Coventor at the APCOM 2007 conference in Kyoto, Japan.
This paper explains the modeling behind CoventorWare-ARCHITECT which will allow you to go further than just plain and simple resonance frequency analysis in Finite Element Software. The biggest problem for Gyro designers is getting past the initial stage. Once the design is analyzed for matching frequencies the design questions get tougher; what is the driving voltage, can I lower my noise floor, etc. In order to answer these questions and more you can't use your Finite Element models anymore because they just take to long to run, you need to add the sensing electrostatic fields and even worse, you need to run transient (i.e. time dependent) simulations with your Sigma-Delta circuit!
The paper describes a modeling technique that uses Finite Element definitions for the 3D mechanics as shown in the figure below:
Figure 1: Schematic model of a MEMS gyroscope with illustrations of the physical geometry represented by some of the schematic symbols.
However, the method they use to simulate the 3D electro-mechanical model is based on Matrix Algebra which does not solve all the internal stresses and strains of the gyro but does compute the force and displacement equilibriums correctly. That's what makes this method so fast and lets you simulate in the time domain including electronic components.
The schematic from the paper models the full 3D electrostatic-mechanical model as shown in this figure:
Figure 4: 3D view of a MEMS schematic model of a double mass gyroscope generated with Scene3D
In addition it has a rich set of parameterization.
If you are a CoventorWare user and want to learn more about Gyro design using this method contact your support or just browse through the documentation.