RCID

MEMS Gyro Analysis

Background

A miniature solid-state gyro has been developed using MEMS (micro-electro-mechanical systems) technology. These devices can detect the rate of turn of objects in motion and their small size and low cost allows them to be used in new applications, particularly in the aerospace, medical and defence fields.

Project Aims

This project aimed to improve the robustness of a prototype device to enable it to withstand severe shocks.

Device Modelling

The RCID modelled one segment of the device in Pro Engineer and imported it into Pro Mechanica for meshing and finite element analysis. The device consists of a silicon ring supported on a glass substrate, and these material properties were included.

Dynamic Analyses

The structural model was checked for accuracy by calculating its resonant frequencies and comparing them to those measured on existing devices. The first twenty modes were identified including those due to whole-body motion of the gyro ring and those caused by resonances in parts of the structure.

Strength Calculations

Calculations showed that, when subjected to the required shock, the device would suffer from high stresses at a critical location. The RCID proposed several modifications which would reduce these stresses to acceptable levels, whilst allowing the gyro to operate satisfactorily.

Results

The production process was changed to incorporate the modifications and the new MEMS gyros are now being manufactured, ready for shock testing.