A Novel Architecture for Digital Control of MEMS Gyros

Rödjegård, H., Sandström, D., Pelin, P., Carlsson, M., Bohman, M., Hedenstierna, N., and Andersson, G. I.
Type of publication: 
Conference item

This paper describes a system for implementation of digital feedback loops and digital signal conditioning to control vibrating MEMS gyroscopes. Compared to conventional analogue solutions this implementation improves the flexibility regarding algorithms and control parameters. The offset stability is also improved since the baseband processing is performed in the digital domain and is thus free from 1/f noise. The algorithms for the digital control loops and the output signal generation are implemented in an FPGA that is connected to the gyro via an interface circuit. This circuit is a configurable analogue ASIC containing high performance capacitive readout amplifiers, ΣΔ-modulators and analogue feedback recovery circuits. An evaluation platform based on the digital concept and PC software has been fabricated. Due to the programmability, the platform significantly speeds up the development process of new algorithms and control parameters. It is also a valuable tool when testing new gyro elements. Until now the system has been evaluated with two different butterfly gyros presently with a lowest resolution of 0.005 deg/s/√Hz. However, it can be used with other capacitive/electrostatic gyros as well.

Published in: 
Proceeding of IEEE Sensors 2004