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Lec27p.GyrosNoise&amp;MDS

# Lec27p.GyrosNoise&amp;MDS - EE 245 Introduction to MEMS...

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Unformatted text preview: EE 245: Introduction to MEMS Lecture 27: Gyros, Noise & MDS CTN 12/3/09 Copyright © 2009 Regents of the University of California EE C245 : Introduction to MEMS Design LecM 15 C. Nguyen 11/18/08 12 • Drive and sense axes must be stable or at least track one another to avoid output drift Sense Electrodes Drive Electrode Tuning Electrodes Tuning Electrodes Quadrature Cancellation Electrodes Drive Electrode ω Amplitude Drive Response T 1 T 2 f o (@ T 1 ) f o (@ T 2 ) Problem : if drive frequency changes relative to sense frequency, output changes Ö bias drift Problem : if drive frequency changes relative to sense frequency, output changes Ö bias drift Drive Sense Need : small or matched drive and sense axis temperature coefficients to suppress drift Need : small or matched drive and sense axis temperature coefficients to suppress drift Sense Response Sense Electrodes MEMS-Based Tuning Fork Gyroscope EE C245 : Introduction to MEMS Design LecM 15 C. Nguyen 11/18/08 13 Mode Matching for Higher Resolution • For higher resolution, can try to match drive and sense axis resonance frequencies and benefit from Q amplification Sense Electrodes Drive Electrode Tuning Electrodes Tuning Electrodes Quadrature Cancellation Electrodes Drive Electrode ω Amplitude Drive Response T 1 T 2 f o (@ T 1 ) f o (@ T 2 ) Problem : mismatch between drive and sense frequencies Ö even larger drift! Problem : mismatch between drive and sense frequencies Ö even larger drift! Drive Sense Need : small or matched drive and sense axis temperature coefficients to make this work Need : small or matched drive and sense axis temperature coefficients to make this work Sense Response EE C245 : Introduction to MEMS Design LecM 15 C. Nguyen 11/18/08 14 Issue : Zero Rate Bias Error • Imbalances in the system can lead to zero rate bias error Drive imbalance Ö off-axis motion of the proof mass Drive imbalance Ö off-axis motion of the proof mass Output signal in phase with the Coriolis acceleration Output signal in phase with the Coriolis acceleration Sense Electrodes Drive Electrode Tuning Electrodes Sense Electrodes Tuning Electrodes Quadrature Cancellation Electrodes Quadrature Cancellation Electrodes Mass imbalance Ö off-axis motion of the proof mass Mass imbalance Ö off-axis motion of the proof mass Quadrature output signal that can be confused with the Coriolis acceleration Quadrature output signal that can be confused with the Coriolis acceleration Drive Electrode EE C245 : Introduction to MEMS Design LecM 15 C. Nguyen 11/18/08 15 Nuclear Magnetic Res. Gyroscope • The ultimate in miniaturized spinning gyroscopes? ª from CSAC, we may now have the technology to do this Atoms Aligned Nuclear Spins 0º-20º 20º 0º-20º 20º Laser Polarizer Rb/Xe Cell Photodiode 3.2 mm 1 mm 1 mm t θ & Soln : Spin polarize Xe 129 nuclei by first polarizing e- of Rb 87 (a la CSAC), then allowing spin exchange Soln : Spin polarize Xe 129 nuclei by first polarizing e- of Rb 87 (a la CSAC), then allowing spin exchange...
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Lec27p.GyrosNoise&amp;MDS - EE 245 Introduction to MEMS...

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