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Comparison of Rocking-Mode Axes Predicted by System Identification with Axes Revealed by Interferometric Measurements
R.
T. M’Closkey, J. Hui, J. S. Gibson As
indicated in Figures 1 and 2, identification of a prototype microgyroscope
has shown that the rocking-mode axes are skewed with respect to the
natural device axes, determined by the silicon springs of the structure.
Figure 1 predicts the orientation of the rocking-mode axes.
This figure is based on system identification with the methods
described subsequently in this section.
With system identification, one estimate of each rocking-mode axis
is based on the sense electrode location, and a second estimate of each
rocking-mode axis is based on the drive electrode location.
Hence the two sets of predicted axes in Figure 1.
The close agreement of these two sets of axes indicates the
self-consistency of the identification results. Figure 2 shows interferometric measurements of
the displacements of the surface of the vibrating microgyroscope and
reveals the true orientations of the rocking-mode axes.
Comparison of Figures 1 and 2 shows that the axis-orientations
predicted by system identification are very accurate.
Of course, for microgyroscopes used in applications, such
interferometric measurements will not be available, and system
identification will be needed to determine the rocking-mode axes.
Figure
1. Rocking-mode axes predicted by system
identification.
Figure
2. Rocking
modes revealed by interferometry. The
green diagonal bands denote zero displacement (i.e., rocking-mode axes).
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