Precision Mode-Matching Gyroscope using In-Run Adjustment of Spring Azimuth

This paper presents a novel precision mode-matching method for Coriolis vibratory gyroscopes with high-Q resonator by adjusting the angle of spring azimuth (θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω</inf> ) using quad demodulation with dual PLL. The proposed method can control the frequency difference (Δf) between the drive and sense resonant frequencies more precisely compared with conventional modematching methods because Δf can be directly measured and θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω</inf> can be independently measured and adjusted during the gyroscopic operation. By applying this method to shell-type resonators having a Q-factor of 230,000 with an initial θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω</inf> of 23 degrees and Δf of 1.6 Hz, θ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ω</inf> can be controlled within 0.013 degrees, thus Δf of 2.02 mHz at 1σ was achieved. This result shows an improvement in accuracy of about 5 times over the conventional mode-matching accuracy of 10mHz [1].