A Set of High Accuracy Low Cost Metallic Resonator CVG

V.V. Chikovani, Yu.A. Yatsenko, A.S. Barabashov, V.A. Kovalenko, and P. Tewksbury

Abstract:	A set of all-digital metallic cylindrical CVGs of different di-ameters are presented in this paper. Innalabs CVG43 with resonator diameter of 43 mm, having natural frequency about 1.5-1.9 kHz and made of low damping and temperature stable material, is placed under vacuum cap with residual pressure of about 0.2 mbar. The resonator Q factor reaches the value of 15000 -20000. CVG43 bias instability is about 0.1-0.2 deg/h at stable temperature and about 1 deg/h in the temperature range were obtained. Innalabs CVG25 as a lower accuracy of about 0.3-0.5 deg/h and smaller size gyro based on 25 mm resonator diameter having natural frequency of 3 . 3.5 kHz is presented in Allan variance graphs at constant temperature and in wide tempera-ture range. Innalabs CVG17 gyro based on 17 mm resonator diameter has an accuracy of about 3- 5 deg/h and can survive many thousands g쳌fs shock. This gyro is presented in Allan variance graphs and photos. This gyro sensor weighs about 20 grams and ideal for unmanned aerial and underwater vehicle appli-cations. Gyro accuracy in wide temperature range is discussed and test results are presented. Three-axis units based on all types of these gyros are presented, as well. Future opportunities of each of these gyros are discussed. INTRODUCTION It is considered, that the basic disadvantages of metallic reso-nator CVGs are their low Q-factor and high temperature sen-sitivity. However, modern metallurgy has created a number of unique alloys providing both high stability of alloy parame-ters to temperature changes, and high Q-factor, high linearity of alloy parameters during heating. For example, Ni-SPAN-„R Alloy 902 temperature coefficient of frequency (TCF) makes approximately 5쳌~10-6 1/„€„R. The 45NiCrTi alloy and a number of other alloys doped by Co and Mo have less TCF and, at the same time, high temperature stability of Yung modulus, and also linearity of parameters of the alloy during heating. The resonators made of such alloys, have Q-factor up to 10000 - 20000 under atmospheric pressure. Resonator쳌fs Q-factor increases 2-3 times in vacuum. Metallic resonator CVG of such Q-factor can provide accuracy from 0.1-0.5 deg/h and above. Small-sized CVG with resonator diameter 17 mm (CVG17) which does not use vacuum provide accuracy 3-5 deg/h [1]. Innalabs CVG43 provides smaller dimensions, than FOG with equal accuracy. By mass unmanned production opportu-nity, that in main defines gyro cost, metallic resonator CVG can be compared with MEMS gyro, at the same time consid-erably exceeds it by accuracy [1]. It means that metallic resonator CVG using different diameter resonators from one side are MEMS competitive on poten-tially cost characteristic and from another side are competitive to fiber optic gyroscopes (FOG) on the accuracy characteris-tics [2]. Coriolis vibratory gyroscope (CVG) using resonator made of different metallic alloys take a position between low accuracy and low-cost MEMS and higher accuracy and higher cost fiber optic gyroscopes (FOG). Now, MEMS technology is improved increasing their accuracy to less than 10 deg/h [3] and even 1.3 deg/h [4]. Accuracy parameters of metallic reso-nator CVGs are increased by using low internal damping ma-terials, resonator vacuumization and digital electronics to reduce temperature dependent drift and instability of control signals.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1345 - 1350
Cite this article:	Chikovani, V.V., Yatsenko, Yu.A., Barabashov, A.S., Kovalenko, V.A., Tewksbury, P., "A Set of High Accuracy Low Cost Metallic Resonator CVG," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1345-1350.
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