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The Hemispherical Resonator Gyroscope (HRG), also called ''wine-glass gyroscope'' or ''mushroom gyro'', makes using a thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by electrostatic forces generated by electrodes which are deposited directly onto separate fused-quartz structures that surround the shell. Gyroscopic effect is obtained from the inertial property of the flexural standing waves. HRG has no moving parts, is extremely reliable and very accurate. == Operation == The HRG makes using a small thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by electrostatic forces generated by electrodes which are deposited directly onto separate fused quartz structures that surround the shell. For a single-piece design (i.e., the hemispherical shell and stem form a monolithic part) made from high-purity fused quartz, it is possible to reach Q-factor over 30-50 millions in vacuum, so, the corresponding random walks are extremely low. The Q is limited by coating (extremely thin film of gold or platinum) and by fixture losses.〔Sarapuloff S.A., Rhee H.-N., and Park S.-J. Avoidance of Internal Resonances in Hemispherical Resonator Assembly from Fused Quartz Connected by Indium Solder //Proceedings of the 23rd KSNVE (Korean Society for Noise & Vibration Engineering) Annual Spring Conference. Yeosu-city, 24–26 April 2013. – P.835-841.〕 Such resonators have to be fine-tuned by ion-beam micro-erosion of the glass or by laser ablation. When coated, tuned and assembled within the housing, the Q factor remains over 10 millions. In application to the HRG shell, Coriolis forces cause a precession of vibration patterns around the axis of rotation. It causes a slow precession of a standing wave around this axis, with an angular rate that differs from input one. This is the wave inertia effect, discovered in 1890 by British scientist George Hartley Bryan (1864–1928).〔Bryan G.H. On the Beats in the Vibrations of a Revolving Cylinder or Bell //Proc. of Cambridge Phil. Soc. 1890, Nov. 24. Vol.VII. Pt.III. - P.101-111.〕 Therefore when subject to rotation around the shell symmetry axis, the standing wave does not totally rotate with the shell. The difference between both rotations is nevertheless perfectly proportional to the input rotation. The device is then able to sense rotation. The electronics which sense the standing waves is also able to drive them. Therefore the gyros can operate in either a “whole angle mode” that sense the standing waves position or a “force rebalance mode” that holds the standing wave in a fixed orientation with respect to the gyro. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hemispherical resonator gyroscope」の詳細全文を読む スポンサード リンク
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