Hemispherical Resonator Gyroscope (HRG)
Hemispherical Resonator Gyroscope (HRG)

The Hemispherical Resonator Gyroscope (HRG), also called wine-glass gyroscope or mushroom gyro, is a compact, low-noise, high-performance angular rate or rotation sensor. An HRG is made 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. The gyroscopic effect is obtained from the inertial property of the flexural standing waves. Although the HRG is a mechanical system, it has no moving parts, and can be very compact.


The HRG makes use of a small thin solid-state hemispherical shell, anchored by a thick stem. This shell is driven to a flexural resonance by dedicated 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[1]) made from high-purity fused quartz, it is possible to reach a Q factor of over 30-50 million in vacuum, thus the corresponding random walks are extremely low. The Q factor is limited by the coating (extremely thin film of gold or platinum) and by fixture losses.[2] Such resonators have to be fine-tuned by ion-beam micro-erosion of the glass or by laser ablation in order to be perfectly dynamically balanced. When coated, tuned, and assembled within the housing, the Q factor remains over 10 million.

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).[3] Therefore, when subject to rotation around the shell symmetry axis, the standing wave does not rotate exactly with the shell, but 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 are 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.

Originally used in space applications (Attitude and Orbit Control Systems for spacecraft),[4] HRG is now used in advanced inertial navigation systems, in attitude and heading reference systems, and HRG gyrocompasses.[5]


The HRG is extremely reliable[6][7] because of its very simple hardware (two or three pieces of machined fused quartz). It has no moving parts; its core is made of a monolithic part which includes the hemispherical shell and its stem.[8] They demonstrated outstanding reliability since their initial use in 1996 on the NEAR Shoemaker spacecraft.[9][10]

The HRG is highly accurate[11][12] and is not sensitive to external environmental perturbations. The resonating shell weighs only a few grams and it is perfectly balanced, which makes it insensitive to vibrations, accelerations, and shocks.

The HRG exhibits superior SWAP (Size, Weight, and Power) characteristics compared to other gyroscope technologies.

The HRG generates neither acoustic nor radiated noise because the resonating shell is perfectly balanced and operates under vacuum.

The material of the resonator, the fused quartz, is naturally radiation hard in any space environment.[13] This confers intrinsic immunity to deleterious space radiation effects to the HRG resonator. Thanks to the extremely high Q factor of the resonating shell, the HRG has an ultra-low angular random walk[14] and extremely low power dissipation.

The HRG, unlike optical gyros (FOG and RLG), has inertial memory: if the power is lost for a short period of time (typically a few seconds), the sensitive element continues to integrate the input motion (angular rate) so that when the power returns, the HRG signals the angle turned while power was off.


The HRG is a very high-tech device which requires sophisticated manufacturing tools and processes. The control electronics required to sense and drive the standing waves are sophisticated. This high level of sophistication limits the availability of this technology; few companies were able to produce it. Currently three companies manufacturing HRG: Northrop Grumman,[15] Safran[16] and Raytheon Anschütz.[17]

Classical HRG is relatively expensive due to the cost of the precision ground and polished hollow quartz hemispheres. This manufacturing cost restricts its use to high-added-value applications such as satellites and spacecraft.[14] Nevertheless manufacturing costs can be dramatically reduced by design changes and engineering controls. Rather than depositing electrodes on an internal hemisphere that must perfectly match the shape of the outer resonating hemisphere, electrodes are deposited on a flat plate that matches the equatorial plane of the resonating hemisphere. In such configuration, HRG becomes very cost effective and is well suitable for high grade but cost sensitive applications.[18]


See also


  1. ^ "Resonator, Hemispherical Resonator GYRO".
  2. ^ 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.
  3. ^ 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.
  4. ^ "Housing, Hemispherical Resonator Gyroscope (HRG)".
  5. ^ "Safran Electronics & Defense logs orders for 3,000 HRG-based inertial navigation systems in 2016, a new record". Safran Group. May 2, 2017.
  6. ^ "Northrop Grumman's Highly Reliable Resonator Gyro Achieves 25 Million Operating Hours in Space". Northrop Grumman Newsroom. Retrieved 2018-12-06.
  7. ^ "Northrop Grumman's Hemispherical Resonator Gyro Achieves 50 Million Operating Hours in Space". Northrop Grumman Newsroom. Retrieved 2019-08-14.
  8. ^ a b "The Hemispherical Resonator Gyro: From Wineglass to the Planets, David M. Rozelle" (PDF). Archived from the original (PDF) on 2013-09-21. Retrieved 2014-02-26.
  9. ^ Hemispherical Resonator Gyro
  10. ^ "Northrop Grumman's Hemispherical Resonator Gyro Achieves Record 30 Million Hours of Continuous Operation". 19 February 2015.
  11. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2013-09-21. Retrieved 2014-02-26.((cite web)): CS1 maint: archived copy as title (link)
  12. ^ Delhaye, Fabrice (2018). "HRG by SAFRAN: The game-changing technology". 2018 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL). pp. 1–4. doi:10.1109/ISISS.2018.8358163. ISBN 978-1-5386-0895-1. S2CID 21660204.
  13. ^ Jerebets, Sergei A. "Gyro Evaluation for the Mission to Jupiter" (PDF).
  14. ^ a b "SIRU - Scalable Inertial Reference Unit for Space". Northrop Grumman. Retrieved 2018-12-06.
  15. ^ "Archived copy". Archived from the original on 2018-01-30. Retrieved 2018-01-14.((cite web)): CS1 maint: archived copy as title (link)
  16. ^ "HRG Crystal". 22 March 2018.
  17. ^ "Standard 30 MF - Maintenance-Free Gyro Compass".
  18. ^ "HRG by Sagem from laboratory to mass production". ResearchGate. Retrieved 2019-06-13.
  19. ^ "FAQ for Scientists Webb Telescope/NASA".
  20. ^ "REGYS 20 | ESA's ARTES Programmes".
  21. ^ "Safran's SpaceNaute navigation system chosen for new Ariane 6 launch vehicle". 30 November 2016.
  22. ^ "Horizon MF Gyro Compass (HRG)". Archived from the original on 2014-02-27. Retrieved 2014-02-26.
  23. ^ a b "Sagem to Highlight Wide Range of Warfare Products at Defexpo 2014".
  24. ^ "At Euronaval Sagem introduced BlueNaute, a new-generation shipborne inertial navigation system".
  25. ^ "EURONAVAL 2018: New family of naval inertial navigation systems by Safran".
  26. ^ "Safran Vectronix AG | Optronic equipment & laser rangefinder technology". Safran Vectronix. Retrieved 2020-02-26.
  27. ^ Sagem wins new order for SIGMA 20 navigators on MBDA surface-to-air weapon systems
  28. ^ Sagem to Supply Seeker and Firing-Posts Optronics for MBDA’s New MMP Medium-Range Missile
  29. ^ Tran, Pierre (2018-06-08). "Eurosatory: This navigation system by Safran doesn't need GPS". Defense News. Retrieved 2018-06-12.
  30. ^ "Safran reveals Geonyx inertial navigation system for assured PNT | Jane's 360". www.janes.com. Retrieved 2018-10-29.
  31. ^ Sagem unveil SkyNaute inertial navigation system
  32. ^ "Sagem carries out first flight test of HRG-based navigation system for commercial aircraft". 21 November 2014.