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HRG by Sagem from laboratory to mass production


Abstract and Figures

For more than two decades, Sagem has built up its expertise through different developments and applications of CVG (Coriolis Vibrating Gyros). One example is the well-known HRG (Hemispherical Resonator Gyroscope). This paper shows the large panel of applications covered with HRG, in a nominal configuration system and in a redundant inertial skewed system. We also evoke the ultimate performance application obtained with specific system configuration, thanks to the remarkable properties of the HRG. In the end, we describe the industrial aspects deployed to address all these applications.
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From Laboratory to Mass Production
Alain Jeanroy, Gilles Grosset, Jean-Claude Goudon, Fabrice Delhaye
Avionics Division, Sagem, Boulogne-Billancourt, France
Abstract—For more than two decades, Sagem has built up its
expertise through different developments and applications of
CVG (Coriolis Vibrating Gyros). One example is the well-known
HRG (Hemispherical Resonator Gyroscope). This paper shows
the large panel of applications covered with HRG, in a nominal
configuration system and in a redundant inertial skewed system.
We also evoke the ultimate performance application obtained
with specific system configuration, thanks to the remarkable
properties of the HRG. In the end, we describe the industrial
aspects deployed to address all these applications.
Keywords—Hemispherical Resonator Gyro, Inertial System,
I. I
When Sagem started development of the Coriolis Vibrating
Gyros in 1985, the technical choices were rapidly based on
three main principles:
The first principle was to use an axisymmetric
resonator: this property leads to resonators exhibiting
naturally good characteristics in terms of frequency
isotropy, damping isotropy and balance.
The second principle was to obtain the best tuned and
balanced resonator possible: a very good isolation of
the vibrating mode of the resonator is necessary if one
needs stable performances, independent from the
environment. Even with an axisymmetric resonator
some complementary tuning and balancing is required.
The third principle was to use the whole angle mode of
control: this mode minimizes the amplitude of the
forces applied for the control of the vibration and
therefore minimizes the errors caused by the
electronics, the detectors and actuators defects. This
mode leads to a very good scale factor (based on the
Bryan factor) and allows high dynamics.
Using these principles as a basis, Sagem has built up its
expertise through different developments and applications of
CVG [1]. One example is the well-known HRG, which uses a
fused Quartz resonator. This material exhibits an extraordinary
high Q factor and is well adapted to high performance when
associated with electrostatic pick-off and actuators. A thin film
metallic deposit on the resonator enables the electrostatic
control of the vibration with moderate impact on the Q factor.
Moreover, a Sagem patent [2] introduces a flat electrodes
design which greatly improves the simplicity of the gyroscope
and the ease of manufacturing. As a result, this type of
resonator vibrates at 7 kHz and exhibits a time constant beyond
500 seconds. Therefore, when associated with the whole angle
mode of control, it meets the highest demanding applications
A. Standalone products
A space radiation hardened rate gyro dedicated to AOCS
(Attitude & Orbital Control System) was the first standalone
product designed with HRG technology in 2007 (Fig. 1). To
date, 8 orbiting telecom satellites are using Sagem HRG and
more than 100 spatial grade gyros have already been delivered.
Fig. 1. Regys 20 high reliability HRG spatial rate gyro unit
Simultaneously, the very low size, weight, and power
consumption of the HRG made possible the design of a
portable north-finder operating with only one gyro, typically
able to reach a 2 mils accuracy within 180 seconds (Fig. 2).
Fig. 2. Sterna ultra lightweight northfinder
These developments led to the inception of the BlueNaute
Marine gyrocompass family in 2011 [3], aimed towards the
maintenance free concept thanks to the exceptional reliability
of the HRG technology. In the same packaging size (6 liters
and 4.5 kg, Fig. 3), the family ranges from a basic IMO
(International Maritime Organization) gyrocompass to a high
978-1-4673-6939-8/16/$31.00 ©2016 IEEE
end Titanium model offering 0.1° rms seclat heading and a
1 Nm/h position accuracy. More recently, a naval version
named Sigma 20M was launched, complying with harsh
military environments without impact on performances. To
date, hundreds of systems equip vessels around the world,
including US Coast Guards ships.
Fig. 3. BlueNaute and Sigma 20M Naval HRG INS
Concurrently, Sagem developed a Tactical Land INS
(Inertial Navigation System) named Sigma 20 (Fig. 4). The
heading accuracy of the family ranges from 8 down to 1 mils
Fig. 4. Sigma 20 HRG Tactical Land INS
In 2015 the SkyNaute family was launched (Fig. 5). The
SkyNaute family of INS is dedicated to Commercial Aircraft
(Fig. 6 shows a compliancy with 2 Nm/h standards). At only 3
liters and 3 kg, the HRG proves once again its ability to
compete with legacy RLG systems, while saving payload and
maintenance costs for the airlines thanks to its outstanding
Fig. 5. SkyNaute HRG INS for Commercial Aircrafts
Fig. 6. Inertial navigation error over a real 12 hour flight
B. Integrated modules
Beside its integrated units, Sagem proposes a complete
IMU (Inertial Measurement Unit) family named Primus
(Fig. 7), which is built around its HRG and dedicated to OEM
applications. Gyro bias stability is the key differentiating driver
between members of the family, ranging from 0.1°/h (Primus
100) up to 0.01°/h (Primus 400).
Fig. 7. Primus HRG IMU family
The AASM Hammer (Air Ground Modular Weapon),
capable of operating in GPS denied environment, benefits from
the HRG accuracy. By introducing the modular approach of the
same guidance kit, Sagem developed a wide range of guidance
kits adapted to different payloads (Fig. 8). The outstanding
accuracy of the weapon mainly relies on its inertial sensors,
contributing to both guidance and control. To date, more than
4,000 units have been produced to serve the AASM Hammer
Fig. 8. The AASM Hammer family, using HRG
Based on the Primus family, Sagem is subsequently
developing a north-finder & north keeper. This technology
requires 3 HRG, designed to be integrated in portable systems
(Fig. 9), in the scope of the JETS program for the PAVAM
(Precision Azimuth & Vertical Angle Module). The SWaP
(Size, Weight & Power) features of HRG are particularly suited
to man portable applications, with a power consumption
requirement below 4 W.
Fig. 9. Long range multi-function infrared binoculars
In parallel and capitalizing on the fusion of in house
optronics and inertia technologies, Sagem integrates a
geolocation function in GPS denied environment within its
Paseo sight dedicated to artillery target locator (Fig. 10).
Fig. 10. Paseo modular advanced stabilized sight
The Primus concept demonstrates once again the industrial
interest of the modular approach.
A. Inertial Redundant Skewed system
Thanks to the ultra-compactness of its HRG shown in
Figure 11, Sagem designs Redundant Inertial Skewed Systems
with an unparalleled volume and mass, aiming to comply with
fail operational and fail safe requirements needed for aircraft or
satellite launchers (ability to detect a sensor failure, isolate it
and reconfigure the inertial system).
Whereas the Ariane 5 navigation system is composed of
two IRS (Inertial Reference System) and includes a
“supervisor” function in charge of switching from the first IRS
to the second one, the Sagem solution [4] would consist in a
single redundant IRS (6 skewed axis) which offers not only a
higher level of accuracy than the present configuration but a
much higher safety level (fail operational / fail safe system)
than the present navigation system (only fail safe).
Even if the total number of sensors remains identical to
current system (6 gyros and 6 accelerometers), Sagem
multisensory architecture provides a real improvement to the
safety: in case of failure, multiple reconfiguration solutions are
available. Thus this architecture is robust to two sensors
failures (for example 2 gyros, or 2 accelerometers, or even 2
gyros & 2 accelerometers) whereas in classical system one non
detected failure can contribute to the loss of the launcher.
The IRS (Fig. 11) is basically composed of:
a strap-down inertial platform: six gyros and six
accelerometers are integrated on a single inertial
redundant electronic boards,
a mechanical hermetic housing,
dampers to protect the inertial assembly from high
Fig. 11. Views of sensors, assembly and mechanical housing
The HRG technology allows a full redundant IRS (6 axis,
fail op/fail safe) with a better SWaP than a classical non
redundant IRS.
B. Ultimate performance application
Some applications require extremely specific performance
characteristics. As far as gyro inertial performance is
concerned, the most demanding application is submarine
navigation, which requires bias stability over days, weeks, or
even months.
The ultimate technology for this application has been the
Electro Static Gyroscope (ESG) that Sagem developed in the
80's and 90's. In fact, an ESG is a really poor gyroscope, with
very low dynamic range and many other limitations. Its real
performance comes not only from its mechanical & electrical
perfection, but also from the way it is operated by the ESG
navigator, in order to compensate short-medium-long term
With the development of the HRG in the 2000's - 2010's,
Sagem has learned how system operation can dramatically
boost the gyro performance by a ratio in the thousands. The
experience gained with ESG, although somewhat different, was
nevertheless extremely useful.
Very long term navigation is now accessible through HRG
technology, either in strap-down or in gimbaled architectures.
Sea tests have already proven that the Sagem HRG meets the
requirements for submerged navigation over the course of days
or months.
In 2012, Safran expanded its Montluçon site in central
France to accommodate a new plant dedicated to the
production of inertial navigation systems. It covers 19,000
square meters of floors, including 6,000 square meters of clean
rooms where the ring laser gyros, hemispherical gyros and
navigation systems are manufactured and assembled. First in
Europe in terms of industrial capacity, the Coriolis facility
(Fig. 12) has become the world’s leading production unit in the
field of hemispherical resonator gyros. This scalable, modular
industrial facility will be in a position to adapt to changing
requirements with the ramp-up in new HRG technology.
Fig. 12. Coriolis plant
Designed to offer large-scale production capacities, to
improve the efficiency of production processes, and to reduce
industrial cycles, the construction of Coriolis followed three
guiding concepts:
The quality of physical flows through the optimization
of staff and equipment traffic, automated stores, and
ergonomic working positions;
The high technical level of the infrastructures for total
control of the manufacturing processes, particularly
through permanent control of the temperature,
humidity and cleanliness of the facility;
The modularity and scalability, giving the facility the
scope to adapt to growing industrial requirements with
the capacity to extend production areas.
Though initially developed for very specific applications,
Sagem dramatically simplified the HRG design, reducing it to
only 6 parts, allowing an optimized process flow to reduce unit
cost. The sensor technologies make use of a mature process
adapted from the microelectronics industry.
Fig. 13. Resonators test
A SPC (Statistical Process Control) is operational, which
provides data validation of the manufacturing repeatability of
key parameters: intrinsic characteristics (e.g.: resonator Quality
Factor, Fig. 13), and sensors performances (e.g.: bias).
Robustness of the definition has been demonstrated by
HASS (Highly Accelerated Stress Screening) with
overstresses, combined random six-degree-of-freedom
vibration and rapid thermal change rate. These tests effectively
force product weak links to emerge by accelerating fatigue.
Long term ageing campaigns, without gyro or electronic
failure, demonstrated long term reliability.
V. C
If the scientific community always regarded the HRG as a
premier gyro with outstanding accuracy and reliability
characteristics, few anticipated that HRG would be capable to
address the mass market. Thanks to innovative design and
massive industrial investment, Sagem was capable to achieve
Fig. 14. HRG by Sagem
With its robust 20mm diameter resonator (Fig. 14), Sagem
is able to address an unmatched range of applications through
scalable electronics and advanced system architecture. From
very cost effective marine compass to ESG grade strategic
navigation, from tripod mounted north finder to space launcher
navigation, the Sagem HRG is able to fulfill needs for accuracy
in harsh environmental conditions while doing so in a very cost
effective way.
HRG is more than an innovative gyro technology; it is a
disruptive technological breakthrough. In the same way, optical
gyros (RLG and FOG) replaced the mechanical gyros, HRG is
redefining the landscape of inertial navigation (Fig. 15).
Fig. 15. Future gyro technology applications
[1] G. Remillieux, F. Delhaye, Sagem Coriolis Vibrating Gyros: a vision
realized, in Proceedings of Karlsruhe Conference on Inertial Sensors and
Systems, 2014
[2] A. Jeanroy, P. Leger, HRG flat electrodes, Patent US 6474161
[3] A. Jeanroy, A. Bouvet, G. Remillieux, HRG and Marine applications in
Proceedings of 20th Saint Petersburg International Conference on
Integrated Navigation Systems, 2013
[4] C. Negri, E. Labarre, C. Lignon, E. Brunstein, E. Salaün, A new
generation of IRS with innovative architecture based on HRG for
satellite launch vehicles applications in Proceedings of 22th Saint
Petersburg International Conference on Integrated Navigation Systems,
... The HRG has the advantages of ultra-high accuracy, small size, long life, low power consumption and high reliability [1][2][3][4]. The HRG has been widely used in aircrafts, land vehicles, ships, individual devices [5][6][7][8][9], etc. The hemispherical resonator is the key component of the HRG. ...
... The resonators are excited at the natural frequency of the n=2 mode with a force of 0.01N. The few seconds that the resonator takes to vibrates from the static[6] ...
... SAFRAN in French has developed a planar-electrode-type HRG and inertial navigation unit, SkyNaute, with a simple structure and assembly for the whole-angle mode. Currently, they have the mass production capacity of HRG with an accuracy range of 0.0005 to 0.005 • /h [5]. ...
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As an inertial sensor with excellent performance, the hemispherical resonator gyro is widely used in aerospace, weapon navigation and other fields due to its advantages of high precision, high reliability, and long life. Due to the uneven distributions of material properties and mass of the resonator in the circumferential direction, the frequencies of the two 4-antinodes vibration modes (operational mode) of resonator in different directions are different, which is called frequency splitting. Frequency splitting is the main error source affecting the accuracy of the hemispherical resonator gyro and must be suppressed. The frequency splitting is related to the structure of the resonator. For the planar-electrode-type hemispherical resonator gyro, in order to suppress the frequency splitting from the structure, improve the accuracy of the hemispherical resonator gyro, and determine and optimize the equivalent bottom angle parameters of the hemispherical resonator, this paper starts from the thin shell theory, and the 4-antinodes vibration mode and waveform precession model of the hemispherical resonator are researched. The effect of the equivalent bottom angle on the 4-antinodes vibration mode frequency value under different boundary conditions is theoretically analyzed and simulated. The simulation results show that the equivalent bottom angle affects the 4-antinodes vibration mode of the hemispherical resonator through radial constraints. The hemispherical resonator with mid-surface radius R=15 mm and shell thickness h=1 mm is the optimization object, and the stem diameter D and fillet radius R1 are experimental factors, with the 4-antinodes vibration mode frequency value and mass sensitivity factor as the response indexes. The central composite design is carried out to optimize the equivalent bottom angle parameters. The optimized structural parameters are: stem diameter D=7 mm, fillet radii R1=1 mm, R2=0.8 mm. The simulation results show that the 4-antinodes vibration mode frequency value is 5441.761 Hz, and the mass sensitivity factor is 3.91 Hz/mg, which meets the working and excitation requirements wonderfully. This research will provide guidance and reference for improving the accuracy of the hemispherical resonator gyro.
... In recent years, vibrating sensors have become ubiquitous [1][2][3]. This is because of their simple design (no moving parts), robustness, and continuous improvements in algorithms and electronics. ...
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In recent years, vibrating sensors have become ubiquitous. This is because of their simple design (no moving parts), robustness, and continuous improvements in algorithms and electronics. Nowadays, vibrating gyroscopes are replacing well-established optical technologies like ring laser and fiber optics gyroscopes. Vibrating gyroscopes are based on the Coriolis Effect. For instance, when a standing wave is excited in an axisymmetric structure (resonator) and an angular rate is applied; the Coriolis acceleration that appears on the structure causes the vibrating pattern to rotate around its symmetry axis, with a velocity proportional to the external angular rate. Non-ideal vibrating sensors suffer from a well-known effect called lock-in. For external angular velocities smaller than the lock-in rate, the standing wave does not rotate and the sensor fails to operate. For instance, Coriolis Vibrating Gyroscopes (CVGs), working in the Whole Angle Mode (WAM), have a lock-in threshold proportional to the difference between the inverse of the maximum and the inverse of the minimum values of the damping time constant. Recently, a Slow Variables (SV) method has been used to demonstrate this effect as well as to calculate the lock-in angle. In this work, using a Fast Variables (FV) method, we derive the lock-in condition without making any assumptions and/or approximations. We solve the dynamics exactly and we find equivalent conditions for the system's eigenvalues to those known for the Damped Harmonic Oscillator (DHO), i.e., angular rate decreasing to zero – over-damped dynamic, lock-in – critically damped dynamic, and free rotation – under-damped dynamic. Therefore, we can explain the lock-in effect without resorting to a nonlinear theory (SV method) but by the form of the roots of an eigenvalue problem of a linear system (FV method).
Assembly and welding of the hemispherical resonator and flat electrode are the core process links in gyro manufacturing, which will affect the electrode excitation, detect gain consistency of the hemispherical resonator gyro and the vibration performance parameters of the resonator, thus ultimately affecting the output accuracy of the gyro. To achieve a high-precision assembly and welding, firstly, this paper establishes the assembly error model of the hemispherical resonator and flat electrode, analyzes the effect of assembly error on static capacitance, and proposes an assembly spacing measurement scheme based on static capacitors. Then, the integrated experimental platform of high-precision assembly and welding is designed and implemented, equipped with a high-precision capacitance detection circuit, and the capacitance detection circuit is calibrated using actuators. Finally, the experimental results show that the average assembly clearance between the hemispherical resonator and the flat electrode reaches 33μm, the peak-to-peak value is less than 3 μm, and the non-uniformity of the assembly gap is less than 9.4%. In addition, to analyze the influence on the vibration parameters of the resonator after assembly and welding, a test platform for measuring the vibration performance parameters of the resonator is built. The experimental results show that the mean reduction of the quality factor of the resonator in the range of 600w~1000w after assembly and welding is less than 8.6%, which verifies the correctness of the theoretical model and the superiority of the assembly and welding scheme.
Compensation for the hemispherical resonator gyroscope detection error significantly improves gyroscope performance as well as provides a basis for the implementation of high precision control algorithms. In this paper, an identification method is proposed in which the precession factor and the detection error parameters including gain error, non-orthogonal angle error, and phase error can be identified simultaneously in a single test. Firstly, we analyze the detection error caused by gyroscope manufacturing as well as the inconsistency in circuit device parameters. Secondly, the detection error is modeled, and the impact of the error on the standing wave azimuth detection and the control system is discussed. Thirdly, a method is presented for identifying the error parameters based on the nonlinear least squares. Finally, experiments are conducted to verify the effectiveness of the identification and compensation method. As a result of compensation, the bias instability decreases by 33 times from 5.08°/h to 0.15°/h, and the scale factor nonlinearity decreases by 4 times from 50.26ppm to 10.23ppm.
In this paper, a novel ultra-high precision mass balancing method for fused quartz hemispherical resonator based on the ion beam etching process is proposed from the perspective of vibration mechanics. Firstly, the motion equations of resonator with mass defect are established to reveal the quantitative relationship between the amplitude of defective mass and frequency split, and the geometrical relationship between the distribution of defective mass and eigenfrequency axis, which is the equivalent morphology of mass defect. Secondly, according to the motion equations, the radial vibration model of resonator lip edge is deduced, then a new identification model for the vibration parameters composed of the frequency split, mechanical time constant, and azimuth of eigenfrequency axis based on the vibration envelope and spectral analysis is established. The vibration parameters are identified by nonlinear optimization method. After that, the mass removal function and etching efficiency function of ion beam acting on the resonator are calibrated by experimental data, then the etching trajectory is planned and the etching time is calculated. Finally, the experimental result of mass balancing indicates that the frequency split is reduced from 0.2354Hz to 0.0006Hz, and the quality factor is greater than 2.2×10 <sup xmlns:mml="" xmlns:xlink="">7</sup> , which can significantly improve the vibration performance of resonator.
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Full-text available
In the early 90's, the concepts chosen by Sagem for his future CVG (Coriolis Vibrating Gyros) developments were based upon three main key principles: • An axisymmetric resonator • A finely balanced resonator • A Whole Angle mode of control. After more than two decades of experience, these visionary choices have proven to be well-grounded. They led to continuous improvement of the company know-how for the benefit of the performances. Associated with the ever-increasing computing power of microcontrollers, it is even possible to continue to improve the performances of the early versions of the Sagem CVGs. The paper shows how these main principles have been applied to Quapason™, to HRG and more recently to advanced high performance MEMS gyro and presents the more recent tests result obtained. The high versatility of the CVG concept is shown through a description of typical applications relying on its key characteristics.
The satellite launch vehicles' evolution goes through a reduction of cost, weight and size of the IRS (Inertial Reference System), while keeping a very high level of performance and safety compatible with this kind of application. The classic approach leads to duplicate this equipment, so assuring a first level redundancy. But this solution is not favourable considering the previous criteria (cost, weight, size) and does not allow detecting a possible slow drift of performance of one of the two IRS because there is no possible majority vote. The approach proposed in this paper is based on a multisensor architecture, integrating 6 gyroscopes and 6 accelerometers, with a triplication of the common functions, which allows using a non-radiation hardened electronics. This integrated architecture facilitates the implementation of FDI techniques (Fault Detection and Isolation), and withstands straight failures and performance drifts of the inertial sensors, the whole being integrated into a single equipment, which allows reducing drastically cost, weight and size. In this context, the use of HRG (Hemispherical Resonant Gyroscope) is particularly relevant because of its low size and weight. As a result, the proposed architecture allows reaching high levels of accuracies, which makes it capable of a wide range of missions. This paper details the proposed inertial and electronic architecture, demonstrates the techniques used for the FDI function and shows the contribution of the HRG for this kind of architecture in terms of accuracy, safety and size.