MEMS Symmetrical Resonating Gyroscope Brief

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Symmetrical Resonating Gyroscope
MEMS Symmetrical Resonating
Gyroscope Brief
INTRODUCTION
Sensors in Motion has created the world’s first MEMS
(Micro-Electro-Mechanical System) based navigation grade gyroscope. Our Symmetrical
Resonating Gyroscopes (SRG) deliver drift less than 0.01 deg/hr and ARW less than 0.005
deg/rt-hr. Current high performance inertial technology is dominated by inertial measurement
units (IMUs) employing large, expensive and power hungry ring laser gyroscopes (RLGs) or
fiber optic gyroscopes (FOGs). Optical gyros suffer from dead-band non-linearity’s and light
source life issues as well. MEMS devices achieved via low cost, batch fabrication methods
have the cost, size, weight and power reduction to benefit augmented GPS, down-hole drilling,
dead-reckoning, autonomous vehicles, platform stabilization and a myriad of strategic defense
and commercial capabilities.
THEORY OF OPERATION
The SRG operates on two modes. A set of DC bias electrodes are used to
tune the resonator using electrostatic spring softening on its two
degenerate oscillation modes to become near perfect degeneracy in
frequency. A sinusoidal voltage is applied to its first set of electrode to
excite its ring structure into oscillation. The second mode is then excited
by the Coriolis force, sensed and fed into amplifiers to nullify the
transferred vibrational energy. The rotation rate can then be extracted from
the feedback voltage used for suppression as they are directly proportional to
one another.
Figure 1. SIM’s Symmetrical
Resonating Gyroscope
DESIGN AND PERFORMANCE
Fifteen years of development starting at NASA’s famed Jet Propulsion Labs and over 20 patents
has led to the highest performing MEMS gyroscope in the world. With sensor volume less than
35 mm3 the SRG surpasses all other MEMS and most traditional gyros in proven performance
through its unique design. The co-etched resonator/electrode structure of the SRG efficiently
maximizes use of the area of the sensor to increase sensing capacitance, thus increasing its
signal-to-noise ratio. Its centrally mounted resonator supports two degenerate elastic inertial
waves for Coriolis sensing result in a very stable mechanical quality factor, limited only by
material damping. The axially
High Performance Gyro
symmetric design of the SRG
Angle
and its single nodal support
Bias
Random
NonLinearity Bandwidth
Stability
ensures minimal coupling to
Walk
(ppm)
(Hz)
( º/hr )
( º/√hr)
package stresses eliminating
Top
3
0.1
1000
55
anchoring losses and enables
Competitors
0.2
0.061
10
100
the device to survive over
0.05
0.009
10
100
2000g shock. SIM’s SRG
SIM SRG’s
0.01
0.005
10
100
specification, and comparison
0.003*
0.002*
10
100
*Best to Date is shown.
Table I. SIM SRG vs Top Competitors Sensors in Motion
Symmetrical Resonating Gyroscope
Figure 2. Allan Deviation Plot of a SIM SRG
Figure 3. SIM SRG vs Competitor’s** Green Chart
**Estimated
1
Rate Allan Deviation (deg/hr)
10
Figure 2 above shows the green chart of a SIM’s SRG gyroscope with a
bias instability of 0.0045 º/hr and an angle random walk of 0.0029 º/√hr.
Figure 3 to the right shows a comparison of variations of SIM’s SRGs
versus a top competitor**.
0
10
-1
10
-2
10
SIM SRG 0.2
SIM SRG 0.05
SIM SRG 0.01
SIM SRG 0.004
Competitor**
-3
10
1
10
Table II. SIM SRG 5000 Specifications Parameter
Number of Sensing Axes
Measurement Range
Angular Acceleration Range
Gyro Fixed Bias
Gyro Bias Repeatability
Gyro Bias Stability
Angle Random Walk
Noise Density
Gyro Scale Factor Error
Gyro Scale Factor Stability
Gyro Axis Alignment Error
Gyro g-Sensitivity
Gyro g2-Sensitivity
Bandwidth
Temperature Bias
Temperature Coefficient
Shock Survivability
Conditions
Min
Full-Scale Range
-700
turn-on to turn-on
in-run
in-run
in-run
Note; Some or all of SIMs SRG’s may be ITAR controlled.
2
3
10
10
Integration Time (sec)
Max
Units
1
+700
1000
< 100
0.1
1
< 0.02
0.005
0.03
50
10
0.1
0.5
0.05
100
1
±20
2000
Axis
º/sec
º/sec2
º/hr
º/hr
º/hr
º/√hr
º/hr/√Hz
ppm
ppm
µrad
º/hr/g
º/hr/g2
Hz
º/hr/ ºC
ppm/ ºC
g
4
10
Symmetrical Resonating Gyroscope
PERFORMANCE COMPARISON
Table III. Product Comparison of High Performance Gyroscopes and IMUs
Product
(TYPE)
Bias
Instability
(°/hr)
Angle
Random Walk
(°/hr/√Hz)
NonLinearity
(% of FS)
Temperature
Coefficient
(%of FS/°C)
Temperature Bias
(°/hr/°C)
Bandwidth
(Hz)
Shock
Survivability
(g)
0.05
0.005
0.005
0.002
1
100
2000
3
0.1
0.1
1
3600
55
Do not drop
exceeding
300mm
0.5
0.15
0.005
N/A
5
262
1500
2.8
0.15
0.05
0.004
4.5
400
2000
N/A
50.4
1
0.01
72
140
3000
0.01
0.002
0.0025
N/A
N/A
500
N/A
2
0.11
N/A
N/A
N/A
N/A
90
1
0.06
N/A
N/A
N/A
N/A
N/A
SIM
SIM500
(MEMS)
Silicon
Sensing
CRS09-11
(MEMS)
Sensonor
STIM300
(MEMS)
Analog
Devices
ADIS16137
(MEMS)
ST Micro
LY330ALH
(MEMS)
Emcore
EMP-1.2K
(FOG)
Northrup
Grumann
LN200
(FOG)
Honeywell
HG1900
(MEMS)
(Source: From Product’s Datasheets) Inertial Measurement Unit
SIM has incorporated its Symmetrical Resonating Gyroscope into a 6 DOF north
finding IMU. The prototype is the world’s first Navigation Grade MEMS INS ever
produced and leads our technology roadmap to a 1.5 in3 system.
CONTACT
Lab and Testing Facility:
Goleta, CA
Mailing Address (Headquarters):
Sensors in Motion
505 Broadway E #124
Seattle, WA 98102
Contact:
[email protected]

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