INERTIAL NEWS
• Hexagon Acquires Novatel: click
here
• Motion Capture System
acquires inertial gyroscopic motion. August
21, 2007 - Able to capture movement using inertial sensors or
gyros attached to lycra suit, IGS-190 records
simultaneous action and reaction of performance. It uses 19 customized InertiaCube(TM) gyroscopic sensors for detecting nuance
of movement and optimizing data output, while global translation system
promotes precision of actor positioning and can be enhanced by addition of
optional ultrasonic tracking technology. System also allows actors to touch
or hug without occlusion.
• Solid-state inertial unit guides aerial decoy -
Design News, September 7, 1998.San Diego, CA--After a year of testing
and evaluation, engineers at Teledyne Ryan Aeronautical selected a
solid-state, six-axis sensor unit as the inertial measurement unit (IMU) for
the Miniature Air Launch Decoy (MALD). Developed by
Crossbow Technology (San Jose,
CA) the DMU-6--or Dynamic
Measurement Unit--combines three accelerometers and three gyro rate sensors
into a high-performance, compact, package.
click
here
• New MEMS IMU with
integrated GPS: click here
• Dustin at GLS does 7 miles of daily land survey production
through the thicket with a ZUPT B-PINS without breaking a sweat… Very good
ties too. Way to go Dustin...
SURVEY NEWS
•
What is Google
Earth Outreach?:
click here
• First ever aerial survey
of Northern Ireland’s
geological resources launched: click here
• 
Swedesurvey has been awarded a contract by the Federal Capital
Development Authority (FCDA) in Abuja, Nigeria for a project for the Establishment of
a Digital Base Map covering the Federal Capital Territory (FCT), Nigeria:
http://www.swedesurvey.se/
• Success mapped out for land surveying
program:
click here
• The UK Land Survey
Register
click here
• Galileo funding finally
agreed upon...
click here
OIL, GAS & SEISMIC NEWS
• PdVSA and the chineseCNPC
joint venture to develop Venezuelan oil field: click here
• Petrobras sees peak production of huge Tupi
field in 10-15 years: click here
• PDVSA, Petrobras form JV for new refinery - Brazil, Venezuela: click
here
• Europa wins France's
Tarbes-Val d'Adour Concession: http://www.oilandgasinternational.com
OTHER NEWS
• Bolivia regions declare autonomy: click here
• A far surer path to democracy in Venezuela… click
here
• U.S. agrees to global warming deal…click
here
A SHORT HISTORY OF INERTIAL
SENSORS (with quotes from Haying Hou's paper, U. Calgary, 2004):click
here
1 - GYROSCOPES
The spinning mass gyroscope
first found a home around 1920 in the single-degree-of freedom rate gyro used
as a basic turn indicator for instrument flying (Smith and Meyraugh 1990).
After continuous evolution and
improvement it was later used to provide lead angle data for aircraft fire
control sights, and later still for aircraft and missile flight control
systems.
The basic configuration of a
rate gyro is a ball bearing rotor housed in a gimbal
whose gyroscopic precession in response to an angular rate is restrained by a
mechanical spring, making it relatively inexpensive, very rugged, and
reliable. Rate gyros dominate the 10 deg/h gyro drift rate and applications such
as flight control, stability augmentation, autopilots, etc (Barbour et al.
1992).
With the need for better
performance, such as in aircraft navigation, it was logical to improve the
rate gyro. When it was identified that the rate gyro’s performance was
limited by its spring.
The integrating gyro is
basically a rate gyro in which the primary restraining torque on the gyro gimbal is a damping reaction with a servo loop to
maintain the gimbal at null.
The floated integrating gyro
progressed from revolutionizing aircraft navigation in the 50s to enabling
strategic missile guidance, autonomous submarine navigation, and space flight
in the 60s, 70s and 80s.
The gas bearing was a
significant part of the floated gyro evolution, leading to better stability, and
a self-aligning capability for strategic missiles, a capability that no other
instrument to date provides. Another benefit of the gas bearing is the
reduction of the angle noise of the floated instrument, so that it is used in
satellite navigation and control; its most recent application is in the
Hubble telescope. Floated integrating gyros have a relatively high cost, are
labor intensive, and have long warm-up (reaction) times bearing.
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The free rotor gyro can be
regarded as a precursor to the two-degree-of-freedom electrostatic gyro
(ESG). The ESG only became viable when machining techniques became available
to generate the very precise finishes and geometry required. The ESG has much
lower drift than the best floated gyros and is small; unfortunately its
applications are limited to relatively benign environments since it has low g
capability. ESGs are being replaced by lower cost
technologies that are better suited for strapdown
applications.
In the early 60s, the dynamically
tuned free rotor gyroscope (DTG) was invented. The DTG is a two-degree-of-freedom
instrument whose rotor is suspended by a universal hinge of zero stiffness at
the turned speed and rotated by a ball 
Because of their relatively low
cost, fast reaction time, small size and ruggedness, DTGs
have dominated the market compared to other mechanical instruments in most
areas where performance is comparable.
At the same time that the DTG
was being invented, the principle of detecting rotation by the Sagnac effect was first demonstrated (1963) in a ring
laser gyroscope (RLG). The RLG operates by setting up clockwise and count
clockwise resonant light beams reflected around a closed cavity by mirrors
and detecting phase shifts between these beams due to a rotation. The laser
is inside the cavity, which contains the lasing medium; hence, the RLG is
termed an active device.
The RLG is an excellent strapdown device because of good scale-factor (SF)
linearity and SF stability in the tens of parts per billion compared with
tens of parts per million for mechanical sensors, and almost negligible g
sensitivity (Merhav 1996). The RLG has other
attractive features such as digital output, very fast reaction times,
excellent dormancy characteristics, lower cost, and the absence of moving
parts. RLG technology is still advancing, but is at the practical limit for
today’s technology (Barbour et al. 1992). 
The fiber-optic gyroscope
(FOG) is implemented using an integrated optics chip constructed in lithium niobate, and fiber-optic sensing coil, diode light
source, and photodetectors (Smith and Meyraugh 1990). This configuration is expected to be
supplemented eventually by quantum well technology, such as gallium arsenide,
which will then allow integration of most of the above components into a
single substrate, increasing reliability, and reducing costs even further.
The most recent emerging
technology is the interferometric
fiber-optic gyro (IFOG). It provides the closed optical path by a
multi-turn optical fiber coil wound on a coil. It is more compact and
potentially of lower cost than the RLG (Smith and Meyraugh
1990).
The growing need for highly
rugged miniature angular rate sensors has initiated a number of studies and
prototype product development programs. These products are potentially
suitable for medium to low accuracy applications.
One principle approach is the Coriolis angular rate sensor. The
underlying idea is to put an accelerometer in motion that is relative to the
rotating vehicle body. The development of the basic concept is given in Merhav (1982), where the realization and analysis are
provided, particularly, for rotating accelerometers. An alternative
mechanization is through vibrating accelerometers, and is also presented in Merhav (1982). The leading idea is that these
accelerometers are potentially much cheaper, smaller, and more rugged than
gyroscopic devices. Micromechanical gyroscopes are primarily Coriolis force sensors.
2 - ACCELEROMETERS
The majority of
electromechanical accelerometers are the restrained mass or force rebalance
types, in which a proof mass is supported in a plane perpendicular to the
input (sense) axis by a flexure, torsion bar, or pivot and jewel (Norling 1990). The motion of this proof mass under
changes of acceleration is detected by a pickoff. A rebalance force may be
generated through a servo feedback loop to restore the proof mass to its null
position. The force rebalance type of accelerometer has been successful not
only because it is relatively small, simple, very rugged, and reliable, but
also because it can be designed to meet different performance and application
requirements by careful selection of the flexure and mass configuration,
electromagnetic pickoffs and forces, servoelectronics,
fluid and damping, and materials (Savage 1978).
Force rebalance
accelerometers can operate in strapdown or gimbaled modes. The output needs to be
digitized (Barbour et. al. 1992).
The highest performance
accelerometer available is the Pendulous Integrating Gyro Accelerometer
(PIGA), which is used for strategic missile guidance. 
The PIG part of the PIGA is
identical to the floated single-degree-freedom, integrating gyro with the
addition of a pendulous mass located on the spin axis. The PIGA is a very
stable, linear device, with very high resolution over a wide dynamic range. PIGAs are relatively complex and perceived to have high
life-cycle costs due to the three rotating mechanisms (gas bearing,
servo-driven member (SDM), and slip ring).
Another type of accelerometer
is the resonator or open-loop type such as the vibrating string
accelerometer. This device has low shock tolerance.
Angular accelerometers were initially
used in the 50s for dynamic compensation of AC (alternating current)
servomechanisms. The basic configuration is a fluid-filled ring with a vane
extending into it. Under rotational motion of the ring, the vane is
restrained by a torquer, whose current indicates
the angular displacement (Norling 1990). Such
devices are used in applications requiring high bandwidth (2000Hz), small
magnitude stabilization, or jitter compensation.
3 - MEMS
In less than 20 years, MEMS
(micro electro-mechanical systems) technology has gone from an interesting
academic exercise to an integral part of many common products (Weinberg
2004). Silicon micromechanical instruments can be made by bulk micromachining
(chemical etching) single crystal silicon or by surface micromachining layers
of polysilicon (Yun and
Howe 1991). Many manufactures are developing gyros
and
accelerometers using this technology.
- Their extremely small size combined with the
strength of silicon makes them ideal for very high acceleration
applications. Silicon sensors provide many advantages over other
materials, such as quartz or metal, for microsized
rate sensor development. These advantages include excellent scale factor
matching and stability, long life, bias stability, virtually no
degradation, and the ability to handle larger stress levels (Yun and Howe 1991).
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INERTIAL
TIPS
• Starting in September 2007, with
manual version 2.1, we are introducing new hardware versions. The backpack-portable
inertial navigation systems (B-PINS) of Zupt LLC,
will now be available in various versions depending on its internal
components.
“Zing”,
the field operations software running on a handheld computer, will offer (in the
“Connection - Setup” screen) to connect to various devices: either Type A or
Type B version 1, or Type B version 2, or Type B version 3 (etc…).
For
each device chosen, the communications parameters will be set automatically.
To
know which “device” is your PINS, please read its name on the device itself:
1) If it is not a backpack or if it
has the word “A-PINS” written on its case, it is an A-PINS device.
2) If it is a backpack sold before
September 2007, it is a “B-PINS version 1” device. These “version 1” packs
have a key switch.
3) If it is any other device, please
remove the orange lid of the backpack and simply read the device version
number on the top of the black sensor case (between the connectors). It
should read “Version 2” or “Version 3” etc…
Please
make sure you choose the correct device in the “Connection - Setup” screen.
If you are unsure, you can try the devices and iteratively try to connect for
each device, and see if the connection establishes itself, until you find the
right device. There will be no hardware consequences for this procedure.
For
all devices Type B version 2 and higher, you must go to the “Connection”
screen to stop the IMU (the backpack) at the end of the survey, since
there is no more key to turn it off.
The
manual will indicate  when a different procedure has to
be followed for different devices.
If there is no
specification of the device version, it means the instruction or information
applies to all PINS hardware devices in the same way.
Use KML format to draw lines on Google Earth ™. It is extremely
easy and quick: send the limits of your next project to a client, trace roads
and access maps, show your last ski run to your friends… Take this example
hereafter showing Zupt office location, replace the coordinates (Lon, Lat, Hgt) by yours, "cut and paste" it in
a text file, rename the extension from ".txt" to “.kml”, and finally double-click on the kml
file…
<kml xmlns="http://www.zupt.com">
<Document>
<Placemark>
<Style>
<LineStyle>
<color>FF00FFFF</color>
<width>1</width>
</LineStyle>
</Style>
<LineString>
<altitudeMode>clamptoground</altitudeMode>
<coordinates>
-95.51665028,29.94222401,0
-95.51689167,29.94246667,0
-95.51713306,29.94222401,0
-95.51665028,29.94222401,0
</coordinates>
</LineString>
</Placemark>
</Document>
</kml>
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ULTRA ACCURATE INERTIAL
SURVEYS
For Metrology and other short
range surveys on land and underwater, the repeatability of inertial survey
with different IMU is being studied at Zupt LLC.
Here are examples of 19 or 20
consecutive tests:
|
|
Time :
|
|
Lat deg
min
|
Lat
(sec)
|
Lon
(deg, min)
|
Lon(sec)
|
Hgt
|
|
|
|
|
|
|
|
|
|
|
1
|
10:58:25
|
B
|
L=N29ø56
|
32.0153
|
G=W095ø31
|
1.3215
|
115.4350
|
|
2
|
11:00:35
|
B
|
L=N29ø56
|
32.0157
|
G=W095ø31
|
1.3235
|
115.2310
|
|
3
|
11:03:19
|
B
|
L=N29ø56
|
32.0163
|
G=W095ø31
|
1.3241
|
115.0790
|
|
4
|
11:06:03
|
B
|
L=N29ø56
|
32.0160
|
G=W095ø31
|
1.3250
|
114.9200
|
|
5
|
11:08:19
|
B
|
L=N29ø56
|
32.0164
|
G=W095ø31
|
1.3255
|
114.7720
|
|
6
|
11:11:01
|
B
|
L=N29ø56
|
32.0163
|
G=W095ø31
|
1.3266
|
114.5780
|
|
7
|
11:13:33
|
B
|
L=N29ø56
|
32.0163
|
G=W095ø31
|
1.3283
|
114.4000
|
|
8
|
11:15:48
|
B
|
L=N29ø56
|
32.0163
|
G=W095ø31
|
1.3288
|
114.2330
|
|
9
|
11:18:54
|
B
|
L=N29ø56
|
32.0166
|
G=W095ø31
|
1.3289
|
114.1680
|
|
10
|
11:21:31
|
B
|
L=N29ø56
|
32.0172
|
G=W095ø31
|
1.3307
|
113.9940
|
|
11
|
11:24:06
|
B
|
L=N29ø56
|
32.0174
|
G=W095ø31
|
1.3312
|
113.8010
|
|
12
|
11:26:41
|
B
|
L=N29ø56
|
32.0175
|
G=W095ø31
|
1.3319
|
113.7090
|
|
13
|
11:29:05
|
B
|
L=N29ø56
|
32.0166
|
G=W095ø31
|
1.3320
|
113.5300
|
|
14
|
11:32:16
|
B
|
L=N29ø56
|
32.0160
|
G=W095ø31
|
1.3323
|
113.4490
|
|
15
|
11:34:47
|
B
|
L=N29ø56
|
32.0160
|
G=W095ø31
|
1.3330
|
113.3590
|
|
16
|
11:36:43
|
B
|
L=N29ø56
|
32.0162
|
G=W095ø31
|
1.3343
|
113.2320
|
|
17
|
11:38:57
|
B
|
L=N29ø56
|
32.0166
|
G=W095ø31
|
1.3340
|
113.1150
|
|
18
|
11:41:21
|
B
|
L=N29ø56
|
32.0146
|
G=W095ø31
|
1.3360
|
112.8010
|
|
19
|
11:43:31
|
B
|
L=N29ø56
|
32.0154
|
G=W095ø31
|
1.3362
|
112.7240
|
|
Average:
|
0.24
|
36.93
|
0.00
|
|
Stdev (m):
|
0.01
|
0.01
|
0.03
|
|
|
|
|
|
|
Min
|
0.23
|
36.90
|
-0.09
|
|
Max
|
0.26
|
36.96
|
0.05
|
|
|
|
|
|
|
Difference
(m):
|
0.03
|
0.06
|
0.14
|
Inertial survey positional
error being a function of distance, extremely accurate measurement can be
done by establishing control points at short range.
Transporting the IMU in a
smoothly running vehicle, a floating vessel or underwater vehicle also
improves dramatically the quality of the navigation.
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