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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:
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Time :
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Lat deg min
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Lat (sec)
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Lon (deg, min)
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Lon(sec)
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Hgt
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1
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10:58:25
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B
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L=N29ø56
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32.0153
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G=W095ø31
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1.3215
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115.4350
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2
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11:00:35
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B
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L=N29ø56
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32.0157
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G=W095ø31
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1.3235
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115.2310
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3
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11:03:19
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B
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L=N29ø56
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32.0163
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G=W095ø31
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1.3241
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115.0790
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4
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11:06:03
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B
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L=N29ø56
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32.0160
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G=W095ø31
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1.3250
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114.9200
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5
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11:08:19
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B
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L=N29ø56
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32.0164
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G=W095ø31
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1.3255
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114.7720
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6
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11:11:01
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B
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L=N29ø56
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32.0163
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G=W095ø31
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1.3266
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114.5780
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7
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11:13:33
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B
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L=N29ø56
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32.0163
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G=W095ø31
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1.3283
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114.4000
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8
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11:15:48
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B
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L=N29ø56
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32.0163
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G=W095ø31
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1.3288
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114.2330
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9
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11:18:54
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B
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L=N29ø56
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32.0166
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G=W095ø31
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1.3289
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114.1680
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10
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11:21:31
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B
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L=N29ø56
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32.0172
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G=W095ø31
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1.3307
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113.9940
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11
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11:24:06
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B
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L=N29ø56
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32.0174
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G=W095ø31
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1.3312
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113.8010
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12
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11:26:41
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B
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L=N29ø56
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32.0175
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G=W095ø31
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1.3319
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113.7090
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13
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11:29:05
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B
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L=N29ø56
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32.0166
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G=W095ø31
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1.3320
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113.5300
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14
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11:32:16
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B
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L=N29ø56
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32.0160
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