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Personal Navigator
TeKnol Personal Navigation System (TeKnolPN) is a low size, low weight and
ultra-low power consumption system capable of solving personal navigation and
urban positioning task. The system continuously and uninterruptedly outputs the
coordinates of the user necessary to determine the full set of navigation data
and attitude parameters as well as motion parameters.
TeKnolPN: Personal Navigator
Currently none of navigation equipment vendors offers a “personal navigation
tool”, a portable navigating device, operating in all conditions. At the same
time, authoritative market research shows a growing demand for portable fully
autonomous positioning system for pedestrians. Such systems are indispensable
for emergency services, when uninterrupted position determination is critical.
Such a task cannot be achieved by GPS alone, because indoor, in forest area, in
the mines satellite signal is weak or not available at all.
About
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TeKnol has developed
the prototype of the personal navigation system (TeKnolPN) based
on the low-size inertial/GPS integrated system. TeKnolPN software uses
sophisticated originally designed inertial navigation and GPS
integration algorithm based on new approach to the problem of pedestrian
navigation solution. TeKnolPN is a fully autonomous system intended for
determination of absolute or relative 3D coordinates (in horizontal
plane and elevation). The system continuously and uninterruptedly
outputs the coordinates of a user, which then can be transmitted over
the selected communication channel.
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TeKnolPN architecture
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The personal navigation system prototype includes the
following hardware:
- The inertial measuring unit (the block of autonomous sensors), which
includes the three-axial blocks of accelerometers, gyroscopes, and
magnetometers, and a tiny bar altimeter.
- GPS receiver, built on a technology of high sensitivity satellite
signals processing (SiRF).
- The device for data recording, displaying and combined data processing
(the handheld computer like notebook).
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The attitude position of the unit relative to the human body is arbitrary,
but it shall not change in time of walking, i.e. the unit is rigid on a strap or
in the pocket.
TeKnolPN architecture
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The TeKnolPN software algorithm block-diagram consists of three
main blocks: classic strap-down algorithm, distance computation and block of
correction. The first block implements the classic strap-down INS algorithm,
this algorithm implements the local-level navigation frame, it provides with
the attitude information of the mounted inertial measurement unit. The known
altitude of the block allows computing the projections of the vector of
Earth magnetic field to the axes of the navigation frame, and, hence,
determining the magnetic heading.
The second block implements the alternative distance computation technique.
This block fulfills step-detecting function and the step length is
calculated. The third block is step length correction block. If GPS data is
available, it is possible to calibrate the step length calculation procedure.
For this purpose the traveled distances, calculated by measurement unit
indications and by GPS indications, are compared, and coefficient is
calibrated.
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The block-diagram of the algorithm
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The third block also implements the heading correction procedure. While GPS
data is available, it is possible to calibrate long-term gyroscopic drift, using
the heading information, obtained from GPS. In this case the influence of the
magnetic disturbances, caused by the operational environment, is minimized, and,
hence, do not lead to the errors in positioning determination. After the two
preliminary calibration procedures are done, the positions are calculated. In
order to minimize the positioning error, caused by integrating of the northern
and eastern increments of position, the final correction procedure is used. If
GPS data is available, the GPS coordinate indications can be used for correction
of the coordinates, provided by the navigation system.
Indoor and outdoor test results
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The TeKnolPN prototype indoor and outdoor tests showed that
system demonstrates the good autonomous accuracy. The hardware-software
combination implemented in TeKnolPN takes the advantage of the complete
strapdown INS architecture to provide the right attitude compensation.
However, the external magnetic disturbance provided by building construction
may cause the significant position error. Such an error may be reduced by
means of more advanced magnetic compass installation or different
positioning technique implementation (map matching, for instance).
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