Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Chapter 4 / Target Tracking
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3.14 Discussion
It is only through a fundamental understanding of sensors and their
limitations that a sound selection of observer architectures and algorithms
can be made for any data fusion process. Data fusion solutions presented in
literature all too often ignore detrimental sensor features. In practice this
leads to inappropriate algorithm selection and eventual requirement creep as
software solutions are sought to overcome hardware deficiencies. In
industry, to be sure of capturing these features manufacturer’s sensor
development models are often used however, these tend to be highly
complex and require too much processing, making them unsuitable for rapid
system level performance assessment. There exists a need for a set of
technologically current sensor models pitched at the systems analysis level -
the key driver for this part of the research.
Following a review of modern missile systems Figure 3-69 shows the
sensors and their measurements that the author believes will have an
enduring impact on future weapon systems in respect of targeting, geodetic
referencing, and aided navigation. Although the latter are rarely used for
air-defence, they perform critical functions such as height keeping in cruise
and sea-skimming missiles. Boundaries that were once distinct are now
blurred, for example, GPS is likely to play an important role in short-range
munitions guided to a terrestrial reference point.
SDINS are the bedrock of most sensor suites, here considered in a Master-
Slave relationship required for transfer alignment, i.e. the calibration of lowgrade
inertial sensors. Although SDINS themselves are not strictly sensors,
they integrate the output from inertial sensors and height stabilisation
instruments to provide long-term navigation data.
FLIR and TIALD can be treated as specific characterisations of the generic
seeker model. Fin transducers are part of the autopilot loop closure
generating the acceleration demanded by the missile guidance law. They
are also required for the pseudo-measurement proposed in §5 for
constraining the missile dynamics in the missile observer.
§3 starts by describing how to select a sensor measurement suite in the
simulation, the activation of each sensor in turn, and how their output at a
digital interface is passed to the state observers. The models are designed so
that they can be added or removed from the sensor suite at the controller
level without interacting with those that remain. The creation of a parallel
set of MATLAB sensor models for verification, and to speed up sensor
development is briefly introduced before dealing with common error
sources. Errors such bias, scale factor and digital interface limitations found
in many sensors are treated generically using a functional notation with
default values provided in-situ. The characteristics associated with digital
input filtering, random noise, 1 st and 2 nd order Gauss-Markov noise, the
ZOH and uniform noise resulting from fixed word-length digital processing
are explored.
3.14-1