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

Chapter 10 / Conclusions
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10.3 Targets
10.4 Sensors
The target simulator generates trajectories using elemental acceleration
models activated and characterised either interactively or by external data.
Stationary, crossing and head-on targets are initialised depending on the
user input data, subject thereafter to acceleration demands filtered to
produce realistic target dynamics. The elemental models comprise earth and
target velocity referenced, piecewise constant acceleration, sinusoidal and
square weaves. Specific models have been embedded in the simulator for
IMM filter tuning, and for performance comparisons.
Sensors were selected for their enduring impact on future weapon system
development. They are broadly categorised as either earth referencing, or
targeting instruments:
• IMU gyroscope and accelerometers
• Barometric and radar altimeters
• RF and IR sensors (Radar and seekers)
• Missile fin transducers
• NAVSTAR global positioning
• Helmet mounted sights
• Air data derived from Pitot tube and temperature detectors
A system level approach provides models that capture the essential
characteristics of an instrument commensurate with its output bandwidth.
Each sensor model is self-contained extracting its input from the reference
state to promote cloning, and transportation to other applications. Any
combination of characteristic errors can be superimposed on the reference
input, the measurements passing through a 1553 digital interface.
Inertial IMU sensors provide absolute and incremental measurements at
800Hz characterised as mechanical, optical, or solid state devices. The
generation of accurate reference inputs from earth referenced data for
distributed master/slave IMU in the presence of body flexure is explored.
The radar altimeter model relies on digital map error characterisation for
nap-of-the-earth navigation. The GPS model provides 1 Hz or 10 Hz earth
referenced position and velocity data rather than pseudo-measurements, data
that depends on the geometry of the satellites selected for triangulation, and
subject to errors such as selective availability. The ground based radar and
missile seeker can be characterised as RF and IR devices and both have
detectors encased in yaw-pitch gimbals that can be locked for strap-down
applications.
10-4