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

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Chapter 5 / Missile State Observer<br />

_ _<br />

Sensor<br />

1<br />

Tracking<br />

Filter 1<br />

Tracking<br />

Filter 2<br />

Tracking<br />

Filter<br />

"N"<br />

IMM track<br />

fusion<br />

5-6<br />

Sensor 2<br />

MISSILE STATE OBSERVER<br />

Centralised<br />

track fusion<br />

Sensor 4<br />

Centralised<br />

measurement<br />

fusion<br />

Sensor<br />

3<br />

Figure 5-6 : Hybrid Track and Measurement Fusion for Air-Defence<br />

Tracks are correlated and fused at track level leading to a non-optimal<br />

result. Measurements are rarely correlated and require no such processing<br />

however, they are prone to individual sensor characteristics. Filter integrity<br />

is important when dealing with measurements from slowly failing sensors<br />

lest they corrupt the observer, particularly those with low measurement<br />

uncertainty, whereas tracks are less susceptible.<br />

5.2 Up-Link Interface<br />

The target states and covariance from the IMM are transmitted to the missile<br />

with the radar missile measurements. The up-link requires that the angle<br />

between the LOS from the transmitter to the missile receiver, and the<br />

missile body axis X B is constrained during trajectory optimisation so that the<br />

transmissions can be received. The up-link interface is modelled in exactly<br />

the same way as the radar output interface in §3.4.9, its functional form for<br />

the missile measurements being,<br />

UL<br />

Z ~<br />

M<br />

: =<br />

IF<br />

ϕ<br />

TD<br />

IF IF IF<br />

( ( ( ( RD Z M ) ) ) ) ~<br />

ϕ ϕ ϕ<br />

Q<br />

LIM<br />

ZOH<br />

Equation 5.2-1<br />

The missile range, range-rate, bearing and elevation measurements with<br />

respect to the Alignment frame pass through a 16 bit digital interface<br />

(signed except for range) at a frequency (ULfO) of 10 Hz. By default<br />

measurements are subject to a one-cycle transmission delay and limits of<br />

[0,60_000] m, ± 1000 m/s, ± 180° and ± 90° respectively. The IMM track<br />

data is subject to the same interface characteristics with signed limits of<br />

± 60 km, ± 1000 m/s and ± 100 m/s 2 respectively.<br />

IF IF IF<br />

+<br />

( ϕ ( ϕ ( ϕ ( ) ) ) )<br />

+ IF<br />

UL X : ϕ<br />

TD Q LIM ZOH IMM<br />

= X<br />

Equation 5.2-2<br />

IF IF IF<br />

−<br />

( ϕ ( ϕ ( ϕ ( ) ) ) )<br />

− IF<br />

UL X : ϕ<br />

TD Q LIM ZOH IMM<br />

= X<br />

Equation 5.2-3

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