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

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Chapter 5 / Missile State Observer<br />

_ _<br />

( Q , Q )<br />

MAA<br />

QQ<br />

MAA<br />

QW<br />

: =<br />

5.7 Up-Linked Target Track Update<br />

5-12<br />

⎛ 2<br />

∆<br />

⎜<br />

⎝ 4<br />

,<br />

1<br />

4<br />

⎛<br />

⎞ ⎜<br />

⎟ ⎜<br />

⎟<br />

⋅<br />

⎠ ⎜<br />

q<br />

⎝<br />

B<br />

A<br />

− q<br />

B<br />

A<br />

⎞<br />

( ) [ ] ⎟ ⎟⎟⎟ B<br />

0 + q ×<br />

A<br />

⎠<br />

Equation 5.6-11<br />

The observer propagates at high frequency with asynchronous updates<br />

thereby avoiding large differences between the current and data reference<br />

times. Had the time difference been significant, the states must be<br />

propagated to the measurement time reference, or stored, so as to form<br />

innovations at the correct time. Covariance data should not vary<br />

significantly over the period and its computationally expensive propagation<br />

can be avoided. When available, the up-linked target track is dealt with<br />

first. If the interval between track up-links is long compared with the target<br />

manoeuvring time the track data can be treated as measurements using the<br />

conventional covariance EKF formulation,<br />

X<br />

K<br />

+<br />

TTL<br />

: =<br />

C<br />

C<br />

−<br />

TLL<br />

−<br />

CTLL<br />

( tk<br />

)<br />

+<br />

( t ) + C ( t )<br />

k<br />

UL<br />

UL<br />

+ −<br />

( X − X )<br />

−<br />

= XTTL<br />

+ K ⋅ UL TTL<br />

:<br />

+<br />

TTL<br />

:<br />

−<br />

[ I − K ] ⋅ C<br />

= 9<br />

TTL<br />

Equation 5.7-1<br />

Equation 5.7-2<br />

Equation 5.7-3<br />

Here the IMM provides weighted target state and covariance data at 10 Hz<br />

which cannot be treated simply as a plot since the data is correlated and<br />

must be fused at track level, Lobbia [L.8] . When dealing with correlated<br />

tracks only new information between track updates must be fused into the<br />

observer,<br />

X<br />

+<br />

TTL<br />

+<br />

+ − CTTL<br />

− −<br />

( X − X ) − ⋅ ( X − X )<br />

+<br />

− CTTL<br />

= XTTL<br />

+ ⋅ + UL TTL<br />

− UL TTL<br />

UL C<br />

UL C<br />

:<br />

[ ] [ ] [ ] [ ] 1<br />

+ −1<br />

− −1<br />

+ −1<br />

− −<br />

C : = C + C − C<br />

TTL<br />

TTL<br />

UL<br />

UL<br />

Equation 5.7-4<br />

Equation 5.7-5<br />

The first two terms in each of these equations represent the standard KF<br />

measurement update. The final term removes previous track data already

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