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

Chapter 6 / Missile Guidance
_ _
accuracy required since weave motion usually contains a spectrum of
frequencies in the target observer space.
6.6.6 CLOS Demand Correction for Constant Velocity Targets
The feed-forward demands are based on polar dynamics that are ideal for
slowly turning targets, but not for straight flying targets. An interesting
piece of research by Lee [L.4] shows that improvement in CLOS performance
is possible if the differential angles are corrected when the target is flying at
a constant velocity. A 3D extension to Lee’s 2D algorithm follows,
ϕ
ϕ
Θ
Ψ
Ψ
Ψ
TV
A
TV
A
>
≤
ϕ
ZT
FF
ϕ
: =
T
FF
FF
6-28
( ) T
YT ZT
ϕ ,
: = η ⋅ ϕ
sin
FF
FF
TV
sin ( ΨA
− ϕΨ
)
TV T
T
( Ψ − Ψ ) ⋅ cos(
ϕ − Ψ )
A
A
Ψ
A
Equation 6.6-14
Equation 6.6-15
TV
sin ( ΘA
+ ϕΘ
)
TV T
T
( Θ + Θ ) ⋅ cos(
ϕ + )
π
YT
⇒ ϕFF
: =
2 sin
Θ
A
A
Ψ
A
Equation 6.6-16
TV
sin ( − ΘA
+ ϕΘ
)
TV T
T
( −Θ
+ Θ ) ⋅ cos ( ϕ + )
π
YT
⇒ ϕFF
: =
2 sin
Θ
A
A
Ψ
A
Equation 6.6-17
( ) ( )
( ) ( ) ⎟⎟
T
t − ∆t
⋅ sin Ψ − ∆ ⎞
A t t
t − ∆t
⋅cos
Ψ t − ∆t
⎛ XT T XT
−1
2 ⋅ P ⋅ Ψ −
= ⎜ t sin A Pt
: tan
⎜ XT T XT
T
⎝ 2 ⋅ Pt
⋅ cos ΨA
− Pt
A
⎠
Equation 6.6-18
( ) ( )
( ) ( ) ⎟⎟
T
t − ∆t
⋅ sin Θ − ∆ ⎞
A t t
t − ∆t
⋅ cosΘ
t − ∆t
⎛ XT T XT
−1
2 ⋅ P ⋅ Θ −
= − ⎜ t sin A Pt
: tan
⎜ XT T XT
T
⎝ 2 ⋅ Pt
⋅ cosΘ
A − Pt
A
⎠
Equation 6.6-19
Implementation requires manoeuvre detection so that the algorithm can be
phased-out for manoeuvring targets. This can be formulated directly from
missile state observer data, or from the up-linked IMM filter probabilities.
To avoid transients in the missile acceleration this algorithm is weighted by
the probability associated with the IMM constant velocity filter,