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

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Chapter 3 / Sensors / Seeker<br />

_ _<br />

Table 3-20 : Complex Gimbal Friction Characteristics<br />

MATH DESCRIPTION PITCH YAW UNITS<br />

SKKG8 Coulomb friction 0.005 0.05 Nm<br />

SKKG9 Stiction threshold 15 15 mrad/s<br />

SKKG10 Stiction level 0.005 0.05 Nm<br />

SKKG11 Viscous friction 2 x 10 -5 4 x 10 -5 Nm/rad/s<br />

The time delay, gimbal noise, ZOH and scale factor errors are identical to<br />

those used in the simple gimbal model,<br />

2000 ZGk : =<br />

ϕ<br />

SF<br />

( ϕ ( Z , f ) + N ( 0 , σ ) )<br />

ZOH<br />

8000<br />

3.9-12<br />

OTF<br />

SK<br />

GR<br />

SK<br />

GRN<br />

Equation 3.9-16<br />

When the gimbals demands are set to zero the time delay and the pickoff<br />

errors represent electronic beam steering inaccuracies - the other gimbal<br />

demand shaping and dynamic errors should be disabled.<br />

3.9.7 Reference Detector Input<br />

The reference range, range rate, bearing and elevation of the target with<br />

respect to the true position of the antennae boresight are updated at the<br />

output interface rate (SKfO),<br />

Θ<br />

S<br />

H<br />

3.9.8 Seeker Measurements<br />

Ψ<br />

m,<br />

t<br />

A<br />

o,<br />

t<br />

P = P − P<br />

P&<br />

: = P • P&<br />

S<br />

H<br />

XS<br />

m,<br />

t<br />

A<br />

m,<br />

t<br />

−1<br />

A<br />

m,<br />

t<br />

A<br />

o,<br />

m<br />

P<br />

m,<br />

t<br />

S<br />

H<br />

( T ( 7 ) ) −<br />

: = − sin<br />

Θ<br />

−1<br />

B<br />

S<br />

S<br />

H<br />

( T ( 4 ) T ( 1 ) ) −<br />

: = tan<br />

Ψ<br />

B<br />

B<br />

B<br />

B<br />

Equation 3.9-17<br />

Equation 3.9-18<br />

Equation 3.9-19<br />

Equation 3.9-20<br />

For convenience, the target parameters provided by the detector, when<br />

combined with gimbal pick-off output, are collectively referred to by,

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