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

Chapter 3 / Sensors / Radar
_ _
LF demands are processed using weave-tuned αβγ filters providing a
smooth input to the gimbal dynamics at 100 Hz. A weave tuned αβγ filter is
used with a bandwidth (ωDB) of 2 Hz and the weave frequency (ωDW) set to
zero, reducing it to a normal αβγ filter. Its output provides target angular
velocity and acceleration estimates that can be used for CLOS guidance.
The high frequency (HF) demands pass through a phase compensation filter
prior to digital to analogue conversion,
ϕ
DAC
WT D
( ϕ ( ϕ ( 10 ZG
+ N ( 0 , RDσGA
) , RDωDB
, RDωDW
) , RDωNC
, RDωDC
) )
DDL
αβδ
3.8-3
D
100
Z
G
: =
Equation 3.8-3
(RDσGA) is the physical misalignment of the radar with respect to the
Alignment frame. This misalignment is constant and initialised using a
zero-mean Gaussian error with a deviation of 3mrad. The compensation
filter characteristics are matched to the phase loss due to the time delay and
2 nd order actuator dynamics that follow,
⎛
⎜
⎝
1
ω
( ) ⎟ ω , ω : = ⎜
,
RD
NC
RD
DC
2 ⋅
RD
ζ
C
⋅
RD
C
+
RD
t
C
RD
1
t
C
⎞
⎠
Equation 3.8-4
( ζ , ω , t ) : = ( ζ , ω , t )
RD
C
RD
C
RD
C
RD
D2L
RD
D2L
Table 3-14 : Gimbal Demand Processing Errors
GB_RD_ER Gimbal Errors
11 Gimbal demand weave filtering
12 Gimbal demand slew rate limiting
13 Gimbal demand control filtering
14 Weave frequency estimate
RD
TD
Equation 3.8-5
The HF demands are converted to analogue using a 12 bit ADC subject to
3 bits of noise with a sampling rate and range matched to the input interface.
The injection of gimbal errors is controlled by the bit pattern of GB_RD_ER
according to Table 3-6. ADC errors are controlled by bits 21-24 the same as
the DAC, the bit controlling the A/A filter being redundant. The additional
gimbal demand processing errors are activated using the spare bits in
GB_RD_ER listed in Table 3-14.