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yils4 = [ GS_flag LOC_flag ]T flags defining the validity of the ILS signals, yils4
Parameters
The following parameters can be defined in the mask dialog of ILS, which can be opened
by double-clicking this block:
• the runway heading yRW,
• the coordinates xRW, yRW, and HRW of the origin of the runway-fixed reference
frame, measured with respect to the Earth-axes,
• the distance xloc from the runway threshold to the localizer antenna, measured along
the runway centerline (see figure 5.1),
• the distance xgs from the threshold to the position on the runway centerline that is
perpendicular to the glideslope antenna (see figure 5.1),
• the distance ygs from the glideslope antenna to the position on the runway centerline
that is perpendicular to the glideslope antenna (see figure 5.1),
• the nominal glideslope angle ggs.
Connections
in: uils is a subset of the state vector x from the nonlinear aircraft model.
out: in the example system ILS example, the outputvector yils1 is sent through the steadystate
error blocks GSerr and LOCerr, which both express ILS offset errors in terms
of electrical currents for the cockpit indications. The other output vectors are normally
primarily used for evaluations of simulation results. ILS example sends all
outputvectors to the MATLAB workspace by means of To Workspace blocks.
Type browse ils at the command-line for on-line help.
10.1. The radio-navigation blocklibrary 185
ILS example Main FDC library / ILS/VOR radio-nav / ILS signals / ILS example
Radio-navigation library / ILS signals / ILS example
Type
Masked subsystem block (contents accessible without unmasking).
Description
The subsystem ILS example demonstrates how the nominal ILS block ILS and the error
blocks GSerr, GSnoise1, LOCerr, and LOCnoise1 can be combined to build a complete
ILS simulation model. The subsystem has been masked to generate an appropriate blockicon,
but its contents are accessible without unmasking (hence, its light-blue background
colour). Slightly modified versions of this block have been included in the autopilot blocklibrary
APlib; see chapter 15 for more information.
Subsystems and/or blocks
The subsystem ILS example contains five masked subsystem blocks:
ILS computes the nominal ILS signals,
GSerr incorporates a steady-state error in the glideslope signal,
GSnoise1 computes glideslope noise,
LOCerr incorporates a steady-state error in the localizer signal,
LOCnoise1 computes localizer noise.
The disturbance models used in ILS example are all based upon ref.[1]. If you want to
apply the alternative noise blocks GSnoise2 and LOCnoise2 it is necessary to update this
subsystem. Since noise will cause simulations to slow down considerably, the ILS blocklibrary
also offers a version of ILS example without the glideslope and localizer noise.
The signals that leave the error blocks represent electrical glideslope and localizer currents,
needed to drive the cockpit instruments. In ILS example, these signals are converted
back to the error angles #gs and Gloc by multiplication with the factors 1/Kgs and 1/Kloc,
respectively.
Inputs
x = [ V a b p q r y q j xe ye H ]T state vector from the aircraft model, x
Outputs
#gs glideslope deviation angle, including system offset and noise, epsilon_gs
Gloc localizer deviation angle, including system offset and noise, Gamma_loc
During simulations, the time-trajectories of the nominal ILS signals (excluding ILS offseterrors
and noise!) and some interim results from the block ILS are collected in the MATLAB
workspace variable yils. Each row from this matrix corresponds to the vector yils at a
certain data-point:
yils = [ yils1
T yils2
T yils3
T yils4
T ]T
with:
yils1 = [ igs iloc ]T nominal currents through ILS indicators, yils1
yils2 = [ #gs Gloc ]T angles between nominal and current ILS planes, yils2
yils3 = [ xf yf Hf dgs Rgs Rloc ]T distances defining the aircraft’s approach position, yils3
yils4 = [ GS_flag LOC_flag ]T flags defining the validity of the ILS signals, yils4
The flags in yils4 provide information about the validity of the ILS signals, based on the
186 Chapter 10. Radio-navigation block reference
ILS coverage depicted in figures 5.5 and 5.3 of chapter 5. See section 5.1.1 for more information
about the nominal ILS signals and approach geometry.
Note: to plot the resulting time-trajectories of the ILS signals, it is necessary to create a
compatible time-basis in the MATLAB workspace as well. This can be achieved by including
a Clock block, which is connected to a To Workspace block, but in the special case
where the subsystem ILS example is connected to the nonlinear aircraft model Beaver (see
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FDC 1.4 – A SIMULINK Toolbox for Flight Dynamics and Contro(89)
