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Updated the airship_added_mass system.
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Signed-off-by: Anders Gidenstam <[email protected]>
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@andgi
andgi committed Dec 5, 2023
1 parent 48e2558 commit 056bb71
Showing 1 changed file with 75 additions and 17 deletions.
92 changes: 75 additions & 17 deletions systems/airship_added_mass.xml
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Airship added/virtual mass model for JSBSim.
Copyright (C) 2008 - 2014 Anders Gidenstam (anders(at)gidenstam.org)
Copyright (C) 2008 - 2018 Anders Gidenstam (anders(at)gidenstam.org)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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Define the following properties:
aero/constants/volume-ft3
aero/constants/length-diameter-ft2 (length^2 + diameter^2)
aero/constants/added-mass/k-axial
aero/constants/added-mass/k-traverse
aero/constants/added-mass/k-rotational
aero/constants/added-mass/tweak-factor (1.0 is the standard value)
aero/constants/added-mass/k-axial (all three are positive but
aero/constants/added-mass/k-transverse can be entered as negative
aero/constants/added-mass/k-rotational for backwards compatibility)
aero/constants/added-mass/tweak-factor (1.0 is the standard value)

Define the following external forces:
aero/constants/added-mass/k-traverse (old misspelling, can be given
to work with older FlightGear)

Define the following external forces and moments:

<force name="added-mass-bx" frame="BODY">
<location unit="">
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</direction>
</force>

<moment name="added-mass-pitch" frame="BODY" unit="LBSFT">
<direction>
<x> 0.0 </x>
<y> 1.0 </y>
<z> 0.0 </z>
</direction>
</moment>
<moment name="added-mass-roll" frame="BODY" unit="LBSFT">
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</moment>
<moment name="added-mass-yaw" frame="BODY" unit="LBSFT">
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z> 1.0 </z>
</direction>
</moment>

The old deprecated force based external moment implementation below is still
supported.

<force name="added-mass-pitch[0]" frame="BODY">
<location unit="">
<x> AERORP X </x>
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</channel>

<property>aero/constants/added-mass/k-transverse</property>
<property>aero/constants/added-mass/k-traverse</property>
<channel name="backward-compatibility">

<!-- Allow vehicles still using the old misspelled k-traverse coefficient. -->
<switch name="aero/constants/added-mass/k-transverse-final">
<default value="aero/constants/added-mass/k-transverse"/>
<test logic="AND" value="aero/constants/added-mass/k-transverse">
aero/constants/added-mass/k-transverse NE 0.0
</test>
<test logic="AND" value="aero/constants/added-mass/k-traverse">
aero/constants/added-mass/k-traverse NE 0.0
</test>
</switch>

</channel>

<channel name="translational">

<fcs_function name="aero/added-mass/force-bx-lbs">
<function>
<product>
<value>-1.0</value>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-axial </property>
<abs><property> aero/constants/added-mass/k-axial </property></abs>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/udot-ft_sec2 </property>
</product>
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<fcs_function name="aero/added-mass/force-by-lbs">
<function>
<product>
<value>-1.0</value>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-traverse </property>
<abs><property> aero/constants/added-mass/k-transverse-final </property></abs>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/vdot-ft_sec2 </property>
</product>
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<fcs_function name="aero/added-mass/force-bz-lbs">
<function>
<product>
<value>-1.0</value>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-traverse </property>
<abs><property> aero/constants/added-mass/k-transverse-final </property></abs>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/wdot-ft_sec2 </property>
</product>
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<function>
<product>
<property> aero/added-mass/active </property>
<value> 0.05 </value>
<value>-0.05 </value>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-rotational </property>
<abs><property> aero/constants/added-mass/k-rotational </property></abs>
<property> aero/constants/volume-ft3 </property>
<property> aero/constants/length-diameter-ft2 </property>
<property> accelerations/qdot-rad_sec2 </property>
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<function>
<product>
<property> aero/added-mass/active </property>
<value> 0.05 </value>
<property> aero/constants/added-mass/k-rotational </property>
<value>-0.05 </value>
<property> atmosphere/rho-slugs_ft3 </property>
<abs><property> aero/constants/added-mass/k-rotational </property></abs>
<property> aero/constants/volume-ft3 </property>
<property> aero/constants/length-diameter-ft2 </property>
<property> accelerations/rdot-rad_sec2 </property>
</product>
</function>
</fcs_function>

<pure_gain name="aero/added-mass/pitch-moment-force-lbs[0]">
<pure_gain name="aero/added-mass/pitch-moment/moment-lbsft">
<input>aero/added-mass/pitch-moment-lbsft</input>
<gain>1.0</gain>
<output>external_reactions/added-mass-pitch/magnitude-lbsft</output>
</pure_gain>
<pure_gain name="aero/added-mass/pitch-moment/force-lbs[0]">
<input> aero/added-mass/pitch-moment-lbsft </input>
<gain>-0.5</gain>
<output> external_reactions/added-mass-pitch[0]/magnitude </output>
</pure_gain>
<pure_gain name="aero/added-mass/pitch-moment-force-lbs[1]">
<pure_gain name="aero/added-mass/pitch-moment/force-lbs[1]">
<input> aero/added-mass/pitch-moment-lbsft </input>
<gain>0.5</gain>
<output> external_reactions/added-mass-pitch[1]/magnitude </output>
</pure_gain>

<pure_gain name="aero/added-mass/yaw-moment-force-lbs[0]">
<pure_gain name="aero/added-mass/yaw-moment/moment-lbsft">
<input>aero/added-mass/yaw-moment-lbsft</input>
<gain>1.0</gain>
<output>external_reactions/added-mass-yaw/magnitude-lbsft</output>
</pure_gain>
<pure_gain name="aero/added-mass/yaw-moment/force-lbs[0]">
<input> aero/added-mass/yaw-moment-lbsft </input>
<gain>-0.5</gain>
<output> external_reactions/added-mass-yaw[0]/magnitude </output>
</pure_gain>
<pure_gain name="aero/added-mass/yaw-moment-force-lbs[1]">
<pure_gain name="aero/added-mass/yaw-moment/force-lbs[1]">
<input> aero/added-mass/yaw-moment-lbsft </input>
<gain>0.5</gain>
<output> external_reactions/added-mass-yaw[1]/magnitude </output>
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