jsbsim.js
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JSBSim flight dynamics model ported to JavaScript
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text/xml
<!--
Airship added/virtual mass model for JSBSim.
Copyright (C) 2008 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
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-->
<system name="added-mass">
<documentation>
This system computes forces and moments due to added/virtual mass.
The model is based on
[Max M. Munk, "Aerodynamic forces on airship hulls", NACA report 184, 1924]
and the introduction in
[Christopher J. Atkinson, Robert G. Urso, "Modeling of Apparent Mass Effects
for the Real-Time Simulation of a Hybrid Airship", AIAA Modeling and
Simulation Technologies Conference, Aug 2006].
Usage:
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)
Define the following external forces:
<force name="added-mass-bx" frame="BODY">
<location unit="">
{ AERORP }
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="added-mass-by" frame="BODY">
<location unit="">
{ AERORP }
</location>
<direction>
<x> 0.0 </x>
<y> 1.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="added-mass-bz" frame="BODY">
<location unit="">
{ AERORP }
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z> 1.0 </z>
</direction>
</force>
<force name="added-mass-pitch[0]" frame="BODY">
<location unit="">
<x> AERORP X </x>
<y> AERORP Y </y>
<z> AERORP Z - 0.3048 </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="added-mass-pitch[1]" frame="BODY">
<location unit="M">
<x> AERORP X </x>
<y> AERORP Y </y>
<z> AERORP Z + 0.3048 </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="added-mass-yaw[0]" frame="BODY">
<location unit="M">
<x> AERORP X </x>
<y> AERORP Y - 0.3048 </y>
<z> 0.0 </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="added-mass-yaw[1]" frame="BODY">
<location unit="M">
<x> AERORP X </x>
<y> AERORP Y + 0.3048 </y>
<z> 0.0 </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
</documentation>
<channel name="startup">
<!-- Allow the vehicle state to stabilize. -->
<fcs_function name="aero/added-mass/active">
<function>
<min>
<property> aero/constants/added-mass/tweak-factor </property>
<max>
<value> 0.0 </value>
<difference>
<property> simulation/sim-time-sec </property>
<value> 2.0 </value>
</difference>
</max>
</min>
</function>
</fcs_function>
</channel>
<channel name="translational">
<fcs_function name="aero/added-mass/force-bx-lbs">
<function>
<product>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-axial </property>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/udot-ft_sec2 </property>
</product>
</function>
<output> external_reactions/added-mass-bx/magnitude </output>
</fcs_function>
<fcs_function name="aero/added-mass/force-by-lbs">
<function>
<product>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-traverse </property>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/vdot-ft_sec2 </property>
</product>
</function>
<output> external_reactions/added-mass-by/magnitude </output>
</fcs_function>
<fcs_function name="aero/added-mass/force-bz-lbs">
<function>
<product>
<property> aero/added-mass/active </property>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-traverse </property>
<property> aero/constants/volume-ft3 </property>
<property> accelerations/wdot-ft_sec2 </property>
</product>
</function>
<output> external_reactions/added-mass-bz/magnitude </output>
</fcs_function>
</channel>
<channel name="rotational">
<fcs_function name="aero/added-mass/pitch-moment-lbsft">
<function>
<product>
<property> aero/added-mass/active </property>
<value> 0.05 </value>
<property> atmosphere/rho-slugs_ft3 </property>
<property> aero/constants/added-mass/k-rotational </property>
<property> aero/constants/volume-ft3 </property>
<property> aero/constants/length-diameter-ft2 </property>
<property> accelerations/qdot-rad_sec2 </property>
</product>
</function>
</fcs_function>
<fcs_function name="aero/added-mass/yaw-moment-lbsft">
<function>
<product>
<property> aero/added-mass/active </property>
<value> 0.05 </value>
<property> aero/constants/added-mass/k-rotational </property>
<property> atmosphere/rho-slugs_ft3 </property>
<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]">
<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]">
<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]">
<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]">
<input> aero/added-mass/yaw-moment-lbsft </input>
<gain>0.5</gain>
<output> external_reactions/added-mass-yaw[1]/magnitude </output>
</pure_gain>
</channel>
</system>