airship-mooring.xml

<?xml version="1.0"?>
<!--

  Airship nose cone and main wire mooring system for JSBSim.

    Copyright (C) 2008 - 2023  Anders Gidenstam  (anders(at)gidenstam.org)

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301
    USA
  
-->
<system name="airship-mooring">

 <description>
  This system models a mast mooring system with a mooring cone connection
  and a mooring wire. The mooring cone MUST be located at the aircraft's
  visual reference point (VRP).

  Usage:

   Include the visual-reference-point-extensions system first.

   Define the following constant properties:
     For the mooring cone connection:
       mooring/mooring-spring-coeff-lbs_ft      [lbs/ft]
       mooring/mooring-damping-coeff-lbs_fps    [lbs*sec/ft]
       mooring/max-mooring-force-lbs            [lbs]

     For the mooring wire:
       mooring/wire-spring-coeff-lbs_ft         [lbs/ft]
       mooring/max-wire-force-lbs               [lbs]
       mooring/max-winch-speed-fps              [ft/sec]

     For the mooring cone connection:
       mooring/mooring-spring-coeff-lbs_ft
       mooring/mooring-damping-coeff-lbs_fps
       mooring/max-mooring-force-lbs

   Define the following external forces:

     <force name="mooring-coupling-north" frame="LOCAL">
      <location unit="M">
       { VRP }
      </location>
      <direction>
       <x> 1.0 </x>
       <y> 0.0 </y>
       <z> 0.0 </z>
      </direction>
     </force>
     <force name="mooring-coupling-east" frame="LOCAL">
      <location unit="M">
       { VRP }
      </location>
      <direction>
       <x> 0.0 </x>
       <y> 1.0 </y>
       <z> 0.0 </z>
      </direction>
     </force>
     <force name="mooring-coupling-down" frame="LOCAL">
      <location unit="M">
       { VRP }
      </location>
      <direction>
       <x> 0.0 </x>
       <y> 0.0 </y>
       <z> 1.0 </z>
      </direction>
     </force>

   The following control the mooring operation:
       mooring/wire-connected          Connect the wire    {0,1.0}
       mooring/winch-speed-fps         Winch speed         [ft/sec]
       mooring/initial-wire-length-ft                      [ft]

   Location of the mooring mast:
       mooring/latitude-deg
       mooring/longitude-deg
       mooring/altitude-ft

 </description>

 <!-- INTERFACE PROPERTIES -->

 <!--  Mooring actions -->
 <property value="0.0"> mooring/wire-connected </property>
 <property value="0.0"> mooring/winch-speed-fps </property>
 <property value="0.0"> mooring/initial-wire-length-ft </property>

 <!--  Mooring mast location. Note: Geodetic latitude and altitude. -->
 <property value="0.0"> mooring/latitude-deg  </property>
 <property value="0.0"> mooring/longitude-deg </property>
 <property value="0.0"> mooring/altitude-ft </property>

 <channel name="Mooring Forces">

   <fcs_function name="mooring/latitude-diff-ft">
    <function>
     <product>
      <property> position/latitude-unit-distance-ft_deg </property>
      <difference>
       <property> mooring/latitude-deg </property>
       <property> position/vrp-latitude-deg </property>
      </difference>
     </product>
    </function>
   </fcs_function>

   <fcs_function name="mooring/longitude-diff-ft">
    <function>
     <product>
      <property> position/longitude-unit-distance-ft_deg </property>
      <difference>
       <property> mooring/longitude-deg </property>
       <property> position/vrp-longitude-deg </property>
      </difference>
     </product>
    </function>
   </fcs_function>

   <fcs_function name="mooring/altitude-diff-ft">
    <function>
     <difference>
      <property> position/vrp-altitude-ft </property>
      <property> mooring/altitude-ft </property>
     </difference>
    </function>
   </fcs_function>

   <fcs_function name="mooring/total-distance-ft">
    <function>
     <pow>
      <sum>
       <pow>
        <property> mooring/latitude-diff-ft </property>
        <value> 2.0 </value>
       </pow>
       <pow>
        <property> mooring/longitude-diff-ft </property>
        <value> 2.0 </value>
       </pow>
       <pow>
        <property> mooring/altitude-diff-ft </property>
        <value> 2.0 </value>
       </pow>
      </sum>
      <value> 0.5 </value>
     </pow>
    </function>
   </fcs_function>

   <switch name="mooring/moored">
    <default value="0.0"/>
    <test logic="AND" value="1.0">
     mooring/wire-connected GE 1.0
     mooring/total-distance-ft LE 5.0
    </test>
   </switch>

   <fcs_function name="mooring/mooring-force-lbs">
    <function>
     <product>
      <property> mooring/moored </property>
      <property> mooring/mooring-spring-coeff-lbs_ft </property>
      <property> mooring/total-distance-ft </property>
     </product>
    </function>
    <clipto>
     <min> 0.0 </min>
     <max> mooring/max-mooring-force-lbs </max>
    </clipto>
   </fcs_function>

   <switch name="mooring/winch-reset">
    <default value="-1.0"/>
    <test logic="AND" value="0.0">
     mooring/wire-connected GT 0.0
    </test>
   </switch>

   <pid name="mooring/wire-length-change-ft">
    <!-- NOTE: The plain integrator component does not reset. -->
    <input> mooring/winch-speed-fps </input>
    <kp>    0.00 </kp>
    <ki>    1.00 </ki>
    <kd>    0.00 </kd>
    <trigger> mooring/winch-reset </trigger>
    <clipto>
     <min>-mooring/initial-wire-length-ft </min>
     <max> 0.0 </max> <!-- Might not be wise. -->
    </clipto>
   </pid>

   <fcs_function name="mooring/wire-length-ft">
    <function>
     <sum>
      <property> mooring/initial-wire-length-ft </property>
      <property> mooring/wire-length-change-ft </property>
     </sum>
    </function>
    <clipto>
     <min> 0.0 </min>
     <max> mooring/initial-wire-length-ft </max> <!-- Might not be wise. -->
    </clipto>
   </fcs_function>

   <fcs_function name="mooring/wire-force-lbs">
    <function>
     <product>
      <property> mooring/wire-connected </property>
      <property> mooring/wire-spring-coeff-lbs_ft </property>
      <max>
       <difference>
        <property> mooring/total-distance-ft </property>
        <property> mooring/wire-length-ft </property>
       </difference>
       <value> 0.0 </value>
      </max>
     </product>
    </function>
    <clipto>
     <min> 0.0 </min>
     <max> mooring/max-wire-force-lbs </max>
    </clipto>
   </fcs_function>

   <fcs_function name="mooring/total-force-lbs">
    <function>
     <sum>
      <property> mooring/wire-force-lbs </property>
      <property> mooring/mooring-force-lbs </property>
     </sum>
    </function>
   </fcs_function>

   <fcs_function name="mooring/force-north-lbs">
    <function>
     <product>
      <property> mooring/wire-connected </property>
      <sum>
       <product>
        <property> mooring/total-force-lbs </property>
        <quotient>
         <property> mooring/latitude-diff-ft </property>
         <property> mooring/total-distance-ft </property>
        </quotient>
       </product>
       <product>
        <property> mooring/moored </property>
        <property> mooring/mooring-damping-coeff-lbs_fps </property>
        <property> velocities/vrp-v-north-fps </property>
       </product>
      </sum>
     </product>
    </function>
    <output> external_reactions/mooring-coupling-north/magnitude </output>
   </fcs_function>

   <fcs_function name="mooring/force-east-lbs">
    <function>
     <product>
      <property> mooring/wire-connected </property>
      <sum>
       <product>
        <property> mooring/total-force-lbs </property>
        <quotient>
         <property> mooring/longitude-diff-ft </property>
         <property> mooring/total-distance-ft </property>
        </quotient>
       </product>
       <product>
        <property> mooring/moored </property>
        <property> mooring/mooring-damping-coeff-lbs_fps </property>
        <property> velocities/vrp-v-east-fps </property>
       </product>
      </sum>
     </product>
    </function>
    <output> external_reactions/mooring-coupling-east/magnitude </output>
   </fcs_function>

   <fcs_function name="mooring/force-down-lbs">
    <function>
     <product>
      <property> mooring/wire-connected </property>
      <sum>
       <product>
        <property> mooring/total-force-lbs </property>
        <quotient>
         <property> mooring/altitude-diff-ft </property>
         <property> mooring/total-distance-ft </property>
        </quotient>
       </product>
       <product>
        <property> mooring/moored </property>
        <property> mooring/mooring-damping-coeff-lbs_fps </property>
        <property> velocities/vrp-v-down-fps </property>
       </product>
      </sum>
     </product>
    </function>
    <output> external_reactions/mooring-coupling-down/magnitude </output>
   </fcs_function>

 </channel>

</system>