jsbsim.js/JSBSim/systems/Autopilot.xml

JSBSim flight dynamics model ported to JavaScript

<?xml version="1.0"?>
<system name="Autopilot"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:noNamespaceSchemaLocation="http://jsbsim.sourceforge.net/JSBSimSystem.xsd">

<!-- #######################################################################

  Author:   Jon Berndt
  Date:     January 2009
  Function: Autopilot

  Description:

  This file contains general purpose autopilot functions for JSBSim aircraft.
  
  Usage
  =====
  
  This file contains algorithms that depend on parameters calculated in the
  file, GNCUtilities.xml, which should be included prior to the inclusion of
  this file, e.g.,
  
  <system file="GNCUtilities"/>

  <system file="Autopilot"/>
   
  Inputs: 

    [Declared Interface Parameters]
    ap/roll-attitude-mode - This should be set to 0 for wings level or to 1
                            for roll angle hold.
    ap/autopilot-roll-on - this is either 0 (off) or 1. This turns the roll
                           autopilot on or off.

    [Overridable constants]
    guidance/roll-angle-limit = 0.524 (default value in radians)
    guidance/roll-rate-limit = 0.174 (default value in radians)

  Introduced parameters (temporary terms):

  Outputs:
    ap/roll-cmd-norm-output - roll command to the flight control roll channel
                              in a normalized range from -1 to +1.

######################################################################## -->

  <property> ap/roll-attitude-mode </property>
  <property> ap/autopilot-roll-on  </property>
  
  <!-- Initial constants (can be overridden in the aircraft file) -->

  <property value="0.524"> guidance/roll-angle-limit </property>
  <property value="0.174"> guidance/roll-rate-limit </property>

  <property value="0"> ap/roll-angle-saturation </property>

<!-- #################################################################### -->

  <channel name="Heading Hold">

    <switch name="ap/roll-control-autopilot-on">
      <default value="0"/>
      <test value="1">
        ap/autopilot-roll-on ne 0.0
      </test>
    </switch>

    <switch name="ap/roll-autopilot-windup-trigger">
      <default value="1"/>
      <test value="1">
        ap/roll-angle-saturation ne 0.0
      </test>
      <test value="0">
        ap/roll-control-autopilot-on gt 0
      </test>
    </switch>

    <pure_gain name="ap/limited-roll-angle-rad">
      <description>
        This component takes as input the angle to the target heading from
        the current heading, as calculated by the Angle to Heading channel
        in the GNC Utilities system file. The output of this component (stored)
        in the component property "ap/limited-roll-angle-rad" is the roll
        angle command, limited at 30 degrees (0.524 radians), though this can be
        overridden.
      </description>
      <input> guidance/angle-to-heading-rad </input>
      <gain> 1.0 </gain>
      <clipto>
        <min> -guidance/roll-angle-limit </min>
        <max>  guidance/roll-angle-limit </max>
      </clipto>
    </pure_gain>

    <switch name="ap/roll-attitude-selector">
      <description>
        This component selects whether to use a roll angle of "0" - which
        is a wings-level attitude - or to use the roll angle commanded by the 
        ap/limited-roll-angle-rad component, above, which is used to acquire
        and hold a heading.
        Set ap/roll-attitude-mode to 1 for roll angle hold,
                                  to 0 for wings level (roll attitude of zero).
      </description>
      <default value="0"/>
      <test value="ap/limited-roll-angle-rad">
        ap/roll-attitude-mode eq 1
      </test>
    </switch>
    
    <summer name="ap/limited-roll-angle-error">
      <description>
        This component computes the error between the calculated target roll
        angle and the actual roll angle. The output is interpreted as a roll
        rate command.
      </description>
      <input>  ap/roll-attitude-selector </input>
      <input> -attitude/phi-rad </input>
    </summer>

    <pid name="ap/roll-rate-pid-control">
      <input> ap/limited-roll-angle-error </input>
      <kp> 30 </kp>
      <ki> 0.1  </ki>
      <kd> 0.1  </kd>
      <trigger> ap/roll-autopilot-windup-trigger </trigger>
      <clipto>
        <min> -guidance/roll-rate-limit </min>
        <max>  guidance/roll-rate-limit </max>
      </clipto>
    </pid>

    <pure_gain name="ap/total-limited-roll-rate">
      <input>guidance/roll-rate-limit</input>
      <gain>2.0</gain>
    </pure_gain>
    
    <deadband name="ap/roll-rate-saturation">
      <input> ap/roll-rate-pid-control </input>
      <width> ap/total-limited-roll-rate </width>
    </deadband>

    <summer name="ap/limited-roll-rate-error">
      <description>
        This component computes the error between the calculated target roll
        rate and the actual roll rate. The output is interpreted as an aileron
        command.
      </description>
      <input> ap/roll-rate-pid-control </input>
      <input> -velocities/p-aero-rad_sec </input>
    </summer>

    <pid name="ap/roll-command-pid-control">
      <input> ap/limited-roll-rate-error </input>
      <kp>2.5</kp>
      <ki>0.0</ki>
      <kd>0.0</kd>
      <trigger> ap/roll-autopilot-windup-trigger </trigger>
    </pid>

    <lag_filter name="ap/roll-cmd-smoother">
      <input> ap/roll-command-pid-control </input>
      <c1> 100.0 </c1>
    </lag_filter>

    <switch name="ap/roll-cmd-norm-output">
      <default value="0"/>
      <test value="ap/roll-cmd-smoother">
        ap/roll-control-autopilot-on ne 0.0
      </test>
    </switch>

    <switch name="ap/roll-command-selector-steering">
      <default value="0.0"/>
      <test value="ap/roll-cmd-norm-output">
        ap/roll-control-autopilot-on == 1
        gear/unit[0]/WOW == 1
      </test>
      <output>fcs/steer-cmd-norm</output>
    </switch>

  </channel>

</system>