jsbsim.js/JSBSim/systems/afcs.xml

JSBSim flight dynamics model ported to JavaScript

<?xml version="1.0"?>
<system name="automated flight control">

<!--  ===================================================================
        Automatic flight control system (AFCS)

        Based on the AFCS for the CH-54/S-64 helicopter described in
        /SH79/, eqns. 13-16.

        The system is adjustable via 'ap/afcs/adj/*' properties, it
        offers basic altitude- and heading-hold features, but can 
        also be turned into a pure 'Rate-Damper' (or SAS, 'Stability
        Augmentation System').


        'Altitude-hold' and 'heading-hold' features.

        Setting ap/afcs/adj/altitude-error-ctrl-gain to zero disables
        the altitude-hold feature. When altitude-hold is used the control
        input can be turned to 'h-sl' by setting 'ap/afcs/h-agl-mode'
        to zero.
        The 'ap/afcs/heading-hold-enable' property switches a simple
        'heading-hold' function on or off.


        SH79: Shaugnessy, J. D., Deaux, Thomas N., and Yenni, Kenneth R.;
              Development and Validation of a Piloted Simulation of a 
              Helicopter and External Sling Load - NASA TP-1285; 1979

      ===================================================================  -->


  <!--  ==================
          OUTPUT
        ==================  -->

  <property value="0.0"> ap/rudder-cmd </property>
  <property value="0.0"> ap/aileron-cmd </property>
  <property value="0.0"> ap/elevator-cmd </property>
  <property value="0.0"> ap/collective-cmd </property>


  <!--  ==================
          ROLL CHANNEL
        ==================  -->

  <!-- 'control' parameters -->
  <property value="0.0"> ap/afcs/roll-channel-active-norm </property>
  <property value="0.0"> ap/afcs/phi-trim-rad </property>
  <property value="0.0"> ap/afcs/lateral-trim </property>
  <!-- afcs 'setup' parameters -->
  <property value="0.33"> ap/afcs/adj/lateral-ctrl-gain </property>
  <property value="-0.133"> ap/afcs/adj/roll-err-ctrl-gain </property>
  <property value="-0.096"> ap/afcs/adj/roll-rate-ctrl-gain </property>

  <channel name="afcs-roll">
    <fcs_function name="ap/afcs/lateral-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/lateral-ctrl-gain </property>
          <difference>
            <property> fcs/lateral-gain </property>
            <property> ap/afcs/lateral-trim </property>
          </difference>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/roll-err-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/roll-err-ctrl-gain </property>
          <difference>
            <property> attitude/phi-rad </property>
            <property> ap/afcs/phi-trim-rad </property>
          </difference>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/roll-rate-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/roll-rate-ctrl-gain </property>
          <property> velocities/p-aero-rad_sec </property>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/roll-cmd-sum">
      <function>
        <product>
          <property> ap/afcs/roll-channel-active-norm </property>
          <sum>
            <property> ap/afcs/lateral-ctrl   </property>
            <property> ap/afcs/roll-err-ctrl  </property>
            <property> ap/afcs/roll-rate-ctrl </property>
          </sum>
        </product>
      </function>
      <output> ap/aileron-cmd </output>
    </fcs_function>
  </channel>

  <!--  ==================
          PITCH CHANNEL
        ==================  -->

  <!-- 'control' parameters -->
  <property value="0.0"> ap/afcs/pitch-channel-active-norm </property>
  <property value="0.0"> ap/afcs/theta-trim-rad </property>
  <property value="0.0"> ap/afcs/longitudinal-trim </property>
  <!-- afcs 'setup' parameters -->
  <property value="0.475"> ap/afcs/adj/longitudinal-ctrl-gain </property>
  <property value="0.281"> ap/afcs/adj/pitch-err-ctrl-gain </property>
  <property value="0.727"> ap/afcs/adj/pitch-rate-ctrl-gain </property>

  <channel name="afcs-pitch">
    <fcs_function name="ap/afcs/longitudinal-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/longitudinal-ctrl-gain </property>
          <difference>
            <property> fcs/longitudinal-gain </property>
            <property> ap/afcs/longitudinal-trim </property>
          </difference>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/pitch-err-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/pitch-err-ctrl-gain </property>
          <difference>
            <property> attitude/theta-rad </property>
            <property> ap/afcs/theta-trim-rad </property>
          </difference>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/pitch-rate-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/pitch-rate-ctrl-gain </property>
          <property> velocities/q-aero-rad_sec </property>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/pitch-cmd-sum">
      <function>
        <product>
          <property> ap/afcs/pitch-channel-active-norm </property>
          <sum>
            <property> ap/afcs/longitudinal-ctrl </property>
            <property> ap/afcs/pitch-err-ctrl    </property>
            <property> ap/afcs/pitch-rate-ctrl   </property>
          </sum>
        </product>
      </function>
      <output> ap/elevator-cmd </output>
    </fcs_function>
  </channel>

  <!--  ==================
          YAW CHANNEL
        ==================  -->

  <!-- 'control' parameters -->
  <property value="0.0"> ap/afcs/yaw-channel-active-norm </property>
  <property value="0.0"> ap/afcs/psi-trim-rad </property>
  <!-- afcs 'setup' parameters -->
  <property value="1.0"> ap/afcs/heading-hold-enable </property>
  <property value="0.0"> ap/afcs/adj/yaw-rate-ctrl-gain </property>

  <channel name="afcs-yaw">

    <fcs_function name="ap/afcs/psi-trim-deg">
      <!-- utility -->
      <function>
        <product>
          <value> 57.2958 </value>
          <property> ap/afcs/psi-trim-rad </property>
        </product>
      </function>
    </fcs_function>

    <!-- if zero the pid integrator is enabled -->
    <!-- if negative the pid integrator is reset -->
    <switch name="ap/afcs/yaw-err-pid-inhibit">
      <default value="-1.0"/>
      <test value="0.0"> ap/afcs/yaw-channel-active-norm GT 0.999 </test>
    </switch>

    <fcs_function name="ap/afcs/psi-error-rad">
      <function>
        <sin>
          <difference>
            <property> attitude/psi-rad </property>
            <property> ap/afcs/psi-trim-rad </property>
          </difference>
        </sin>
      </function>
    </fcs_function>

    <pid name="ap/afcs/yaw-err-pid">
      <input> ap/afcs/psi-error-rad </input>
      <kp> 0.33 </kp>
      <ki> 0.0025 </ki>
      <kd> 0.0 </kd>
      <trigger> ap/afcs/yaw-err-pid-inhibit </trigger>
      <clipto>
        <min> -0.25 </min>
        <max>  0.25 </max>
      </clipto>
    </pid>
    <fcs_function name="ap/afcs/yaw-rate-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/yaw-rate-ctrl-gain </property>
          <property> velocities/r-aero-rad_sec </property>
        </product>
      </function>
      <clipto>
        <min> -0.20 </min>
        <max>  0.20 </max>
      </clipto>
    </fcs_function>
    <fcs_function name="ap/afcs/yaw-cmd-sum">
      <function>
        <product>
          <property> ap/afcs/yaw-channel-active-norm </property>
          <sum>
            <product>
              <property> ap/afcs/heading-hold-enable </property>
              <property> ap/afcs/yaw-err-pid </property>
            </product>
            <property> ap/afcs/yaw-rate-ctrl </property>
          </sum>
        </product>
      </function>
      <output> ap/rudder-cmd </output>
   </fcs_function>

  </channel>

  <!--  =====================
          ALTITUDE CHANNEL
        =====================  -->

  <!-- 'control' parameters -->
  <property value="0.0"> ap/afcs/altitude-channel-active-norm </property>
  <property value="50.0"> ap/afcs/altitude-trim-ft </property>
  <!-- afcs 'setup' parameters -->
  <property value="1.0"> ap/afcs/h-agl-mode </property>
  <property value="-0.00035"> ap/afcs/adj/altitude-error-ctrl-gain </property>
  <property value="0.00"> ap/afcs/adj/altitude-rate-ctrl-gain </property>


  <channel name="afcs-altitude">
    <!-- smooth out terrain jumps -->
    <lag_filter name="position/h-agl-ft-lag">
      <input> position/h-agl-ft </input>
      <c1>    1.0 </c1>
    </lag_filter>

    <switch name="ap/afcs/altitude-input">
      <default value="position/h-sl-ft"/>
      <test value="position/h-agl-ft-lag">
        ap/afcs/h-agl-mode == 1
      </test>
    </switch>

    <fcs_function name="ap/afcs/altitude-error-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/altitude-error-ctrl-gain </property>
          <difference>
            <property> ap/afcs/altitude-input </property>
            <property> ap/afcs/altitude-trim-ft </property>
          </difference>
        </product>
      </function>
      <clipto>
        <min> -0.40 </min>
        <max>  0.40 </max>
      </clipto>
    </fcs_function>

    <fcs_function name="ap/afcs/altitude-rate-ctrl">
      <function>
        <product>
          <property> ap/afcs/adj/altitude-rate-ctrl-gain </property>
          <property> velocities/h-dot-fps </property><!-- velocities/w-fps ?? -->
        </product>
      </function>
      <clipto>
        <min> -0.40 </min>
        <max>  0.40 </max>
      </clipto>
    </fcs_function>

    <fcs_function name="ap/afcs/collective-cmd-sum">
      <function>
        <product>
          <property> ap/afcs/altitude-channel-active-norm </property>
          <sum>
            <property> ap/afcs/altitude-error-ctrl </property>
            <property> ap/afcs/altitude-rate-ctrl  </property>
          </sum>
        </product>
      </function>
      <output> ap/collective-cmd </output>
    </fcs_function>

  </channel>

</system>