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Howto:Implement a Fly-By-Wire System for Airliners: Difference between revisions

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Howto:Implement a Fly-By-Wire System for Airliners (view source)

Revision as of 14:04, 7 February 2012

3,170 bytes added ,  7 February 2012
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* -set.xml
* -set.xml
* fbw.nas
* fbw.nas
* FDM xml file
* fly-by-wire.xml
* FDM xml


Note that as the new 787 uses JSBSim, this tutorial will focus on implementing the FBW to an aircraft running with JSBSim.
Note that as the new 787 uses JSBSim, this tutorial will focus on implementing the FBW to an aircraft running with JSBSim.
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* Reduces thrust when exceeding 250 knots under 10000 ft MSL and when reaching Vne above 10000 ft MSL
* Reduces thrust when exceeding 250 knots under 10000 ft MSL and when reaching Vne above 10000 ft MSL
* Dampens the controls to prevent sudden movements
* Dampens the controls to prevent sudden movements
* Automatically holds the current aircraft pitch and roll degree when stick is brought back to the center! < NEW!




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<syntaxhighlight lang="php">
<syntaxhighlight lang="php">
#########################################
#########################################
## FLY BY WIRE SYSTEM FOR FLIGHTGEAR  ##
## FLY BY WIRE SYSTEM FOR BOEING 787-8 ##
#########################################
#########################################
## Designed by Omega Pilot and Redneck ##
## Designed by Omega Pilot and Redneck ##
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me.throttle = 0;
me.throttle = 0;
me.throttlefix = 0;
me.throttlefix = 0;
me.vsinit = 0;
me.throttleinit = 0;
me.throttleinit = 0;
me.targetthrottle = 0;
me.targetthrottle = 0;
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me.targetrudder = 0;
me.targetrudder = 0;
me.adjustelevators = 0;
me.adjustelevators = 0;
me.stabilize = 0;
me.stabpitch = 0;
me.stabroll = 0;


me.disconnectannounce = 0;
me.disconnectannounce = 0;
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## Fix Damp Rate according to Framerate
## Fix Damp Rate according to Framerate


var fpsfix=1;
if (getprop("/sim/frame-rate") != nil) var fpsfix = 25 / getprop("/sim/frame-rate");
if (getprop("/sim/frame-rate") != nil) fpsfix = 25 / getprop("/sim/frame-rate");
else fpsfix = 1;


## Bank Limit Setting
## Bank Limit Setting
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var airspeedkt = getprop("/velocities/airspeed-kt");
var airspeedkt = getprop("/velocities/airspeed-kt");


var vsfps = getprop("/velocities/vertical-speed-fps");
## Flight Control System Properties


## Flight Control System Properties
var elevtrim = getprop("/controls/flight/elevator-trim");
var ailtrim = getprop("/controls/flight/aileron-trim");


var aileronin = getprop(fcs~"aileron-cmd-norm");
var aileronin = getprop(fcs~"aileron-cmd-norm");
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if (getprop("/systems/electrical/outputs/efis") != nil) {
if (getprop("/systems/electrical/outputs/efis") != nil) {
if ((getprop("/systems/electrical/outputs/efis") < 9) and (altitudeagl >= 200)) {
if ((getprop("/systems/electrical/outputs/efis") < 9) and (altitudeagl >= 200)) {
  setprop("/controls/fbw/active", 0);
setprop("/controls/fbw/active", 0);
  if (me.disconnectannounce == 0) {
if (me.disconnectannounce == 0) {
  screen.log.write("Fly By Wire Disconnected!", 1, 0, 0);
screen.log.write("Fly By Wire Disconnected!", 1, 0, 0);
  me.disconnectannounce = 1;
me.disconnectannounce = 1;
  } # end of disconnect announce
} } }
} # end of efis/agl check
}


if (getprop("/controls/fbw/active")) {
if (getprop("/controls/fbw/active")) {
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if (elevatorin > elevatorout) elevatorout += 0.05 * fpsfix;
if (elevatorin > elevatorout) elevatorout += 0.05 * fpsfix;
if (elevatorin < elevatorout) elevatorout -= 0.05 * fpsfix;
if (elevatorin < elevatorout) elevatorout -= 0.05 * fpsfix;


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if ((elevatorout - elevatorin < 0.05) and (elevatorin - elevatorout < 0)) elevatorout -= 0.01;  
if ((elevatorout - elevatorin < 0.05) and (elevatorin - elevatorout < 0)) elevatorout -= 0.01;  


### Use elevator to stabilize VS on turns
## AUTO-STABILIZATION
 
### Get the aircraft to maintain pitch and roll when stick is at the center


if ((roll <= -5) or (roll >= 5)) {
if ((elevatorin <= 0.1) and (elevatorin >= -0.1) and (aileronin <= 0.1) and (aileronin >= -0.1)) {


if (me.adjustelevators == 0) {
if (me.stabilize == 0) {
me.adjustelevators = 1;
setprop("/controls/fbw/stabpitch-deg", pitch);
me.vsinit = vsfps;
setprop("/controls/fbw/stabroll-deg", roll);
me.stabilize = 1;
}
}


if (vsfps < me.vsinit) elevatorout -= 0.02;
if ((airspeedkt >= 220) and (altitudeagl >= 3500)) {
if (vsfps > me.vsinit) elevatorout += 0.02;
setprop("/controls/fbw/autostable", 1);
 
} else {
} else {
if (me.adjustelevators == 1) {
setprop("/controls/fbw/autostable", 0);
if (elevtrim > 0) elevtrim -= 0.05;
if (elevtrim < 0) elevtrim += 0.05;
if (ailtrim > 0) ailtrim -= 0.05;
if (ailtrim < 0) ailtrim += 0.05;


if (vsfps < me.vsinit) elevatorout -= 0.02;
setprop("/controls/flight/elevator-trim", elevtrim);
elsif (vsfps > me.vsinit) elevatorout += 0.02;
setprop("/controls/flight/aileron-trim", ailtrim);
else me.adjustelevators = 0;


}
}
} else {
me.stabilize = 0;
setprop("/controls/fbw/autostable", 0);
}
}
## THROTTLE CONTROLS
## THROTTLE CONTROLS


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throttle0 -= 0.001 * fpsfix;
throttle0 -= 0.001 * fpsfix;
throttle1 -= 0.001 * fpsfix;
throttle1 -= 0.001 * fpsfix;
}
}  
 


}
}
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# *Power-by-wire : corresponds to power steering in cars
# *Power-by-wire : corresponds to power steering in cars
</syntaxhighlight>
</syntaxhighlight>
=== fly-by-wire.xml ===
Open your aircraft's Systems directory and create a file called 'fly-by-wire.xml'. Copy and paste the following pid controller code in that file and save it.
<syntaxhighlight lang="xml">
<?xml version="1.0"?>
<!-- Fly By Wire, Auto Stabilize Pitch and Roll -->
<PropertyList>
<!-- =============================================================== -->
<!-- Roll Deg Hold -->
<!-- =============================================================== -->
<pid-controller>
<name>FBW Roll Deg Hold</name>
<debug type="bool">false</debug>
<enable>
<prop>/controls/fbw/autostable</prop>
</enable>
<input>
<prop>/orientation/roll-deg</prop>
</input>
<reference>
<prop>/controls/fbw/stabroll-deg</prop>
</reference>
<output>
<prop>/controls/flight/aileron-trim</prop>
</output>
<config>
<Kp>0.05</Kp>
<beta>1</beta>
<alpha>0.1</alpha>
<gamma>0</gamma>
<Ti>10</Ti>
<Td>0.00001</Td>
<u_min>-2</u_min>
<u_max>2</u_max>
</config>
</pid-controller>
<!-- =============================================================== -->
<!-- Pitch Hold -->
<!-- =============================================================== -->
<pid-controller>
    <name>Pitch hold</name>
    <debug>false</debug>
    <enable>
<prop>/controls/fbw/autostable</prop>
    </enable>
    <input>
    <prop>/orientation/pitch-deg</prop>
  </input>
  <reference>
    <prop>/controls/fbw/stabpitch-deg</prop>
  </reference>
  <output>
    <prop>/controls/flight/elevator-trim</prop>
  </output>
  <config>
    <Kp>-0.05</Kp>      <!-- proportional gain -->
    <beta>1.0</beta>    <!-- input value weighing factor -->
    <alpha>0.1</alpha>  <!-- low pass filter weighing factor -->
    <gamma>0.0</gamma>  <!-- input value weighing factor for -->
                        <!-- unfiltered derivative error -->
    <Ti>1.0</Ti>        <!-- integrator time -->
    <Td>0.00001</Td>    <!-- derivator time -->
    <u_min>-1.0</u_min> <!-- minimum output clamp -->
    <u_max>1.0</u_max>  <!-- maximum output clamp -->
  </config>
  </pid-controller>
</PropertyList>
</syntaxhighlight>
Note that the above PID Controller is configured for smooth control of the 787-8. You migh thave to tweak the values inside the <config> .. </config> tags to get to smooth with your aircraft.


=== -set.xml ===
=== -set.xml ===
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</syntaxhighlight>
</syntaxhighlight>


Replace '787-8' with your aircraft folder name.
And also add the following code under </sim>
 
<syntaxhighlight lang="xml">
<systems>
<autopilot>
<path>Aircraft/787-8/Systems/fly-by-wire.xml</path>
</autopilot>
</systems>
</syntaxhighlight>
 
Replace '787-8' with your aircraft folder name in both instances.


=== JSBSim FDM ===
=== JSBSim FDM ===
Omega1174
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