256 lines
8.6 KiB
Text
256 lines
8.6 KiB
Text
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AUTOMATIC PUSHBACK FOR FLIGHTGEAR
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http://gitlab.com/mdanil/flightgear-autopush
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Version 2.0.1
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Copyright (c) 2018 Autopush authors:
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Michael Danilov <mike.d.ft402 -eh- gmail.com>
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Joshua Davidson http://github.com/Octal450
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Merspieler http://gitlab.com/merspieler
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Some of the code (c) FlightGear
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Distribute under the terms of GPLv2.
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This project aims to develop a generic pushback for JSBSim and YASim
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aircraft, with the following characteristics.
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1. Do the pushback procedure automatically.
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2. Scale to different aircraft with minimum changes to their logic.
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3. Use no computer resources in flight.
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INSTALLATION
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Minimum FlightGear version: 2018.0
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NOTE: these steps cover the minimal testing setup. To get the most
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realism out of Autopush, you will have to add logic aircraft-side as
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described in the last step.
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1. Copy the autopush.config.xml.template into your aircraft directory
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and the Goldhofert.xml into <your-airfraft>/Models/Autopush/
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2. Set up the pushback logic.
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Add the following line under <sim><model> of your set.xml
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<autopush include="autopush-config.xml"/>
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Rename autopush-config.xml.template to autopush-config.xml and edit
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the file as described below.
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Alternatively, you can copy the contents of
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autopush-config.xml.template to under <sim><model><autopush> of your
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set.xml and make these modifications there.
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Change the aliases to point to the following data:
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steer-cmd-norm nose wheel steering command norm
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yaw nose wheel steering output norm or angle (see below)
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chocks chocks command bool (or leave it until step 7)
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available pushback availability bool (or leave it until step 7)
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Replace the MULTIPLIER in yaw-mult with:
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max steering angle if yaw is norm
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1.0 if yaw is degrees
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57.3 if yaw is radians
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Replace PITCH with the pushback's pitch relative to aircraft. If your
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aircraft's ground pitch varies greatly, you can make an alias to
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property with calculated relative pitch.
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Replace MIN_RADIUS with the minimum allowed turning radius in m of the
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center of the aircraft during pushback procedure.
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NOTE: on some aircraft the turning radius is different for taxi and
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pushback. Please check the aircraft's literature.
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Replace STOP_DIST with the stopping distance in m from pushback speed.
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Add under <nasal> of your set.xml:
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<autopush>
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<file>Nasal/Autopush/autopush.nas</file>
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</autopush>
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<autopush_driver>
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<file>Nasal/Autopush/driver.nas</file>
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</autopush_driver>
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<dynarr>
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<file>Nasal/Autopush/dynarr.nas</file>
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</dynarr>
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<autopush_route>
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<file>Nasal/Autopush/route.nas</file>
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</autopush_route>
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Add under <sim><aircraft-data> of your set.xml:
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<path>/sim/model/autopush/route/show</path>
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<path>/sim/model/autopush/route/show-wingtip</path>
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3. Connect the force to FDM.
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3.a. JSBSim:
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3.a.1. Add the following under <external_reactions> of your JSBSim
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XML.
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<force name="tractor" frame="BODY">
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<location unit="M">
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<x>FRONT-X</x>
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<y>FRONT-Y</y>
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<z>FRONT-Z</z>
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</location>
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<direction>
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<x>1.0</x>
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<y>0.0</y>
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<z>0.0</z>
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</direction>
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</force>
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Replace FRONT-X, FRONT-Y, FRONT-Z with coordinates of your front
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bogey.
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3.a.2. Add the following under <fdm><jsbsim><external_reactions> of
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your set.xml.
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<tractor>
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<magnitude alias="/sim/model/autopush/force-lbf"/>
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<x alias="/sim/model/autopush/force-x"/>
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<y alias="/sim/model/autopush/force-y"/>
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<z alias="/sim/model/autopush/force-z"/>
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</tractor>
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3.b. YASim. Add the following under <airplane> of your YASim xml.
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<thruster x="FRONT-X" y="FRONT-Y" z="FRONT-Z" vx="1" vy="0" vz="0" thrust="100000.0">
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<control-input axis="/sim/model/autopush/force-x-yasim" control="THROTTLE" src0="-1" src1="1" dst0="-1" dst1="1"/>
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</thruster>
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<thruster x="FRONT-X" y="FRONT-Y" z="FRONT-Z" vx="0" vy="1" vz="0" thrust="100000.0">
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<control-input axis="/sim/model/autopush/force-y-yasim" control="THROTTLE" src0="-1" src1="1" dst0="-1" dst1="1"/>
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</thruster>
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<thruster x="FRONT-X" y="FRONT-Y" z="FRONT-Z" vx="0" vy="0" vz="1" thrust="100000.0">
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<control-input axis="/sim/model/autopush/force-z-yasim" control="THROTTLE" src0="-1" src1="1" dst0="-1" dst1="1"/>
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</thruster>
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Replace FRONT-X, FRONT-Y, FRONT-Z with coordinates of your front
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bogey.
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4. Add the pushback model to your Model XML:
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<model>
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<name>Pushback</name>
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<path>MODEL</path>
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<offsets>
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<x-m>FRONT-X</x-m>
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<y-m>FRONT-Y</y-m>
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<z-m>FRONT-Z</z-m>
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</offsets>
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</model>
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Replace FRONT-X, FRONT-Y, FRONT-Z with coordinates of your front
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bogey. Replace MODEL with one of the following file names:
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Autopush/Goldhofert.xml for Goldhofer towbarless pushback
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Edit the "SETTINGS" part in the beginning of the Goldhofert.xml to match
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your setup.
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5. Add gui/dialogs/autopush.xml to your aircraft's menu (see
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FlightGear documentation for editing the menu).
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6. If you have a bug tracker, please add a note, that autopush related
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bugs should be reported here:
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https://gitlab.com/mdanil/flightgear-autopush/issues
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7. Launch the simulator and try Autopush. After making sure it works,
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complete the support by implementing some logic in your aircraft
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and connecting the rest of the interface.
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CAUTION.
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1. Make sure to HAVE A BACK-UP COPY of your work.
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2. If anything is not clear in the instruction below, do not guess --
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contact the authors.
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7.1. When pushback is connected ("/sim/model/autopush/connected"),
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nose wheel steering must actuate at different speed, depending
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on its rollspeed. The exact dependency is different per aircraft
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and used pushback visual, and for most aircraft the only way to
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find it is trial and error until it "looks right":
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- the input must be taken from pushback steering command norm
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(set by autopush-config.xml, default:
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"/controls/flight/rudder");
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- the output must be written to pushback orientation in degrees,
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radians or norm (set by autopush-config.xml, default:
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"/gear/gear[0]/steering-norm").
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7.2. Set or alias (in autopush-config.xml) the availability property
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"/sim/model/autopush/available". It must be false if e.g. the
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aircraft is moving too fast, the front wheel is not touching
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the ground, the aircraft is damaged or is outside of an airport
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etc.
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7.3. Make Autopush remove wheel chocks by setting the alias in
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autopush-config.xml to the chocks property. (default:
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"/controls/gear/wheel-chocks").
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7.4. Optionally, Autopush may be made visible in multiplayer by
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duplicating the properties used in its model.xml into some
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unused MP properties. See the list in
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https://sourceforge.net/p/flightgear/flightgear/ci/next/tree/src/MultiPlayer/multiplaymgr.cxx
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around line 215, and then using those properties in the
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"SETTINGS" part of Autopush model.xml.
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After making these changes check the Autopush model.xml's settings
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and make sure they match the setup. Launch the simulator and try
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Autopush.
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TUNING
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There should normally be no need to change the coefficients, because
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the inertia of different aircraft is already taken into account. But
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the gear setup may differ enough to require some tuning.
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If these settings are changed during simulation, they take effect
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after disconnecting and reconnecting the pushback.
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Pushback (/sim/model/autopush):
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Coefficient Unit Description
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K_p ((km/h)/s)/(km/h) Proportional coefficient of PID.
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Defines the start/stop throttle
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and immediate response to speed
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difference deltaV = V_set - V.
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F_p (km/h)/s Proportional clipping.
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K_i ((km/h)/s)/((km/h)*s) Integral coefficient of PID.
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Defines how fast the steady
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throttle is ramped during the
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push.
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F_i (km/h)/s Integral clipping.
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K_d -((km/h)/s)/((km/h)/s) Differential coefficient of PID.
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Stabilizes the approaching of
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steady throttle.
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F_d (km/h)/s Differential clipping.
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Pushback driver (/sim/model/autopush/driver):
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Coefficient Unit Description
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F_V km/h Max towing speed in auto mode.
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K_psi 1/deg Amount of steering per heading correction.
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F_psi 1/deg Max steering per heading correction.
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K_deltapsi -1/(deg/s) Amount of steering compensation per heading
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derivative.
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F_psi 1/(deg/s) Max amount of steering compensation per
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heading derivative.
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