Questions about Scripts and Properties #592

mrwangyou · 2022-02-25T08:15:28Z

mrwangyou
Feb 25, 2022

Hello everybody,

I am new to JSBSim and intend to use it in an application based on reinforcement learning.

I have some troubles getting start with JSBSim and here are my questions:

I read section 2.4 of JSBSim Reference Manual – Properties and JSBSim Script Tutorial 1, and yet I don’t understand what exactly properties are. In the case below (which is from page 13):

Could the name of fcs/pitch-trim-cmd-norm be changed to anything else, and if it couldn't, where can I get the list of "known static properties";
Where can the “Pitch” channel be called when I want to adjust the aircraft’s pose in the script? Should I write something like codes below? What's the meaning of name in set and does it lead to other component in the project? And I also want to know where I can learn specific writing rules of scripts.

<event>
  <condition>...</condition>
  <set name="Pitch" value=...>
  ...
<\event>

My mother tongue is not English and I'd never started a discussion on github before, thus if there is any offence or representation unclear, please let me know. Thank you!

seanmcleod · 2022-02-25T09:04:01Z

seanmcleod
Feb 25, 2022
Maintainer

Where can the “Pitch” channel be called when I want to adjust the aircraft’s pose in the script

First off, you don't get to set the pitch attitude directly, other than during initialization. In other words at some point during the execution you can't simply set the aircraft's pitch attitude to say 30 degrees as part of it's pose.

Rather what your script, or python code gets to do is set the control positions, i.e. the angle for elevators, ailerons, rudders, throttle, i.e. as if your script was a physical pilot moving the controls.

The resulting position of these control surfaces are then used by JSBSim to calculate the forces and moments and using the equations of motion etc. to then calculate the aircraft's pose for each simulation time step.

The Pitch Channel is used to map control inputs, typically from a pilot, to a control surface position. This can be as simple as a simple linear mapping of say the stick's longitudinal position/command typically normalized to [-1, +1] to the elevator's angular deflection, e.g. [-20 degrees, +20 degrees].

But often the channel setups will be a lot more complicated, e.g. often at a minimum adding up a trim command plus a stick command.

Typically a reinforcement learning system will basically input what the pilot would've via the control inputs.

2 replies

mrwangyou Feb 26, 2022
Author

Thank you for your reply!

mrwangyou Feb 26, 2022
Author

I'm sorry I have one more question.

What does name="..." of <set> tag leading to? For example, line 21 in 'scripts/f16_test.xml':

<set name="propulsion/cutoff_cmd" value="0"/>

JSBSim Reference Manual says that 'The name attribute is the property that will be set.' But I can't find properties 'cutoff_cmd' in neither 'f16_test.xml' nor 'aircraft/f16/f16.xml'. Where's the definition of properties mentioned in scripts? In case cutoff_cmd is a common used properties in all scripts, is there a list record all the properties which are "setable" and their usage?

Thank you very much!

seanmcleod · 2022-02-26T18:24:54Z

seanmcleod
Feb 26, 2022
Maintainer

There are a number of properties that are created by JSBSim and exported, some are read-only and some are read and writeable. They are exported by the various models, for example here is the list exported by FGPropulsion.

jsbsim/src/models/FGPropulsion.cpp

Lines 793 to 816 in 6461c86

    
           PropertyManager->Tie("propulsion/set-running", this, (iPMF)nullptr, &FGPropulsion::InitRunning); 
        
           if (HaveTurboEngine) { 
        
             PropertyManager->Tie("propulsion/starter_cmd", this, &FGPropulsion::GetStarter, &FGPropulsion::SetStarter); 
        
             PropertyManager->Tie("propulsion/cutoff_cmd", this,  &FGPropulsion::GetCutoff, &FGPropulsion::SetCutoff); 
        
           } 
        
           if (HavePistonEngine) { 
        
             PropertyManager->Tie("propulsion/starter_cmd", this, &FGPropulsion::GetStarter, &FGPropulsion::SetStarter); 
        
             PropertyManager->Tie("propulsion/magneto_cmd", this, (iPMF)nullptr, &FGPropulsion::SetMagnetos); 
        
           } 
        
           PropertyManager->Tie("propulsion/active_engine", this, &FGPropulsion::GetActiveEngine, 
        
                                 &FGPropulsion::SetActiveEngine); 
        
           PropertyManager->Tie("forces/fbx-prop-lbs", this, eX, &FGPropulsion::GetForces); 
        
           PropertyManager->Tie("forces/fby-prop-lbs", this, eY, &FGPropulsion::GetForces); 
        
           PropertyManager->Tie("forces/fbz-prop-lbs", this, eZ, &FGPropulsion::GetForces); 
        
           PropertyManager->Tie("moments/l-prop-lbsft", this, eX, &FGPropulsion::GetMoments); 
        
           PropertyManager->Tie("moments/m-prop-lbsft", this, eY, &FGPropulsion::GetMoments); 
        
           PropertyManager->Tie("moments/n-prop-lbsft", this, eZ, &FGPropulsion::GetMoments); 
        
           PropertyManager->Tie("propulsion/total-fuel-lbs", &TotalFuelQuantity); 
        
           PropertyManager->Tie("propulsion/total-oxidizer-lbs", &TotalOxidizerQuantity); 
        
           PropertyManager->Tie("propulsion/refuel", &refuel); 
        
           PropertyManager->Tie("propulsion/fuel_dump", &dump); 
        
           PropertyManager->Tie("propulsion/fuel_freeze", this, (bPMF)nullptr, &FGPropulsion::SetFuelFreeze);

If I come across a property that is referenced in a script etc. that I want more information on I generally search the source code, like I just did for propulsion\cutoff_cmd to see if it is defined by JSBSim. And if it is then I can take a look at the code to see if there are both getters and setters, and also look into the relevant code to see how the property is implemented in terms of some of the logic behind how it gets it's value etc.

In terms of property info etc. also take a look at this discussion - #403 It also mentions some reinforcement learning stuff with regards to JSBSim.

In terms of getting a comprehensive list also take a look at the --catalog option, e.g.

(base) C:\source\jsbsim>.\Debug\JSBSim.exe --aircraft=737 --catalog


     JSBSim Flight Dynamics Model v1.0.0 Feb  2 2022 20:29:28
            [JSBSim-ML v2.0]

JSBSim startup beginning ...


In file aircraft/737/737.xml: line 901
      Property fcs/aileron-cmd-norm is already defined.

In file aircraft/737/737.xml: line 902
      Property fcs/elevator-cmd-norm is already defined.

In file aircraft/737/737.xml: line 903
      Property fcs/rudder-cmd-norm is already defined.

In file aircraft/737/737.xml: line 904
      Property fcs/throttle-cmd-norm[0] is already defined.

In file aircraft/737/737.xml: line 905
      Property fcs/throttle-cmd-norm[1] is already defined.

In file aircraft/737/737.xml: line 906
      Property simulation/terminate is already defined.

  Property Catalog for 737

    inertial/sea-level-radius_ft (R)
    simulation/gravity-model (RW)
    simulation/integrator/rate/rotational (RW)
    simulation/integrator/rate/translational (RW)
    simulation/integrator/position/rotational (RW)
    simulation/integrator/position/translational (RW)
    simulation/write-state-file (W)
    simulation/channel-dt (R)
    simulation/gravitational-torque (RW)
    simulation/force-output (W)
    simulation/do_simple_trim (W)
    simulation/reset (W)
    simulation/disperse (R)
    simulation/randomseed (RW)
    simulation/terminate (RW)
    simulation/pause (RW)
    simulation/sim-time-sec (R)
    simulation/dt (R)
    simulation/jsbsim-debug (RW)
    simulation/frame (RW)
    simulation/trim-completed (RW)
    simulation/frame_start_time (RW)
    simulation/cycle_duration (RW)
    simulation/output/log_rate_hz (RW)
    simulation/output/enabled (RW)
    velocities/h-dot-fps (R)
    velocities/v-north-fps (R)
    velocities/v-east-fps (R)
    velocities/v-down-fps (R)
    velocities/u-fps (R)
    velocities/v-fps (R)
    velocities/w-fps (R)
    velocities/p-rad_sec (R)
    velocities/q-rad_sec (R)
    velocities/r-rad_sec (R)
    velocities/pi-rad_sec (R)
    velocities/qi-rad_sec (R)
    velocities/ri-rad_sec (R)
    velocities/eci-x-fps (R)
    velocities/eci-y-fps (R)
    velocities/eci-z-fps (R)
    velocities/eci-velocity-mag-fps (R)
    velocities/ned-velocity-mag-fps (R)
    velocities/vc-fps (R)
    velocities/vc-kts (R)
    velocities/ve-fps (R)
    velocities/ve-kts (R)
    velocities/vtrue-fps (R)
    velocities/vtrue-kts (R)
    velocities/machU (R)
    velocities/p-aero-rad_sec (R)
    velocities/q-aero-rad_sec (R)
    velocities/r-aero-rad_sec (R)
    velocities/phidot-rad_sec (R)
    velocities/thetadot-rad_sec (R)
    velocities/psidot-rad_sec (R)
    velocities/u-aero-fps (R)
    velocities/v-aero-fps (R)
    velocities/w-aero-fps (R)
    velocities/vt-fps (R)
    velocities/mach (R)
    velocities/vg-fps (R)
    position/h-sl-ft (RW)
    position/h-sl-meters (RW)
    position/lat-gc-rad (RW)
    position/long-gc-rad (RW)
    position/lat-gc-deg (RW)
    position/long-gc-deg (RW)
    position/lat-geod-rad (R)
    position/lat-geod-deg (R)
    position/geod-alt-ft (R)
    position/h-agl-ft (RW)
    position/geod-alt-km (R)
    position/h-agl-km (RW)
    position/radius-to-vehicle-ft (R)
    position/terrain-elevation-asl-ft (RW)
    position/eci-x-ft (R)
    position/eci-y-ft (R)
    position/eci-z-ft (R)
    position/ecef-x-ft (R)
    position/ecef-y-ft (R)
    position/ecef-z-ft (R)
    position/epa-rad (R)
    position/distance-from-start-lon-mt (R)
    position/distance-from-start-lat-mt (R)
    position/distance-from-start-mag-mt (R)
    position/vrp-gc-latitude_deg (R)
    position/vrp-longitude_deg (R)
    position/vrp-radius-ft (R)
    metrics/terrain-radius (R)
    metrics/Sw-sqft (RW)
    metrics/bw-ft (R)
    metrics/cbarw-ft (R)
    metrics/iw-rad (R)
    metrics/iw-deg (R)
    metrics/Sh-sqft (R)
    metrics/lh-ft (R)
    metrics/Sv-sqft (R)
    metrics/lv-ft (R)
    metrics/lh-norm (R)
    metrics/lv-norm (R)
    metrics/vbarh-norm (R)
    metrics/vbarv-norm (R)
    metrics/aero-rp-x-in (RW)
    metrics/aero-rp-y-in (RW)
    metrics/aero-rp-z-in (RW)
    metrics/eyepoint-x-in (R)
    metrics/eyepoint-y-in (R)
    metrics/eyepoint-z-in (R)
    metrics/visualrefpoint-x-in (R)
    metrics/visualrefpoint-y-in (R)
    metrics/visualrefpoint-z-in (R)
    attitude/phi-rad (R)
    attitude/theta-rad (R)
    attitude/psi-rad (R)
    attitude/phi-deg (R)
    attitude/theta-deg (R)
    attitude/psi-deg (R)
    attitude/roll-rad (R)
    attitude/pitch-rad (R)
    attitude/heading-true-rad (R)
    orbital/specific-angular-momentum-ft2_sec (RW)
    orbital/inclination-deg (RW)
    orbital/right-ascension-deg (RW)
    orbital/eccentricity (RW)
    orbital/argument-of-perigee-deg (RW)
    orbital/true-anomaly-deg (RW)
    orbital/apoapsis-radius-ft (RW)
    orbital/periapsis-radius-ft (RW)
    orbital/period-sec (RW)
    atmosphere/T-R (R)
    atmosphere/rho-slugs_ft3 (R)
    atmosphere/P-psf (R)
    atmosphere/a-fps (R)
    atmosphere/T-sl-R (R)
    atmosphere/rho-sl-slugs_ft3 (R)
    atmosphere/a-sl-fps (R)
    atmosphere/theta (R)
    atmosphere/sigma (R)
    atmosphere/delta (R)
    atmosphere/a-ratio (R)
    atmosphere/density-altitude (R)
    atmosphere/pressure-altitude (R)
    atmosphere/delta-T (RW)
    atmosphere/SL-graded-delta-T (RW)
    atmosphere/P-sl-psf (RW)
    atmosphere/dew-point-R (RW)
    atmosphere/vapor-pressure-psf (RW)
    atmosphere/saturated-vapor-pressure-psf (R)
    atmosphere/RH (RW)
    atmosphere/vapor-fraction-ppm (RW)
    atmosphere/psiw-rad (RW)
    atmosphere/wind-north-fps (RW)
    atmosphere/wind-east-fps (RW)
    atmosphere/wind-down-fps (RW)
    atmosphere/wind-mag-fps (RW)
    atmosphere/gust-north-fps (RW)
    atmosphere/gust-east-fps (RW)
    atmosphere/gust-down-fps (RW)
    atmosphere/cosine-gust/startup-duration-sec (W)
    atmosphere/cosine-gust/steady-duration-sec (W)
    atmosphere/cosine-gust/end-duration-sec (W)
    atmosphere/cosine-gust/magnitude-ft_sec (W)
    atmosphere/cosine-gust/frame (W)
    atmosphere/cosine-gust/X-velocity-ft_sec (W)
    atmosphere/cosine-gust/Y-velocity-ft_sec (W)
    atmosphere/cosine-gust/Z-velocity-ft_sec (W)
    atmosphere/cosine-gust/start (W)
    atmosphere/updownburst/number-of-cells (W)
    atmosphere/turb-north-fps (RW)
    atmosphere/turb-east-fps (RW)
    atmosphere/turb-down-fps (RW)
    atmosphere/p-turb-rad_sec (R)
    atmosphere/q-turb-rad_sec (R)
    atmosphere/r-turb-rad_sec (R)
    atmosphere/turb-type (RW)
    atmosphere/turb-rate (RW)
    atmosphere/turb-gain (RW)
    atmosphere/turb-rhythmicity (RW)
    atmosphere/turbulence/milspec/windspeed_at_20ft_AGL-fps (RW)
    atmosphere/turbulence/milspec/severity (RW)
    atmosphere/total-wind-north-fps (R)
    atmosphere/total-wind-east-fps (R)
    atmosphere/total-wind-down-fps (R)
    fcs/aileron-cmd-norm (RW)
    fcs/elevator-cmd-norm (RW)
    fcs/rudder-cmd-norm (RW)
    fcs/flap-cmd-norm (RW)
    fcs/speedbrake-cmd-norm (RW)
    fcs/spoiler-cmd-norm (RW)
    fcs/pitch-trim-cmd-norm (RW)
    fcs/roll-trim-cmd-norm (RW)
    fcs/yaw-trim-cmd-norm (RW)
    fcs/left-aileron-pos-rad (RW)
    fcs/left-aileron-pos-deg (RW)
    fcs/left-aileron-pos-norm (RW)
    fcs/mag-left-aileron-pos-rad (R)
    fcs/right-aileron-pos-rad (RW)
    fcs/right-aileron-pos-deg (RW)
    fcs/right-aileron-pos-norm (RW)
    fcs/mag-right-aileron-pos-rad (R)
    fcs/elevator-pos-rad (RW)
    fcs/elevator-pos-deg (RW)
    fcs/elevator-pos-norm (RW)
    fcs/mag-elevator-pos-rad (R)
    fcs/rudder-pos-rad (RW)
    fcs/rudder-pos-deg (RW)
    fcs/rudder-pos-norm (RW)
    fcs/mag-rudder-pos-rad (R)
    fcs/flap-pos-rad (RW)
    fcs/flap-pos-deg (RW)
    fcs/flap-pos-norm (RW)
    fcs/speedbrake-pos-rad (RW)
    fcs/speedbrake-pos-deg (RW)
    fcs/speedbrake-pos-norm (RW)
    fcs/mag-speedbrake-pos-rad (R)
    fcs/spoiler-pos-rad (RW)
    fcs/spoiler-pos-deg (RW)
    fcs/spoiler-pos-norm (RW)
    fcs/mag-spoiler-pos-rad (R)
    fcs/left-brake-cmd-norm (RW)
    fcs/right-brake-cmd-norm (RW)
    fcs/center-brake-cmd-norm (RW)
    fcs/wing-fold-pos-norm (RW)
    fcs/steer-cmd-norm (RW)
    fcs/steer-pos-deg (RW)
    fcs/throttle-cmd-norm (RW)
    fcs/throttle-pos-norm (RW)
    fcs/mixture-cmd-norm (RW)
    fcs/mixture-pos-norm (RW)
    fcs/advance-cmd-norm (RW)
    fcs/advance-pos-norm (RW)
    fcs/feather-cmd-norm (RW)
    fcs/feather-pos-norm (RW)
    fcs/throttle-cmd-norm[1] (RW)
    fcs/throttle-pos-norm[1] (RW)
    fcs/mixture-cmd-norm[1] (RW)
    fcs/mixture-pos-norm[1] (RW)
    fcs/advance-cmd-norm[1] (RW)
    fcs/advance-pos-norm[1] (RW)
    fcs/feather-cmd-norm[1] (RW)
    fcs/feather-pos-norm[1] (RW)
    fcs/pitch-trim-sum (RW)
    fcs/elevator-control (RW)
.........

5 replies

mrwangyou Feb 28, 2022
Author

Thank you for your detailed reply. That's exactly what I want to know 👍

mrwangyou Jul 9, 2022
Author

@seanmcleod Hi. Sorry to disturb you again.

I find that --catalog seems to be undefined some time when I try to run it.

(base) wnn@lth:~$ cd .local/share/JSBSim/
(base) wnn@lth:~/.local/share/JSBSim$ JSBSim --aircraft=f16/f16 --catalog
usage: JSBSim [-h] [--version] [--outputlogfile <filename>] [--logdirectivefile <filename>] [--root <path>] [--aircraft <filename>] [--script <filename>] [--initfile <filename>] [--end <time double>] [--realtime] [--nice] [input]
JSBSim: error: unrecognized arguments: --catalog

I run it successfully on Windows 11 WSL about 6 months ago. This time I run it on the Ubuntu 18.04.

Thank you!

bcoconni Jul 9, 2022
Maintainer

@mrwangyou, you are most likely using the python version of JSBSim which indeed does not support the --catalog option.

mrwangyou Jul 9, 2022
Author

@mrwangyou, you are most likely using the python version of JSBSim which indeed does not support the --catalog option.

Got it. I'll try other type of JSBSim. Thank you for your reply :)

bcoconni Jul 9, 2022
Maintainer

I pushed the commit be8dfe1 on the master branch to add the --catalog option to the JSBSim Python script.

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Questions about Scripts and Properties #592

mrwangyou Feb 25, 2022

Replies: 2 comments · 7 replies

seanmcleod Feb 25, 2022 Maintainer

mrwangyou Feb 26, 2022 Author

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mrwangyou
Feb 25, 2022

Replies: 2 comments 7 replies

seanmcleod
Feb 25, 2022
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mrwangyou Feb 26, 2022
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mrwangyou Feb 26, 2022
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seanmcleod
Feb 26, 2022
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mrwangyou Feb 28, 2022
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mrwangyou Jul 9, 2022
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bcoconni Jul 9, 2022
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mrwangyou Jul 9, 2022
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bcoconni Jul 9, 2022
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