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High Fidelity Flight Dynamics and Tech/Academic Initial Demonstration


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F-16 High Fidelity Flight Dynamics and Tech/Academic Initial Demonstration...

 

**** SEE NEW VERSION WITH CONTRIBUTIONS FROM RAGNARDA AND SKATEZILLA BELOW *****

 

Hi All, not sure where to put this but here since this is not necessarily going to be a released project but will be used for technology and academic purposes to assist my learning process towards other TeamVRC projects and to help the "How To" community in getting on their feet as we are all learning together...

 

Please note that this is NOT one of the intended products to be released by TeamVRC, just a stepping stone in that process.

 

The goal of the F-16 high fidelity model, as it matures, is to make it a "tutorial" of sorts to help others where I have stumbled in utilizing the external flight model. There is currently minimal documentation and most of my efforts were trial and error and it appears that we are going into very unknown territory. So far, this is purely a demonstration of the current progress as many flight dynamic features are missing in this video (leading edge flap aerodynamics, control mixing, higher order control logic, etc..)

 

In any case, this F-16 high fidelity flight model data is sourced from wind tunnel data that NASA collected for use in their motion simulator. This data is very expansive as it covers Alpha from -20 to 90 and beta from -30 to 30 as well as incorporating all combinations of control surface deflections. Most of my time was spent actually putting the wind tunnel data into a useable look-up table format within the external flight model.

 

Some statistics:

- Lines of code: >5000

- Aerodynamic look-up tables: >24

- Breakpoints (data resolution): tables range from 5 breakpoints up to 1900 for most of them

- Data source - NASA technical papers

 

Finally, here is a video demonstration of the fight model in action. Keep in mind I have yet to do actuator modeling or flight control computer logic, so the airframe will let you pull 20g’s if you want to. There is also no mixing logic yet. Another disclaimer, I am not a modeler and am very new to DCS modding, other members of my team are much more experienced in that and will learn from them...

 

As I hope you can see the "feel" of the aircraft is like one that is actually moving through a fluid, not just on rails.

 

Further plan of action...

-Clean and comment code so that others can actually see what I'm doing

-Leading edge slat and flap aerodynamic coded but control logic not in yet

-Model engine lag/delays

-Model control actuators

-Model higher-order flight control and stability augmentation logic

-We have other team members helping out with this to put additional goodies on this aircraft, not sure if I want to go there yet as this is currently just my pet project to help the team and the community

 

Again, this is a flight dynamics model demonstration and would like to keep the subject on utilizing the external flight model for that purpose. It appears that when you decide to use the external flight model, you have to also control all 3D animations as well as ground reaction modeling within the external flight model code as well. The only thing that it appears DCS still handles internally is the weight force of the aircraft...Enjoy!

 

Also, some stuff I want to tackle in this project to help others where I was scratching my head for days:

- How forces are applied and the code logic to process it correctly

- The units and directions for values within DCS

- Ways to organize the code project

 

Again, I'm still just learning but wanted to share as soon as I could as we all have questions and can learn from each other. I was having issues after issue and wanted to share as soon as I had something flying...

 

EDIT: Why did I choose the F-16? It had readily available wind tunnel data and a ton of available flight control information on it...that's the only reason

 

------------------------------------------------------------------------------------

EDIT: Initial Closed Source Release!

 

Hi all, so here is the download link for the closed source version (only dlls, no flight model source). The source code will be coming shortly when I finish getting it documented.

 

Some things to keep in mind (more info, such as data source, including in the readmehttps://forums.eagle.ru/images/editor/color.gif):

 

How accurate is the flight model (aerodynamics)?

- As accurate as possible with all flight data available (mostly from wind tunnels)

 

How accurate is the control system?

- As accurate as the NASA manned sim, using the same math model and block diagrams

- Modeling of the mechanical servo-dynamics are in there as well

 

How accurate is the engine model?

- Extrapolated equations from the NASA manned sim

 

Is there ground reaction?

- No ground reaction due to public limitation of EFM API

- The FCS controls get jittery when on the ground, this is because the raw sensor values coming from DCS are wack when on the ground. Typical FCS systems use weight on wheels to use a different controller logic, but I can't accurately determine weight on wheels due to limitations of the public EFM API. I tried to filter the sensor values as much as possible without negative affect on the FCS system.

 

Is there aircraft system?

- No, not even fuel burn

- No weapons

- Only aircraft system modeled is the FCS that is always active in the flight model code

 

Can I operate the gear?

- No manual gear operation, again due to limitations, I've got a cockpit system that automatically deploys the gear below 200ft, but you can edit that out in the lua code if you want

 

Is there a cockpit?

- Nope, sorry!

 

Is there a new 3D model?

- Not in this release, but will be soon!

 

The aircraft is really meant to fly around in the air...you can do touch and goes but there is NO ground reaction, no braking, no frictions, no steering.

 

To be clear once again, this project is meant to be sort of an extension to the "Wunderluft" project...it pretty much explores everything that is possible with the public EFM API and, more importantly, shows the limitations. Again, I hope to have the source code out to you guys soon!

 

Enjoy :)

 

Download Link:

* New Link:

RagnarDa Updated and Expanded Version (March 10, 2014) GitHub

PS...If you are on an x86 system make sure you swap the dll in the bin directory with the on in the bin/x86 directory


Edited by CptSmiley
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"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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is VTAI still working on their F-16 Model? Could propose a Co-Project with them.

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Very nice looking flight model :)

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Nice work & very good of you to open source and share.

 

Yep, the provided sticky message is great for getting started to setting up your mod, but so far I have not found much, if any, documentation to help those get started with the external flight model. What better than an actual example, right?

"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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Looks pretty nice!

 

All I miss is compare diagram for real and in-game parameters, and correlation coefficient between them :D

Like here, Yo-Yo show real and ingame Mustang compare

http://forums.eagle.ru/showthread.php?t=87966

 

Keep info coming!

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Looks pretty nice!

 

All I miss is compare diagram for real and in-game parameters, and correlation coefficient between them :D

Like here, Yo-Yo show real and ingame Mustang compare

http://forums.eagle.ru/showthread.php?t=87966

 

Keep info coming!

 

hey Sevas, yep I fully intend to compare performance charts just like that

"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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Great stuff, quite impressed at your pace. (I think I saw you just getting set up with this only weeks ago?) I'll be interested to see your code, definitely excited to get started with EFMs as soon as I have time.

 

Yeah just started a couple weeks ago with this after I realized it was possible, I was pumped.

 

I still have a ways to go but I fully intend on providing the code that backs this up :)

"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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Nice video, but please stop panning - it destroys any sense of motion. Keep the camera in a fixed spot. It is easier it judge its motion then. :)

 

Good luck with your efforts! What are you using for the physics engine?

 

Best regards,

Tango.


Edited by Tango
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Nice video, but please stop panning - it destroys any sense of motion. Keep the camera in a fixed spot. It is easier it judge its motion then. :)

 

Best regards,

Tango.

 

Maybe you want a cockpit view of a low level flight :p

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Same here.....

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Yeah just started a couple weeks ago with this after I realized it was possible, I was pumped.

 

I still have a ways to go but I fully intend on providing the code that backs this up :)

 

I may have to get in touch with you about your methods, then, because that's quite efficient! :) With progress like that, you make me think I do have time to build an EFM after all! Like I said, very impressed.

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I may have to get in touch with you about your methods, then, because that's quite efficient! :) With progress like that, you make me think I do have time to build an EFM after all! Like I said, very impressed.

 

Not to knock the OPs efforts, but AFAIK you will have a hard time building a LUT based FM of the same quality for anything else but the Viper, simply because there is nothing of sorts like the NASA report in the public domain for other fighters. It requires a real motherload of data. :)

 

Very nice project though, anything that expands the documentation so people can get into the API more easily is direly needed at this point.

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Please note that this is NOT one of the intended products to be released by TeamVRC, just a stepping stone in that process

 

That's a great pity.

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Not to knock the OPs efforts, but AFAIK you will have a hard time building a LUT based FM of the same quality for anything else but the Viper, simply because there is nothing of sorts like the NASA report in the public domain for other fighters. It requires a real motherload of data. :)

 

Very nice project though, anything that expands the documentation so people can get into the API more easily is direly needed at this point.

 

You are absolutely correct, the F-16 has a wide database easily available, I think the only other one that might be available for fighter type aircraft is the F-18.

 

However, there are many analysis tools and if the aircraft is properly modeled can provide decent non-linear coefficient databases.

 

Even with the F-16 data readily available it probably took up 80% of the development time figuring out a way to get it into a format that was easily usable by DCS.

"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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That's a great pity.

 

This does not mean it won't be available for you to fly with!

"Witness mere F-14s taking off from adjacent flight decks, gracefully canting left and right, afterburners flaming, and there’s something that sweeps you away—or at least it does me. And no amount of knowledge of the potential abuses of carrier task forces can affect the depth of that feeling. It simply speaks to another part of me. It doesn’t want recriminations or politics. It just wants to fly.”

― Carl Sagan

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Excellent work. Just yesterday I started working on an F-16 flight model for my sim using the same sources you mentioned.

 

I'm not sure whether you are aware but there is an open source implementation of that NASA paper at Caltech:

http://www.cds.caltech.edu/~murray/projects/afosr95-vehicles/models/f16/

 

I used the Java implementation, since I want to use multi-threading to allow full flight models to be used for each aircraft.

 

The NASA model is ok in flight but the implementation has quite severe deficiencies such as:

* Not-a-Number produced at zero airspeed.

* no support for negative airspeed (tailslide!)

* no model for fuel consumption or transfer between tanks.

* no model of mass distribution (important once you add weapons, or stall).

* missing the relationship between pilot command and control surface deflection, as in the flight control system (fortunately there is other material out there for this)

* no model of ground handling

* etc.

 

I don't mean to denigrate your work in any way - it is an awesome achievement to get it into DCS, and so quickly too. All I mean is that the NASA model should be seen as a starting point, but you probably already know this :)

 

Keep up the great work.

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