F-16 High Fidelity Flight Dynamics

[Silver_Dragon]

http://forums.eagle.ru/showthread.php?t=95985

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

 

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 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 is appears DCS still handles 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

 

un video

http://youtu.be/A-JdKVbwFlk

[occam]

WTF!!!!

pero no va a ser nada, que pena...

[Revientor]

Coño si se mueve como en BMS en un puto rail... lo mismo es que el modelo de BMS es tan jodidamente bueno que es tan real como es y esa sensación de los aviones rusos del FC2 y DCS es que son unos putos aviones de mierda que no saben volar recto y nivelado porque no tienen una hidráulica como dios manda y tienen un diseño de fabrica propio de un cono...

[Tom Raisen]

entonces va a parecer que el modelo por vectores triunfa definitivamente al modelo por mecánica de fluidos... :roll:

[Revientor]

mientras que haya limones rellenos de cocacola da igual...

[alius]

Uhhh...tanquilos muchachos...tengan en cuenta que esto no es de ED. Tengan en cuenta que es apenas una pequeña demo.....no está finalizado....el pibe es nuevo como DCS modding y que quizas esto nunca será liberado. Dejen trabajar al hombre....que está aprendiendo de a poco. Saludos

[occam]

Alius te digo lo del otro dia. Calla y ven a volar. :ok:

[alius]

Occam cerrá la boca...hoy a las 23:00....acabo de romper una cita con una Polaca infartante. Besos

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... stcount=46

Originally Posted by NECK

Could you please explain what you mean by that? Will you guys create a flyable F16, with all its systems?( radar, target pod, weapons etc)?

 

Would love a DCS F16 that can replace/ supplement to falcon 4.0BMS

 

Either way, keep up the good work and good luck

Nope, my skill set nor free time do not allow for aircraft systems and weapons modeling.

 

My goal is to create a working advanced flight model example for other to work from.

 

Like Tango said, I am working to organize it in a way that make sense, document the flow, comment the units to be used. As it stand now it does not even have a cockpit...

 

This does not prevent others from taking the model and doing as they wish and you can certainly fly it as is when I publish it.

 

I hope this helps!

 

http://forums.eagle.ru/showpost.php?p=1 ... stcount=50

Progress Update:

- Leading edge flap control law logic complete

- Actuator logic for all surfaces complete

 

To do this weekend:

- Higher level control laws

 

We'll be testing it internally and should have another video up soon of the improvements...

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... stcount=85

Hey all here is another demonstration video done by one of our VRC guys.

 

This current version has...

- Aerodynamics Model - NASA aerodynamics database

- Flight Control Laws - NASA and AFIT simulator study and flight controls documents

- Engine Model - NASA and AFIT simulator study documents

 

Enjoy!

 

[Tom Raisen]

bueno, sí, está bien... aunque no veo nada que no tengamos ya (respecto al f16 me refiero)... supongo que será cuestión de tiempo que mejoren algo al f4/bms... porque supongo que la peña hace cosas nuevas pa mejorarlas no?...

Gracias por el aporte y por el link Silver Dragon! :birras:

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... stcount=88

Hey guys just an update...

 

- Engine modeling and throttle logic added to match NASA sim document (previously was using all standard day sea level values, causing you to be able to fly into space) now you have proper max speed and operational ceiling

- Trailing edge flaps control laws (need to find aerodynamic info of trailing edge flaps)

- Correct moments of inertia (thanks to Alex O'kean!)

- Fixed flutter on multiple controls

 

The aircraft now flies smooth as silk...the FCS control laws really keep the aircraft steady but nimble as ever. I'm excited to have this out for you guys soon, updates to happen:

 

- Continue code clean-up

- Optimize look-up tables

- Add aerodynamic effects for trailing edge flaps

 

After that, I'm at the limit of what I've been able to dig up for the external flight model. The one thing I'd like to have is atleast setting gear state, but I've pm'ed multiple times and made a thread on it with no help...

 

I really hope this will be a nice template for you guys wanting to write your own flight models.

 

Not sure of a timeline for release, been getting busier with work and school but I work on this project whenever I get the time, will keep you guys updated.

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=115

 

So I've gotten distracted with other facets of modding besides the flight model! I've got a basic static collision model made and with Skatezilla's help I've learned how to get stuff animated with the new model, so I am working on that.

 

My plan is to complete the animations for the visual model then do the animations for the collision model. Once I get that done it's back to the flight model code!

 

Work and school have kept me really busy so the progress is slow but in the last couple weeks I've learned a whole lot more than the EFM with help from various community members, thanks all.

 

I was hoping ED could chime in on the external stores issue. My suspicion is that it is not the forces, but rather the defined moments of inertia are completely goofed for the missiles...They must be enormously huge as that is what is preventing the applied forces from inducing a delta in the acceleration of the aircraft in any axis or direction or rotation! (missiles_data.lua has a ton of info but nothing related to inertias, but does have Cx parameters [drag] settings...I might try messing with that file to see if I get different response to confirm my inertia suspicion.

 

Anyway, I also wanted to give the F-16 Demo a little better presentation so grabbed a simple background and icon:

 

:shock: :roll:

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=118

 

Quote:

Originally Posted by aaron886

Well, Alex has been around the forums, but he might be really busy?

Yep last post he made was his HUGE help on the moment of inertia definitions...I've already bugged him with a ton of PMs but I think he is busy.

 

Quote:

Avionics?

This is really meant to be a flight model demonstrator, so the flight control systems is as far as I intended on going. However, I'm already diving into 3D modeling and I am not going to stop any of the other motivated VRC members from coding up other various systems...we'll just see how this project goes. But it is mainly intended on being a EFM flight model demonstrator example.

 

I don't intend on including any weapons either...seems impossible right now anyhow with the external stores/EFM issue.

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=124

Originally Posted by SilentEagle

Any progress on the gear/ground modelling? Are any dynamics present by default?

Hey good question, the short answer is No

 

Long answer...

 

I have a collision model, I have connectors setup as best as I can see from looking at examples (A-10, KA-50, P-51) but there is absolutely no consistency with them.

 

I have such that the gear impacts the ground, but it acts like it is a crash impact...you hear crash noises, smoke goes everywhere, etc...

 

This was my assumptions of what would happen, since I can't see a way that DCS magically knows that it is my gear touching the ground and not some other portion of the aircraft this is not intended to hit ground (wind tip, nose, etc..)

 

So what happens now is when you touch down the aircraft essentially shakes about till it flips over or something (kinda like if you come down with the A-10 with broken tires and just the struts) The dynamics are not present by default and until ED clues us in, there is no indication on how to make this happen. I've decided to go back and concentrate on the flight model and get the animations working for the new 3D model.

 

There are the major issues we are facing right now, that is sounds like everyone his having a problem with the EFM...

1. Gear modeling, ground reaction handling and detection

2. Handling of inputs that are not axis (buttons, discretes, etc...) from the EFM code, but you can do it from coding it up as a cockpit system in LUA

3. Moments of inertia screwed up for external stores on EFM aircraft.

 

I believe I've PM'd Alex about this but haven't heard from him in a while or any posts from him so he might be away for a bit...not sure when those issues will be addressed.

 

http://forums.eagle.ru/showpost.php?p=1 ... tcount=131

Broke through a huge roadblock today...I have the gear impact model working, minus proper friction and braking, but it knows it is the wheels that are on the ground Here is the internal SVN changelog

 

- Working gear impact model! Now default to gear down...will have animations done soon

- Working flaps aerodynamics...do proper approaches now!

- Added TEF mixing and differential stab mixing into 3D model

 

What next to do:

- Speedbrake animation and aerodynamics (using JBSim F-16 config for this)

- Gear aerodynamics Cd and Cm effects due to gear down

- Gear 3D model animation (halfway done)

- Continue code clean up

 

http://youtu.be/1B-7_1L_-0w

F-16 with proper approach using flap scheduling and aerodynamics along with proper gear modeling (minus the correct friction and braking!)

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=183

Hi All...

 

I have a couple days off so I am going to try to publish this out to you guys very soon! At a minimum it will be closed source at first to let you guys fly it around and get some feedback.

 

What it will have

- DCS base 3D Model, not the new one

- No cockpit! (licensing reasons)

- High fidelity flight model

- No weapons except guns (EFM bug)

- No aircraft systems (except the FCS of course)

 

Talking with some who have 3rd party status it is clear that some features are easily implemented with the current API/build so I am halting any further development on the F-16 since I am trying to hack something that already has easy hooks in it apparently and have hit the limit of what I can do with what I have available to me

 

I hope that VRC receives 3rd party status soon so that I can port over my knowledge to our F-100.

 

Unless something happens, I hope to have it posted late today or early tomorrow

[Ancla]

Coño si se mueve como en BMS en un puto rail... lo mismo es que el modelo de BMS es tan jodidamente bueno que es tan real como es y esa sensación de los aviones rusos del FC2 y DCS es que son unos putos aviones de mierda que no saben volar recto y nivelado porque no tienen una hidráulica como dios manda y tienen un diseño de fabrica propio de un cono...

 

Eso por que el que lo esté creando no tiene ni idea de ponerlo en condiciones :mrgreen:

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=191

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 readme):

 

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:

F-16 Demo Version 0.1

 

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

[Silver_Dragon]

http://forums.eagle.ru/showpost.php?p=1 ... tcount=202

Hi all...decided to post the state of the code, I'll get to documenting source pages for the control logic over the holidays.

 

Download Link:

* Updated to Version 0.2 (Includes Source Code)

F-16 Demo Version 0.2

 

The source code is in "Flight Model" directory.

 

An important piece of the flight model is the GeneralFilter, but I had to make it a static library for certain reasons, but it is just a general tustin filter and you guys can code that up or just use these functions, sorry I can't provide the source code for that.

 

Have fun, and happy holidays!