jsbsim-devel

Re: [Jsbsim-devel] Multiple property tree problem/soution

[Jon S. B. <jon...@co...>]

I think you are missing the point. Multiple FDMs would be designed to work within Flightgear or standalone. The main model would always have the base property tree names. I assume that any other capability or feature such as nasal would not be affected. 

-----Original Message-----
From: gerard robin <gh...@gm...>
Sent: Friday, June 26, 2009 4:29 PM
To: Development issues <jsb...@li...>
Subject: Re: [Jsbsim-devel] Multiple property tree problem/soution

On vendredi 26 juin 2009, Erik Hofman wrote:
> Jon S. Berndt wrote:
> >> I hope both solutions didn't cross each other and cause any troubles
> >> that way. I've added an update that only increases the counter when not
> >> running inside FlightGear.
> >
> > I saw that. I removed it temporarily to see if Ron's fix works for all
> > cases. Theoretically, multiple FDMs would be desirable in all
> > environments.
>
> Ok, lets see how it works out then.
>
> Erik
>

Erik
To me ,Your last FG CVS  update is right.

In any case with FG only one JSBSIM property tree  ( [0] ) , must be 
available, since there is a close relationship with FG Property tree itself, 
for instance the Engine CutOff.
And,  if we have to include some additional Nasal script the difficulty would 

[The entire original message is not included]

Re: [Jsbsim-devel] Multiple property tree problem/soution

[gerard r. <gh...@gm...>]

On vendredi 26 juin 2009, Jon S. Berndt wrote:
> I think you are missing the point. Multiple FDMs would be designed to work
> within Flightgear or standalone.

Yes and .....NO :)
How FG will be able to manage several multiple FDM ?
OR, how the user/developper will be able to tell to FG which FDM must be in 
use ?

I experienced recently ( before that last Erik update ) the problem.
I got both  /fdm/Jsbsim   and /fdm/jsbsim[1] , the first one was stupid, 
anyhow, it gave some data to the main FG branch, the second one  was right , 
it gave some others and most of the right values to the main FG branch.
The result was a not working Aircraft.


> The main model would always have the base 
> property tree names. I assume that any other capability or feature such as
> nasal would not be affected.
>
Not with Nasal, the script could want a getprop from a  jsbsim fdm property, 
in that case,  which /fdm/jsbsim[?],    0, 1, 2 , 3 ......... ? 
We don't know........ since we can't control that incremental value.

-- 
Gérard
http://pagesperso-orange.fr/GRTux/

J'ai décidé d'être heureux parce que c'est bon pour la santé. 
Voltaire

Re: [Jsbsim-devel] Multiple property tree problem/soution

[Jon S. B. <jon...@co...>]

> On vendredi 26 juin 2009, Jon S. Berndt wrote:
> > I think you are missing the point. Multiple FDMs would be designed to
> work
> > within Flightgear or standalone.
> 
> Yes and .....NO :)
> How FG will be able to manage several multiple FDM ?
> OR, how the user/developper will be able to tell to FG which FDM must
> be in use ?

FlightGear would not know the difference - this is not a FlightGear
capability. Multiple FDMs would be managed and run using JSBSim features.
There is no difference between a single FDM and multi-FDM with JSBSim as far
as FlightGear is concerned. The base aircraft will always be the base
property tree - the first property tree. Let's say that the aircraft is the
B-52 carrying the X-15. In the B-52 there may be a switch that tells a
JSBSim system to drop the X-15. At that point, the X-15 would begin flying
(the integration of the X-15 Equations of Motion would start). Obviously,
there would need to be a way to link up a 3D model with a specific child
flight model, but I don't expect that would be a major issue.

I expect that for the near term (and I use the word "near" as a joke, since
this multi-body capability has been in-work for many years), I expect
FlightGear would not use this multi-body capability. I think it would be
mostly a JSBSim batch mode feature. I'd like to see it used for multi-stage
rockets, too, for instance.

The challenge is to make sure that FlightGear is not adversely affected by
the inclusion of this capability. I think Ron's suggested fix does that.

Jon

Re: [Jsbsim-devel] Multiple property tree problem/soution

[gerard r. <gh...@gm...>]

On dimanche 28 juin 2009, Jon S. Berndt wrote:

>
> FlightGear would not know the difference - this is not a FlightGear
> capability. Multiple FDMs would be managed and run using JSBSim features.
> There is no difference between a single FDM and multi-FDM with JSBSim as
> far as FlightGear is concerned. The base aircraft will always be the base
> property tree - the first property tree. Let's say that the aircraft is the
> B-52 carrying the X-15. In the B-52 there may be a switch that tells a
> JSBSim system to drop the X-15. At that point, the X-15 would begin flying
> (the integration of the X-15 Equations of Motion would start). Obviously,
> there would need to be a way to link up a 3D model with a specific child
> flight model, but I don't expect that would be a major issue.
>
> I expect that for the near term (and I use the word "near" as a joke, since
> this multi-body capability has been in-work for many years), I expect
> FlightGear would not use this multi-body capability. I think it would be
> mostly a JSBSim batch mode feature. I'd like to see it used for multi-stage
> rockets, too, for instance.
>
> The challenge is to make sure that FlightGear is not adversely affected by
> the inclusion of this capability. I think Ron's suggested fix does that.
>
> Jon
>

Jon,
Thanks for that explanation.

That will be a great feature, i hope it will be available soon, and 
that "near" won't be  only a joke but a reality :).

The challenge regarding the integration within FlighGear  is an other "story" 
since today, like i said before,  we get some mistmatch  when FG is working 
with several instances of JSBSim.

Regards


-- 
Gérard
http://pagesperso-orange.fr/GRTux/

J'ai décidé d'être heureux parce que c'est bon pour la santé. 
Voltaire