jsbsim-devel — JSBSim development issues

Re: [Jsbsim-devel] Thermal street lift

[Dave C. <dav...@co...>]

atmosphere/wind-down-fps

I believe an updraft would be a negative value.


-- Dave


On 4/12/20 10:28 PM, Simon Julie Morley via Jsbsim-devel wrote:
> Hi guys,
>
> I believe what I'm looking to adjust is within the atmosphere 
> properties but I don't know which one I'd adjust to generate a 
> constant thermal lift of say 3ft sec
>
> Any help would be appreciated
>
> Regards
>
> Simon.
>
>
> _______________________________________________
> Jsbsim-devel mailing list
> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
>

[Jsbsim-devel] Thermal street lift

[Simon J. M. <sim...@go...>]

Hi guys,

I believe what I'm looking to adjust is within the atmosphere properties
but I don't know which one I'd adjust to generate a constant thermal lift
of say 3ft sec

Any help would be appreciated

Regards

Simon.

[Jsbsim-devel] C++11 support

[Erik H. <er...@eh...>]

Hi,

Does anybody have any thoughts on using C++11 for JSBSim?

I'm tracking a problem which involves the use of an uninitialized 
parameter in FlightGear and C++11 allows declaring a default value to a 
parameter when defining it which is not just easier to read but also 
more foolproof.

class A {
   A() = default;
   virtual ~A() = default;

   int x = 0, y = 0, z = 0;
};

Erik


-- 
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High performance synthesizer and virtual reality audio software.

Re: [Jsbsim-devel] A few questions...

[linux g. <lin...@gm...>]

Thank you for the reply.

"You are probably looking for Latitude, Longitude, and altitude."   From
which class ?   I want to write code that uses the current position in
C++.  Not for use in an initialization xml file.

Does FGLocation::GetLattitude(), for example, return the current latitude ?
Why is there a FGLocation::SetPosition, but no FGLocation::GetPosition ?






On Mon, Dec 16, 2019 at 6:01 PM Bill Galbraith <bil...@gm...>
wrote:

> Well, since no one else is answering…
>
>
>
> You are probably looking for Latitude, Longitude, and altitude. You will
> also probably want pitch, roll, and heading. Look for those values in the
> list of parameters available in JSBSim. They are all referenced to the
> aircraft center of gravity (CG).
>
>
>
> There are equations available on the internet for finding the
> lat/long/altitude of a point a certain x/y/z distance from the aircraft.
> Sorry, I don’t have them at my fingertips right now. Keep in mind that you
> are dealing with a sphere.
>
>
>
> Bill
>
>
>
>
>
> *From:* linux guy [mailto:lin...@gm...]
> *Sent:* Monday, December 16, 2019 12:06 PM
> *To:* jsb...@li...
> *Subject:* [Jsbsim-devel] A few questions...
>
>
>
> Hi people.  Thank you for your great work on JSBSim !
>
>
>
> I have a few questions....
>
>
>
> In code, how do I get the current location of the airframe ?    And to
> what point is the current location referenced to on the airframe ?
>
>
>
> How can I (easily) define a point at a distance(x,y,z) from the current
> location ?
>
>
>
> What exactly is a ColumnVector3 ?
>
>
>
> Thanks
>
>
>
>
>
>
>
> [image: Image removed by sender.]
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>
> _______________________________________________
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> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
>
>

Re: [Jsbsim-devel] A few questions...

[Bill G. <bil...@gm...>]

Well, since no one else is answering…

 

You are probably looking for Latitude, Longitude, and altitude. You will also probably want pitch, roll, and heading. Look for those values in the list of parameters available in JSBSim. They are all referenced to the aircraft center of gravity (CG).

 

There are equations available on the internet for finding the lat/long/altitude of a point a certain x/y/z distance from the aircraft. Sorry, I don’t have them at my fingertips right now. Keep in mind that you are dealing with a sphere.

 

Bill

 

 

From: linux guy [mailto:lin...@gm...] 
Sent: Monday, December 16, 2019 12:06 PM
To: jsb...@li...
Subject: [Jsbsim-devel] A few questions...

 

Hi people.  Thank you for your great work on JSBSim !

 

I have a few questions....

 

In code, how do I get the current location of the airframe ?    And to what point is the current location referenced to on the airframe ?

 

How can I (easily) define a point at a distance(x,y,z) from the current location ?

 

What exactly is a ColumnVector3 ?

 

Thanks

 

 

 


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[Jsbsim-devel] A few questions...

[linux g. <lin...@gm...>]

Hi people.  Thank you for your great work on JSBSim !

I have a few questions....

In code, how do I get the current location of the airframe ?    And to what
point is the current location referenced to on the airframe ?

How can I (easily) define a point at a distance(x,y,z) from the current
location ?

What exactly is a ColumnVector3 ?

Thanks

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Alan T. <ajt...@v-...>]

On 05/09/2019 07:10, Richard Harrison wrote:
> On 04/09/2019 02:11, Alan Teeder wrote:
>> JSBSim Output to make a .csv file which seems to give me  all the
>> parameters that I need to see what is going on.  .csv data goes nicely
>> into a spreadsheet which is ideal for this purpose.
>>
> I think it's worth mentioning that I use LiveGraph 
> (https://sourceforge.net/projects/live-graph/files/) to do both real 
> time and offline plotting.
>
>
Thanks Richard. That looks useful.

Alan

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Richard H. <rj...@za...>]

On 04/09/2019 02:11, Alan Teeder wrote:
> JSBSim Output to make a .csv file which seems to give me  all the
> parameters that I need to see what is going on.  .csv data goes nicely
> into a spreadsheet which is ideal for this purpose.
>
I think it's worth mentioning that I use LiveGraph  
(https://sourceforge.net/projects/live-graph/files/) to do both real 
time and offline plotting.

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Alan T. <ajt...@v-...>]

On 03/09/2019 23:57, Ron Jensen wrote:
>
> On Monday 02 September 2019 02:34:13 pm Alan Teeder wrote:
>
>> It would have been better to work with stand-alone JSBSim, but this
>> particular FDM has many hooks to Flightgear systems which would all need
>> sorting out.
>>
>> Alan
> Do you have a link to this particular aircraft's FDM? I haven't used FG in
> quite awhile now.
>
> Ron

Ron

The latest version is at https://github.com/FGMEMBERS/J3Cub.

Following Bertrand´s reply I seem to be getting somewhere. I now use 
JSBSim Output to make a .csv file which seems to give me  all the 
parameters that I need to see what is going on.  .csv data goes nicely 
into a spreadsheet which is ideal for this purpose.

It is making some sense, but the numbers add up to nose right instead of 
nose left. A large contribution was a fixed rudder trim ( on the Cub the 
owner would do this by bending the rudder). Making this zero helped but 
was not sufficient. However the presence of this fixed trim makes me 
think that it was needed in the past to counteract a nose left swing.

I have plenty  of parameters remaining to look at.

Alan

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Ron J. <wi...@je...>]

On Monday 02 September 2019 02:34:13 pm Alan Teeder wrote:

> It would have been better to work with stand-alone JSBSim, but this
> particular FDM has many hooks to Flightgear systems which would all need
> sorting out.
>
> Alan

Do you have a link to this particular aircraft's FDM? I haven't used FG in 
quite awhile now.

Ron

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Alan T. <ajt...@v-...>]

On 02/09/2019 21:11, Bertrand Coconnier wrote:
> Hi Alan,
>
> Le dim. 1 sept. 2019 à 23:30, Alan Teeder <ajt...@v-... 
> <mailto:ajt...@v-...>> a écrit :
>
>
>     I have made some progress by adding the following code to FGLGear
>     bind(). (near line 798) I can now see these properties in Flightgear.
>
>        property_name = base_property_name + "/wheel-XForce-lbs";
>        PropertyManager->Tie(property_name.c_str(), &vFn(eX));
>        property_name = base_property_name + "/wheel-YForce-lbs";
>        PropertyManager->Tie(property_name.c_str(), &vFn(eY));
>        property_name = base_property_name + "/wheel-ZForce-lbs";
>        PropertyManager->Tie(property_name.c_str(), &vFn(eZ));
>
>        property_name = base_property_name + "/strutforce-lbs";
>        PropertyManager->Tie(property_name.c_str(), &StrutForce);
>
>     The result of this is similar numbers in the property tree for
>     wheel-ZForce-lbs and strutforce-lbs. With the throttle opened the
>     numbers are larger for the left gear than the right gear, as
>     expected.
>     The value gets smaller as the aircraft accelerates on the runway.
>
>     However  the properties wheel-XForce-lbs and wheel-YForce-lbs are
>     zero.
>     They stay this way  even with the brakes applied despite the aircraft
>     coming to a halt.
>
>     Is there any reason why vFn(eX) and vFn(eY) are zero?
>
>
> Friction components are assessed at the global level i.e. when the 
> sums of all the forces and moments acting on the aircraft are available.
> Therefore the computation of friction forces is taking place in 
> FGAccelerations::CalculateFrictionForces

Bertrand

Thanks .

I will look there. I am doing my latest tests with an artificially high 
yaw inertia - thus locking the yaw axis and avoiding yaw contributions 
due to the(unstable) taildragger wheel layout.  I wait until the tail 
has lifted before freezing the sim and making my measurements, thus 
removing any tail wheel contributions.

It would have been better to work with stand-alone JSBSim, but this 
particular FDM has many hooks to Flightgear systems which would all need 
sorting out.

Alan

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Bertrand C. <bco...@gm...>]

Hi Alan,

Le dim. 1 sept. 2019 à 23:30, Alan Teeder <ajt...@v-...> a écrit :

>
> I have made some progress by adding the following code to FGLGear
> bind(). (near line 798) I can now see these properties in Flightgear.
>
>    property_name = base_property_name + "/wheel-XForce-lbs";
>    PropertyManager->Tie(property_name.c_str(), &vFn(eX));
>    property_name = base_property_name + "/wheel-YForce-lbs";
>    PropertyManager->Tie(property_name.c_str(), &vFn(eY));
>    property_name = base_property_name + "/wheel-ZForce-lbs";
>    PropertyManager->Tie(property_name.c_str(), &vFn(eZ));
>
>    property_name = base_property_name + "/strutforce-lbs";
>    PropertyManager->Tie(property_name.c_str(), &StrutForce);
>
> The result of this is similar numbers in the property tree for
> wheel-ZForce-lbs and strutforce-lbs. With the throttle opened the
> numbers are larger for the left gear than the right gear, as expected.
> The value gets smaller as the aircraft accelerates on the runway.
>
> However  the properties wheel-XForce-lbs and wheel-YForce-lbs are zero.
> They stay this way  even with the brakes applied despite the aircraft
> coming to a halt.
>
> Is there any reason why vFn(eX) and vFn(eY) are zero?
>

Friction components are assessed at the global level i.e. when the sums of
all the forces and moments acting on the aircraft are available.
Therefore the computation of friction forces is taking place in
FGAccelerations::CalculateFrictionForces


>
> Regards
>
> Alan
>

Re: [Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Alan T. <ajt...@v-...>]

I have made some progress by adding the following code to FGLGear  
bind(). (near line 798) I can now see these properties in Flightgear.

   property_name = base_property_name + "/wheel-XForce-lbs";
   PropertyManager->Tie(property_name.c_str(), &vFn(eX));
   property_name = base_property_name + "/wheel-YForce-lbs";
   PropertyManager->Tie(property_name.c_str(), &vFn(eY));
   property_name = base_property_name + "/wheel-ZForce-lbs";
   PropertyManager->Tie(property_name.c_str(), &vFn(eZ));

   property_name = base_property_name + "/strutforce-lbs";
   PropertyManager->Tie(property_name.c_str(), &StrutForce);

The result of this is similar numbers in the property tree for 
wheel-ZForce-lbs and strutforce-lbs. With the throttle opened the 
numbers are larger for the left gear than the right gear, as expected. 
The value gets smaller as the aircraft accelerates on the runway.

However  the properties wheel-XForce-lbs and wheel-YForce-lbs are zero. 
They stay this way  even with the brakes applied despite the aircraft 
coming to a halt.

Is there any reason why vFn(eX) and vFn(eY) are zero?

Regards

Alan

[Jsbsim-devel] Prop aircraft yaws to the right on take-off.

[Alan T. <ajt...@v-...>]

I am trying to understand why a JSBSim propeller aircraft (Piper Cub in 
Flightgear) yaws to the right on take-off.

It has a conventional clockwise (from the pilot) propeller, and with the 
brakes on the left wing goes down slightly when the throttle is 
advanced.  The JSBsim properties gear/unit[1]/compression-ft and 
gear/unit[2]/compression-ft show that the left leg is compressed more 
than the right one. So far so good. ;)

However, on releasing the brakes,the property moments/n-gear-lbsft  
rapidly becomes positive  and the aircraft yaws to the right. I can 
control this with rudder, but believe that the yaw should be to the 
left, not right.

I have added "version 1.1" to the propeller config file, but this will 
only affect the sign of the propeller  gyro moment.

Could strut,  friction and side forces for each U/C unit be added to the 
exposed properties to help me debug this?

Thanks

Re: [Jsbsim-devel] Flaps command not changing flaps position

[Martin H. <mar...@gm...>]

Am Di., 6. Aug. 2019 um 01:33 Uhr schrieb Ron Jensen <wi...@je...>:

> Caveat: I have never used the library, only standalone and flightgear
>
> On Monday 05 August 2019 02:29:29 pm Martin Hoffmann wrote:
> >       - ...
> >       - FCS->SetDfCmd(10.0d); // set flaps to 10 percent
> >       - ...
>
> Should this be in the range [0-1] with 1 being 100%?
>

API docs state that input is in percent, but no matter if I use [0-1] or
[0-100], the result is the same.


>


> in my tree:
> src/models/FGFCS.h:  double GetDfCmd(void) const { return DfCmd; }
> src/models/FGFCS.h:  void SetDfCmd(double cmd) { DfCmd = cmd; }
>

These are exactly the functions my code is using.


>
> src/models/FGFCS.cpp:  PropertyManager->Tie("fcs/flap-cmd-norm", this,
> &FGFCS::GetDfCmd, &FGFCS::SetDfCmd);
>
>
> >       - aircraftStatus.FlapsPos = FCS->GetDfPos();
>
> This call seems to take an argument from src/models/FGFCS.h
> typedef enum { ofRad=0, ofDeg, ofNorm, ofMag , NForms} OutputForm;
>

> try FCS->GetDfPos(ofNorm); ?
>

You can select multiple output formats, but it has no impact of my flaps
not reacting at all.


>
> > I'm using the C172p model for a first test
>
> Is that the JSBSim model or the FlightGear model? Make sure there is xml
> in
> the flightcontrol tag that creates fcs/flap-pos-deg and doesn't do any
> failure modes on you. I notice the latest c172p from FlightGear includes
> some
> electrical system logic...
>
>         <channel name="Flaps">
>             <kinematic name="Flaps Control">
>                 <input>fcs/flap-cmd-norm</input>
>                 <traverse>
>                     <setting>
>                         <position>0</position>
>                         <time>0</time>
>                     </setting>
>                     <setting>
>                         <position>10</position>
>                         <time>2</time>
>                     </setting>
>                     <setting>
>                         <position>20</position>
>                         <time>1</time>
>                     </setting>
>                     <setting>
>                         <position>30</position>
>                         <time>1</time>
>                     </setting>
>                 </traverse>
>                 <output>fcs/flap-pos-deg</output>
>             </kinematic>
>         </channel>
>
> And note the time in the xml is in seconds, so it takes 4 seconds to apply
> full flaps.
>

I checked that the Flaps section is available in the XML. As I am using the
JSBSim model, there should no electrical systems logic that has an
influence. My loop runs for one simulated minute, so flaps should have
plenty of time to reacht.

I also tried to track down flaps management in the debugger, but I was
unable to locate the place in code where flaps are managed. Maybe someone
can point me at the right location?

Thanks again!


>
>
> _______________________________________________
> Jsbsim-devel mailing list
> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
>
>

Re: [Jsbsim-devel] Flaps command not changing flaps position

[Ron J. <wi...@je...>]

Caveat: I have never used the library, only standalone and flightgear

On Monday 05 August 2019 02:29:29 pm Martin Hoffmann wrote:
>       - ...
>       - FCS->SetDfCmd(10.0d); // set flaps to 10 percent
>       - ...

Should this be in the range [0-1] with 1 being 100%?

in my tree:
src/models/FGFCS.h:  double GetDfCmd(void) const { return DfCmd; }
src/models/FGFCS.h:  void SetDfCmd(double cmd) { DfCmd = cmd; }

src/models/FGFCS.cpp:  PropertyManager->Tie("fcs/flap-cmd-norm", this, 
&FGFCS::GetDfCmd, &FGFCS::SetDfCmd);


>       - aircraftStatus.FlapsPos = FCS->GetDfPos();

This call seems to take an argument from src/models/FGFCS.h 
typedef enum { ofRad=0, ofDeg, ofNorm, ofMag , NForms} OutputForm;

try FCS->GetDfPos(ofNorm); ?

> I'm using the C172p model for a first test

Is that the JSBSim model or the FlightGear model? Make sure there is xml in 
the flightcontrol tag that creates fcs/flap-pos-deg and doesn't do any 
failure modes on you. I notice the latest c172p from FlightGear includes some 
electrical system logic...

        <channel name="Flaps">
            <kinematic name="Flaps Control">
                <input>fcs/flap-cmd-norm</input>
                <traverse>
                    <setting>
                        <position>0</position>
                        <time>0</time>
                    </setting>
                    <setting>
                        <position>10</position>
                        <time>2</time>
                    </setting>
                    <setting>
                        <position>20</position>
                        <time>1</time>
                    </setting>
                    <setting>
                        <position>30</position>
                        <time>1</time>
                    </setting>
                </traverse>
                <output>fcs/flap-pos-deg</output>
            </kinematic>
        </channel>

And note the time in the xml is in seconds, so it takes 4 seconds to apply 
full flaps.

Re: [Jsbsim-devel] Flaps command not changing flaps position

[Martin H. <mar...@gm...>]

Bill,

Thanks for your suggestion. I tried to replicate your parameters, but the
result is still the same - the model does not react on flaps input. I set
the flaps to a non-zero state at the beginning using
FCS->SetDfPos(JSBSim::ofDeg, 30.0). Using this command, the flaps are set
accordingly, but they still don't react on the flaps command
FCS->SetDfCmd(10.0d) in the main loop.

Martin

Am Mo., 5. Aug. 2019 um 22:35 Uhr schrieb Bill Galbraith <
bil...@gm...>:

> Martin,
>
>
>
> I do all of my testing with scripts in JSBSim, but the concepts and
> parameters should be the same. From a Flaps-Up test:
>
>
>
>     <!-- Specify the initial conditions -->
>
>     <property value="7629.0"> ic/h-sl-ft </property>
>
>     <property value="118.0">  ic/vc-kts  </property>
>
>     <property value="0.375"> fcs/flap-cmd-norm </property>
>
>     <property value="15.0"> fcs/flap-pos-deg </property>
>
>     <property value="0.0"> gear/gear-cmd-norm </property>
>
>     <property value="0.0"> gear/gear-pos-norm </property>
>
>
>
>     <!-- Set the engines running and trim the aircraft. -->
>
>     <event name="Trim">
>
>       <condition> simulation/sim-time-sec ge 0.0 </condition>
>
>       <set name="propulsion/set-running"    value="-1"/>
>
>       <set name="simulation/do_simple_trim" value="1"/>
>
>     </event>
>
>
>
>     <!-- After 4 seconds, move the flap control in 0.25 seconds. -->
>
>     <event>
>
>       <condition> simulation/sim-time-sec ge 4.0 </condition>
>
>       <set name="fcs/flap-cmd-norm" value="0.0" action="FG_RAMP"
> tc="0.25"/>
>
>     </event>
>
>
>
> Hope this helps,
>
> Bill
>
>
>
> *From:* Martin Hoffmann [mailto:mar...@gm...]
> *Sent:* Monday, August 05, 2019 4:29 PM
> *To:* jsb...@li...
> *Subject:* [Jsbsim-devel] Flaps command not changing flaps position
>
>
>
> Hi all,
>
>
>
> I am trying to get JSBSim running as the flight model for a project using
> the Unity Game Engine. To get there, I built a DLL wrapper around JSBSim
> that makes it available to Unity as a third party component. Marshalling C#
> data to and from JSBSim works without any problems, and I have a running
> sim loop in Unity. I'm using the C172p model for a first test. So far, I
> set the engine controls in Unity, marshal them to JSB and receive engine
> data back in Unity. Engine behavior looks as expected with RPM increasing
> at the beginning and stabilizing after a few seconds into the sim loop.
>
>
>
> Next step would be setting the flaps according to the user's input, and
> this is where I got stuck. I am setting the flaps command, but the flaps
> don't react - flap position is always zero.
>
>
> This is the sequence I am using (following roughly the FlightGear
> implementation):
>
>
>
>    - Load aircraft model
>    - Set initial conditions:
>
>
>    - ...
>       - FCS->SetDfCmd(10.0d); // set flaps to 10 percent
>       - ...
>
>
>    - fdmex->RunIC();
>    - fdmex->DoTrim(JSBSim::tGround);
>    - Start the sim loop with with a frequency of 120 iterations per second
>
>
>    - fdmex->Setdt(120.0d);
>       - FCS->SetDfCmd(10.0d);
>       - fdmex->Run();
>       - aircraftStatus.FlapsPos = FCS->GetDfPos();
>
> No matter what DfCmd is set to, the result of GetDfPos() is always zero. I
> tested this with multilple single prop models. and the behavior is always
> the same. As already mentioned, other FDM parameters react as expected.
>
>
>
> Side note: The above test is running outside Unity, so Unity does not have
> an influence on the behavior.
>
>
>
> Any suggestions are highly appreciated!
>
>
>
> Cheers,
> Martin
>
>
>
>
>
>
>
> [image: Image removed by sender.]
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
> Virus-free. www.avg.com
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient>
>
>
> _______________________________________________
> Jsbsim-devel mailing list
> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
>
>

-- 
Dr. Martin Hoffmann
Rietburgstraße 2
67141 Neuhofen
Tel.: 06236/699022
Mobil: 0163/5698053
E-Mail: mar...@gm...

Re: [Jsbsim-devel] Flaps command not changing flaps position

[Bill G. <bil...@gm...>]

Martin,

 

I do all of my testing with scripts in JSBSim, but the concepts and parameters should be the same. From a Flaps-Up test:

 

    <!-- Specify the initial conditions -->

    <property value="7629.0"> ic/h-sl-ft </property>

    <property value="118.0">  ic/vc-kts  </property>

    <property value="0.375"> fcs/flap-cmd-norm </property>

    <property value="15.0"> fcs/flap-pos-deg </property>

    <property value="0.0"> gear/gear-cmd-norm </property>

    <property value="0.0"> gear/gear-pos-norm </property>

 

    <!-- Set the engines running and trim the aircraft. -->

    <event name="Trim">

      <condition> simulation/sim-time-sec ge 0.0 </condition>

      <set name="propulsion/set-running"    value="-1"/>

      <set name="simulation/do_simple_trim" value="1"/>

    </event>

 

    <!-- After 4 seconds, move the flap control in 0.25 seconds. -->

    <event>

      <condition> simulation/sim-time-sec ge 4.0 </condition>

      <set name="fcs/flap-cmd-norm" value="0.0" action="FG_RAMP" tc="0.25"/>

    </event>

 

Hope this helps,

Bill

 

From: Martin Hoffmann [mailto:mar...@gm...] 
Sent: Monday, August 05, 2019 4:29 PM
To: jsb...@li...
Subject: [Jsbsim-devel] Flaps command not changing flaps position

 

Hi all,

 

I am trying to get JSBSim running as the flight model for a project using the Unity Game Engine. To get there, I built a DLL wrapper around JSBSim that makes it available to Unity as a third party component. Marshalling C# data to and from JSBSim works without any problems, and I have a running sim loop in Unity. I'm using the C172p model for a first test. So far, I set the engine controls in Unity, marshal them to JSB and receive engine data back in Unity. Engine behavior looks as expected with RPM increasing at the beginning and stabilizing after a few seconds into the sim loop.

 

Next step would be setting the flaps according to the user's input, and this is where I got stuck. I am setting the flaps command, but the flaps don't react - flap position is always zero.


This is the sequence I am using (following roughly the FlightGear implementation):

 

*	Load aircraft model
*	Set initial conditions:

*	...
*	FCS->SetDfCmd(10.0d); // set flaps to 10 percent
*	...

*	fdmex->RunIC();
*	fdmex->DoTrim(JSBSim::tGround);
*	Start the sim loop with with a frequency of 120 iterations per second

*	fdmex->Setdt(120.0d);
*	FCS->SetDfCmd(10.0d);
*	fdmex->Run();
*	aircraftStatus.FlapsPos = FCS->GetDfPos();

No matter what DfCmd is set to, the result of GetDfPos() is always zero. I tested this with multilple single prop models. and the behavior is always the same. As already mentioned, other FDM parameters react as expected.

 

Side note: The above test is running outside Unity, so Unity does not have an influence on the behavior.

 

Any suggestions are highly appreciated!

 

Cheers,
Martin

 

 

 


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[Jsbsim-devel] Flaps command not changing flaps position

[Martin H. <mar...@gm...>]

Hi all,

I am trying to get JSBSim running as the flight model for a project using
the Unity Game Engine. To get there, I built a DLL wrapper around JSBSim
that makes it available to Unity as a third party component. Marshalling C#
data to and from JSBSim works without any problems, and I have a running
sim loop in Unity. I'm using the C172p model for a first test. So far, I
set the engine controls in Unity, marshal them to JSB and receive engine
data back in Unity. Engine behavior looks as expected with RPM increasing
at the beginning and stabilizing after a few seconds into the sim loop.

Next step would be setting the flaps according to the user's input, and
this is where I got stuck. I am setting the flaps command, but the flaps
don't react - flap position is always zero.

This is the sequence I am using (following roughly the FlightGear
implementation):


   - Load aircraft model
   - Set initial conditions:
      - ...
      - FCS->SetDfCmd(10.0d); // set flaps to 10 percent
      - ...
   - fdmex->RunIC();
   - fdmex->DoTrim(JSBSim::tGround);
   - Start the sim loop with with a frequency of 120 iterations per second
      - fdmex->Setdt(120.0d);
      - FCS->SetDfCmd(10.0d);
      - fdmex->Run();
      - aircraftStatus.FlapsPos = FCS->GetDfPos();

No matter what DfCmd is set to, the result of GetDfPos() is always zero. I
tested this with multilple single prop models. and the behavior is always
the same. As already mentioned, other FDM parameters react as expected.

Side note: The above test is running outside Unity, so Unity does not have
an influence on the behavior.

Any suggestions are highly appreciated!

Cheers,
Martin

Re: [Jsbsim-devel] alphalimits, hysteresis_limits

[Alan T. <ajt...@v-...>]

Sean

Thanks for taking the time to look this up. I am also glad to see that 
the new documentation mentions it.

Is it possible to put a link to this new documention on 
http://jsbsim.sourceforge.net/documentation.html?

Alan

Re: [Jsbsim-devel] alphalimits, hysteresis_limits

[Sean M. <se...@se...>]

Hi Alan

I've taken a quick glance at the code.

The alpha limits are read in if they exist and exposed as properties:

  PropertyManager->Tie("aero/alpha-max-rad",   this, &FGAerodynamics::GetAlphaCLMax, &FGAerodynamics::SetAlphaCLMax, true);
  PropertyManager->Tie("aero/alpha-min-rad",   this, &FGAerodynamics::GetAlphaCLMin, &FGAerodynamics::SetAlphaCLMin, true);

The trim code makes use of the alpha limits in FGTrimAxis::FGTrimAxis().

  case tAlpha:
    control_min=fdmex->GetAerodynamics()->GetAlphaCLMin();
    control_max=fdmex->GetAerodynamics()->GetAlphaCLMax();
    if(control_max <= control_min) {
      control_max=20*degtorad;
      control_min=-5*degtorad;
    }
    control_value= (control_min+control_max)/2;
    control_convert=radtodeg;
    solver_eps=tolerance/100;
    break;

In terms of FGAerodynamics I only see it making use of alphaclmax to expose a stall warning property. I don't see any JSBSim code itself doing anything the stall warning.

double GetStallWarn(void) const { return impending_stall; }
PropertyManager->Tie("systems/stall-warn-norm", this, &FGAerodynamics::GetStallWarn);

FGAerodynamics::Run() - 

  if (alphaclmax != 0) {
    if (in.Alpha > 0.85*alphaclmax) {
      impending_stall = 10*(in.Alpha/alphaclmax - 0.85);
    } else {
      impending_stall = 0;
    }
  }

In terms hysteresis:

double GetHysteresisParm(void) const { return stall_hyst; }
  PropertyManager->Tie("aero/stall-hyst-norm", this, &FGAerodynamics::GetHysteresisParm);

FGAerodynamics::Run() -

  if (alphahystmax != 0.0 && alphahystmin != 0.0) {
    if (in.Alpha > alphahystmax) {
      stall_hyst = 1;
    } else if (in.Alpha < alphahystmin) {
      stall_hyst = 0;
    }
  }

Talking of hysteresis take a look at the example at:

https://jsbsim-team.github.io/jsbsim-reference-manual/mypages/user-manual-forces-and-moments/

Cheers

-----Original Message-----
From: Alan Teeder <ajt...@v-...> 
Sent: Saturday, May 25, 2019 1:43 AM
To: jsb...@li...
Subject: Re: [Jsbsim-devel] alphalimits, hysteresis_limits


On 24/05/2019 23:37, mik...@gm... wrote:
> Far as I have heard, alphalimits are used to indicate the modeled 
> range of AoAs

Thanks Mike.

That makes some kind of sense.

Does JSBSim do anything else with "alphalimits" or "hysteresis_limits", and are there flags which say when they are exceeded?  If not, do they serve any useful purpose?

This all came about because I am looking at a Datcom based FDM for Flightgear´s Piper Cub which I am working on. At the moment this simulation can easily get into a completely uncontrollable state. I am still checking , but it seems to happen if side-slip is allowed to build up.

Alan




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https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
_______________________________________________
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Re: [Jsbsim-devel] alphalimits, hysteresis_limits

[Alan T. <ajt...@v-...>]

On 24/05/2019 23:37, mik...@gm... wrote:
> Far as I have heard, alphalimits are used to indicate the modeled
> range of AoAs

Thanks Mike.

That makes some kind of sense.

Does JSBSim do anything else with "alphalimits" or "hysteresis_limits",  
and are there flags which say when they are exceeded?  If not, do they 
serve any useful purpose?

This all came about because I am looking at a Datcom based FDM for 
Flightgear´s Piper Cub which I am working on. At the moment this 
simulation can easily get into a completely uncontrollable state. I am 
still checking , but it seems to happen if side-slip is allowed to build up.

Alan

Re: [Jsbsim-devel] alphalimits, hysteresis_limits

[<mik...@gm...>]

Far as I have heard, alphalimits are used to indicate the modeled
range of AoAs?

On Fri, May 24, 2019 at 11:31:29PM +0100, Alan Teeder wrote:
> alphalimits, hysteresis_limits. Does anybody know what these do? I can not
> find any documentation describing their effects.
> 
> My assumption is that they are to do with some form of stall simulation.
> 
> Regards
> 
> Alan
> 
> 
> 
> _______________________________________________
> Jsbsim-devel mailing list
> Jsb...@li...
> https://lists.sourceforge.net/lists/listinfo/jsbsim-devel
> _______________________________________________
> The JSBSim Flight Dynamics Model project
> http://www.JSBSim.org
> _______________________________________________
> 

[Jsbsim-devel] alphalimits, hysteresis_limits

[Alan T. <ajt...@v-...>]

alphalimits, hysteresis_limits. Does anybody know what these do? I can 
not find any documentation describing their effects.

My assumption is that they are to do with some form of stall simulation.

Regards

Alan

Re: [Jsbsim-devel] Helicopter models

[Thomas K. <t.k...@we...>]

Hello together,

The following was meant to hit the list (Sean, sorry for spamming).

Thomas

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

Hello Sean,

At least there is a Alouette-III available at:

https://sourceforge.net/projects/grtuxsimfg/

The other ones listed on the page aren't available (?).

Regards,
	Thomas



On 04/12/19 11:17, Sean McLeod wrote:
> Hi
>
> I'm looking for some examples of helicopter models in JSBSim. I've seen the AH1S that's included in the JSBSim source distribution, but haven't had much luck finding any others online. All the ones I've found online are based on using Yasim as the FDM.
>
> Does anyone have any links to other JSBSim based helicopter models?
>
> Cheers