Re: [Flightgear-devel] Paraglider model
On Saturday 28 February 2004 22:00, Gunnstein Lye wrote: On Saturday 28 February 2004 21:49, Gunnstein Lye wrote: On Saturday 28 February 2004 00:16, David Culp wrote: --aircraft=paraglider-jsbsim Just remember to change the paths of course. I have no experience in paragliders, so this model was just a guess. There is no paraglider included with flightgear as far as I can tell, but thanks for the other tips in your script. Correction: There is no paraglider in my version of flightgear. I just found a reference to your model on the flightmodel mailing list, I'll get flightgear 0.9.3 and try it out. I have tested paraglider-jsbsim now, and unfortunately I must say it flies like a plane, not like a paraglider. No offence, and I understand it's not easy to model when you don't have first-hand experience. When I push the stick to the right, it rolls like a plane, turning only slightly. I should have turned (yawed), first with a slight opposite roll, then with the correct roll, due to the pendulum effect. When I push the stick forwards, it will dive straight down like a plane. That's not possible in a paraglider, because of the distance between the center of gravity (the pilot) and the center of drag (the wing). The only way to dive is in a spiral dive. As soon as you stop spiraling, the dive stops (quite violently if you're rushing it, a spiral dive that's ended too quickly can end with a loop). I'm a bit concerned about the physics model of flightgear. Are there certain physical limitations built into the sim, that makes paraglider physics impossible to model? I'm thinking particularly about the pendulum effect. Of course, everything is possible when you have access to the source code, but you know what I mean... Or is this simply a matter of improving David's paraglider model? I'd like to know more about this before I spend any time coding... best regards, -- Gunnstein Lye Systems engineer [EMAIL PROTECTED] | eZ systems | ez.no ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Paraglider model
I'm a bit concerned about the physics model of flightgear. Are there certain physical limitations built into the sim, that makes paraglider physics impossible to model? I'm thinking particularly about the pendulum effect. Of course, everything is possible when you have access to the source code, but you know what I mean... Or is this simply a matter of improving David's paraglider model? There are several physics models for FlightGear. The main ones, JSBSim and YASim are, I believe, both capable of handling a paraglider. However, it is also possible that two of the other FDMs, LaRCSim and UIUC-Larcsim could be useful. Andy Ross (author of YASim) would be able to tell you about modeling a paraglider with YASim (which uses aircraft geometry and performance figures to model flight physics, to give a very broad description of that approach). The JSBSim model, to my knowledge, has not been used much, and is a rough, first-cut, model. I have a hunch that some tweaking will give you a better match for what you expect, and the first thing I'd change is the location of the CG and the aero reference point. If neither of the two (YASim and JSBSim) are appropriate for your expectations, you can code a special flight model in C within LaRCSim or perhaps set up a special model in UIUC-LaRCSim, although I am not very familiar with that. The point is, (and I say this from the point of view of someone who works with flight simulators every day) with the total set of four FDMs (flight dynamics model) you will have the ability to model a paraglider. But it will require some work and study on your part. Jon -- Project Coordinator JSBSim Flight Dynamics Model http://www.jsbsim.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
Jon Berndt wrote: If neither of the two (YASim and JSBSim) are appropriate for your expectations, you can code a special flight model in C within LaRCSim or perhaps set up a special model in UIUC-LaRCSim, although I am not very familiar with that. Right, but that's roughly equivalent to writing your own operating system to support your spreadsheet. If there's something that you cannot get from YASim or JSBSim, we'd prefer to improve them if we can, since other people might need the same functionality in the future. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
On Mon, 01 Mar 2004 07:46:16 -0500 David Megginson [EMAIL PROTECTED] wrote: Jon Berndt wrote: If neither of the two (YASim and JSBSim) are appropriate for your expectations, you can code a special flight model in C within LaRCSim or perhaps set up a special model in UIUC-LaRCSim, although I am not very familiar with that. Right, but that's roughly equivalent to writing your own operating system to support your spreadsheet. If there's something that you cannot get from YASim or JSBSim, we'd prefer to improve them if we can, since other people might need the same functionality in the future. David Good point. I was just pointing out that sometimes code changes are required for special needs, such as in the icing studies done using UIUC-Larcsim. I would think we ought to be able to model a paraglider within JSBSim as it is, currently, but I haven't had time to think about that much. Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
On Monday 01 March 2004 13:28, Jon Berndt wrote: I'm a bit concerned about the physics model of flightgear. Are there certain physical limitations built into the sim, that makes paraglider physics impossible to model? I'm thinking particularly about the pendulum effect. Of course, everything is possible when you have access to the source code, but you know what I mean... Or is this simply a matter of improving David's paraglider model? There are several physics models for FlightGear. The main ones, JSBSim and YASim are, I believe, both capable of handling a paraglider. However, it is also possible that two of the other FDMs, LaRCSim and UIUC-Larcsim could be useful. Andy Ross (author of YASim) would be able to tell you about modeling a paraglider with YASim (which uses aircraft geometry and performance figures to model flight physics, to give a very broad description of that approach). The JSBSim model, to my knowledge, has not been used much, and is a rough, first-cut, model. I have a hunch that some tweaking will give you a better match for what you expect, and the first thing I'd change is the location of the CG and the aero reference point. If neither of the two (YASim and JSBSim) are appropriate for your expectations, you can code a special flight model in C within LaRCSim or perhaps set up a special model in UIUC-LaRCSim, although I am not very familiar with that. The point is, (and I say this from the point of view of someone who works with flight simulators every day) with the total set of four FDMs (flight dynamics model) you will have the ability to model a paraglider. But it will require some work and study on your part. Thanks, I'll begin reading. I didn't expect this to be easy... =) But you've at least convinced me it's possible. Is this list the right forum for further discussion of the project, or should I go to the flightmodel or users list? best regards, -- Gunnstein Lye Systems engineer [EMAIL PROTECTED] | eZ systems | ez.no ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
Jon S Berndt wrote: Good point. I was just pointing out that sometimes code changes are required for special needs, such as in the icing studies done using UIUC-Larcsim. I would think we ought to be able to model a paraglider within JSBSim as it is, currently, but I haven't had time to think about that much. I've thought a lot about that, and in fact, I think that JSBSim would be able to do a fairly good job of simulating the effects of icing from a pilot's perspective with a few coefficients, using icing-severity (or perhaps rime-icing-severity, clear-icing-severity, and mixed-icing-severity) as inputs. The main effects are on overall lift and drag, and on the ability of the elevator to control pitch (though that also depends on flap position). All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
David Megginson wrote: Jon Berndt wrote: If neither of the two (YASim and JSBSim) are appropriate for your expectations, you can code a special flight model in C within LaRCSim or perhaps set up a special model in UIUC-LaRCSim, although I am not very familiar with that. Right, but that's roughly equivalent to writing your own operating system to support your spreadsheet. If there's something that you cannot get from YASim or JSBSim, we'd prefer to improve them if we can, since other people might need the same functionality in the future. There shouldn't be anything really weird about a paraglider. The big differences from airplane behavior are due to funny mass distribution: the engine acts near the c.g., but the lift and drag are rather high above it. My guess this is the source of the original complaint. In a YASim model, you could try playing with ballast tags to move the default weight distribution around. This holds so long as the parachute stays inflated. Handling the non-rigid behavior of a flopping chute is going to be hard, but that's more of a failure mode than a flight simulation issue. :) Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
On Monday 01 March 2004 18:19, Andy Ross wrote: There shouldn't be anything really weird about a paraglider. The big differences from airplane behavior are due to funny mass distribution: the engine acts near the c.g., but the lift and drag are rather high above it. My guess this is the source of the original complaint. In a YASim model, you could try playing with ballast tags to move the default weight distribution around. I will have a look at it, thanks. Do you think YASim is better for this purpose? I would think so, since as far as I understand it uses the shape of the wing to calculate lift and drag. This holds so long as the parachute stays inflated. Handling the non-rigid behavior of a flopping chute is going to be hard, but that's more of a failure mode than a flight simulation issue. :) Not necessarily. Controlled deflation is used as a way of controling the glider. Wingtip collapses (big ears) reduce the glide ratio, which can be useful for landings, and B-stall allows you to descend vertically in a controlled manner. If I have full programming control of the wing shape, then big ears can be at least partially simulated. The drag effect of the collapsed wing tips would be difficult, of course. best regards, -- Gunnstein Lye Systems engineer [EMAIL PROTECTED] | eZ systems | ez.no ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
Gunnstein Lye said: On Monday 01 March 2004 18:19, Andy Ross wrote: There shouldn't be anything really weird about a paraglider. The big differences from airplane behavior are due to funny mass distribution: the engine acts near the c.g., but the lift and drag are rather high above it. My guess this is the source of the original complaint. In a YASim model, you could try playing with ballast tags to move the default weight distribution around. I will have a look at it, thanks. Do you think YASim is better for this purpose? I would think so, since as far as I understand it uses the shape of the wing to calculate lift and drag. This holds so long as the parachute stays inflated. Handling the non-rigid behavior of a flopping chute is going to be hard, but that's more of a failure mode than a flight simulation issue. :) Not necessarily. Controlled deflation is used as a way of controling the glider. Wingtip collapses (big ears) reduce the glide ratio, which can be useful for landings, and B-stall allows you to descend vertically in a controlled manner. If I have full programming control of the wing shape, then big ears can be at least partially simulated. The drag effect of the collapsed wing tips would be difficult, of course. This was the issue that made me first think that YASim might actually not be a good choice for this application. Maybe others have an opinion on this before Gunnstein goes too far in one direction? Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
On Saturday 28 February 2004 00:16, David Culp wrote: Which FDM should I use? I'm thinking YASim but I'm not sure. Try running FlightGear with this script: #!/bin/bash cmdline= --fg-root=/home/dave/FlightGear/data --aircraft=paraglider-jsbsim --airport-id=KSFO --in-air --notrim --altitude=1000 --heading=280 --uBody=10 --wBody=8 --geometry=1024x768 --visibility-miles=10.0 --disable-sound --disable-clouds --disable-hud --start-date-gmt=2003:01:20:16:00:00 /home/dave/bin/fgfs $cmdline exit 0 Just remember to change the paths of course. I have no experience in paragliders, so this model was just a guess. There is no paraglider included with flightgear as far as I can tell, but thanks for the other tips in your script. (My question was not How to fly a paraglider in flightgear, but rather Would it be possible to model a paraglider in flightgear, and if so then how. best regards, -- Gunnstein Lye Systems engineer [EMAIL PROTECTED] | eZ systems | ez.no ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Paraglider model
Which FDM should I use? I'm thinking YASim but I'm not sure. Try running FlightGear with this script: #!/bin/bash cmdline= --fg-root=/home/dave/FlightGear/data --aircraft=paraglider-jsbsim --airport-id=KSFO --in-air --notrim --altitude=1000 --heading=280 --uBody=10 --wBody=8 --geometry=1024x768 --visibility-miles=10.0 --disable-sound --disable-clouds --disable-hud --start-date-gmt=2003:01:20:16:00:00 /home/dave/bin/fgfs $cmdline exit 0 Just remember to change the paths of course. I have no experience in paragliders, so this model was just a guess. Dave -- David Culp davidculp2[at]comcast.net ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
