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 $cmdline exit 0 Just remember to change the paths of course. I have no experience in paragliders, so this model was just a guess. There is no paraglider included with flightgear as far as I can tell, but thanks for the other tips in your script. (My question was not How to fly a paraglider in flightgear, but rather Would it be possible to model a paraglider in flightgear, and if so then how. best regards, -- Gunnstein Lye Systems engineer [EMAIL PROTECTED] | eZ systems | ez.no ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] Paraglider model
Hi all, (I'm new to this list, my apologies if this is the wrong forum for my questions.) I am a paraglider pilot who have been toying with the idea of modelling a paraglider in a flight simulator. I made a model in X-Plane first, but had to give up because X-Plane was too limited to be able to model the controls of a paraglider. (And because my model preferred spinning wildly out of control to actual flying...) I hope that the project can be done in FlightGear. At least it seams so, based on what I've read in the FAQs and docs. I have decent C++ programming experience, but only rudimentary 3D graphics knowledge. Just so that we are all clear on the subject: A lot of people confuse paragliders, parachutes and hanggliders. This is a paraglider (large image): http://mail.egroup.no/HLSK/Galleriet.nsf/0/E13D5199716A1920C1256BD6004D5F15/$FILE/EPSN0072.jpg In text, a paraglider is a ram-air inflated, flexible fabric wing, differing from a hangglider in that it has no spars, and from a square parachute in its higher aspect ratio and better glide angle. The pilot hangs suspended below the wing. It can be a glider or powered by a light engine. Do you think it can be done? Some challenges / more information: Take off and landing is usually done by foot, but a trike can be used (must be used for the simulation). Pendulum effect: The pilot, who weighs 10-18 times as much as the wing, is situated 8 meters below the wing. This means that the center of gravity is about 7 meters below the center of lift. Result: Extreme stability. You can let go of the controls in almost any situation, and the wing will soon fly straight. However, the pendulum effect can be used for various acrobatic manouvers: wing-overs, spiral dive, flat spin, SAT, etc., even loops. (The wing can never dive in a straight line, though.) If flightgear has a real physics engine, then this should be possible to simulate. Making a turn is radically different from a normal plane: A turn to the left is done by pulling down the trailing edge on the left side of the wing. This increases the lift on the left side, which first causes a roll to the right. However, the increased lift gives more drag, which causes a yaw force to the left, and as the wing turns the pendulum effect then causes a roll to the left. Weight shift is also used for turning. This counteracts the wrong roll at the beginning of a turn. The wing can be steered by weight shift alone, but the turn rate is less. Speed controll: To brake, pull down both sides of the wing equal amounts, thus increasing AOA. To speed up, there is a pulley system that pitches the wing profile down, decreasing AOA. Glide ratio control: To get a steeper glide, the wing tips can be folded backwards, which reduces wing area and aspect ratio. (This should be possible with flightgear too, I guess, by a little programming.) Other controlled wing deformations are also possible. Collapses: A paraglider will collapse if negative AOA occurs. This will be the most difficult property to model, I think. Collapses can be symmetric or assymetric, and of various sizes. A good simulation of collapse and recovery will be next to impossible, but it should be possible to do some crude approximations. Extreme terrain detail: To give a reasonably good flight experince the terrain detail must be a lot higher than in normal flight sims. Paragliders fly low and slow. Terrain resolution down to 1 meter, with textures down to maybe 10 pixels/meter, would be great. Also, trees would improve the feel a lot. This would of course require that only the closest terrain is modeled at this accuracy, and the areas that are further away use progressively less detail. Thermals and rigde lift for soaring would be great, is this supported? Some standard glider specs, for whom it may concern: Weight: 6 kg (wing) 10-15 kg (harness) 70-130 kg (with pilot) Speed: 20-50 (60) km/h Min. sink rate: 1 m/s (continous, can be 0 when flaring) Max. sink rate (in spiral dive): 20 m/s Best glide ratio: 7-9 Flat area: 25-35 sqm Flat wingspan: 11-13 m Flat aspect ratio: 4.5-6.5 Projected wingspan: 9-10 m Some other questions: Which FDM should I use? I'm thinking YASim but I'm not sure. Is the 3D-model mini-howto from 2002 still up to date? http://www.flightgear.org/Docs/fgfs-model-howto.html 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
