Re: [Flightgear-devel] YASim sliding helicopters bug
Jon S. Berndt jonsber...@comcast.net wrote: The wheel slip angle, for instance, varies wildly in JSBSim when no filtering or other compensation is used: [...] If the forces are ramped down to zero below some threshold, the dynamics improve greatly: This one shows the nose wheel _velocity_ over a timespan, the other three diagrams are showing the slip _angle_. To draw a reasonable conclusion it would be interesting to see the same measurand, say the slip velocity for all of the involved cases and not only for the nose wheel but for for the main gear as well. BUT, basically, I'd say this is not the point at all - these are interesting theoretical approaches to the problem, but for the 'real' user who's getting veered off the apron while he is simply doing a proper run-up at a windy location, this is entirely irrelevant. So, I have to ask you: what is proper tire/ground reaction? With a few lines of code I've reduced the ground reactions artifacts for the f-16 to very small levels - and I really haven't optimized them, yet. They could maybe be improved even more. So what is the cost/benefit to adding more code to do gear modeling more precisely? How much would the user really notice the difference? If we model the ground reactions to such high fidelity, should we then also model the aero characteristics using the Navier Stokes equations? There are always tradeoffs in simulation. In the case of JSBSim, I am hoping to model ground reactions so that the end user is satisfied with the response. I'll tell you that quite a bunch of users is unsatisfied but many of them take the current situation as given because they didn't know that a proper solution had been available. So, please correct me if my conclusion is at fault: 1.) The current, unfortunate state of tire/ground reactions in JSBSim, the fact that FlightGear's default aircraft is slipping over the tarmac is _NOT_ caused by the fact that there's nobody around wo knew better as alledged by this posting of 2007-11-22: Jon S. Berndt j...@hal-pc.org wrote: Maybe it would help to talk to the CDM guys instead of the FDM guys. http://www.google.com/search?q=car-dynamics-model http://www.google.com/search?q=car-dynamics-model+nascar I reckon the car-dynamics guys have a pretty good model of static friction and quasi-static rolling friction. After all, that is their raison d'tre. Whatever they've got is surely more than good enough for our purposes. Yes. I have looked at car dynamics casually. It would be nice to get one of those guys onboard. As far as I can tell, this posting had been written _after_ a patch to implement proper simulation of tire/ground reactions had been submitted to JSBSim. 2.) The current state is also _NOT_ a question of having a budget to pay someone doing rocket science - 2009-02-03: Jon S. Berndt jonsber...@comcast.net wrote: * Jon S. Berndt -- Tuesday 03 February 2009: It's a tough problem, [...[ Maybe we should hire a rocket scientist? :-] [...] With our *huge* budget? :-) NO, it's simply due to the fact that the FlightGear project decided to tie themselves to the development goals of JSBSim of which the 'project steering committee' decided against adding proper ground reaction code - which had been availale for free - for the sake of a smaller line count. FlightGear is suffering from a 'political' decision which has been made at JSBsim. which brings me back to - oh - my own words, written last month: Overall, I think some day the crowd should start making up their mind about wether relying on an externally maintained FDM is still the way to go. Developing a copy of the FDM _in_ FlightGear might return a much higher benefit at reduced effort. Just for the sake of completeness: Think of a scenario on the carrier, you're approaching the catapult from behind oh, too far, you're idling the engine, letting the wind blow you backwards while you're slowly manoeuvering your aircraft right into the catapult position solely by nose wheel steering. That's what I call proper simulation of tire ground reactions. FlightGear _could_ do that - it they didn't depend decisions made at JSBSim. Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net
Re: [Flightgear-devel] YASim sliding helicopters bug
From: Martin Spott [mailto:martin.sp...@mgras.net] This one shows the nose wheel _velocity_ over a timespan, the other three diagrams are showing the slip _angle_. To draw a reasonable conclusion it would be interesting to see the same measurand, say the slip velocity for all of the involved cases and not only for the nose wheel but for for the main gear as well. Oh, blast it. I printed the wrong chart. Well, it was very late ... :-( BUT, basically, I'd say this is not the point at all - these are interesting theoretical approaches to the problem, but for the 'real' user who's getting veered off the apron while he is simply doing a proper run-up at a windy location, this is entirely irrelevant. If this is truly the case, and if it is due to a gear modeling fidelity issue, then I agree. But, the kind of problem you describe would be a different issue. Since wind effects are only ramped in as velocity increases, the example you describe above should not happen with JSBSim. I'll tell you that quite a bunch of users is unsatisfied but many of them take the current situation as given because they didn't know that a proper solution had been available. It's vitally important that we see such problem reports. I've helped people tune their gear models successfully. If I don't see the error reports, I can't help. There is a bug reporting page at the JSBSim web site that should be used for this: http://sourceforge.net/tracker/?atid=119399group_id=19399func=browse You may have to try loading this page twice, since it seems SourceForge is having problems with its web site, periodically. Just for the sake of completeness: Think of a scenario on the carrier, you're approaching the catapult from behind oh, too far, you're idling the engine, letting the wind blow you backwards while you're slowly manoeuvering your aircraft right into the catapult position solely by nose wheel steering. That's what I call proper simulation of tire ground reactions. FlightGear _could_ do that - it they didn't depend decisions made at JSBSim. Cheers, Martin. JSBSim also does not (quite yet) do blade element modeling, so it's not easy to do a proper snap roll. Nor do we model multiple articulated landing gear struts. Nor do we ... As with any FDM, there are caveats and limitations. Your last paragraph is a good example of something I hadn't considered - that one would actually want to use the wind to do something while at almost zero velocity on the ground. I can look into that. Apart from that, do you have a specific proposal in mind? We should move this to a new thread. Jon -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
If this is truly the case, and if it is due to a gear modeling fidelity issue, then I agree. But, the kind of problem you describe would be a different issue. Since wind effects are only ramped in as velocity increases, the example you describe above should not happen with JSBSim. I just put the default Cessna at EDLN RWY 13 with parking brake applied, the wind is 11009KT. It took approx. three and a half minutes to let the aircraft slip backwards by the length of a main gear cover. Exactly. Given what was happening prior to the fix, this is pretty good. I think with some additional tweaking, this could be improved even more. But, I'm not sure what your point is, here? We should probably specify some requirements. How long should an aircraft stick at one spott? With what kind of tolerance? There is a long, huge, list of items that could be included in landing gear modeling and ground reactions. Anything from tire spin-up/wind-up to castering jitter, strut dynamics, etc. Obviously, we have to make some decisions about how far we want to go in modeling this or that feature. To this point, the focus has been on stability and control, aerodynamics, and such. I'm not opposed to improving the landing gear model. But, I'm not certain I hav e a good feel for how big of an annoyance this is among the larger user base. Consider this a solicitation for input! :-) My proposal is either to develop a copy of the FDM inside FlightGear and to focus primarily on FlightGear's needs (and to try getting a copy of the respective patch) or to have the changes applied to JSBSim's code tree and to later merge this into FlightGear. I don't think having a copy of JSBSim in FlightGear CVS for development purposes is a good idea. I do like the idea of more frequent synchs between JSBSim CVS and FlightGear CVS. But, JSBSim is used on a broader scale than FlightGear (OpenEaagles, for one, and many more ). I think that is a strength - not a weakness. I don't think it would be a good idea to split it up. You may not be aware of this, but the patch previously submitted years ago would not work at all any more. In fact, one of the problems with the patch was that even at that time, JSBSim was undergoing a restructuring. That made it especially difficult for the patch author. In order for the same approach to be applied at this time, one would have to essentially start over. Some of the parts might be applicable and usable, but I believe much of it would have to be rewritten. But, forget about the patch as it was. Even if we wanted to, there's no way it could be applied as-is, at this point. Also, your characterization of the lack of willingness to commit the changes as being due to a concern about line count is incorrect. That's a gross over-simplification, and implies a lack of concern or care about the work that I know went into creating the patch. Obviously, at some point, one has to weigh the amount of code added to address a specific problem. Is doubling the size of the codebase to address a single problem acceptable? Think of the implications for maintenance, comprehension, and documentation. There is a saying that the squeaky wheel gets the grease (although in this case maybe we need less grease!). If we could improve the gear model by adding two lines of code, I would have added that code years ago. If any fix doubles the size of the codebase, no, I'd be looking for a better way to address the problem. With anything in-between, it gets vague, and the rules become less strict. Let me say this, in closing. I've worked with some very heavy duty simulations over the past twenty+ years. Most (all?) of them are horribly incomprehensible for even experienced simulation engineers, let alone students. JSBSim has been complimented in the past because it is straightforward and fairly easy to understand the code, at least as far as the basic stuff goes. Some design choices have been made so far that not everyone agrees with. One of those areas is that landing gear is modeled only with enough fidelity to make it appear to users that the aircraft drives in a realistic manner. Where that is not the case, I need to see specific examples so we can address that. If we can address it with a small amount of code as is currently the case, that's an acceptable solution, in my eyes. If it turns out that we really cannot address any problems without a more serious solution, and the ground reactions are seen as plain-and-simple not plausible, and there is a huge outcry that this should be fixed because it is intolerable, then maybe we'd revisit a modification to our integation scheme to use RK4 and simultaneous solution of a set of equations. That would involve a long and painful surgery, though. It's not an easy thing to manage such a project, with some competing interests, and to keep users and developers happy and feeling good about their contributions
Re: [Flightgear-devel] YASim sliding helicopters bug
Jon S. Berndt jonsber...@comcast.net wrote: From: Martin Spott [mailto:martin.sp...@mgras.net] BUT, basically, I'd say this is not the point at all - these are interesting theoretical approaches to the problem, but for the 'real' user who's getting veered off the apron while he is simply doing a proper run-up at a windy location, this is entirely irrelevant. If this is truly the case, and if it is due to a gear modeling fidelity issue, then I agree. But, the kind of problem you describe would be a different issue. Since wind effects are only ramped in as velocity increases, the example you describe above should not happen with JSBSim. I just put the default Cessna at EDLN RWY 13 with parking brake applied, the wind is 11009KT. It took approx. three and a half minutes to let the aircraft slip backwards by the length of a main gear cover. And, _no_, don't even think of it ;-)) it's definitely _not_ a proper solution to work around such a case by clamping the aircaft to a fixed position as long the brakes are applied :-) Just for the sake of completeness: Think of a scenario on the carrier, you're approaching the catapult from behind oh, too far, you're idling the engine, letting the wind blow you backwards while you're slowly manoeuvering your aircraft right into the catapult position solely by nose wheel steering. That's what I call proper simulation of tire ground reactions. FlightGear _could_ do that - it they didn't depend decisions made at JSBSim. JSBSim also does not (quite yet) do blade element modeling, so it's not easy to do a proper snap roll. Nor do we model multiple articulated landing gear struts. Nor do we ... As far as I can tell, nobody's asking JSBSim to do blade element modeling - to my opinion this is mostly a buzzword. Being able to fly an aircraft by table lookups derived from real life flight test data is quite an appealing approach. Instead, I'm talking about what I'd call a 'misfeature' to which a proper fix had already been submitted (years ago) and I'm convinced that you may apply as many workarounds, filters, whatever you like to the current gear/ground simulation, there'll be always a relevant corner case which remains uncaught as long as you stick to the current approach of gear modelling. I know that the patch which had been submitted to you uses a fundamentally different approach at modelling the tire/surface reactions and forces, but to my understanding this is by far the best way to get rid of the perpetually arising discussions about ground handling. Apart from that, do you have a specific proposal in mind? My proposal is either to develop a copy of the FDM inside FlightGear and to focus primarily on FlightGear's needs (and to try getting a copy of the respective patch) or to have the changes applied to JSBSim's code tree and to later merge this into FlightGear. We should move this to a new thread. Feel free to do that. From my point everything's been said - the sole purpose why I've actually been jumping into this discussion has been to dissect and/or explain the background which has led to the current situation wrt. gear/tire/surface modelling in JSBSim. I actually knew about it for a long time but I wanted to hear both sides. Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
Jon S. Berndt jonsber...@comcast.net wrote: Well, just very few years ago 'we' (TM) had a patch in our budget that would have allowed JSBSim to do excellent simulation of a tire's contact area. Some of us have seen with their own eyes that the guy (the submitter of the respective patch) obviously knows about how to properly deal with the topic. Can you give me some more information about the specifics of the patch you are talking about? Feel free to contact me via email, if needed. If you are referring to the patch I think you are referring to, I certainly agree that the guy knows what he is doing with respect to the solution of such a difficult modeling problem. If I recall correctly (and I'm not certain that I do - particularly today because I am home with a really nasty fever and cold) there was a lot of additional overhead and infrastructure that was needed to make it work, and it was a pretty large alteration of the existing JSBSim codebase. I may be recalling the wrong modification. Well, this matches with my memories about the respective patch - as far as I can tell there was just this single approach at contributing a rewrite of the tire/ground reaction feature to JSBSim. If I summarize correctly then we a) still don't have a single FDM in FlightGear that does proper simulation of this feature and b) it looks like major changes are required to get it going. To put it a bit provoking (no personal offense intended!) for the sake of getting the status right, this looks to me that we're never going to have this feature of proper tire/ground reaction simulation in FlightGear simply because the involved folks prefer to play around with smaller, 'approximative' workarounds forever instead of biting the bullet just once. Right ? Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
To put it a bit provoking (no personal offense intended!) for the sake of getting the status right, this looks to me that we're never going to have this feature of proper tire/ground reaction simulation in FlightGear simply because the involved folks prefer to play around with smaller, 'approximative' workarounds forever instead of biting the bullet just once. Right ? Cheers, Martin. Not quite. I'll write more this evening. Off to work, now. JB -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
Em Qui, 2009-02-05 às 11:34 +, Martin Spott escreveu: To put it a bit provoking (no personal offense intended!) for the sake of getting the status right, this looks to me that we're never going to have this feature of proper tire/ground reaction simulation in FlightGear simply because the involved folks prefer to play around with smaller, 'approximative' workarounds forever instead of biting the bullet just once. Right ? As far as I know, this spring and damper around a stuck point is the method used even on race simulators. The best way to explain its principle is to compare it to the flexibility of the wheel rubber and the gear structure itself. After all fixed body physics don't really exist. Right now my code uses a 1cm long spring, it is not that much and I believe it could be reduced even more. To really give the best result with every plane, more information on the gear, and changes to the aircraft definition format, would be required. What I think may be acceptable. The bigger problem with this approach is the Carrier, but I don't see why it shouldn't work. Although I haven't got it working so far. I hope this can be solved soon, so I can send the patch as a proof of concept. IMHO it is working pretty well on land. Diogo -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
* Diogo Kastrup -- Thursday 05 February 2009: The bigger problem with this approach is the Carrier, but I don't see why it shouldn't work. Although I haven't got it working so far. I hope this can be solved soon, so I can send the patch as a proof of concept. IMHO it is working pretty well on land. Excellent! And even if it doesn't work that well on the carrier, that's still a whole lot better than now, where it doesn't work well on either the carrier or on land. Carrier decks only cover a small part of the world, too. ;-) m. -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
To put it a bit provoking (no personal offense intended!) for the sake of getting the status right, this looks to me that we're never going to have this feature of proper tire/ground reaction simulation in FlightGear simply because the involved folks prefer to play around with smaller, 'approximative' workarounds forever instead of biting the bullet just once. Right ? Cheers, Martin. Not quite. I'll write more this evening. Off to work, now. JB OK. The answer to your question (which is really more like an assertion disguised as a question ;^) follows below. There are many kinds of simulations, that all address particular needs. Are we talking about a training simulator, or an engineering simulator, or an entertainment simulator, or ... ? In my day job I work on a sophisticated launch vehicle simulator. For our specific uses, we are not overly concerned about the exact dynamics of the vehicle during its flight, but we are concerned that the launch vehicle arrives at a particular point in time and space with a particular state, so we can test the abort systems. The level of fidelity for the various subsystem models should be driven by the purpose or intended use of the simulator. In the case of ground reactions for JSBSim, from the start we noticed that it is difficult to model ground reactions when at rest or at small velocity. The wheel slip angle, for instance, varies wildly in JSBSim when no filtering or other compensation is used: http://jsbsim.sourceforge.net/NoFiltering.png If the output is filtered at the frame rate, the slip angle doesn't oscillate quite so fast, but it's still bad: http://jsbsim.sourceforge.net/FilteringOn.png If the forces are ramped down to zero below some threshold, the dynamics improve greatly: http://jsbsim.sourceforge.net/FilterAndRamp.png Finally, adjusting the longitudinal and lateral ramp thresholds can improve response even more. Note the scale on the left side of the plot: http://jsbsim.sourceforge.net/FilterAndRamp2.png So, I have to ask you: what is proper tire/ground reaction? With a few lines of code I've reduced the ground reactions artifacts for the f-16 to very small levels - and I really haven't optimized them, yet. They could maybe be improved even more. So what is the cost/benefit to adding more code to do gear modeling more precisely? How much would the user really notice the difference? If we model the ground reactions to such high fidelity, should we then also model the aero characteristics using the Navier Stokes equations? There are always tradeoffs in simulation. In the case of JSBSim, I am hoping to model ground reactions so that the end user is satisfied with the response. There's not a simple answer to this question. There is definitely a need for more documentation on our gear modeling, and perhaps some software tools for people to use when creating the landing gear portion of a JSBSim configuration file. Jon -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Maik Justus wrote: Hi, Melchior FRANZ schrieb am 02.02.2009 18:43: Ever since helicopter support was added to the YASim FDM there's an annoying bug: even when parked, with rotor off and braked, helicopters slide happily around on the ground. some time ago I dug into this problem and tried to fix it. My idea was, to check, if the movement is smaller than a very small number epsilon, and if yes, set the movement to zero. The movement need to be measured against the ground, which could be the carrier. This should fix the sliding on ground. But the fix didn't work, because there is no very small movement. All gears I was looking at (only a very small number) were oscillating with a frequency of 60Hz. The amplitude was much to large to neglect. I was not able, to kill these oscillations. The cause, why you can see this problem mainly on helicopters, are some simplifications in the rotor calculations, which cause the rotors to generate a very small force, even when not rotating. Non rotor aircrafts should show the same problem, if some wind is blowing. Maik Maybe then the solution is to try the epsilon trick with the rotors/wings and not the gear. Josh -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* LeeE -- Tuesday 03 February 2009: Have the people having bad problems with this tried increasing the values for the sfric dfric gear sub-elements? Yes, of course. I really, really hope that I haven't forgotton about other, similarly obvious things in the many hours that I tried to fix the problem, or discussed it with Andy. But one never knows. :-) m. -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
On Tuesday 03 February 2009, Melchior FRANZ wrote: * LeeE -- Tuesday 03 February 2009: Have the people having bad problems with this tried increasing the values for the sfric dfric gear sub-elements? Yes, of course. I really, really hope that I haven't forgotton about other, similarly obvious things in the many hours that I tried to fix the problem, or discussed it with Andy. But one never knows. :-) m. I just had a look at the latest version of the bo105 that I have here and the sfric is set to 0.5 and the dfric to 0.4, which are both lower than default values of 0.8 0.7. It's possible that these values have been changed since I last updated but you might want to check these. Something else you might not have tried is to include a series of gear elements along the length of each of the skids, instead of just one at each end, and then slightly raise the end gear elements so that they only touch down once the intermediate gear elements have compressed or when the aircraft pitches. You'll need to adjust the spring and compression values for the intermediate gear elements. If the end-skid elements only come in to play on heavy landings, or while pitching, you could keep those pretty stiff. LeeE -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* LeeE -- Tuesday 03 February 2009: Do you still get problems if you set the windspeed to zero? Yes. With pretty much the same sliding speed. m. -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* Jon S. Berndt -- Tuesday 03 February 2009: It's a tough problem, [...[ Maybe we should hire a rocket scientist? :-] m. -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* LeeE -- Tuesday 03 February 2009: I just had a look at the latest version of the bo105 that I have here and the sfric is set to 0.5 and the dfric to 0.4, which are both lower than default values of 0.8 0.7. I know. But I also tried 1.0 for both (the maximum), and it had no effect. Other changes didn't have the desired effect either, such as using gear instead of skid -- to encourage longitudinal movement and discourage lateral one -- something that one would expect from skids. But with all the sliding there's not much to see here, so I left the old values. Something else you might not have tried is to include a series of gear elements along the length of each of the skids, instead of just one at each end [...] OK, that's something I hadn't tried yet. I'll do that. m. -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
On Tuesday 03 February 2009, Melchior FRANZ wrote: * LeeE -- Tuesday 03 February 2009: Do you still get problems if you set the windspeed to zero? Yes. With pretty much the same sliding speed. m. That's interesting, and a bit at odds with what I've experienced. LeeE -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
On Tuesday 03 February 2009, Melchior FRANZ wrote: * LeeE -- Tuesday 03 February 2009: Have the people having bad problems with this tried increasing the values for the sfric dfric gear sub-elements? Yes, of course. I really, really hope that I haven't forgotton about other, similarly obvious things in the many hours that I tried to fix the problem, or discussed it with Andy. But one never knows. :-) m. Do you still get problems if you set the windspeed to zero? LeeE -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* Jon S. Berndt -- Tuesday 03 February 2009: It's a tough problem, [...[ Maybe we should hire a rocket scientist? :-] m. With our *huge* budget? :-) JB -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
On Tue, Feb 3, 2009 at 10:50 AM, Jon S. Berndt wrote: * Jon S. Berndt -- Tuesday 03 February 2009: It's a tough problem, [...[ Maybe we should hire a rocket scientist? :-] m. With our *huge* budget? :-) I have noticed a measurable uptick in FlightGear interest since MS announced that they have laid off their entire simulator staff. I sincerely believe there is going to be more and more opportunities available for individual FlightGear consultants to help companies push forward with their FlightGear related projects. There have been a couple things over the past years that have come across my plate which I have snatched up. Recently there have been a few more things come through that I just don't have time for. In some cases I've tried to identify individual developers that I know have a matching skill set and contacted them directly. And in the case of this recent NASA project, when they had trouble finding a specific individual, I put a call out to the entire devel team list. Unfortunately (for us) with this NASA project I recently posted about, they found an internal person after one of their other projects was cut. But I'm sure there's a NASA employee that is current exhaling a big sigh of relief. :-) So I believe this subject is going to come up more and more often where any number of companies or research groups will determine that FlightGear is their best way forward and are willing to hire individual developers (probably as a temporary consultant, but maybe sometimes as full time employees) to fill in functionality gaps, fix bugs that are show stoppers to them, or interface with their existing software or hardware. I think 2009 will be a very exciting year for the FlightGear project. Curt. -- Curtis Olson: http://baron.flightgear.org/~curt/ -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
Jon S. Berndt jonsber...@comcast.net wrote: * Jon S. Berndt -- Tuesday 03 February 2009: It's a tough problem, [...[ Maybe we should hire a rocket scientist? :-] With our *huge* budget? :-) I may also remind of this related posting, written late in November 2007: Subject: Re: [Flightgear-devel] slip angle Jon S. Berndt j...@hal-pc.org wrote: Yes. I have looked at car dynamics casually. It would be nice to get one of those guys onboard. Well, just very few years ago 'we' (TM) had a patch in our budget that would have allowed JSBSim to do excellent simulation of a tire's contact area. Some of us have seen with their own eyes that the guy (the submitter of the respective patch) obviously knows about how to properly deal with the topic. Nevertheless we have not yet seen any public statement why the patch finally never made it into JSBSim and why FlightGear is therefore still suffering from the mentioned issues. I'd be happy to know a little bit more about why the patch had been rejected. In which way does the development style have to be changed in order to allow for such contribution ? Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Hi, Melchior FRANZ schrieb am 02.02.2009 18:43: Ever since helicopter support was added to the YASim FDM there's an annoying bug: even when parked, with rotor off and braked, helicopters slide happily around on the ground. some time ago I dug into this problem and tried to fix it. My idea was, to check, if the movement is smaller than a very small number epsilon, and if yes, set the movement to zero. The movement need to be measured against the ground, which could be the carrier. This should fix the sliding on ground. But the fix didn't work, because there is no very small movement. All gears I was looking at (only a very small number) were oscillating with a frequency of 60Hz. The amplitude was much to large to neglect. I was not able, to kill these oscillations. The cause, why you can see this problem mainly on helicopters, are some simplifications in the rotor calculations, which cause the rotors to generate a very small force, even when not rotating. Non rotor aircrafts should show the same problem, if some wind is blowing. Maik -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
some time ago I dug into this problem and tried to fix it. My idea was, to check, if the movement is smaller than a very small number epsilon, and if yes, set the movement to zero. The movement need to be measured against the ground, which could be the carrier. This should fix the sliding on ground. But the fix didn't work, because there is no very small movement. All gears I was looking at (only a very small number) were oscillating with a frequency of 60Hz. The amplitude was much to large to neglect. I was not able, to kill these oscillations. ... Maik This is very much along the lines of the approach I took with JSBSim. It was pretty obvious looking at the data (and intuitive given the problem itself) that the oscillation was taking place at the frame rate. But, putting in the filter was not enough by itself. Ramping out the ground plane gear forces at low velocity was also added. As well, *all* external forces (wind, etc.) is nulled out when the aircraft is at rest, and ramped in at a particular velocity, as long as the aircraft is on the ground. Jon -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug
Well, just very few years ago 'we' (TM) had a patch in our budget that would have allowed JSBSim to do excellent simulation of a tire's contact area. Some of us have seen with their own eyes that the guy (the submitter of the respective patch) obviously knows about how to properly deal with the topic. Nevertheless we have not yet seen any public statement why the patch finally never made it into JSBSim and why FlightGear is therefore still suffering from the mentioned issues. I'd be happy to know a little bit more about why the patch had been rejected. In which way does the development style have to be changed in order to allow for such contribution ? Cheers, Martin. Can you give me some more information about the specifics of the patch you are talking about? Feel free to contact me via email, if needed. If you are referring to the patch I think you are referring to, I certainly agree that the guy knows what he is doing with respect to the solution of such a difficult modeling problem. If I recall correctly (and I'm not certain that I do - particularly today because I am home with a really nasty fever and cold) there was a lot of additional overhead and infrastructure that was needed to make it work, and it was a pretty large alteration of the existing JSBSim codebase. I may be recalling the wrong modification. Jon -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Ever since helicopter support was added to the YASim FDM there's an annoying bug: even when parked, with rotor off and braked, helicopters slide happily around on the ground. Andy knows about it and explained why it happens, but claims that there's nothing to be fixed in the FDM code. Instead, he suggested to place masses and weights appropriately in the FDM config. Then the sliding would stop. I've spent many hours on that, without success. And I even doubt that is works: after all, there are adjustable pilot and passenger weights, different loads (MG, missiles, etc.), changing fuel level. So, how could one find a working mass distribution for all these different states?! I've tried a lot of other things -- most of it were ugly hacks. Different gear (skid) parameters, masses that would only get activated when the helicopter is parked, thrusters that would counter any movement, thrusters that would press the helicopter down. Nothing worked. (Oh, and I tried to fix the gear code itself -- without success. Not that Andy would accept a patch, I guess.) A few days ago I found the best remedy so far: a thruster that *lifts* the helicopter when it's parked. This stabilizes it a lot, though when the rotor spins, all the sliding is back. Has anyone ever found a solution to the gear bug? Something that's not a hack? (I'd accept an alternative FDM as well. What about JSBSIM? :-) m. -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Hardly. I can adjust static masses, but not all the additional loads. They just are where they are in real life. More or less. That's why I gave up this idea real fast -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Hello, I have posted on this list before but I guess I never introduced myself. I am a Brazilian system analyst with experience in C programming and a little C++. I have no real pilot experience and no physics formation. I have a crude patch to improve gear friction in yasim using the method cited by Andy if I am not mistaken. It uses a spring and damper around a stuck point to simulate the static friction. This patch started just for fun to see if I could help this sliding problem, that annoyed me a lot since I love flying helicopters. The code isn't very clean and it still have a problem with moving platforms. The problem is that I have to keep the stuck point moving with the carrier but the carrier update is not on the same frequency than the FDM update. I have tried to extrapolate the carrier position using it's speed and the dt but there was too much jitter, maybe because errors in the dt? I couldn't find the source. It is working well on land though. Maybe if someone with a better insight on the internals could give me a hint on how I could get the updated carrier position from the FDM, then I could finish this patch. If someone wants to try it I can try to clean it a little bit and send the patch. I will just need some time though since the patch is abandoned in my local copy and I will have to refresh my memory. At least it is working with the latest CVS revision. Regards, Diogo Em Seg, 2009-02-02 às 18:43 +0100, Melchior FRANZ escreveu: Ever since helicopter support was added to the YASim FDM there's an annoying bug: even when parked, with rotor off and braked, helicopters slide happily around on the ground. Andy knows about it and explained why it happens, but claims that there's nothing to be fixed in the FDM code. Instead, he suggested to place masses and weights appropriately in the FDM config. Then the sliding would stop. I've spent many hours on that, without success. And I even doubt that is works: after all, there are adjustable pilot and passenger weights, different loads (MG, missiles, etc.), changing fuel level. So, how could one find a working mass distribution for all these different states?! I've tried a lot of other things -- most of it were ugly hacks. Different gear (skid) parameters, masses that would only get activated when the helicopter is parked, thrusters that would counter any movement, thrusters that would press the helicopter down. Nothing worked. (Oh, and I tried to fix the gear code itself -- without success. Not that Andy would accept a patch, I guess.) A few days ago I found the best remedy so far: a thruster that *lifts* the helicopter when it's parked. This stabilizes it a lot, though when the rotor spins, all the sliding is back. Has anyone ever found a solution to the gear bug? Something that's not a hack? (I'd accept an alternative FDM as well. What about JSBSIM? :-) m. -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* Diogo Kastrup -- Monday 02 February 2009: This patch started just for fun to see if I could help this sliding problem, that annoyed me a lot since I love flying helicopters. A true fix would indeed be nice. The problem is that I have to keep the stuck point moving with the carrier but the carrier update is not on the same frequency than the FDM update. A dependency on the AI update rate would probably not be very welcomed. BTW: I just tried my lift-thruster hack on the Nimitz, and it didn't work very well there, either. :-/ Didn't JSBSim have a similar problem, and fix it there? By using a different method for friction calculation at very low speeds? You should be able to get the relative movement to the underground (no matter if it's solid ground or a moving carrier) from the ground cache. Not that I've any experience with that. m. -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Em Seg, 2009-02-02 às 20:02 +0100, Melchior FRANZ escreveu: The problem is that I have to keep the stuck point moving with the carrier but the carrier update is not on the same frequency than the FDM update. A dependency on the AI update rate would probably not be very welcomed. BTW: I just tried my lift-thruster hack on the Nimitz, and it didn't work very well there, either. :-/ Didn't JSBSim have a similar problem, and fix it there? By using a different method for friction calculation at very low speeds? You should be able to get the relative movement to the underground (no matter if it's solid ground or a moving carrier) from the ground cache. Not that I've any experience with that. If I'm not mistaken, the launchbar code takes the position from the ground cache, but the carrier position is not updated there neither. So it does extrapolation anyway. I tried the same thing already but there was much jitter also. I guess the launchbar isn't that sensible about the jitter, but the friction spring is only 1cm long and the jitter is bigger than that. So the dynamic friction kicks in and the sliding comes back. Diogo -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Melchior FRANZ mfr...@aon.at wrote: Didn't JSBSim have a similar problem, and fix it there? No, unfortunately not The visible effect has been reduced quite efficiently, but the underlying problem is still there. I know of just one single FDM for FlightGear that does proper modelling of ground friction, but it's not (yet) ready for prime time, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Melchior FRANZ wrote: Ever since helicopter support was added to the YASim FDM there's an annoying bug: even when parked, with rotor off and braked, helicopters slide happily around on the ground. Andy knows about it and explained why it happens, but claims that there's nothing to be fixed in the FDM code. Instead, he suggested to place masses and weights appropriately in the FDM config. Then the sliding would stop. I've spent many hours on that, without success. And I even doubt that is works: after all, there are adjustable pilot and passenger weights, different loads (MG, missiles, etc.), changing fuel level. So, how could one find a working mass distribution for all these different states?! I've tried a lot of other things -- most of it were ugly hacks. Different gear (skid) parameters, masses that would only get activated when the helicopter is parked, thrusters that would counter any movement, thrusters that would press the helicopter down. Nothing worked. (Oh, and I tried to fix the gear code itself -- without success. Not that Andy would accept a patch, I guess.) A few days ago I found the best remedy so far: a thruster that *lifts* the helicopter when it's parked. This stabilizes it a lot, though when the rotor spins, all the sliding is back. Has anyone ever found a solution to the gear bug? Something that's not a hack? (I'd accept an alternative FDM as well. What about JSBSIM? :-) m. Hi Melchior... and Andy I don't know about helos, but preventing an aicraft to slip on the carrier is *a real PITA*. The way to fix this leads to unrealistic smooth gear struts, not to talk about the time consumed. Well it may not be a bug in YASim, but actually it's a real unfriendly feature. I guess I wont do better than Melchior with the gear code, so I hereby add a friendly feature preventing aircraft to slip to the YASim wishlist. Huge tanks in advance, Alexis -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
Hello, Has anyone ever found a solution to the gear bug? Something that's not a hack? (I'd accept an alternative FDM as well. What about JSBSIM? :-) Yeah, why not JSBSim? Would be a fine alternative :-) Well, I noticed today that putting all ballast at one spot helps a lot. Means: all ballast used has the same coordinates. I did try this on the ec135 and ec130 and it seems to work good. But it don't work on the bo105 due to the named things by m. I guess. And it doesn't prevent from sliding after getting the rotors turning which is quite unrealistic. HHS -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
* Heiko Schulz -- Monday 02 February 2009: Well, I noticed today that putting all ballast at one spot helps a lot. Means: all ballast used has the same coordinates. [...] But it don't work on the bo105 due to the named things by m. I guess. Hardly. I can adjust static masses, but not all the additional loads. They just are where they are in real life. More or less. BTW: another hack that I had tried: to virtually tie the bo105 down with ropes, using Maik's aerotow/anchor system. Didn't work either, of course. :-) m. -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YASim sliding helicopters bug (+ ugly fix)
In JSBSim we got around it differently by filtering the gear forces (and other parameters) at the frame rate, which significantly reduces the jitter, and by also attenuating gear forces (correctly) at low velocity. This requires some tuning on a per-aircraft basis, but when given the proper attention, the results are very, very solid. It's not the only solution - or even the best one - but it works pretty well. Jon We have noticed another problem, which I have found to be a little bit humorous. If the aircraft is resting on its landing gear either nose down or nose up, it will roll one way or the other (up or down-hill). I know basically what's causing it, but haven't had time to track down the problem code, yet. JB -- Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
