Re: [Flightgear-devel] small bug in YASim-gears
"Jon S. Berndt" wrote: > > As far as my memory serves, more than one year ago you had been offered > > a patch to JSBSim that implemented 'working' (TM) ground handling, but > > you rejected it because you thought you knew better. I still wonder, > > why you did so > Not exactly. Long story. Let's just say that your statement above is not > completely accurate, and not accurately complete. I consider your statement as a bit too vague, not precise enough to make it a satisfying statement Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] small bug in YASim-gears
> "Berndt, Jon S" wrote: > > > There are probably a couple of approaches at least. I've been looking > > hard at this over the past two years, and especially over the past month > > or two. > > As far as my memory serves, more than one year ago you had been offered > a patch to JSBSim that implemented 'working' (TM) ground handling, but > you rejected it because you thought you knew better. I still wonder, > why you did so > > Martin. Not exactly. Long story. Let's just say that your statement above is not completely accurate, and not accurately complete. Jon - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] small bug in YASim-gears
"Berndt, Jon S" wrote: > There are probably a couple of approaches at least. I've been looking > hard at this over the past two years, and especially over the past month > or two. As far as my memory serves, more than one year ago you had been offered a patch to JSBSim that implemented 'working' (TM) ground handling, but you rejected it because you thought you knew better. I still wonder, why you did so Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] small bug in YASim-gears
> The slipping is a numerics effect, not a modeling one. > The only way to get the gear jitter to produce a stable > solution over time is to push the coefficients *down*. But > that will produce more slipping, not less. The solution to > this problem is a rewrite of the static gear friction to use > a damped spring model around a "stuck" > point. But that's hard for the case of rolling gear. > > Andy There are probably a couple of approaches at least. I've been looking hard at this over the past two years, and especially over the past month or two. I've reached a point where the gear jitter for a parked aircraft has been *massively* reduced in tests, and I am very pleased. I have yet to try this while integrated with FlightGear. I may post some plots showing the reduction. I'm considering writing this approach up as an AIAA paper for the modeling and simulation technical conference next August. In any case, I'll be describing the approach later, perhaps in the next JSBSim newsletter. Jon - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] small bug in YASim-gears
Maik Justus wrote: > there is a minor bug in YASim in the gear code. The sfric and dfric > tags in the aircrafts .xml are ignored. I didn't even know those were tunable. Actual tires have a very narrow range of friction coefficients, except for special cases like "knobby" off-road tires or special surfaces like ice or water. Did I add this code? But I agree, taking those lines out looks right to me. > Maybe this helps to solve the slipping of parked aircrafts (by > adjusting sfric). Very unlikely. The slipping is a numerics effect, not a modeling one. The only way to get the gear jitter to produce a stable solution over time is to push the coefficients *down*. But that will produce more slipping, not less. The solution to this problem is a rewrite of the static gear friction to use a damped spring model around a "stuck" point. But that's hard for the case of rolling gear. Andy - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] small bug in YASim-gears
Hi, there is a minor bug in YASim in the gear code. The sfric and dfric tags in the aircrafts .xml are ignored. In the function void Airplane::solveGear() these values are always set to default values: // These are pretty generic gr->gear->setStaticFriction(0.8f); gr->gear->setDynamicFriction(0.7f); These three lines need to be deleted. Maybe this helps to solve the slipping of parked aircrafts (by adjusting sfric). If some aircrafts behave worse on ground: use these values .8 and .7 for sfric and dfric. Maik - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
