dave perry wrote: > Laurence Vanek wrote: > >> dave perry wrote: >> >> >>> Thanks Jon, >>> >>> I have not used jsbsim to model any aircraft in flight gear. So I was >>> not aware of where the adverse-aileron yaw was modeled in jsbsim. I was >>> only reacting to what seems to me a very exaggerated response. Perhaps >>> we need to consider such a scaling as default as the c172p also seems to >>> suffer from this exagferated yaw response. >>> >>> -Dave Perry >>> >>> >>> >>> >>> >> Dave - >> >> I tried the 0.3 scale factor. It does calm things down a bit for OSG >> version. >> >> >> > I also tried the 0.3 scale factor and agree it helps in the presence of > turbulence. But even w/o the scaling, if I make sure the turbulence is > really zero, the cvs SenecaII shows no oscillations all the way to the > runway using the AP to follow the LOC/GS. > >> I believe, however, that something else is going on with the A/P during >> ILS approach. I do not get the behavior you report on approach. The A/P >> begins to make large over corrections about one mile out, to the point >> where I need to disable the A/P & make the approach manually using the >> HSI. Not good if in poor IMC conditions with no visual refs. until at DH >> (~200 ft). >> >> > I get this behavior with any non zero turbulence even with the 0.3 > scaling. If I open the Weather menu and the Weather Conditions sub menu > and make sure all the turbulence tabs are slid all the way to the left > and then click on apply, the SenecaII settles down and follows the ILS > down to the runway. You cannot just use the fgrun advanced options > weather tab to zero the turbulence as it does not really zero the > turbulence. Make sure the property > /environment/turbulence/magnitude-norm is '0' (double). With fgrun > advanced weather turbulence set to zero, this property will still be > 0.00067 ... which is enough to cause the oscillations on my system. > > With the yasim pa24-250 and this value set to 0.33, and the Century III > AP which is nearly identical to the Altimatic IIIc, I do not get the > oscillations. I do get what fells like moderate turbulence. But the AP > takes you right down the GS and the LOC stays centered. The yoke is > moving in response to the bumps, but the needles stay centered and the > yaw response is quite realistic. > > The fact is that turbulence seems to be well modeled in yasim, and as > Jon Berndt indicated, it needs significant work in jsbsim. As Jon > indicated on the developers list, he has modified jsbsim to ignore the > turbulence setting (i.e. turns off turbulence modeling) in jsbsim cvs. > This has not been ported to fgfs. > > >> Perhaps this is another OSG vs. PLIB difference (although I cant see how)? >> >> > I don't have an osg version running right now. I agree that this is > unlikely to be the issue. Do any others see this issue with the > turbulence really zero? > >> Im running Linux Fedora 8. >> >> > I am running Fedora 7 on a Athlon XP 3200+ with 2G DDR ram and an Nvidia > GeForce 7800 GS OC. > > One other possible AP "tuning" issue. What frame rate are you getting? > The controller affective time constants vary with frame rate. My > testing is at frame rates that vary from about 50 to 70 fps. > > -Dave Perry > > Dave -
We may be comparing an apple with an orange here, concerning OSG & PLIB :-) As I stated I am building from OSG svn & FG cvs head. I find no fgrun in my install. I do have a " runfgfs.bat" that I do not use (looks like a windows file). Only these files in /usr/local/bin: al-info fgfs gl-info metar osgconv osgviewer yasim est-epsilon fgjs js_demo osgarchive osgversion terrasync I run FG (fgfs) directly from there. I set preferences in my ~/.fgfsrc file (things like --turbulence=0.0). I see that turbulence is also set in my ~/FlightGear-0.9/data/preferences.xml file, with different values at different elevations. Not sure how the .fgfsrc file & the preferences.xml reconcile. Maybe thats where we are different. Our system capabilities are similar, I have an Intel core 2 duo cpu, 2 G RAM, Nvidia 7600 GS (256 Megs of VRAM). I am throttled in my ~/.fgfsrc to give similar frames rates as you with no indication of stutter or hesitation (thank God, at last). My instincts tell me this is a controller issue relating to rate changes. Is there any possibility that that our ~/FlightGear-0.9/data/Aircraft/SenecaII/Systems/CENTURYIII.xml files have different controller parameters? Does PLIB version you are running use identical file? thanks for staying with me on this. ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Flightgear-users mailing list Flightgear-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-users
