--- Michael Selig <[EMAIL PROTECTED]> wrote: > At 4/12/02, you wrote: > >Michael Selig writes: > > > > > OK, I think I am just getting confused trying > to decipher *all* parts of > > > what you are doing in those files. It's like a > puzzle to me. > > > >The JSBSim files can be overwhelming -- they were > far worse for me, > >with no background in aerodynamics (or even > physics, for that matter) > >-- but the top-level arrangement is very simple and > similar to UIUC's. > >There are six top-level sections: > > > >1. METRICS (= UIUC "geometry" and "mass") > >2. UNDERCARRIAGE (= UIUC "gear" ??) > >3. PROPULSION (= UIUC "engine") > >4. FLIGHT_CONTROL (= UIUC "controlSurface") > >5. AERODYNAMICS (= UIUC "CL", "CD", etc.) > >6. OUTPUT (= UIUC "record") > > > >The AERODYNAMICS section contains six AXIS > subsections: LIFT, DRAG, > >SIDE, ROLL, PITCH, and YAW. Inside each of those > subsections are > >definitions for all the coefficients that act on > that axis. JSBSim > >seems more complicated only because it lets you > define new > >coefficients are runtime, rather than hardcoding > them in the C++. For > >example, where UIUC has simply > > > > CL CL_adot 1.7 # [/rad] FG > c172_aero.c > > > >JSBSim has > > > > <COEFFICIENT NAME="CLadot" TYPE="VALUE"> > > Lift_due_to_alpha_rate > > FG_QBAR|FG_WINGAREA|FG_ALPHADOT|FG_CI2VEL > > 1.7 > > </COEFFICIENT> > > > >The JSBSim C++ code doesn't actually know anything > about CLadot (we > >could have called it "CLfoobar" if we had wanted), > but the effect is > >the same -- both examples contain exactly the same > aerodynamic > >information. > > > > > >All the best, > > > > > >David > > > Ahhhhh ... thank you ... I see it now. The fact > that "CLadot" gets > included on the fly is pretty neat. As our list of > hard-coded coefficient > capabilities grows longer and longer w/ the uiuc_ > code, we've been seeing a > need for something like this. > > I now see the need to include the foobar string > "FG_QBAR|FG_WINGAREA|FG_ALPHADOT|FG_CI2VEL" together > w/ XYZfoobar? It > includes all the things multiplying the foobar coef. > > For the Pioneer nonlinear model, we have 1605 lines > of lookup data: > [297] > m-selig@qtee:/home/m-seligSim/work/fgfsbase-0.7.9/Aircraft/UIUC/pioneerUAV-v2-nl> > > wc -l *.dat > 210 aircraft.dat > 28 CDfa.dat > 244 CDfade.dat > 155 Clfada.dat > 28 CLfa.dat > 244 CLfade.dat > 28 Cmfa.dat > 201 Cmfade.dat > 197 Cnfada.dat > 254 Cnfbetadr.dat > 16 CYfbetadr.dat > 1605 total > > For our Twin Otter we have 14,000 lines of nonlinear > aero data: > [331] > m-selig@qtee:/home/m-seligSim/work/uiuc-aircraft/011112-TwinOtterNonlinWithFlaps> > > wc -l *.dat > 236 aircraft.dat > 298 Clfabetaf0.dat > 298 Clfabetaf20.dat > 298 Clfabetaf40.dat > 326 Clfadaf0.dat > 326 Clfadaf20.dat > 326 Clfadaf40.dat > 126 Clfadrf0.dat > 226 Clfapf0.dat > 226 Clfapf20.dat > 226 Clfapf40.dat > 154 Clfarf0.dat > 154 Clfarf40.dat > 276 Cmfabetaf0.dat > 276 Cmfabetaf20.dat > 276 Cmfabetaf40.dat > 151 Cmfadef0.dat > 151 Cmfadef20.dat > 151 Cmfadef40.dat > 155 Cmfaqf0.dat > 155 Cmfaqf20.dat > 155 Cmfaqf40.dat > 276 Cnfabetaf0.dat > 276 Cnfabetaf20.dat > 276 Cnfabetaf40.dat > 326 Cnfadaf0.dat > 326 Cnfadaf20.dat > 326 Cnfadaf40.dat > 126 Cnfadrf0.dat > 226 Cnfapf0.dat > 226 Cnfapf20.dat > 226 Cnfapf40.dat > 154 Cnfarf0.dat > 154 Cnfarf40.dat > 276 CXfabetaf0.dat > 275 CXfabetaf20.dat > 276 CXfabetaf40.dat > 201 CXfadef0.dat > 201 CXfadef20.dat > 201 CXfadef40.dat > 155 CXfaqf0.dat > 155 CXfaqf20.dat > 155 CXfaqf40.dat > 276 CYfabetaf0.dat > 276 CYfabetaf20.dat > 276 CYfabetaf40.dat > 326 CYfadaf0.dat > 326 CYfadaf20.dat > 326 CYfadaf40.dat > 126 CYfadrf0.dat > 226 CYfapf0.dat > 226 CYfapf20.dat > 226 CYfapf40.dat > 154 CYfarf0.dat > 154 CYfarf40.dat > 276 CZfabetaf0.dat > 276 CZfabetaf20.dat > 276 CZfabetaf40.dat > 151 CZfadef0.dat > 151 CZfadef20.dat > 151 CZfadef40.dat > 155 CZfaqf0.dat > 155 CZfaqf20.dat > 155 CZfaqf40.dat > 14443 total > > The point - are plans underway to have JSBSim > include nonlinear aero data > via path/filename, rather than including all that > nonlinear data in the > single xml file?
We've not given any consideration to this -- though I can see how it might be advantageous. > > Also, does JSBSim accept aero data in the body axes > as well as the > stability axes? Currently, we accept wind axes data only. > > Can JSBSim do 3D interpolation for, say, data as a > function of angle of > attack, sideslip and flaps? No. Right now you'd have to do two tables, one that's f(alpha, flap) plus the sideslip increment f(beta,flap). Multi-dimensional table capability is planned, however. We have this in our > Twin Otter setup, for example > 276 CYfabetaf0.dat > 276 CYfabetaf20.dat > 276 CYfabetaf40.dat > decodes to > CY as a function of alfa, beta & 0, 20, and 40 deg > flap (fabeta + f0/20/40) > > Thanks, > Michael > > >-- > >David Megginson > >[EMAIL PROTECTED] > > > > > >_______________________________________________ > >Flightgear-devel mailing list > >[EMAIL PROTECTED] > >http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > > > === message truncated === __________________________________________________ Do You Yahoo!? Yahoo! Tax Center - online filing with TurboTax http://taxes.yahoo.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
