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?
Also, does JSBSim accept aero data in the body axes as well as the
stability axes?
Can JSBSim do 3D interpolation for, say, data as a function of angle of
attack, sideslip and flaps? 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]
>
>
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**************************************************
Prof. Michael S. Selig
Dept. of Aero/Astro Engineering
University of Illinois at Urbana-Champaign
306 Talbot Laboratory
104 South Wright Street
Urbana, IL 61801-2935
(217) 244-5757 (o), (509) 691-1373 (fax)
mailto:[EMAIL PROTECTED]
http://www.uiuc.edu/ph/www/m-selig
http://www.uiuc.edu/ph/www/m-selig/faq.html (FAQ)
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