Open mjburton11 opened 8 years ago
Yeah that model is not particularly robust -- it seems to be dependent on the objective function. Trying to fix this at some point in the not-too-distant future.
Oh ok. Didn't realize you were already aware of this.
Should that model have rho <= ...
just to make this weakness clearer?
sounds good to me
Interesting... this actually fixed the density except during the first cruise portion. Now if you compare h
to rho
you actually get meaning values except during the cruise portion (2nd leg).
\rho : [ 1.06 0.279 0.771 0.771 ... ] [kg/m**3] air density
h : [ 5e+03 5e+03 1.5e+04 1.5e+04 ... ] [ft] altitude
The underlying issue is that the atmospheric model constraints need to hold with equality, and we want to relax those equalities into inequalities, but the correct relaxation depends on applied pressures external to the atmosphere model.
Let's leave this open in hopes of coming up with better ways of dealing with these posynomial/signomial equality constraints. One approach is to try to derive the correct relaxation prior to solving. Another is to implement a real signomial equality algorithm with trust regions. I think the latter might make sense for atmosphere.
@whoburg and @pgkirsch, we were getting some funny density readings (0.3 kg/m^3 @ 15000 ft) from this model. I think it was because
T_atm
can be lower than than its supposed to be andrho
wanted to be lower to lower the weight.Output