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[cameni]

There seems to be some NaN values appearing in JSBSim when it computes wind relative speed. I'm not sure if this is the problem though, must figure out how to move past this trap in debugger.

[cameni]

Okay, after fixing the wind relative speed bug in JSBSim it no longer generates NaNs. Updated jsbsim binaries here:
https://drive.google.com/file/d/0B2spgr2B2dvNODc3bi1zLWo3dFU/edit?usp=sharing

[bomber]

Thanks Cameni, downloaded and will take a look...

[bomber]

Sorry Cameni still fails....

Hopefully you've downloaded and flown the glider ask-13...

The image below shows one of three sections of the code that I've identified as causing a problem, I've commented out the code and added the alternative...

I'd like to use the commented out code as it's important for stalling.



Hopefully this'll help you identify the culprit.

Regards

Simon

[cameni]

Hmm, I was using your ask-13 file, which has this in it:

Code: [Select]

<sum name="T4T/moments/Roll_wing">
<product name="T4T/moments/Z-Roll_wing_left">
<property>T4T/forces/z-vector_wing_left</property>
<property>T4T/moments/wing_left_CoL-Y</property>
<!--<property>T4T/structure/wing_left_4/y</property>  -->
</product>
<product name="T4T/moments/Z-Roll_wing_right">
<property>T4T/forces/z-vector_wing_right</property>
<property>T4T/moments/wing_right_CoL-Y</property>
<!-- <property>T4T/structure/wing_right_4/y</property>  -->
</product>
</sum>

No more NaN messages and no asserts, but the aircraft spins quite wildly. However, I now tried it on another computer, and got a NaN when evaluating property T4T/forces/drag/wing_left_induced_vortex, deeper down when it was trying to get value for qbar-psf 

[bomber]

but the aircraft spins quite wildly.

oh stop teasing   


And yes that's another one of the 3 sections of code, here I've commented it out to make the glider fly...

Code: [Select]

<function name="T4T/forces/drag/TOTAL_DRAG">
<description>Drag</description>
<sum>
<product>
<property>T4T/forces/x-vector-fuselage</property>
<value> -1 </value>
</product>
<product name="T4T/forces/drag/TOTAL_WIND-DRAG">
<property>T4T/metrics/drag_modifier</property>
<sum>
<!-- <property>T4T/forces/drag/wing_left_induced_vortex</property>
<property>T4T/forces/drag/wing_right_induced_vortex</property> -->
<property>T4T/forces/drag/wing_left-parasite</property>
<property>T4T/forces/drag/wing_right-parasite</property>
<property>T4T/forces/drag/fuselage-plan_left-parasite</property>
<property>T4T/forces/drag/fuselage-plan_right-parasite</property>
<property>T4T/forces/drag/fuselage-side-parasite</property>
</sum>
</product>
</sum>
</function>

[cameni]

So after stuffing it with asserts:

Code: [Select]

    <function name="T4T/aero/h-stab_right_roll-adjustment">
        <description>The adjustment to the AoA from the roll rate</description>
<product>
<value> 57.288 </value> <!-- Converts Rads to Degs -->
<atan> <!-- angle in Rads -->
<quotient> <!-- tan of the angle -->
<product>
<!-- Revolutions per Second -->
<quotient>
<property>velocities/p-aero-rad_sec</property>
<value> 6.284 </value>
</quotient>
<!-- Circumference -->
<value> 6.283 </value> <!-- 2 x Pi -->
<property>T4T/structure/h-stab_right/y</property>
</product>
<property> velocities/vt-fps </property>
</quotient>
</atan>
</product>
    </function>

Quotient with velocities/vt-fps = 0.0 in denominator.

[bomber]

We don't have a problem with that bit of code though

[cameni]

How so? It produces NaN/Inf value that propagates through the property tree.

[bomber]

OK I'll see if I can initialise it with a small value...

[bomber]

Changed it to a value of 1 and still no work..... it's not this... it's to do with the induced drag.

Code: [Select]

    <function name="T4T/aero/wing_right_roll-adjustment">
        <description>The adjustment to the AoA from the roll rate</description>
<product>
<value> -57.288 </value> <!-- Converts Rads to Degs -->
<atan> <!-- angle in Rads -->
<quotient> <!-- tan of the angle -->
<product>
<!-- Revolutions per Second -->
<quotient>
<property>velocities/p-aero-rad_sec</property>
<value> 6.284 </value>
</quotient>
<!-- Circumference -->
<value> 6.283 </value> <!-- 2 x Pi -->
<property>T4T/structure/wing_left_4/y</property>
</product>
<value> 1 </value>
</quotient>
</atan>
</product>
    </function>

[bomber]

Ok resolved the first issue.... just added the small value to the left and right normals... it's always good to talk.

Code: [Select]

<function name="T4T/forces/wing_normal_left"> <!-- normal force generated by the wing -->
<description>force normal left wing</description>
<sum>
<value> 0.000001 </value>
<property>T4T/forces/wing_normal_left_8</property>
<property>T4T/forces/wing_normal_left_7</property>
<property>T4T/forces/wing_normal_left_6</property>
<property>T4T/forces/wing_normal_left_5</property>
<property>T4T/forces/wing_normal_left_4</property>
<property>T4T/forces/wing_normal_left_3</property>
<property>T4T/forces/wing_normal_left_2</property>
<property>T4T/forces/wing_normal_left_1</property>
</sum>
</function>

[bomber]

AND THE CROWD GOES WILD !

Ok found the pesky beast... had to add the 0.00001 value

Code: [Select]

<function name="T4T/forces/drag/wing_right_induced_vortex">
<description>Induced drag from the right wing</description>
<sum>
<value> 0.1 </value>
<product><!-- http://www.grc.nasa.gov/WWW/K-12/airplane/induced_html -->
<quotient name="T4T/coefficients/cdi-wing_right"> <!-- Coefficient of Induced Drag on right wing-->
<pow> <!-- (average)Cf squared -->
<quotient name="T4T/coefficients/cl-wing_right">
<product>
<cos><property>T4T/aero/alpha_positive-rad</property></cos>
<property>T4T/forces/wing_normal_right</property>
</product>
<sum>
<value> 0.00001 </value>
<product>
<value> 0.5 </value>
<property>metrics/Sw-sqft</property> <!-- Area of right wing -->
<property>aero/qbar-psf</property> <!-- dynamic pressure on the wing -->
</product>
</sum>
</quotient>
<value> 2.0 </value>
</pow>
<product> <!-- pi*AR*e-->
<value>3.142</value> <!-- pi -->
<property>T4T/metrics/wing_aspect</property>
<property>T4T/metrics/wing_efficiency</property><!-- efficiency value 1.0 for eliptical & 0.7 for straight wing-->
</product>
</quotient>
<property>aero/qbar-psf</property> <!-- dynamic pressure on the wing -->
<value> 0.5 </value>
<property>metrics/Sw-sqft</property> <!-- Area of right wing -->
<table>
<independentVar><property>aero/alpha-deg</property></independentVar>
<independentVar lookup="column">fcs/right-aileron-pos-norm</independentVar>
<tableData>
-1 0 1
-30 0 0 0
-24 0 0 1
-16 0 1 1
-1 1 1 1
9 1 1 1
14 1 1 0
27 1 0 0
30 0 0 0
</tableData>
</table>
</product>
</sum>
</function>

[cameni]

Yea these 0/0 cases are tricky. There should be some quotient variant that gives 0 there instead of NaN, if one knows it would be the valid result.