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BUG: Incorrect vector rotation in GenericSurface.compute_forces_and_moments #932
Description
Activity
I reduced this to three unit force vectors at
alpha = 0.2 radandbeta = 0.1 rad. Currentdevelopiscb6106a717207dd8fc2dfe1446d80ff75022f21b.For the aerodynamic vector
[Q, -L, -D], the current code applies the positive-alpha/negative-beta rotation. Applying the direction-cosine mappingRx(-alpha) @ Ry(+beta)gives:Unit coefficient Current body result DCM body result side ( Q=1)[0.995004165, -0.019833838, 0.097843395][0.995004165, -0.019833838, -0.097843395]lift ( L=1)[0, -0.980066578, -0.198669331][0, -0.980066578, 0.198669331]drag ( D=1)[0.099833417, 0.197676812, -0.975170327][-0.099833417, -0.197676812, -0.975170327]Draft PR #1064, head
84d3b6a9f0b4a8074d764130dc3d189bdc402036, produces the DCM column for all three cases through its wind-to-body coefficient conversion. That makes it an implementation candidate for this issue, although #1064 contains a much broader aerodynamic refactor.Would you prefer to keep this fix and its three basis-vector regression cases in #1064, or split the rotation correction into a smaller PR against
develop? I have not opened a duplicate while #932 is assigned and #1064 is active.Environment: Python 3.12.6; NumPy 2.5.2; macOS 26.5.2 arm64.
@ting-hong-shieh let's wait until #1064 is merged please
@ting-hong-shieh Does this bug mean that using Generic surface in the current PyPi version (1.13.0), will lead to a wrong flight prediction?
Describe the bug
Incorrect vector rotation in GenericSurface.compute_forces_and_moments().
Here, we want to represent the black
L,D,Qvectors in the blue body frame.The M_BA matrix should be direction cosine matrix (DCM), however it is given in vector rotation matrices. Vector rotation matrices rotate the vector without changing/rotating reference frame.
Current implementation rotates the force vectors to match body axis, but results are however presented in aero frame.
If it is intended to use rotation matrix instead of DCM, the rotation should be:
Q,L,Dvectors matching+X,-Y,-Zin body frame (i.e. Vector([side, -lift, -drag]) )-alphaon X axis andbetaon Y axis.Q,L,Dvectors and presented in body frameAnother POV:
-alphaon X axis andbetaon Y axis.To Reproduce & Expected behavior & Screenshots
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Additional context
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