fix definition of roll, yaw, p, and r for standard positive sign. fix…

…es stability derivatives (and rolling and yawing moments)

.gitignore

@@ -57,3 +57,5 @@ velocity-deficit.pdf
 commands
 output
 avl3.35
+
+.vscode

src/nearfield.jl

@@ -600,6 +600,10 @@ function body_forces(surfaces, properties, ref, fs, symmetric, frame)
     reference_length = SVector(ref.b, ref.c, ref.b)
     CM = CM ./ reference_length
 
+    # positive Mx corresponds to negative roll, and positive Mz corresponds to negative yaw
+    convention_change = [-1.0, 1.0, -1.0]
+    CM = CM .* convention_change
+
     # switch to specified frame
     CF, CM = body_to_frame(CF, CM, ref, fs, frame)
 
@@ -799,6 +803,14 @@ performed to obtain the panel forces.
     CM_q = CM_q ./ reference_length
     CM_r = CM_r ./ reference_length
 
+    # positive Mx corresponds to negative roll, and positive Mz corresponds to negative yaw
+    convention_change = [-1.0, 1.0, -1.0]
+    CM_a = CM_a .* convention_change
+    CM_b = CM_b .* convention_change
+    CM_p = CM_p .* convention_change
+    CM_q = CM_q .* convention_change
+    CM_r = CM_r .* convention_change
+
     # pack up derivatives
     dCF = (CF_a, CF_b, CF_p, CF_q, CF_r)
     dCM = (CM_a, CM_b, CM_p, CM_q, CM_r)

src/stability.jl

@@ -41,6 +41,10 @@ function body_derivatives(system)
     CM_v = CM_b*b_v
     CM_w = CM_a*a_w
 
+    # p and r are have opposite signs compared to Omega_x, Omega_z
+    CF_p *= -1; CM_p *= -1
+    CF_r *= -1; CM_r *= -1
+
     # pack up derivatives as named tuples
     dCF = (u=CF_u, v=CF_v, w=CF_w, p=CF_p, q=CF_q, r=CF_r)
     dCM = (u=CM_u, v=CM_v, w=CM_w, p=CM_p, q=CM_q, r=CM_r)
@@ -131,6 +135,10 @@ function stability_derivatives(system)
     CM_q = (CMs_qs*2*ref.V/ref.c) ./ reference_length
     CM_r = (CMs_rs*2*ref.V/ref.b) ./ reference_length
 
+    # p and r are have opposite signs compared to Omega_x, Omega_z
+    CF_p *= -1; CM_p *= -1
+    CF_r *= -1; CM_r *= -1
+
     # pack up derivatives as named tuples
     dCF = (alpha=CF_a, beta=CF_b, p=CF_p, q=CF_q, r=CF_r)
     dCM = (alpha=CM_a, beta=CM_b, p=CM_p, q=CM_q, r=CM_r)

test/runtests.jl

@@ -743,8 +743,8 @@ end
     @test isapprox(CDiff, 0.0022852, atol=1e-5)
     @test isapprox(Cm, -0.02101, atol=1e-4)
     @test isapprox(CY, 0.0, atol=1e-5)
-    @test isapprox(Cl, 0.00644, atol=1e-4)
-    @test isapprox(Cn, -0.00012, atol=2e-4)
+    @test isapprox(Cl, -0.00644, atol=1e-4)
+    @test isapprox(Cn, 0.00012, atol=2e-4)
 end
 
 @testset "AVL - Run 11 - Wing Stability Derivatives" begin
@@ -802,11 +802,11 @@ end
     @test isapprox(CYa, 0.0, atol=ztol)
     @test isapprox(CYb, -0.000007, atol=1e-4)
     @test isapprox(Cla, 0.0, atol=ztol)
-    @test isapprox(Clb, 0.025749, rtol=0.015)
+    @test isapprox(Clb, -0.025749, atol=0.001)
     @test isapprox(Cma, -0.429247, rtol=0.01)
     @test isapprox(Cmb, 0.0, atol=ztol)
     @test isapprox(Cna, 0.0, atol=ztol)
-    # @test isapprox(Cnb, -0.000466, atol=1e-4)
+    @test isapprox(Cnb, 0.000466, atol=1e-3)
     @test isapprox(Clp, -0.518725, rtol=0.01)
     @test isapprox(Clq, 0.0, atol=ztol)
     @test isapprox(Clr, 0.064243, rtol=0.01)