Fix ComplexConjugateControl reactive-gain sign error (K_r double-negative)

docs/CONTROLLERS.md

@@ -65,7 +65,7 @@ Frequency-domain coefficients A(ω₀), B(ω₀) are computed from the stored RI
 
 ### Gain derivation (from impedance.cpp)
 ```
-K_r = −ω₀² · (I_flap + A₅₅(ω₀)) + K_hs,55
+K_r =  ω₀² · (I_flap + A₅₅(ω₀)) − K_hs,55   (intrinsic pitch reactance to be cancelled)
 B_r =  B_rad,55(ω₀)
 ```
 

src/active_pto.h

@@ -53,7 +53,7 @@ class OptimalPassive : public seastack::pto::IPTOModel {
 // =============================================================================
 // (C) ComplexConjugateControl — reactive CC control at ω₀
 //     Gains pre-computed by caller via impedance.h::ComputeCCGains():
-//       K_r = −ω₀²·(I_flap + A₅₅(ω₀)) + K_hs,55
+//       K_r =  ω₀²·(I_flap + A₅₅(ω₀)) − K_hs,55   (intrinsic pitch reactance to be cancelled)
 //       B_r =  B_rad,55(ω₀)
 //     τ = −K_r · θ − B_r · ω
 // =============================================================================

src/impedance.cpp

@@ -94,7 +94,9 @@ CCGains ComputeCCGains(const seastack::hydro::HydroData& data,
     const double K_hs55   = data.GetHydrostaticStiffnessVal(flap_body_idx, kPitchDOF, kPitchDOF);
 
     CCGains gains;
-    gains.K_r = -omega0 * omega0 * (I_flap_kgm2 + A55) + K_hs55;
+    // K_r is the intrinsic pitch reactance X·ω = ω²(I+A) − K_hs to be cancelled;
+    // the control law applies the conjugate sign: τ_react = −K_r·θ.
+    gains.K_r = omega0 * omega0 * (I_flap_kgm2 + A55) - K_hs55;
     gains.B_r = B55;
     return gains;
 }

src/impedance.h

@@ -35,7 +35,7 @@ double PitchImpedanceMagnitude(const seastack::hydro::HydroData& data,
                                 double I_flap_kgm2);
 
 /// Complex-conjugate reactive control gains at ω₀.
-///   K_r = −ω₀² · (I_flap + A₅₅(ω₀)) + K_hs,55
+///   K_r =  ω₀² · (I_flap + A₅₅(ω₀)) − K_hs,55   (intrinsic pitch reactance to be cancelled)
 ///   B_r =  B_rad,55(ω₀)
 struct CCGains {
     double K_r;   ///< Reactive stiffness [N·m/rad]