Here is a wrap-up of the latest changes to JSBSim. It still is flaky, but

much less so due to returning the aero reference point stuff to the config
files. Don't know what happened there ...

Additionally, I have added a new field to the config file: CFG_VERSION. A
version number, currently 1.1, is assigned to the config file and a matching
definition is found in FGDefs.h. The two need to match. Tony has also added
code into FGAircraft.cpp to handle if aero reference point is not specified.

src/FDM/JSBSim/FGAircraft.cpp

@@ -159,6 +159,7 @@ bool FGAircraft::LoadAircraft(string aircraft_path, string engine_path, string f
   streampos gpos;
   int axis;
   string axis_descript;
+  bool readAeroRp=false;
 
   axis = -1;
   aircraftDef = aircraft_path + "/" + fname + "/" + fname + ".cfg";
@@ -169,6 +170,8 @@ bool FGAircraft::LoadAircraft(string aircraft_path, string engine_path, string f
   numTanks = numEngines = 0;
   numSelectedOxiTanks = numSelectedFuelTanks = 0;
 
+  Xcg=Ycg=Zcg=0; //protection for no cg specified in file
+
   while (!aircraftfile.fail()) {
     holding_string.erase();
     aircraftfile >> holding_string;
@@ -218,6 +221,7 @@ bool FGAircraft::LoadAircraft(string aircraft_path, string engine_path, string f
         cout << "Aircraft Empty Weight: " << EmptyWeight << endl;
       } else if (holding_string == "AC_AERORP") {
         aircraftfile >> Xrp >> Yrp >> Zrp;
+        readAeroRp=true;
         cout << "Aerodynamic Reference Point: " << Xrp << " " << Yrp << " " << Zrp << endl;
       } else if (holding_string == "AC_CGLOC") {
         aircraftfile >> baseXcg >> baseYcg >> baseZcg;
@@ -310,8 +314,15 @@ bool FGAircraft::LoadAircraft(string aircraft_path, string engine_path, string f
       aircraftfile.getline(scratch, 127);
     }
   }
-  cout << "End of Configuration File Parsing." << endl;
+  
+    if(!readAeroRp) {
+    Xrp = Xcg;
+    Yrp = Ycg;
+    Zrp = Zcg;
+    cout << "Aerodynamic reference point not found, set to empty weight cg location" << endl;
+  }	
 
+  cout << "End of Configuration File Parsing." << endl;
   return true;
 }
 
@@ -431,32 +442,31 @@ void FGAircraft::MassChange()
 void FGAircraft::FMAero(void)
 {
   float F[3];
-  float Fxaero,Fyaero,Fzaero;
   float dxcg,dycg,dzcg;
+  float ca, cb, sa, sb;
   int axis_ctr,ctr;
   F[0] = F[1] = F[2] = 0.0;
 
-  for (axis_ctr = 0; axis_ctr < 3; axis_ctr++)
-    for (ctr=0; ctr < coeff_ctr[axis_ctr]; ctr++)
+  for (axis_ctr = 0; axis_ctr < 3; axis_ctr++) {
+    for (ctr=0; ctr < coeff_ctr[axis_ctr]; ctr++) {
       F[axis_ctr] += Coeff[axis_ctr][ctr]->TotalValue();
+      Coeff[axis_ctr][ctr]->DumpSD();
+    }
+  }
 
-  Fxaero = - F[DragCoeff]*cos(alpha)*cos(beta)
-           - F[SideCoeff]*cos(alpha)*sin(beta)
-           + F[LiftCoeff]*sin(alpha);
-  Fyaero =   F[DragCoeff]*sin(beta)
-             + F[SideCoeff]*cos(beta);
-  Fzaero = - F[DragCoeff]*sin(alpha)*cos(beta)
-           - F[SideCoeff]*sin(alpha)*sin(beta)
-           - F[LiftCoeff]*cos(alpha);
+  ca = cos(alpha);
+  sa = sin(alpha);
+  cb = cos(beta);
+  sb = sin(beta);
 
-  Forces[0] += - F[DragCoeff]*cos(alpha)*cos(beta)
-               - F[SideCoeff]*cos(alpha)*sin(beta)
-               + F[LiftCoeff]*sin(alpha);
-  Forces[1] +=   F[DragCoeff]*sin(beta)
-                 + F[SideCoeff]*cos(beta);
-  Forces[2] += - F[DragCoeff]*sin(alpha)*cos(beta)
-               - F[SideCoeff]*sin(alpha)*sin(beta)
-               - F[LiftCoeff]*cos(alpha);
+  Forces[0] += - F[DragCoeff]*ca*cb
+               - F[SideCoeff]*ca*sb
+               + F[LiftCoeff]*sa;
+  Forces[1] +=   F[DragCoeff]*sb
+                 + F[SideCoeff]*cb;
+  Forces[2] += - F[DragCoeff]*sa*cb
+               - F[SideCoeff]*sa*sb
+               - F[LiftCoeff]*ca;
 
   // The d*cg distances below, given in inches, are the distances FROM the c.g.
   // TO the reference point. Since the c.g. and ref point are given in inches in
@@ -468,13 +478,14 @@ void FGAircraft::FMAero(void)
   dycg =  (Yrp - Ycg)/12;
   dzcg = -(Zrp - Zcg)/12;
 
-  Moments[0] +=  Fzaero*dycg - Fyaero*dzcg; //rolling moment
-  Moments[1] +=  Fxaero*dzcg - Fzaero*dxcg; //pitching moment
-  Moments[2] += -Fxaero*dycg + Fyaero*dxcg; //yawing moment
+  Moments[0] +=  Forces[2]*dycg - Forces[1]*dzcg; //rolling moment
+  Moments[1] +=  Forces[0]*dzcg - Forces[2]*dxcg; //pitching moment
+  Moments[2] += -Forces[0]*dycg + Forces[1]*dxcg; //yawing moment
 
   for (axis_ctr = 0; axis_ctr < 3; axis_ctr++) {
     for (ctr = 0; ctr < coeff_ctr[axis_ctr+3]; ctr++) {
       Moments[axis_ctr] += Coeff[axis_ctr+3][ctr]->TotalValue();
+      Coeff[axis_ctr+3][ctr]->DumpSD();
     }
   }
 }

src/FDM/JSBSim/FGCoefficient.cpp

@@ -352,7 +352,7 @@ float FGCoefficient::Value(float rVal, float cVal)
   col1temp = rFactor*(Table3D[r][c-1] - Table3D[r-1][c-1]) + Table3D[r-1][c-1];
   col2temp = rFactor*(Table3D[r][c] - Table3D[r-1][c]) + Table3D[r-1][c];
 
-  Value = col1temp + cFactor*(col2temp - col1temp);
+  SD = Value = col1temp + cFactor*(col2temp - col1temp);
 
   for (midx=0;midx<mult_count;midx++) {
     Value *= GetCoeffVal(mult_idx[midx]);
@@ -379,7 +379,7 @@ float FGCoefficient::Value(float Val)
     Factor = 1.0;
   }
 
-  Value = Factor*(Table3D[r][1] - Table3D[r-1][1]) + Table3D[r-1][1];
+  SD = Value = Factor*(Table3D[r][1] - Table3D[r-1][1]) + Table3D[r-1][1];
 
   for (midx=0;midx<mult_count;midx++) {
     Value *= GetCoeffVal(mult_idx[midx]);
@@ -394,7 +394,7 @@ float FGCoefficient::Value(void)
 	float Value;
 	int midx;
 	
-	Value = StaticValue;
+	SD = Value = StaticValue;
 
   for (midx=0;midx<mult_count;midx++) {
     Value *= GetCoeffVal(mult_idx[midx]);
@@ -463,3 +463,8 @@ float FGCoefficient::GetCoeffVal(int val_idx)
   return 0;
 }
 
+
+void FGCoefficient::DumpSD(void)
+{
+  cout << "   " << name << " = " << SD << endl;
+}

src/FDM/JSBSim/FGCoefficient.h

@@ -133,6 +133,9 @@ public:
   float Value(float);
   float Value(void);
   float TotalValue(void);
+  inline float GetSDValue(void) {return SD;}
+  inline void SetSDValue(float tt) {SD = tt;}
+  void DumpSD(void);
   enum Type {UNKNOWN, VALUE, VECTOR, TABLE, EQUATION};
 
 protected:
@@ -153,6 +156,7 @@ private:
   Type type;
   int multipliers;
   int mult_count;
+  float SD; // Actual stability derivative (or other coefficient) value
 
   float GetCoeffVal(int);
 

src/FDM/JSBSim/FGControls.cpp

@@ -35,13 +35,13 @@ FGControls::FGControls() :
     elevator_trim( 1.969572E-03 ),
     rudder( 0.0 )
 {
-    for ( int engine = 0; engine < MAX_ENGINES; engine++ ) {
-	throttle[engine] = 0.0;
-    }
+  for ( int engine = 0; engine < MAX_ENGINES; engine++ ) {
+    throttle[engine] = 0.0;
+  }
 
-    for ( int wheel = 0; wheel < MAX_WHEELS; wheel++ ) {
-        brake[wheel] = 0.0;
-    }
+  for ( int wheel = 0; wheel < MAX_WHEELS; wheel++ ) {
+    brake[wheel] = 0.0;
+  }
 }
 
 
@@ -51,6 +51,16 @@ FGControls::~FGControls() {
 
 
 // $Log$
+// Revision 1.7  1999/12/30 17:01:59  curt
+// Here is a wrap-up of the latest changes to JSBSim. It still is flaky, but
+// much less so due to returning the aero reference point stuff to the config
+// files. Don't know what happened there ...
+//
+// Additionally, I have added a new field to the config file: CFG_VERSION. A
+// version number, currently 1.1, is assigned to the config file and a matching
+// definition is found in FGDefs.h. The two need to match. Tony has also added
+// code into FGAircraft.cpp to handle if aero reference point is not specified.
+//
 // Revision 1.6  1999/09/07 21:15:45  curt
 // Updates to get engine working.
 //

src/FDM/JSBSim/FGFDMExec.cpp

@@ -119,7 +119,7 @@ FGFDMExec::FGFDMExec(void)
   Schedule(Translation, 1);
   Schedule(Position,    1);
   Schedule(Auxiliary,   1);
-  Schedule(Output,      120);
+  Schedule(Output,      1);
 
   terminate = false;
   frozen = false;