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Dynamic calculation of CG and inertias.

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This commit is contained in:
curt 1999-09-28 14:19:34 +00:00
parent 96b4460ac4
commit 6eaf06957d
4 changed files with 77 additions and 13 deletions
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55
src/FDM/JSBSim/FGAircraft.cpp
View file

@ -190,24 +190,24 @@ bool FGAircraft::LoadAircraft(string aircraft_path, string engine_path, string f
aircraftfile >> cbar;
cout << "Aircraft Chord: " << cbar << endl;
} else if (holding_string == "AC_IXX") {
aircraftfile >> Ixx;
cout << "Aircraft Ixx: " << Ixx << endl;
aircraftfile >> baseIxx;
cout << "Aircraft Base Ixx: " << baseIxx << endl;
} else if (holding_string == "AC_IYY") {
aircraftfile >> Iyy;
cout << "Aircraft Iyy: " << Iyy << endl;
aircraftfile >> baseIyy;
cout << "Aircraft Base Iyy: " << baseIyy << endl;
} else if (holding_string == "AC_IZZ") {
aircraftfile >> Izz;
cout << "Aircraft Izz: " << Izz << endl;
aircraftfile >> baseIzz;
cout << "Aircraft Base Izz: " << baseIzz << endl;
} else if (holding_string == "AC_IXZ") {
aircraftfile >> Ixz;
cout << "Aircraft Ixz: " << Ixz << endl;
aircraftfile >> baseIxz;
cout << "Aircraft Base Ixz: " << baseIxz << endl;
} else if (holding_string == "AC_EMPTYWT") {
aircraftfile >> EmptyWeight;
EmptyMass = EmptyWeight / GRAVITY;
cout << "Aircraft Empty Weight: " << EmptyWeight << endl;
} else if (holding_string == "AC_CGLOC") {
aircraftfile >> Xcg >> Ycg >> Zcg;
cout << "Aircraft C.G.: " << Xcg << " " << Ycg << " " << Zcg << endl;
aircraftfile >> baseXcg >> baseYcg >> baseZcg;
cout << "Aircraft Base C.G.: " << baseXcg << " " << baseYcg << " " << baseZcg << endl;
} else if (holding_string == "AC_EYEPTLOC") {
aircraftfile >> Xep >> Yep >> Zep;
cout << "Pilot Eyepoint: " << Xep << " " << Yep << " " << Zep << endl;
@ -319,6 +319,9 @@ bool FGAircraft::Run(void)
void FGAircraft::MassChange()
{
float Xt, Xw, Yt, Yw, Zt, Zw, Tw;
float IXXt, IYYt, IZZt, IXZt;
// UPDATE TANK CONTENTS
//
// For each engine, cycle through the tanks and draw an equal amount of
@ -372,6 +375,38 @@ void FGAircraft::MassChange()
Weight += Tank[t]->GetContents();
Mass = Weight / GRAVITY;
// Calculate new CG here.
Xt = Yt = Zt = 0;
Xw = Yw = Zw = 0;
for (int t=0; t<numTanks; t++) {
Xt += Tank[t]->GetX()*Tank[t]->GetContents();
Yt += Tank[t]->GetY()*Tank[t]->GetContents();
Zt += Tank[t]->GetZ()*Tank[t]->GetContents();
Tw += Tank[t]->GetContents();
}
Xcg = (Xt + EmptyWeight*baseXcg) / (Tw + EmptyWeight);
Ycg = (Yt + EmptyWeight*baseYcg) / (Tw + EmptyWeight);
Zcg = (Zt + EmptyWeight*baseZcg) / (Tw + EmptyWeight);
// Calculate new moments of inertia here
IXXt = IYYt = IZZt = IXZt = 0.0;
for (int t=0; t<numTanks; t++) {
IXXt += ((Tank[t]->GetX()-Xcg)/12.0)*((Tank[t]->GetX() - Xcg)/12.0)*Tank[t]->GetContents()/GRAVITY;
IYYt += ((Tank[t]->GetY()-Ycg)/12.0)*((Tank[t]->GetY() - Ycg)/12.0)*Tank[t]->GetContents()/GRAVITY;
IZZt += ((Tank[t]->GetZ()-Zcg)/12.0)*((Tank[t]->GetZ() - Zcg)/12.0)*Tank[t]->GetContents()/GRAVITY;
IXZt += ((Tank[t]->GetX()-Xcg)/12.0)*((Tank[t]->GetZ() - Zcg)/12.0)*Tank[t]->GetContents()/GRAVITY;
}
Ixx = baseIxx + IXXt;
Iyy = baseIyy + IYYt;
Izz = baseIzz + IZZt;
Ixz = baseIxz + IXZt;
}

4
src/FDM/JSBSim/FGAircraft.h
View file

@ -167,7 +167,9 @@ private:
float Moments[3];
float Forces[3];
string AircraftName;
float Ixx, Iyy, Izz, Ixz, EmptyMass, Mass;
float baseIxx, baseIyy, baseIzz, baseIxz, EmptyMass, Mass;
float Ixx, Iyy, Izz, Ixz;
float baseXcg, baseYcg, baseZcg;
float Xcg, Ycg, Zcg;
float Xep, Yep, Zep;
float rho, qbar, Vt;

28
src/FDM/JSBSim/FGOutput.cpp
View file

@ -95,6 +95,12 @@ void FGOutput::DelimitedOutput(void)
cout << "Udot,";
cout << "Vdot,";
cout << "Wdot,";
cout << "P,";
cout << "Q,";
cout << "R,";
cout << "PDot,";
cout << "QDot,";
cout << "RDot,";
cout << "Fx,";
cout << "Fy,";
cout << "Fz,";
@ -114,7 +120,7 @@ void FGOutput::DelimitedOutput(void)
cout << Rotation->Getphi() << ",";
cout << Rotation->Gettht() << ",";
cout << Rotation->Getpsi() << ",";
cout << Atmosphere->Getrho() << ",";
cout << Atmosphere->GetDensity() << ",";
cout << State->GetVt() << ",";
cout << Translation->GetU() << ",";
cout << Translation->GetV() << ",";
@ -125,6 +131,12 @@ void FGOutput::DelimitedOutput(void)
cout << Translation->GetUdot() << ",";
cout << Translation->GetVdot() << ",";
cout << Translation->GetWdot() << ",";
cout << Rotation->GetP() << ",";
cout << Rotation->GetQ() << ",";
cout << Rotation->GetR() << ",";
cout << Rotation->GetPdot() << ",";
cout << Rotation->GetQdot() << ",";
cout << Rotation->GetRdot() << ",";
cout << Aircraft->GetFx() << ",";
cout << Aircraft->GetFy() << ",";
cout << Aircraft->GetFz() << ",";
@ -160,6 +172,12 @@ void FGOutput::DelimitedOutput(string fname)
datafile << "Udot,";
datafile << "Vdot,";
datafile << "Wdot,";
datafile << "P,";
datafile << "Q,";
datafile << "R,";
datafile << "PDot,";
datafile << "QDot,";
datafile << "RDot,";
datafile << "Fx,";
datafile << "Fy,";
datafile << "Fz,";
@ -179,7 +197,7 @@ void FGOutput::DelimitedOutput(string fname)
datafile << Rotation->Getphi() << ",";
datafile << Rotation->Gettht() << ",";
datafile << Rotation->Getpsi() << ",";
datafile << Atmosphere->Getrho() << ",";
datafile << Atmosphere->GetDensity() << ",";
datafile << State->GetVt() << ",";
datafile << Translation->GetU() << ",";
datafile << Translation->GetV() << ",";
@ -190,6 +208,12 @@ void FGOutput::DelimitedOutput(string fname)
datafile << Translation->GetUdot() << ",";
datafile << Translation->GetVdot() << ",";
datafile << Translation->GetWdot() << ",";
datafile << Rotation->GetP() << ",";
datafile << Rotation->GetQ() << ",";
datafile << Rotation->GetR() << ",";
datafile << Rotation->GetPdot() << ",";
datafile << Rotation->GetQdot() << ",";
datafile << Rotation->GetRdot() << ",";
datafile << Aircraft->GetFx() << ",";
datafile << Aircraft->GetFy() << ",";
datafile << Aircraft->GetFz() << ",";

3
src/FDM/JSBSim/FGTank.h
View file

@ -78,6 +78,9 @@ public:
bool GetSelected(void) {return Selected;}
float GetPctFull(void) {return PctFull;}
float GetContents(void) {return Contents;}
float inline GetX(void) {return X;}
float inline GetY(void) {return Y;}
float inline GetZ(void) {return Z;}
enum TankType {ttUNKNOWN, ttFUEL, ttOXIDIZER};