Fixed faulty frame transformation of moment of inertia.
Thanks to Jon for finding the problem.
This commit is contained in:
Anders Gidenstam
parent
4fd1e219a4
commit
69905cc45b
4 changed files with 52 additions and 63 deletions
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@ -5,7 +5,7 @@
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Date started: 01/21/08
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Purpose: Encapsulates the buoyant forces
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------------- Copyright (C) 2008 - 2010 Anders Gidenstam -------------
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------------- Copyright (C) 2008 - 2011 Anders Gidenstam -------------
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------------- Copyright (C) 2008 Jon S. Berndt (jon@jsbsim.org) -------------
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This program is free software; you can redistribute it and/or modify it under
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@ -45,7 +45,7 @@ using namespace std;
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namespace JSBSim {
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static const char *IdSrc = "$Id: FGBuoyantForces.cpp,v 1.17 2011/05/20 03:18:36 jberndt Exp $";
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static const char *IdSrc = "$Id: FGBuoyantForces.cpp,v 1.19 2011/07/01 21:22:25 andgi Exp $";
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static const char *IdHdr = ID_BUOYANTFORCES;
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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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@ -179,16 +179,7 @@ const FGMatrix33& FGBuoyantForces::GetGasMassInertia(void)
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gasCellJ = FGMatrix33();
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for (unsigned int i=0; i < size; i++) {
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FGColumnVector3 v = FDMExec->GetMassBalance()->StructuralToBody( Cells[i]->GetXYZ() );
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// Body basis is in FT.
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const double mass = Cells[i]->GetMass();
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// FIXME: Verify that this is the correct way to change between the
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// coordinate frames.
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gasCellJ += Cells[i]->GetInertia() +
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FGMatrix33( 0, - mass*v(1)*v(2), - mass*v(1)*v(3),
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- mass*v(2)*v(1), 0, - mass*v(2)*v(3),
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- mass*v(3)*v(1), - mass*v(3)*v(2), 0 );
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gasCellJ += Cells[i]->GetInertia();
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}
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return gasCellJ;
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@ -4,7 +4,7 @@
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Author: Anders Gidenstam, Jon S. Berndt
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Date started: 01/21/08
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------------- Copyright (C) 2008 - 2010 Anders Gidenstam -------------
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------------- Copyright (C) 2008 - 2011 Anders Gidenstam -------------
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------------- Copyright (C) 2008 Jon S. Berndt (jon@jsbsim.org) -------------
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This program is free software; you can redistribute it and/or modify it under
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@ -51,7 +51,7 @@ INCLUDES
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DEFINITIONS
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
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#define ID_BUOYANTFORCES "$Id: FGBuoyantForces.h,v 1.12 2011/05/20 03:18:36 jberndt Exp $"
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#define ID_BUOYANTFORCES "$Id: FGBuoyantForces.h,v 1.13 2011/07/01 21:22:25 andgi Exp $"
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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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FORWARD DECLARATIONS
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@ -96,7 +96,7 @@ CLASS DOCUMENTATION
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See FGGasCell for the full configuration file format for gas cells.
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@author Anders Gidenstam, Jon S. Berndt
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@version $Id: FGBuoyantForces.h,v 1.12 2011/05/20 03:18:36 jberndt Exp $
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@version $Id: FGBuoyantForces.h,v 1.13 2011/07/01 21:22:25 andgi Exp $
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*/
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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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@ -132,19 +132,19 @@ public:
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bool Load(Element* element);
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/** Gets the total Buoyant force vector.
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@return a force vector. */
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@return a force vector in lbs. */
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const FGColumnVector3& GetForces(void) const {return vTotalForces;}
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/** Gets a component of the total Buoyant force vector.
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@return a component of the force vector. */
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@return a component of the force vector in lbs. */
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double GetForces(int idx) const {return vTotalForces(idx);}
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/** Gets the total Buoyancy moment vector.
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@return a moment vector. */
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@return a moment vector in the body frame in lbs ft. */
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const FGColumnVector3& GetMoments(void) const {return vTotalMoments;}
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/** Gets a component of the total Buoyancy moment vector.
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@return a component of the moment vector. */
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@return a component of the moment vector in the body frame in lbs ft. */
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double GetMoments(int idx) const {return vTotalMoments(idx);}
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/** Gets the total gas mass. The gas mass is part of the aircraft's
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@ -153,11 +153,12 @@ public:
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double GetGasMass(void);
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/** Gets the total moment from the gas mass.
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@return a moment vector. */
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@return a moment vector in the structural frame in lbs in. */
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const FGColumnVector3& GetGasMassMoment(void);
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/** Gets the total moments of inertia for the gas mass.
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@return . */
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/** Gets the total moments of inertia for the gas mass in the body frame.
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@return moments of inertia matrix in the body frame
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in slug ft<sup>2</sup>. */
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const FGMatrix33& GetGasMassInertia(void);
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/** Gets the strings for the current set of gas cells.
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@ -174,13 +175,13 @@ public:
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private:
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vector <FGGasCell*> Cells;
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// Buoyant forces and moments. Excluding the gas weight.
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FGColumnVector3 vTotalForces;
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FGColumnVector3 vTotalMoments;
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FGColumnVector3 vTotalForces; // [lbs]
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FGColumnVector3 vTotalMoments; // [lbs ft]
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// Gas mass related masses, inertias and moments.
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FGMatrix33 gasCellJ;
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FGMatrix33 gasCellJ; // [slug ft^2]
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FGColumnVector3 vGasCellXYZ;
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FGColumnVector3 vXYZgasCell_arm;
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FGColumnVector3 vXYZgasCell_arm; // [lbs in]
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bool NoneDefined;
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@ -4,7 +4,7 @@
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Author: Anders Gidenstam
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Date started: 01/21/2006
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----- Copyright (C) 2006 - 2008 Anders Gidenstam (anders(at)gidenstam.org) --
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----- Copyright (C) 2006 - 2011 Anders Gidenstam (anders(at)gidenstam.org) --
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License as published by the Free Software
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@ -53,7 +53,7 @@ using std::max;
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namespace JSBSim {
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static const char *IdSrc = "$Id: FGGasCell.cpp,v 1.13 2010/12/29 22:39:25 andgi Exp $";
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static const char *IdSrc = "$Id: FGGasCell.cpp,v 1.14 2011/07/01 21:22:25 andgi Exp $";
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static const char *IdHdr = ID_GASCELL;
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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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@ -405,6 +405,9 @@ void FGGasCell::Calculate(double dt)
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gasCellJ(2,2) = Iyy;
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gasCellJ(3,3) = Izz;
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Mass = mass;
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// Transform the moments of inertia to the body frame.
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gasCellJ += MassBalance->GetPointmassInertia(Mass, GetXYZ());
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gasCellM.InitMatrix();
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gasCellM(eX) +=
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GetXYZ(eX) * Mass*slugtolb;
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@ -415,12 +418,10 @@ void FGGasCell::Calculate(double dt)
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if (no_ballonets > 0) {
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// Add the mass, moment and inertia of any ballonets.
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const FGColumnVector3 p = MassBalance->StructuralToBody( GetXYZ() );
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for (i = 0; i < no_ballonets; i++) {
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Mass += Ballonet[i]->GetMass();
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// Add ballonet moments.
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// Add ballonet moments due to mass (in the structural frame).
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gasCellM(eX) +=
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Ballonet[i]->GetXYZ(eX) * Ballonet[i]->GetMass()*slugtolb;
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gasCellM(eY) +=
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@ -428,15 +429,7 @@ void FGGasCell::Calculate(double dt)
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gasCellM(eZ) +=
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Ballonet[i]->GetXYZ(eZ) * Ballonet[i]->GetMass()*slugtolb;
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// Moments of inertia must be converted to the gas cell frame here.
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FGColumnVector3 v =
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MassBalance->StructuralToBody( Ballonet[i]->GetXYZ() ) - p;
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// Body basis is in FT.
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const double mass = Ballonet[i]->GetMass();
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gasCellJ += Ballonet[i]->GetInertia() +
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FGMatrix33( 0, - mass*v(1)*v(2), - mass*v(1)*v(3),
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- mass*v(2)*v(1), 0, - mass*v(2)*v(3),
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- mass*v(3)*v(1), - mass*v(3)*v(2), 0 );
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gasCellJ += Ballonet[i]->GetInertia();
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}
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}
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}
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@ -525,6 +518,7 @@ FGBallonet::FGBallonet(FGFDMExec* exec, Element* el, int num, FGGasCell* parent)
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Atmosphere = exec->GetAtmosphere();
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PropertyManager = exec->GetPropertyManager();
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Inertial = exec->GetInertial();
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MassBalance = exec->GetMassBalance();
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ballonetJ = FGMatrix33();
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@ -791,6 +785,8 @@ void FGBallonet::Calculate(double dt)
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ballonetJ(1,1) = Ixx;
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ballonetJ(2,2) = Iyy;
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ballonetJ(3,3) = Izz;
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// Transform the moments of inertia to the body frame.
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ballonetJ += MassBalance->GetPointmassInertia(GetMass(), GetXYZ());
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}
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//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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@ -4,7 +4,7 @@
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Author: Anders Gidenstam
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Date started: 01/21/2006
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----- Copyright (C) 2006 - 2008 Anders Gidenstam (anders(at)gidenstam.org) --
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----- Copyright (C) 2006 - 2011 Anders Gidenstam (anders(at)gidenstam.org) --
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License as published by the Free Software
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@ -50,7 +50,7 @@ INCLUDES
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DEFINITIONS
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
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#define ID_GASCELL "$Id: FGGasCell.h,v 1.10 2009/10/24 22:59:30 jberndt Exp $"
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#define ID_GASCELL "$Id: FGGasCell.h,v 1.11 2011/07/01 21:22:25 andgi Exp $"
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/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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FORWARD DECLARATIONS
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@ -189,12 +189,12 @@ public:
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/** Get the center of gravity location of the gas cell
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(including any ballonets)
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@return CoG location in the structural frame. */
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@return CoG location in the structural frame in inches. */
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const FGColumnVector3& GetXYZ(void) const {return vXYZ;}
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/** Get the center of gravity location of the gas cell
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(including any ballonets)
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@return CoG location in the structural frame. */
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@return CoG location in the structural frame in inches. */
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double GetXYZ(int idx) const {return vXYZ(idx);}
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/** Get the current mass of the gas cell (including any ballonets)
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@ -202,7 +202,7 @@ public:
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double GetMass(void) const {return Mass;}
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/** Get the moments of inertia of the gas cell (including any ballonets)
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@return moments of inertia matrix relative the gas cell location
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@return moments of inertia matrix in the body frame
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in slug ft<sup>2</sup>. */
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const FGMatrix33& GetInertia(void) const {return gasCellJ;}
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@ -210,7 +210,7 @@ public:
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Note that the buoyancy of the gas cell is handled separately by the
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FGForce part and not included here.
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@return moment vector in lbs ft. */
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@return moment vector in the structural frame in lbs in. */
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const FGColumnVector3& GetMassMoment(void) const {return gasCellM;}
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/** Get the current gas temperature inside the gas cell
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@ -229,8 +229,8 @@ private:
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std::string type;
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int CellNum;
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// Structural constants
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double MaxVolume; // [ft<EFBFBD>]
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double MaxOverpressure; // [lbs/ft<EFBFBD>]
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double MaxVolume; // [ft^2]
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double MaxOverpressure; // [lbs/ft^2]
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FGColumnVector3 vXYZ; // [in]
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double Xradius, Yradius, Zradius; // [ft]
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double Xwidth, Ywidth, Zwidth; // [ft]
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@ -240,17 +240,17 @@ private:
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typedef vector <FGBallonet*> BallonetArray;
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BallonetArray Ballonet;
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// Variables
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double Pressure; // [lbs/ft<EFBFBD>]
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double Pressure; // [lbs/ft^2]
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double Contents; // [mol]
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double Volume; // [ft<EFBFBD>]
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double dVolumeIdeal; // [ft<EFBFBD>]
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double Volume; // [ft^2]
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double dVolumeIdeal; // [ft^2]
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double Temperature; // [Rankine]
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double Buoyancy; // [lbs] Note: Gross lift.
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// Does not include the weight of the gas itself.
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double ValveOpen; // 0 <= ValveOpen <= 1 (or higher).
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double Mass; // [slug]
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FGMatrix33 gasCellJ; // [slug foot<EFBFBD>]
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FGColumnVector3 gasCellM; // [lbs ft]
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FGMatrix33 gasCellJ; // [slug foot^2]
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FGColumnVector3 gasCellM; // [lbs in]
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FGAuxiliary* Auxiliary;
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FGAtmosphere* Atmosphere;
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@ -295,7 +295,6 @@ private:
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//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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/** Models a ballonet inside a gas cell.
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Models a ballonet inside a gas cell.
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Not intended to be used outside FGGasCell.
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See FGGasCell for the configuration file format.
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@author Anders Gidenstam
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@ -312,10 +311,10 @@ public:
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/** Get the center of gravity location of the ballonet
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@return CoG location in the structural frame. */
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@return CoG location in the structural frame in inches. */
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const FGColumnVector3& GetXYZ(void) const {return vXYZ;}
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/** Get the center of gravity location of the ballonet
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@return CoG location in the structural frame. */
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@return CoG location in the structural frame in inches. */
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double GetXYZ(int idx) const {return vXYZ(idx);}
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/** Get the current mass of the ballonets
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@ -323,7 +322,8 @@ public:
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double GetMass(void) const {return Contents * M_air;}
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/** Get the moments of inertia of the ballonet
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@return moments of inertia matrix in slug ft<sup>2</sup>. */
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@return moments of inertia matrix in the body frame in
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slug ft<sup>2</sup>. */
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const FGMatrix33& GetInertia(void) const {return ballonetJ;}
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/** Get the current volume of the ballonet
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@ -336,8 +336,8 @@ public:
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private:
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int CellNum;
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// Structural constants
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double MaxVolume; // [ft<EFBFBD>]
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double MaxOverpressure; // [lbs/ft<EFBFBD>]
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double MaxVolume; // [ft^2]
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double MaxOverpressure; // [lbs/ft^2]
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FGColumnVector3 vXYZ; // [in]
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double Xradius, Yradius, Zradius; // [ft]
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double Xwidth, Ywidth, Zwidth; // [ft]
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@ -347,19 +347,20 @@ private:
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FGFunction* BlowerInput; // [ft^3 / sec]
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FGGasCell* Parent;
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// Variables
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double Pressure; // [lbs/ft<EFBFBD>]
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double Pressure; // [lbs/ft^2]
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double Contents; // [mol]
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double Volume; // [ft<EFBFBD>]
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double dVolumeIdeal; // [ft<EFBFBD>]
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double Volume; // [ft^2]
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double dVolumeIdeal; // [ft^2]
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double dU; // [lbs ft / sec]
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double Temperature; // [Rankine]
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double ValveOpen; // 0 <= ValveOpen <= 1 (or higher).
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FGMatrix33 ballonetJ; // [slug foot<EFBFBD>]
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FGMatrix33 ballonetJ; // [slug foot^2]
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FGAuxiliary* Auxiliary;
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FGAtmosphere* Atmosphere;
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FGPropertyManager* PropertyManager;
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FGInertial* Inertial;
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FGMassBalance* MassBalance;
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void Debug(int from);
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/* Constants. */
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