Detailed Description

Models inertial forces (e.g.

centripetal and coriolis accelerations). Starting conversion to WGS84.

Definition at line 65 of file FGInertial.h.

#include <FGInertial.h>

Inheritance diagram for FGInertial:

Collaboration diagram for FGInertial:

Classes
struct	Inputs

Public Types
enum	eGravType { gtStandard , gtWGS84 }
	These define the indices use to select the gravitation models. More...

Public Types inherited from FGJSBBase
enum	{ eL = 1 , eM , eN }
	Moments L, M, N. More...

enum	{ eP = 1 , eQ , eR }
	Rates P, Q, R. More...

enum	{ eU = 1 , eV , eW }
	Velocities U, V, W. More...

enum	{ eX = 1 , eY , eZ }
	Positions X, Y, Z. More...

enum	{ ePhi = 1 , eTht , ePsi }
	Euler angles Phi, Theta, Psi. More...

enum	{ eDrag = 1 , eSide , eLift }
	Stability axis forces, Drag, Side force, Lift. More...

enum	{ eRoll = 1 , ePitch , eYaw }
	Local frame orientation Roll, Pitch, Yaw. More...

enum	{ eNorth = 1 , eEast , eDown }
	Local frame position North, East, Down. More...

enum	{ eLat = 1 , eLong , eRad }
	Locations Radius, Latitude, Longitude. More...

enum	{ inNone = 0 , inDegrees , inRadians , inMeters , inFeet }
	Conversion specifiers. More...

Public Member Functions
	FGInertial (FGFDMExec *)

double	GetGM (void) const

const FGColumnVector3 &	GetGravity (void) const

int	GetGravityType (void) const
	Get the gravity type.

const FGColumnVector3 &	GetOmegaPlanet () const

double	GetSemimajor (void) const

double	GetSemiminor (void) const

FGMatrix33	GetTec2l (const FGLocation &location) const
	Transform matrix from the earth centered to local horizontal frame.

FGMatrix33	GetTl2ec (const FGLocation &location) const
	Transform matrix from the local horizontal frame to earth centered.

bool	Load (Element *el) override

bool	Run (bool Holding) override
	Runs the Inertial model; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold.

void	SetGravityType (int gt)
	Set the gravity type.

void	SetGroundCallback (FGGroundCallback *gc)
	Sets the ground callback pointer.

void	SetOmegaPlanet (double rate)

Functions that rely on the ground callback
The following functions allow to set and get the vehicle position above the ground. The ground level is obtained by interrogating an instance of FGGroundCallback. A ground callback must therefore be set with SetGroundCallback() before calling any of these functions.
double	GetContactPoint (const FGLocation &location, FGLocation &contact, FGColumnVector3 &normal, FGColumnVector3 &velocity, FGColumnVector3 &ang_velocity) const
	Get terrain contact point information below the current location.

double	GetAltitudeAGL (const FGLocation &location) const
	Get the altitude above ground level.

void	SetAltitudeAGL (FGLocation &location, double altitudeAGL)
	Set the altitude above ground level.

void	SetTerrainElevation (double h)
	Set the terrain elevation above sea level.

void	SetTime (double time)
	Set the simulation time.

Public Member Functions inherited from FGModel
	FGModel (FGFDMExec *)
	Constructor.

	~FGModel () override
	Destructor.

virtual SGPath	FindFullPathName (const SGPath &path) const

FGFDMExec *	GetExec (void) const

const std::string &	GetName (void) const

unsigned int	GetRate (void) const
	Get the output rate for the model in frames.

bool	InitModel (void) override

void	SetPropertyManager (std::shared_ptr< FGPropertyManager > fgpm)

void	SetRate (unsigned int tt)
	Set the ouput rate for the model in frames.

Public Member Functions inherited from FGModelFunctions
std::string	GetFunctionStrings (const std::string &delimeter) const
	Gets the strings for the current set of functions.

std::string	GetFunctionValues (const std::string &delimeter) const
	Gets the function values.

std::shared_ptr< FGFunction >	GetPreFunction (const std::string &name)
	Get one of the "pre" function.

bool	Load (Element el, FGFDMExec fdmex, std::string prefix="")

void	PostLoad (Element el, FGFDMExec fdmex, std::string prefix="")

void	PreLoad (Element el, FGFDMExec fdmex, std::string prefix="")

void	RunPostFunctions (void)

void	RunPreFunctions (void)

Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

void	disableHighLighting (void)
	Disables highlighting in the console output.

Static Public Member Functions
static constexpr double	GetStandardGravity (void)

Static Public Member Functions inherited from FGJSBBase
static const std::string &	GetVersion (void)
	Returns the version number of JSBSim.

static constexpr double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit.

static constexpr double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine.

static constexpr double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius.

static constexpr double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine.

static constexpr double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin.

static constexpr double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius.

static constexpr double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit.

static constexpr double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin.

static constexpr double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius.

static constexpr double	FeetToMeters (double measure)
	Converts from feet to meters.

static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison.

static constexpr double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

static constexpr double	sign (double num)

Public Attributes
struct JSBSim::FGInertial::Inputs	in

Additional Inherited Members
Static Public Attributes inherited from FGJSBBase
static char	highint [5] = {27, '[', '1', 'm', '\0' }
	highlights text

static char	halfint [5] = {27, '[', '2', 'm', '\0' }
	low intensity text

static char	normint [6] = {27, '[', '2', '2', 'm', '\0' }
	normal intensity text

static char	reset [5] = {27, '[', '0', 'm', '\0' }
	resets text properties

static char	underon [5] = {27, '[', '4', 'm', '\0' }
	underlines text

static char	underoff [6] = {27, '[', '2', '4', 'm', '\0' }
	underline off

static char	fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
	blue text

static char	fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
	cyan text

static char	fgred [6] = {27, '[', '3', '1', 'm', '\0' }
	red text

static char	fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
	green text

static char	fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
	default text

static short	debug_lvl = 1

Protected Member Functions inherited from FGModel
bool	Upload (Element *el, bool preLoad)
	Uploads this model in memory.

Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Protected Attributes inherited from FGModel
unsigned int	exe_ctr

FGFDMExec *	FDMExec

std::string	Name

std::shared_ptr< FGPropertyManager >	PropertyManager

unsigned int	rate

Protected Attributes inherited from FGModelFunctions
FGPropertyReader	LocalProperties

std::vector< std::shared_ptr< FGFunction > >	PostFunctions

std::vector< std::shared_ptr< FGFunction > >	PreFunctions

Static Protected Attributes inherited from FGJSBBase
static constexpr double	radtodeg = 180. / M_PI

static constexpr double	degtorad = M_PI / 180.

static constexpr double	hptoftlbssec = 550.0

static constexpr double	psftoinhg = 0.014138

static constexpr double	psftopa = 47.88

static constexpr double	fttom = 0.3048

static constexpr double	ktstofps = 1852./(3600*fttom)

static constexpr double	fpstokts = 1.0 / ktstofps

static constexpr double	inchtoft = 1.0/12.0

static constexpr double	m3toft3 = 1.0/(fttomfttomfttom)

static constexpr double	in3tom3 = inchtoftinchtoftinchtoft/m3toft3

static constexpr double	inhgtopa = 3386.38

static constexpr double	slugtolb = 32.174049
	Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff.

static constexpr double	lbtoslug = 1.0/slugtolb

static constexpr double	kgtolb = 2.20462

static constexpr double	kgtoslug = 0.06852168

static const std::string	needed_cfg_version = "2.0"

static const std::string	JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__

Member Enumeration Documentation

◆ eGravType

enum eGravType

These define the indices use to select the gravitation models.

Enumerator
gtStandard	Evaluate gravity using Newton's classical formula assuming the Earth is spherical.
gtWGS84	Evaluate gravity using WGS84 formulas that take the Earth oblateness into account.

Definition at line 154 of file FGInertial.h.

                 {
    gtStandard,
    gtWGS84
  };

Constructor & Destructor Documentation

◆ FGInertial()

FGInertial ( FGFDMExec * fgex )

explicit

Definition at line 53 of file FGInertial.cpp.

  : FGModel(fgex)
{
  Name = "Earth";
 
  // Earth defaults
  double RotationRate    = 0.00007292115;
  GM              = 14.0764417572E15;   // WGS84 value
  J2              = 1.08262982E-03;     // WGS84 value for J2
  a               = 20925646.32546;     // WGS84 semimajor axis length in feet
  b               = 20855486.5951;      // WGS84 semiminor axis length in feet
  gravType = gtWGS84;
 
  // Lunar defaults
  /*
  double RotationRate    = 0.0000026617;
  GM              = 1.7314079E14;         // Lunar GM
  J2              = 2.033542482111609E-4; // value for J2
  a               = 5702559.05;           // semimajor axis length in feet
  b               = 5695439.63;           // semiminor axis length in feet
  */
 
  vOmegaPlanet = { 0.0, 0.0, RotationRate };
  GroundCallback = std::make_unique<FGDefaultGroundCallback>(a, b);
 
  bind();
 
  Debug(0);
}

◆ ~FGInertial()

~FGInertial ( void )

Definition at line 85 of file FGInertial.cpp.

{
  Debug(1);
}

Member Function Documentation

◆ GetAltitudeAGL()

double GetAltitudeAGL ( const FGLocation & location ) const

inline

Get the altitude above ground level.

Returns: the altitude AGL in feet.

Parameters

location Location at which the AGL is evaluated.

See also: SetGroundCallback

Definition at line 115 of file FGInertial.h.

                                                          {
    FGLocation lDummy;
    FGColumnVector3 vDummy;
    return GroundCallback->GetAGLevel(location, lDummy, vDummy, vDummy,
                                      vDummy);
  }

◆ GetContactPoint()

double GetContactPoint	(	const FGLocation &	location,
		FGLocation &	contact,
		FGColumnVector3 &	normal,
		FGColumnVector3 &	velocity,
		FGColumnVector3 &	ang_velocity
	)		const

inline

Get terrain contact point information below the current location.

Parameters

location	Location at which the contact point is evaluated.
contact	Contact point location
normal	Terrain normal vector in contact point (ECEF frame)
velocity	Terrain linear velocity in contact point (ECEF frame)
ang_velocity	Terrain angular velocity in contact point (ECEF frame)

Returns: Location altitude above contact point (AGL) in feet.

See also: SetGroundCallback

Definition at line 104 of file FGInertial.h.

  {
    return GroundCallback->GetAGLevel(location, contact, normal, velocity,
                                      ang_velocity); }

◆ GetGM()

double GetGM ( void ) const

inline

Definition at line 88 of file FGInertial.h.

88{return GM;}

◆ GetGravity()

const FGColumnVector3 & GetGravity ( void ) const

inline

Definition at line 81 of file FGInertial.h.

81{return vGravAccel;}

◆ GetGravityType()

int GetGravityType ( void ) const

inline

Get the gravity type.

Definition at line 164 of file FGInertial.h.

164{ return gravType; }

◆ GetOmegaPlanet()

const FGColumnVector3 & GetOmegaPlanet ( ) const

inline

Definition at line 82 of file FGInertial.h.

82{return vOmegaPlanet;}

◆ GetSemimajor()

double GetSemimajor ( void ) const

inline

Definition at line 86 of file FGInertial.h.

86{return a;}

◆ GetSemiminor()

double GetSemiminor ( void ) const

inline

Definition at line 87 of file FGInertial.h.

87{return b;}

◆ GetStandardGravity()

static constexpr double GetStandardGravity ( void )

inlinestaticconstexpr

Definition at line 80 of file FGInertial.h.

80{ return gAccelReference; }

◆ GetTec2l()

FGMatrix33 GetTec2l ( const FGLocation & location ) const

inline

Transform matrix from the earth centered to local horizontal frame.

The local frame is the NED (North-East-Down) frame. Since the Down direction depends on the gravity so is the local frame. The East direction is tangent to the spheroid with a null component along the Z axis. The North direction is obtained from the cross product between East and Down.

Parameters

location The location at which the transform matrix must be evaluated.

Returns: a rotation matrix of the transform from the earth centered frame to the local horizontal frame.

Definition at line 195 of file FGInertial.h.

196 { return GetTl2ec(location).Transposed(); }

JSBSim::FGInertial::GetTl2ec

FGMatrix33 GetTl2ec(const FGLocation &location) const

Transform matrix from the local horizontal frame to earth centered.

Definition FGInertial.cpp:162

JSBSim::FGMatrix33::Transposed

FGMatrix33 Transposed(void) const

Transposed matrix.

Definition FGMatrix33.h:221

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◆ GetTl2ec()

FGMatrix33 GetTl2ec ( const FGLocation & location ) const

Transform matrix from the local horizontal frame to earth centered.

The local frame is the NED (North-East-Down) frame. Since the Down direction depends on the gravity so is the local frame. The East direction is tangent to the spheroid with a null component along the Z axis. The North direction is obtained from the cross product between East and Down.

Parameters

location The location at which the transform matrix must be evaluated.

Returns: a rotation matrix of the transform from the earth centered frame to the local horizontal frame.

Definition at line 162 of file FGInertial.cpp.

{
  FGColumnVector3 North, Down, East{-location(eY), location(eX), 0.};
 
  switch (gravType) {
  case gtStandard:
    {
      Down = location;
      Down *= -1.0;
    }
    break;
  case gtWGS84:
    {
      FGLocation sea_level = location;
      sea_level.SetPositionGeodetic(location.GetLongitude(),
                                    location.GetGeodLatitudeRad(), 0.0);
      Down = GetGravityJ2(location);
      Down -= vOmegaPlanet*(vOmegaPlanet*sea_level);}
    }
  Down.Normalize();
  East.Normalize();
  North = East*Down;
 
  return FGMatrix33{North(eX), East(eX), Down(eX),
                    North(eY), East(eY), Down(eY),
                    North(eZ), 0.0,      Down(eZ)};
}

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◆ Load()

bool Load ( Element * el )

overridevirtual

Reimplemented from FGModel.

Definition at line 92 of file FGInertial.cpp.

{
  if (!Upload(el, true)) return false;
 
  Name = el->GetAttributeValue("name");
 
  if (el->FindElement("semimajor_axis"))
    a = el->FindElementValueAsNumberConvertTo("semimajor_axis", "FT");
  else if (el->FindElement("equatorial_radius"))
    a = el->FindElementValueAsNumberConvertTo("equatorial_radius", "FT");
  if (el->FindElement("semiminor_axis"))
    b = el->FindElementValueAsNumberConvertTo("semiminor_axis", "FT");
  else if (el->FindElement("polar_radius"))
    b = el->FindElementValueAsNumberConvertTo("polar_radius", "FT");
  // Trigger GeographicLib exceptions if the equatorial or polar radii are
  // ill-defined.
  // This intercepts the exception before being thrown by a destructor.
  GeographicLib::Geodesic geod(a, 1.-b/a);
 
  if (el->FindElement("rotation_rate")) {
    double RotationRate = el->FindElementValueAsNumberConvertTo("rotation_rate", "RAD/SEC");
    vOmegaPlanet = {0., 0., RotationRate};
  }
  if (el->FindElement("GM"))
    GM = el->FindElementValueAsNumberConvertTo("GM", "FT3/SEC2");
  if (el->FindElement("J2"))
    J2 = el->FindElementValueAsNumber("J2"); // Dimensionless
 
  GroundCallback->SetEllipse(a, b);
 
  // Messages to warn the user about possible inconsistencies.
  if (debug_lvl > 0) {
    FGLogging log(LogLevel::WARN);
    if (a != b && J2 == 0.0)
      log << "Gravitational constant J2 is null for a non-spherical planet." << endl;
    if (a == b && J2 != 0.0)
      log << "Gravitational constant J2 is non-zero for a spherical planet." << endl;
  }
 
  Debug(2);
 
  return true;
}

◆ Run()

bool Run ( bool Holding )

overridevirtual

Runs the Inertial model; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold.

Parameters

Holding if true, the executive has been directed to hold the sim from advancing time. Some models may ignore this flag, such as the Input model, which may need to be active to listen on a socket for the "Resume" command to be given.

Returns: false if no error

Reimplemented from FGModel.

Definition at line 138 of file FGInertial.cpp.

{
  // Fast return if we have nothing to do ...
  if (FGModel::Run(Holding)) return true;
  if (Holding) return false;
 
  // Gravitation accel
  switch (gravType) {
  case gtStandard:
    {
      double radius = in.Position.GetRadius();
      vGravAccel = -(GetGAccel(radius) / radius) * in.Position;
    }
    break;
  case gtWGS84:
    vGravAccel = GetGravityJ2(in.Position);
    break;
  }
 
  return false;
}

◆ SetAltitudeAGL()

void SetAltitudeAGL	(	FGLocation &	location,
		double	altitudeAGL
	)

Set the altitude above ground level.

Parameters

location	Location at which the AGL is set.
altitudeAGL	Altitude above Ground Level in feet.

See also: SetGroundCallback

Definition at line 227 of file FGInertial.cpp.

{
  FGColumnVector3 vDummy;
  FGLocation contact;
  contact.SetEllipse(a, b);
  GroundCallback->GetAGLevel(location, contact, vDummy, vDummy, vDummy);
  double groundHeight = contact.GetGeodAltitude();
  double longitude = location.GetLongitude();
  double geodLat = location.GetGeodLatitudeRad();
  location.SetPositionGeodetic(longitude, geodLat,
                               groundHeight + altitudeAGL);
}

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◆ SetGravityType()

void SetGravityType ( int gt )

Set the gravity type.

Definition at line 242 of file FGInertial.cpp.

{
  // Messages to warn the user about possible inconsistencies.
  FGLogging log(LogLevel::WARN);
  switch (gt)
  {
  case eGravType::gtStandard:
    if (a != b)
      log << "Standard gravity model has been set for a non-spherical planet" << endl;
    break;
  case eGravType::gtWGS84:
    if (J2 == 0.0)
      log << "WGS84 gravity model has been set without specifying the J2 gravitational constant." << endl;
  }
 
  gravType = gt;
}

◆ SetGroundCallback()

void SetGroundCallback ( FGGroundCallback * gc )

inline

Sets the ground callback pointer.

FGInertial will take ownership of the pointer which must therefore be located in the heap.

Parameters

gc	A pointer to a ground callback object

See also: FGGroundCallback

Definition at line 151 of file FGInertial.h.

151{ GroundCallback.reset(gc); }

◆ SetOmegaPlanet()

void SetOmegaPlanet ( double rate )

inline

Definition at line 83 of file FGInertial.h.

                                   {
    vOmegaPlanet = FGColumnVector3(0.0, 0.0, rate);
  }

◆ SetTerrainElevation()

void SetTerrainElevation ( double h )

inline

Set the terrain elevation above sea level.

Parameters

h	Terrain elevation in ft.

See also: SetGroundcallback

Definition at line 131 of file FGInertial.h.

                                     {
    GroundCallback->SetTerrainElevation(h);
  }

◆ SetTime()

void SetTime ( double time )

inline

Set the simulation time.

The elapsed time can be used by the ground callback to assess the planet rotation or the movement of objects.

Parameters

time	elapsed time in seconds since the simulation started.

Definition at line 140 of file FGInertial.h.

                            {
    GroundCallback->SetTime(time);
  }

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The documentation for this class was generated from the following files:

Detailed Description

Classes

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Additional Inherited Members

Member Enumeration Documentation

◆ eGravType

Constructor & Destructor Documentation

◆ FGInertial()

◆ ~FGInertial()

Member Function Documentation

◆ GetAltitudeAGL()

◆ GetContactPoint()

◆ GetGM()

◆ GetGravity()

◆ GetGravityType()

◆ GetOmegaPlanet()

◆ GetSemimajor()

◆ GetSemiminor()

◆ GetStandardGravity()

◆ GetTec2l()

◆ GetTl2ec()

◆ Load()

◆ Run()

◆ SetAltitudeAGL()

◆ SetGravityType()

◆ SetGroundCallback()

◆ SetOmegaPlanet()

◆ SetTerrainElevation()

◆ SetTime()