FlightGear: JSBSim::FGMassBalance Class Reference

Models weight, balance and moment of inertia information. More...

#include <FGMassBalance.h>

Classes
struct	Inputs

Public Member Functions
	FGMassBalance (FGFDMExec *)

	~FGMassBalance ()

bool	Load (Element *el) override

bool	InitModel (void) override

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

double	GetMass (void) const

double	GetWeight (void) const

double	GetEmptyWeight (void) const

const FGColumnVector3 &	GetXYZcg (void) const
	Returns the coordinates of the center of gravity expressed in the structural frame.

double	GetXYZcg (int axis) const

const FGColumnVector3 &	GetDeltaXYZcg (void) const

double	GetDeltaXYZcg (int axis) const

FGMatrix33	GetPointmassInertia (double mass_sl, const FGColumnVector3 &r) const
	Computes the inertia contribution of a pointmass.

FGColumnVector3	StructuralToBody (const FGColumnVector3 &r) const
	Conversion from the structural frame to the body frame.

void	SetEmptyWeight (double EW)

void	SetBaseCG (const FGColumnVector3 &CG)

void	AddPointMass (Element *el)

double	GetTotalPointMassWeight (void) const

const FGColumnVector3 &	GetPointMassMoment (void)

const FGMatrix33 &	GetJ (void) const
	Returns the inertia matrix expressed in the body frame.

const FGMatrix33 &	GetJinv (void) const
	Returns the inverse of the inertia matrix expressed in the body frame.

void	SetAircraftBaseInertias (const FGMatrix33 &BaseJ)

void	GetMassPropertiesReport (int i)

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

	~FGModel () override
	Destructor.

bool	InitModel (void) override

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

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

FGFDMExec *	GetExec (void)

void	SetPropertyManager (FGPropertyManager *fgpm)

virtual SGPath	FindFullPathName (const SGPath &path) const

const std::string &	GetName (void)

Public Member Functions inherited from JSBSim::FGModelFunctions
virtual	~FGModelFunctions ()

void	RunPreFunctions (void)

void	RunPostFunctions (void)

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

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

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

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.

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

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

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

void	PutMessage (const Message &msg)
	Places a Message structure on the Message queue.

void	PutMessage (const std::string &text)
	Creates a message with the given text and places it on the queue.

void	PutMessage (const std::string &text, bool bVal)
	Creates a message with the given text and boolean value and places it on the queue.

void	PutMessage (const std::string &text, int iVal)
	Creates a message with the given text and integer value and places it on the queue.

void	PutMessage (const std::string &text, double dVal)
	Creates a message with the given text and double value and places it on the queue.

int	SomeMessages (void) const
	Reads the message on the queue (but does not delete it).

void	ProcessMessage (void)
	Reads the message on the queue and removes it from the queue.

Message *	ProcessNextMessage (void)
	Reads the next message on the queue and removes it from the queue.

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

Public Attributes
struct JSBSim::FGMassBalance::Inputs	in

Additional Inherited Members
Public Types inherited from JSBSim::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...

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 double	PitotTotalPressure (double mach, double p)
	Compute the total pressure in front of the Pitot tube.

static double	MachFromImpactPressure (double qc, double p)
	Compute the Mach number from the differential pressure (qc) and the static pressure.

static double	VcalibratedFromMach (double mach, double p)
	Calculate the calibrated airspeed from the Mach number.

static double	MachFromVcalibrated (double vcas, double p)
	Calculate the Mach number from the calibrated airspeed.Based on the formulas in the US Air Force Aircraft Performance Flight Testing Manual (AFFTC-TIH-99-01).

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)

static double	GaussianRandomNumber (void)

Static Public Attributes inherited from JSBSim::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 JSBSim::FGModel
bool	Upload (Element *el, bool preLoad)
	Uploads this model in memory.

static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Protected Attributes inherited from JSBSim::FGModel
unsigned int	exe_ctr

unsigned int	rate

std::string	Name

FGFDMExec *	FDMExec

FGPropertyManager *	PropertyManager

Protected Attributes inherited from JSBSim::FGModelFunctions
std::vector< FGFunction * >	PreFunctions

std::vector< FGFunction * >	PostFunctions

FGPropertyReader	LocalProperties

static Message	localMsg

static std::queue< Message >	Messages

static unsigned int	messageId = 0

static constexpr double	radtodeg = 180. / 3.14159265358979323846

static constexpr double	degtorad = 3.14159265358979323846 / 180.

static constexpr double	hptoftlbssec = 550.0

static constexpr double	psftoinhg = 0.014138

static constexpr double	psftopa = 47.88

static constexpr double	ktstofps = 1.68781

static constexpr double	fpstokts = 1.0 / ktstofps

static constexpr double	inchtoft = 1.0/12.0

static constexpr double	fttom = 0.3048

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__

static int	gaussian_random_number_phase = 0

Detailed Description

Models weight, balance and moment of inertia information.

Maintains a vector of point masses. Sums the contribution of all, and provides this to FGPropagate. Loads the <mass_balance> section of the aircraft configuration file. There can be any number of <pointmasses>. Each can also have a shape which - if present - causes an associated moment of inertia to be calculated based on the shape. Note that a cylinder is solid, a tube is hollow, a ball is solid and a sphere is hollow.

The inertia tensor must be specified in the structural frame (x axis positive aft, y axis positive out of the right wing and z axis upward). The sign of the inertia cross products are optional by JSBSim. if negated_crossproduct_inertia == "true", then define: ixy = -integral( x * y * dm ), ixz = -integral( x * z * dm ), iyz = -integral( y * z * dm ). else if negated_crossproduct_inertia == "false", then define: ixy = integral( x * y * dm ), ixz = integral( x * z * dm ), iyz = integral( y * z * dm ). default is negated_crossproduct_inertia = "true". We strongly recommend defining negated_crossproduct_inertia = "false", which is consistent with the specifications in the field of flight dynamics.

Configuration File Format for <mass_balance> Section:

<mass_balance negated_crossproduct_inertia="true|false">
    <ixx unit="{SLUG*FT2 | KG*M2}"> {number} </ixx>
    <iyy unit="{SLUG*FT2 | KG*M2}"> {number} </iyy>
    <izz unit="{SLUG*FT2 | KG*M2}"> {number} </izz>
    <ixy unit="{SLUG*FT2 | KG*M2}"> {number} </ixy>
    <ixz unit="{SLUG*FT2 | KG*M2}"> {number} </ixz>
    <iyz unit="{SLUG*FT2 | KG*M2}"> {number} </iyz>
    <emptywt unit="{LBS | KG"> {number} </emptywt>
    <location name="CG" unit="{IN | FT | M}">
        <x> {number} </x>
        <y> {number} </y>
        <z> {number} </z>
    </location>
    [<pointmass name="{string}">
        <form shape="{tube | cylinder | sphere | ball}">
           <radius unit="{IN | FT | M}"> {number} </radius>
           <length unit="{IN | FT | M}"> {number} </length>
        </form> 
        <weight unit="{LBS | KG}"> {number} </weight>
        <location name="{string}" unit="{IN | FT | M}">
            <x> {number} </x>
            <y> {number} </y>
            <z> {number} </z>
        </location>
    </pointmass>
    ... other point masses ...]
</mass_balance>

@see Stevens and Lewis, "Flight Control & Simulation"
@see Bernard Etkin, " Dynamics Of Atmosferic Flight"
@see https://en.wikipedia.org/wiki/Moment_of_inertia#Inertia_tensor
@see https://www.mathworks.com/help/physmod/sm/ug/specify-custom-inertia.html

Definition at line 122 of file FGMassBalance.h.

Constructor & Destructor Documentation

◆ FGMassBalance()

JSBSim::FGMassBalance::FGMassBalance ( FGFDMExec * fdmex )

explicit

Definition at line 56 of file FGMassBalance.cpp.

◆ ~FGMassBalance()

JSBSim::FGMassBalance::~FGMassBalance ( )

Definition at line 79 of file FGMassBalance.cpp.

Member Function Documentation

◆ AddPointMass()

void JSBSim::FGMassBalance::AddPointMass ( Element * el )

Definition at line 266 of file FGMassBalance.cpp.

◆ GetDeltaXYZcg() [1/2]

double JSBSim::FGMassBalance::GetDeltaXYZcg ( int axis ) const

inline

Definition at line 149 of file FGMassBalance.h.

◆ GetDeltaXYZcg() [2/2]

const FGColumnVector3 & JSBSim::FGMassBalance::GetDeltaXYZcg ( void ) const

inline

Definition at line 148 of file FGMassBalance.h.

◆ GetEmptyWeight()

double JSBSim::FGMassBalance::GetEmptyWeight ( void ) const

inline

Definition at line 143 of file FGMassBalance.h.

◆ GetJ()

const FGMatrix33 & JSBSim::FGMassBalance::GetJ ( void ) const

inline

Returns the inertia matrix expressed in the body frame.

Definition at line 193 of file FGMassBalance.h.

◆ GetJinv()

const FGMatrix33 & JSBSim::FGMassBalance::GetJinv ( void ) const

inline

Returns the inverse of the inertia matrix expressed in the body frame.

Definition at line 195 of file FGMassBalance.h.

◆ GetMass()

double JSBSim::FGMassBalance::GetMass ( void ) const

inline

Definition at line 141 of file FGMassBalance.h.

◆ GetMassPropertiesReport()

void JSBSim::FGMassBalance::GetMassPropertiesReport ( int i )

Definition at line 452 of file FGMassBalance.cpp.

◆ GetPointmassInertia()

FGMatrix33 JSBSim::FGMassBalance::GetPointmassInertia	(	double	mass_sl,
		const FGColumnVector3 &	r ) const

inline

Computes the inertia contribution of a pointmass.

Computes and returns the inertia matrix of a pointmass of mass slugs at the given vector r in the structural frame. The units should be for the mass in slug and the vector in the structural frame as usual in inches.

Parameters

mass_sl	the mass of this single pointmass given in slugs
r	the location of this single pointmass in the structural frame

Definition at line 159 of file FGMassBalance.h.

◆ GetPointMassMoment()

const FGColumnVector3 & JSBSim::FGMassBalance::GetPointMassMoment ( void )

Definition at line 336 of file FGMassBalance.cpp.

◆ GetTotalPointMassWeight()

double JSBSim::FGMassBalance::GetTotalPointMassWeight ( void ) const

Definition at line 324 of file FGMassBalance.cpp.

◆ GetWeight()

double JSBSim::FGMassBalance::GetWeight ( void ) const

inline

Definition at line 142 of file FGMassBalance.h.

◆ GetXYZcg() [1/2]

double JSBSim::FGMassBalance::GetXYZcg ( int axis ) const

inline

Definition at line 147 of file FGMassBalance.h.

◆ GetXYZcg() [2/2]

const FGColumnVector3 & JSBSim::FGMassBalance::GetXYZcg ( void ) const

inline

Returns the coordinates of the center of gravity expressed in the structural frame.

Definition at line 146 of file FGMassBalance.h.

◆ InitModel()

bool JSBSim::FGMassBalance::InitModel ( void )

overridevirtual

Reimplemented from JSBSim::FGModelFunctions.

Definition at line 88 of file FGMassBalance.cpp.

◆ Load()

bool JSBSim::FGMassBalance::Load ( Element * el )

overridevirtual

Reimplemented from JSBSim::FGModel.

Definition at line 132 of file FGMassBalance.cpp.

◆ Run()

bool JSBSim::FGMassBalance::Run ( bool Holding )

overridevirtual

Runs the Mass Balance 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 JSBSim::FGModel.

Definition at line 181 of file FGMassBalance.cpp.

◆ SetAircraftBaseInertias()

void JSBSim::FGMassBalance::SetAircraftBaseInertias ( const FGMatrix33 & BaseJ )

inline

Definition at line 196 of file FGMassBalance.h.

◆ SetBaseCG()

void JSBSim::FGMassBalance::SetBaseCG ( const FGColumnVector3 & CG )

inline

Definition at line 186 of file FGMassBalance.h.

◆ SetEmptyWeight()

void JSBSim::FGMassBalance::SetEmptyWeight ( double EW )

inline

Definition at line 185 of file FGMassBalance.h.

◆ StructuralToBody()

FGColumnVector3 JSBSim::FGMassBalance::StructuralToBody ( const FGColumnVector3 & r ) const

Conversion from the structural frame to the body frame.

Converts the location given in the structural frame coordinate system to the body frame. The units of the structural frame are assumed to be in inches. The unit of the result is in ft.

Parameters

r	vector coordinate in the structural reference frame (X positive aft, measurements in inches).

Returns: vector coordinate in the body frame, in feet.

Definition at line 364 of file FGMassBalance.cpp.

Member Data Documentation

◆ in

struct JSBSim::FGMassBalance::Inputs JSBSim::FGMassBalance::in

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

Classes

Public Member Functions

Public Attributes

Additional Inherited Members

Detailed Description

Configuration File Format for <mass_balance> Section:

Constructor & Destructor Documentation

◆ FGMassBalance()

◆ ~FGMassBalance()

Member Function Documentation

◆ AddPointMass()

◆ GetDeltaXYZcg() [1/2]

◆ GetDeltaXYZcg() [2/2]

◆ GetEmptyWeight()

◆ GetJ()

◆ GetJinv()

◆ GetMass()

◆ GetMassPropertiesReport()

◆ GetPointmassInertia()

◆ GetPointMassMoment()

◆ GetTotalPointMassWeight()

◆ GetWeight()

◆ GetXYZcg() [1/2]

◆ GetXYZcg() [2/2]

◆ InitModel()

◆ Load()

◆ Run()

◆ SetAircraftBaseInertias()

◆ SetBaseCG()

◆ SetEmptyWeight()

◆ StructuralToBody()

Member Data Documentation

◆ in