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JSBSim::FGExternalForce Class Reference

Encapsulates code that models an individual arbitrary force, moment or a combination thereof. More...

#include <FGExternalForce.h>

Inherits JSBSim::FGForce.

Public Member Functions

 FGExternalForce (FGFDMExec *FDMExec)
 Constructor.
 
 FGExternalForce (const FGExternalForce &extForce)
 Copy Constructor.
 
 ~FGExternalForce () override
 Destructor.
 
void setForce (Element *el)
 
void setMoment (Element *el)
 
const FGColumnVector3 & GetBodyForces (void) override
 
- Public Member Functions inherited from JSBSim::FGForce
 FGForce (FGFDMExec *FDMExec)
 Constructor.
 
 FGForce (const FGForce &force)
 
virtual ~FGForce ()
 Destructor.
 
double GetBodyXForce (void) const
 
double GetBodyYForce (void) const
 
double GetBodyZForce (void) const
 
const FGColumnVector3 & GetMoments (void) const
 
void SetLocation (double x, double y, double z)
 
void SetActingLocation (double x, double y, double z)
 Acting point of application.
 
void SetLocationX (double x)
 
void SetLocationY (double y)
 
void SetLocationZ (double z)
 
double SetActingLocationX (double x)
 
double SetActingLocationY (double y)
 
double SetActingLocationZ (double z)
 
void SetLocation (const FGColumnVector3 &vv)
 
void SetActingLocation (const FGColumnVector3 &vv)
 
double GetLocationX (void) const
 
double GetLocationY (void) const
 
double GetLocationZ (void) const
 
double GetActingLocationX (void) const
 
double GetActingLocationY (void) const
 
double GetActingLocationZ (void) const
 
const FGColumnVector3 & GetLocation (void) const
 
const FGColumnVector3 & GetActingLocation (void) const
 
void SetAnglesToBody (double broll, double bpitch, double byaw)
 
void SetAnglesToBody (const FGColumnVector3 &vv)
 
void UpdateCustomTransformMatrix (void)
 
void SetPitch (double pitch)
 
void SetYaw (double yaw)
 
double GetPitch (void) const
 
double GetYaw (void) const
 
const FGColumnVector3 & GetAnglesToBody (void) const
 
double GetAnglesToBody (int axis) const
 
void SetTransformType (TransformType ii)
 
TransformType GetTransformType (void) const
 
const FGMatrix33 & Transform (void) const
 
- 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.
 

Additional Inherited Members

- Public Types inherited from JSBSim::FGForce
enum  TransformType { tNone , tWindBody , tLocalBody , tCustom }
 
- 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
 
static std::string CreateIndexedPropertyName (const std::string &Property, int index)
 
- Protected Attributes inherited from JSBSim::FGForce
FGFDMExec * fdmex
 
FGMassBalance * MassBalance
 
FGColumnVector3 vFn
 
FGColumnVector3 vMn
 
FGColumnVector3 vOrient
 
TransformType ttype
 
FGColumnVector3 vXYZn
 
FGColumnVector3 vActingXYZn
 
FGMatrix33 mT
 
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/(fttom*fttom*fttom)
 
static constexpr double in3tom3 = inchtoft*inchtoft*inchtoft/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

Encapsulates code that models an individual arbitrary force, moment or a combination thereof.

This class encapsulates an individual reaction applied at the specified location on the vehicle, and oriented as specified in one of three frames:

  • BODY frame is defined with the X axis positive forward, the Y axis positive out the right wing, and the Z axis completing the set positive downward out the belly of the aircraft.
  • LOCAL frame is a world-based frame, with X positive north, Y positive east and Z completing the right handed system positive down towards the center of the Earth.
  • WIND frame (rotated) has X negative into the wind vector (in other words drag is along the positive X axis), the Z axis is perpendicular to X and positive up (lift) but in the aircraft XZ plane, and Y completes the right handed system. This is modified from a normal wind frame definition, which is rotated about the Y axis 180 degrees from this WIND frame.

Much of the substance of this class is located in the FGForce base class, from which this class is derived.

Here is the XML definition of a force (optional items are in []):

<force name="name" frame="BODY | LOCAL | WIND">
[<function> ... </function>]
<location unit="{IN | M}">
<x> {number} </x>
<y> {number} </y>
<z> {number} </z>
</location>
[<direction> <!-- optional initial direction vector -->
<x> {number} </x>
<y> {number} </y>
<z> {number} </z>
</direction>]
</force>
name
const char * name
Definition fg_commands.cxx:1136

The location of the force vector, in structural coordinates, can be set at runtime through the following properties:

external_reactions/{force name}/location-x-in
external_reactions/{force name}/location-y-in
external_reactions/{force name}/location-z-in

The XML definition of a moment (optional items are in []) is a bit simpler because you do not need to specify the location:

<moment name="name" frame="BODY | LOCAL | WIND">
[<function> ... </function>]
[<direction> <!-- optional initial direction vector -->
<x> {number} </x>
<y> {number} </y>
<z> {number} </z>
</direction>]
</moment>

The initial direction can optionally be set by specifying a unit vector in the chosen frame (body, local, or wind).

As an example, a parachute can be defined oriented in the wind axis frame so the drag always acts in the drag direction - opposite the positive X axis. That does not include the effects of parachute oscillations, but those could be handled in the calling application.

The force (or moment) direction is not actually required to be specified as a unit vector, but prior to the force (or moment) vector being calculated, the direction vector is normalized when initialized.

The force direction can be specified at runtime through setting any/all of the following properties:

external_reactions/{force name}/x
external_reactions/{force name}/y
external_reactions/{force name}/z

The moment direction can be specified at runtime through setting any/all of the following properties:

external_reactions/{moment name}/l
external_reactions/{moment name}/m
external_reactions/{moment name}/n

However in that case, the direction is no longer normalized.

When no <function> has been provided in the force definition, its magnitude can be specified through the following property:

external_reactions/{force name}/magnitude

When no <function> has been provided in the moment definition, its magnitude can be specified through the following property:

external_reactions/{moment name}/magnitude-lbsft

Definition at line 208 of file FGExternalForce.h.

Constructor & Destructor Documentation

◆ FGExternalForce() [1/2]

JSBSim::FGExternalForce::FGExternalForce ( FGFDMExec * FDMExec)
inlineexplicit

Constructor.

Parameters
FDMExecpointer to the main executive class.
elpointer to the XML element defining an individual force.

Definition at line 215 of file FGExternalForce.h.

◆ FGExternalForce() [2/2]

JSBSim::FGExternalForce::FGExternalForce ( const FGExternalForce & extForce)

Copy Constructor.

Parameters
extForcea reference to an existing FGExternalForce object

◆ ~FGExternalForce()

JSBSim::FGExternalForce::~FGExternalForce ( )
override

Destructor.

Definition at line 185 of file FGExternalForce.cpp.

Member Function Documentation

◆ GetBodyForces()

const FGColumnVector3 & JSBSim::FGExternalForce::GetBodyForces ( void )
overridevirtual

Reimplemented from JSBSim::FGForce.

Definition at line 194 of file FGExternalForce.cpp.

◆ setForce()

void JSBSim::FGExternalForce::setForce ( Element * el)

Definition at line 143 of file FGExternalForce.cpp.

◆ setMoment()

void JSBSim::FGExternalForce::setMoment ( Element * el)

Definition at line 171 of file FGExternalForce.cpp.

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