FGExternalForce Class Reference

#include <FGExternalForce.h>

Detailed Description

This class encapsulates an individual force 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>

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

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 direction is not actually required to be specified as a unit vector, but prior to the force vector being calculated, the direction vector is normalized.

Definition at line 131 of file FGExternalForce.h.


Public Member Functions
	FGExternalForce (const FGExternalForce &extForce)
	Copy Constructor.
	FGExternalForce (FGFDMExec FDMExec, Element el, int index)
	Constructor.
	FGExternalForce (FGFDMExec *FDMExec)
	Constructor.
double	GetAzimuth (void) const
FGColumnVector3 &	GetBodyForces (void)
double	GetMagnitude (void) const
double	GetX (void) const
double	GetY (void) const
double	GetZ (void) const
void	SetAzimuth (double az)
void	SetMagnitude (double mag)
void	SetX (double x)
void	SetY (double y)
void	SetZ (double z)
	~FGExternalForce ()
	Destructor.

Constructor & Destructor Documentation

FGExternalForce ( FGFDMExec * FDMExec )

Parameters:

FDMExec

pointer to the main executive class.

FGExternalForce	(	FGFDMExec *	FDMExec,
		Element *	el,
		int	index
	)

Parameters:

	FDMExec	pointer to the main executive class.
	el	pointer to the XML element defining an individual force.
	index	the position of this force object in the whole list.

Definition at line 64 of file FGExternalForce.cpp.

FGExternalForce ( const FGExternalForce & extForce )

Parameters:

extForce

a reference to an existing FGExternalForce object

Definition at line 138 of file FGExternalForce.cpp.

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

FGExternalForce Class Reference

Detailed Description

Public Member Functions

Constructor & Destructor Documentation