FlightGear: JSBSim::FGGain Class Reference

Encapsulates a gain component for the flight control system. More...

#include <FGGain.h>

Public Member Functions
	FGGain (FGFCS fcs, Element element)

	~FGGain ()

bool	Run (void) override

Public Member Functions inherited from JSBSim::FGFCSComponent
	FGFCSComponent (FGFCS fcs, Element el)
	Constructor.

virtual	~FGFCSComponent ()
	Destructor.

virtual void	SetOutput (void)

double	GetOutput (void) const

std::string	GetName (void) const

std::string	GetType (void) const

virtual double	GetOutputPct (void) const

virtual void	ResetPastStates (void)

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::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::FGFCSComponent
void	Delay (void)

void	Clip (void)

void	CheckInputNodes (size_t MinNodes, size_t MaxNodes, Element *el)

virtual void	bind (Element *el)

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

Protected Attributes inherited from JSBSim::FGFCSComponent
FGFCS *	fcs

FGPropertyManager *	PropertyManager

std::vector< FGPropertyNode_ptr >	OutputNodes

FGParameter_ptr	ClipMin

FGParameter_ptr	ClipMax

std::vector< FGPropertyValue_ptr >	InitNodes

std::vector< FGPropertyValue_ptr >	InputNodes

std::vector< double >	output_array

std::string	Type

std::string	Name

double	Input

double	Output

double	delay_time

unsigned int	delay

int	index

double	dt

bool	clip

bool	cyclic_clip

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

Encapsulates a gain component for the flight control system.

The gain component merely multiplies the input by a gain. The pure gain form of the component specification is:

<pure_gain name="name">
  <input> {[-]property} </input>
  <gain> {property name | value} </gain>
  [<clipto>
    <min> {property name | value} </min>
    <max> {property name | value} </max>
  </clipto>]
  [<output> {property} </output>]
</pure_gain>

Example:

<pure_gain name="Roll AP Wing Leveler">
  <input>fcs/attitude/sensor/phi-rad</input>
  <gain>2.0</gain>
  <clipto>
    <min>-0.255</min>
    <max>0.255</max>
  </clipto>
</pure_gain>

Note: the input property name may be immediately preceded by a minus sign to invert that signal.

The scheduled gain component multiplies the input by a variable gain that is dependent on another property (such as qbar, altitude, etc.). The lookup mapping is in the form of a table. This kind of component might be used, for example, in a case where aerosurface deflection must only be commanded to acceptable settings - i.e at higher qbar the commanded elevator setting might be attenuated. The form of the scheduled gain component specification is:

<scheduled_gain name="name">
  <input> {[-]property} </input>
  <table>
    <tableData>
      ...
    </tableData>
  </table>
  [<clipto>
    <min> {[-]property name | value} </min>
    <max> {[-]property name | value} </max>
  </clipto>]
  [<gain> {property name | value} </gain>]
  [<output> {property} </output>]
</scheduled_gain>

Example:

<scheduled_gain name="Scheduled Steer Pos Deg">
    <input>fcs/steer-cmd-norm</input>
    <table>
        <independentVar>velocities/vg-fps</independentVar>
        <tableData>
            10.0        80.0
            50.0        15.0
            150.0       2.0
        </tableData>
    </table>
    <gain>0.017</gain>
    <output>fcs/steer-pos-rad</output>
</scheduled_gain>

An overall GAIN may be supplied that is multiplicative with the scheduled gain.

Note: the input property name may be immediately preceded by a minus sign to invert that signal.

In the example above, we see the utility of the overall gain value in effecting a degrees-to-radians conversion.

The aerosurface scale component is a modified version of the simple gain component. The purpose for this component is to take control inputs from the domain minimum and maximum, as specified (or from -1 to +1 by default) and scale them to map to a specified range. This can be done, for instance, to match the component outputs to the expected inputs to a flight control system.

The zero_centered element dictates whether the domain-to-range mapping is linear or centered about zero. For example, if zero_centered is false, and if the domain or range is not symmetric about zero, and an input value is zero, the output will not be zero. Let's say that the domain is min=-2 and max=+4, with a range of -1 to +1. If the input is 0.0, then the "normalized" input is calculated to be 33% of the way from the minimum to the maximum. That input would be mapped to an output of -0.33, which is 33% of the way from the range minimum to maximum. If zero_centered is set to true (or 1) then an input of 0.0 will be mapped to an output of 0.0, although if either the domain or range are unsymmetric about 0.0, then the scales for the positive and negative portions of the input domain (above and below 0.0) will be different. The zero_centered element is true by default. Note that this feature may be important for some control surface mappings, where the maximum upper and lower deflections may be different, but where a zero setting is desired to be the "undeflected" value, and where full travel of the stick is desired to cause a full deflection of the control surface.

The form of the aerosurface scaling component specification is:

<aerosurface_scale name="name">
  <input> {[-]property name} </input>
  <domain>
    <min> {value} </min>   <!-- If omitted, default is -1.0 ->
    <max> {value} </max>   <!-- If omitted, default is  1.0 ->
  </domain>
  <range>
    <min> {value} </min>   <!-- If omitted, default is 0 ->
    <max> {value} </max>   <!-- If omitted, default is 0 ->
  </range>
  <zero_centered< value </zero_centered>
  [<clipto>
    <min> {[-]property name | value} </min>
    <max> {[-]property name | value} </max>
  </clipto>]
  [<gain> {property name | value} </gain>]
  [<output> {property} </output>]
</aerosurface_scale>

Note: the input property name may be immediately preceded by a minus sign to invert that signal.

For instance, the normal and expected ability of a pilot to push or pull on a control stick is about 50 pounds. The input to the pitch channel block diagram of a flight control system is often in units of pounds. Yet, the joystick control input usually defines a span from -1 to +1. The aerosurface_scale form of the gain component maps the inputs to the desired output range. The example below shoes a simple aerosurface_scale component that maps the joystick input to a range of +/- 50, which represents pilot stick force in pounds for the F-16.

<aerosurface_scale name="Pilot input">
  <input>fcs/elevator-cmd-norm</input>
  <range>
    <min> -50 </min>   <!-- If omitted, default is 0 ->
    <max>  50 </max>   <!-- If omitted, default is 0 ->
  </range>
</aerosurface_scale>

Author: Jon S. Berndt

Version: $Revision$

Definition at line 217 of file FGGain.h.

Constructor & Destructor Documentation

◆ FGGain()

JSBSim::FGGain::FGGain	(	FGFCS *	fcs,
		Element *	element )

Definition at line 52 of file FGGain.cpp.

◆ ~FGGain()

JSBSim::FGGain::~FGGain ( )

Definition at line 127 of file FGGain.cpp.

Member Function Documentation

◆ Run()

bool JSBSim::FGGain::Run ( void )

overridevirtual

Reimplemented from JSBSim::FGFCSComponent.

Definition at line 136 of file FGGain.cpp.

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

Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ FGGain()

◆ ~FGGain()

Member Function Documentation

◆ Run()