JSBSim Flight Dynamics Model  1.0 (02 March 2017)
An Open Source Flight Dynamics and Control Software Library in C++
FGGain Class Reference

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

#include <FGGain.h>

+ Inheritance diagram for FGGain:
+ Collaboration diagram for FGGain:

Public Member Functions

 FGGain (FGFCS *fcs, Element *element)
 
bool Run (void)
 
- Public Member Functions inherited from FGFCSComponent
 FGFCSComponent (FGFCS *fcs, Element *el)
 Constructor.
 
virtual ~FGFCSComponent ()
 Destructor.
 
std::string GetName (void) const
 
double GetOutput (void) const
 
virtual double GetOutputPct (void) const
 
std::string GetType (void) const
 
virtual void ResetPastStates (void)
 
void SetDtForFrameCount (int FrameCount)
 
virtual void SetOutput (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.
 
std::string GetVersion (void)
 Returns the version number of JSBSim. More...
 
void PutMessage (const Message &msg)
 Places a Message structure on the Message queue. More...
 
void PutMessage (const std::string &text)
 Creates a message with the given text and places it on the queue. More...
 
void PutMessage (const std::string &text, bool bVal)
 Creates a message with the given text and boolean value and places it on the queue. More...
 
void PutMessage (const std::string &text, int iVal)
 Creates a message with the given text and integer value and places it on the queue. More...
 
void PutMessage (const std::string &text, double dVal)
 Creates a message with the given text and double value and places it on the queue. More...
 
int SomeMessages (void)
 Reads the message on the queue (but does not delete it). More...
 
void ProcessMessage (void)
 Reads the message on the queue and removes it from the queue. More...
 
MessageProcessNextMessage (void)
 Reads the next message on the queue and removes it from the queue. More...
 

Additional Inherited Members

- Public Types inherited from FGJSBBase
enum  { eL = 1, eM, eN }
 Moments L, M, N.
 
enum  { eP = 1, eQ, eR }
 Rates P, Q, R.
 
enum  { eU = 1, eV, eW }
 Velocities U, V, W.
 
enum  { eX = 1, eY, eZ }
 Positions X, Y, Z.
 
enum  { ePhi = 1, eTht, ePsi }
 Euler angles Phi, Theta, Psi.
 
enum  { eDrag = 1, eSide, eLift }
 Stability axis forces, Drag, Side force, Lift.
 
enum  { eRoll = 1, ePitch, eYaw }
 Local frame orientation Roll, Pitch, Yaw.
 
enum  { eNorth = 1, eEast, eDown }
 Local frame position North, East, Down.
 
enum  { eLat = 1, eLong, eRad }
 Locations Radius, Latitude, Longitude.
 
enum  {
  inNone = 0, inDegrees, inRadians, inMeters,
  inFeet
}
 Conversion specifiers.
 
- Static Public Member Functions inherited from FGJSBBase
static double CelsiusToFahrenheit (double celsius)
 Converts from degrees Celsius to degrees Fahrenheit. More...
 
static double CelsiusToKelvin (double celsius)
 Converts from degrees Celsius to degrees Kelvin. More...
 
static double CelsiusToRankine (double celsius)
 Converts from degrees Celsius to degrees Rankine. More...
 
static double Constrain (double min, double value, double max)
 Constrain a value between a minimum and a maximum value.
 
static bool EqualToRoundoff (double a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, float b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (double a, float b)
 Finite precision comparison. More...
 
static double FahrenheitToCelsius (double fahrenheit)
 Converts from degrees Fahrenheit to degrees Celsius. More...
 
static double FeetToMeters (double measure)
 Converts from feet to meters. More...
 
static double GaussianRandomNumber (void)
 
static double KelvinToCelsius (double kelvin)
 Converts from degrees Kelvin to degrees Celsius. More...
 
static double KelvinToFahrenheit (double kelvin)
 Converts from degrees Kelvin to degrees Fahrenheit. More...
 
static double KelvinToRankine (double kelvin)
 Converts from degrees Kelvin to degrees Rankine. More...
 
static double MachFromVcalibrated (double vcas, double p, double psl, double rhosl)
 Calculate the Mach number from the calibrated airspeed. More...
 
static double PitotTotalPressure (double mach, double p)
 Compute the total pressure in front of the Pitot tube. More...
 
static double RankineToCelsius (double rankine)
 Converts from degrees Rankine to degrees Celsius. More...
 
static double RankineToKelvin (double rankine)
 Converts from degrees Rankine to degrees Kelvin. More...
 
static double sign (double num)
 
static double VcalibratedFromMach (double mach, double p, double psl, double rhosl)
 Calculate the calibrated airspeed from the Mach number. More...
 
- Static Public Attributes inherited from FGJSBBase
static short debug_lvl = 1
 
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
 
- Protected Member Functions inherited from FGFCSComponent
virtual void bind ()
 
void Clip (void)
 
void Delay (void)
 
- Protected Member Functions inherited from FGJSBBase
void Debug (int)
 
- Static Protected Member Functions inherited from FGJSBBase
static std::string CreateIndexedPropertyName (const std::string &Property, int index)
 
- Protected Attributes inherited from FGFCSComponent
bool clip
 
double clipmax
 
FGPropertyNode_ptr ClipMaxPropertyNode
 
float clipMaxSign
 
double clipmin
 
FGPropertyNode_ptr ClipMinPropertyNode
 
float clipMinSign
 
unsigned int delay
 
double delay_time
 
double dt
 
FGFCSfcs
 
int index
 
std::vector< std::string > InitNames
 
std::vector< FGPropertyValue * > InitNodes
 
std::vector< float > InitSigns
 
double Input
 
std::vector< std::string > InputNames
 
std::vector< FGPropertyValue * > InputNodes
 
std::vector< float > InputSigns
 
bool IsOutput
 
std::string Name
 
double Output
 
std::vector< double > output_array
 
std::vector< FGPropertyNode_ptr > OutputNodes
 
FGPropertyManagerPropertyManager
 
FGPropertyNode_ptr treenode
 
std::string Type
 
- Static Protected Attributes inherited from FGJSBBase
static const double degtorad = 0.017453292519943295769236907684886
 
static const double fpstokts = 1.0/ktstofps
 
static const double fttom = 0.3048
 
static int gaussian_random_number_phase = 0
 
static const double hptoftlbssec = 550.0
 
static const double in3tom3 = 1.638706E-5
 
static const double inchtoft = 0.08333333
 
static const double inhgtopa = 3386.38
 
static const std::string JSBSim_version = "1.0 " __DATE__ " " __TIME__
 
static const double kgtolb = 2.20462
 
static const double kgtoslug = 0.06852168
 
static const double ktstofps = 1.68781
 
static const double lbtoslug = 1.0/slugtolb
 
static Message localMsg
 
static const double m3toft3 = 1.0/(fttom*fttom*fttom)
 
static double Mair = 28.9645
 
static unsigned int messageId = 0
 
static std::queue< MessageMessages
 
static const std::string needed_cfg_version = "2.0"
 
static const double psftoinhg = 0.014138
 
static const double psftopa = 47.88
 
static const double radtodeg = 57.295779513082320876798154814105
 
static double Reng = 1716.56
 
static double Rstar = 1545.348
 
static const double SHRatio = 1.40
 
static const double slugtolb = 32.174049
 

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
1.15

Definition at line 218 of file FGGain.h.


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