FGKinemat Class Reference

Detailed Description

Encapsulates a kinematic (mechanical) component for the flight control system.

This component models the action of a moving effector, such as an aerosurface or other mechanized entity such as a landing gear strut for the purpose of effecting vehicle control or configuration. The form of the component specification is:

<kinematic name="Gear Control">
  <input> [-]property </input>
  [<noscale/>]
  <traverse>
    <setting>
      <position> number </position>
      <time> number </time>
    </setting>
    ...
  </traverse>
  [<clipto>
    <min> {[-]property name | value} </min>
    <max> {[-]property name | value} </max>
  </clipto>]
  [<gain> {property name | value} </gain>]
  [<output> {property} </output>]
</kinematic>

The detent is the position that the component takes, and the lag is the time it takes to get to that position from an adjacent setting. For example:

<kinematic name="Gear Control">
  <input>gear/gear-cmd-norm</input>
  <traverse>
    <setting>
      <position>0</position>
      <time>0</time>
    </setting>
    <setting>
      <position>1</position>
      <time>5</time>
    </setting>
  </traverse>
  <output>gear/gear-pos-norm</output>
</kinematic>

In this case, it takes 5 seconds to get to a 1 setting. As this is a software mechanization of a servo-actuator, there should be an output specified.

Positions must be given in ascending order.

By default, the input is assumed to be in the range [-1;1] and is scaled to the value specified in the last <position> tag. This behavior can be modified by adding a <noscale> tag to the component definition: in that case, the input value is directly used to determine the current position of the component.

Definition at line 113 of file FGKinemat.h.

#include <FGKinemat.h>

Inheritance diagram for FGKinemat:

Collaboration diagram for FGKinemat:

Public Member Functions
	FGKinemat (FGFCS *fcs, Element *element)
	Constructor.
	~FGKinemat ()
	Destructor.
double	GetOutputPct () const override
	Kinematic component output value.
bool	Run (void) override
	Run method, overrides FGModel::Run().
Public Member Functions inherited from FGFCSComponent
	FGFCSComponent (FGFCS *fcs, Element *el)
	Constructor.
virtual	~FGFCSComponent ()
	Destructor.
std::string	GetName (void) const
double	GetOutput (void) const
std::string	GetType (void) const
virtual void	ResetPastStates (void)
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.

Additional Inherited Members
Public Types inherited from 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 Public Member Functions inherited from FGJSBBase
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 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 Public Attributes inherited from 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 FGFCSComponent
virtual void	bind (Element *el, FGPropertyManager *pm)
void	CheckInputNodes (size_t MinNodes, size_t MaxNodes, Element *el)
void	Clip (void)
void	Delay (void)
Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)
Protected Attributes inherited from FGFCSComponent
bool	clip
FGParameter_ptr	ClipMax
FGParameter_ptr	ClipMin
bool	cyclic_clip
unsigned int	delay
double	delay_time
double	dt
FGFCS *	fcs
int	index
std::vector< FGPropertyValue_ptr >	InitNodes
double	Input
std::vector< FGPropertyValue_ptr >	InputNodes
std::string	Name
double	Output
std::vector< double >	output_array
std::vector< SGPropertyNode_ptr >	OutputNodes
std::string	Type
Static Protected Attributes inherited from FGJSBBase
static constexpr double	radtodeg = 180. / M_PI
static constexpr double	degtorad = M_PI / 180.
static constexpr double	hptoftlbssec = 550.0
static constexpr double	psftoinhg = 0.014138
static constexpr double	psftopa = 47.88
static constexpr double	fttom = 0.3048
static constexpr double	ktstofps = 1852./(3600*fttom)
static constexpr double	fpstokts = 1.0 / ktstofps
static constexpr double	inchtoft = 1.0/12.0
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__

Constructor & Destructor Documentation

FGKinemat()

FGKinemat	(	FGFCS *	fcs,
		Element *	element
	)

Constructor.

Parameters

fcs	A reference to the current flight control system.
element	reference to the current configuration file node.

Definition at line 52 of file FGKinemat.cpp.

  : FGFCSComponent(fcs, element)
{
  CheckInputNodes(1, 1, element);
 
  Output = 0;
  DoScale = true;
 
  if (element->FindElement("noscale")) DoScale = false;
 
  Element* traverse_element = element->FindElement("traverse");
  Element* setting_element = traverse_element->FindElement("setting");
  while (setting_element) {
    double tmpDetent = setting_element->FindElementValueAsNumber("position");
    double tmpTime = setting_element->FindElementValueAsNumber("time");
    Detents.push_back(tmpDetent);
    TransitionTimes.push_back(tmpTime);
    setting_element = traverse_element->FindNextElement("setting");
  }
 
  if (Detents.size() <= 1) {
    stringstream s;
    s << "Kinematic component " << Name
      << " must have more than 1 setting element";
    cerr << element->ReadFrom() << endl << s.str() << endl;
    throw BaseException(s.str());
  }
 
  bind(element, fcs->GetPropertyManager().get());
 
  Debug(0);
}

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~FGKinemat()

~FGKinemat

(

)

Destructor.

Definition at line 87 of file FGKinemat.cpp.

{
  Debug(1);
}

Member Function Documentation

GetOutputPct()

double GetOutputPct ( void  ) const

inlineoverridevirtual

Kinematic component output value.

Returns

the current output of the kinematic object on the range of [0,1].

Reimplemented from FGFCSComponent.

Definition at line 126 of file FGKinemat.h.

  { return (Output-Detents[0])/(Detents.back()-Detents[0]); }

Run()

bool Run ( void  )

overridevirtual

Run method, overrides FGModel::Run().

Returns

false on success, true on failure. The routine doing the work.

Reimplemented from FGFCSComponent.

Definition at line 94 of file FGKinemat.cpp.

{
  double dt0 = dt;
 
  Input = InputNodes[0]->getDoubleValue();
 
  if (DoScale) Input *= Detents.back();
 
  if (!OutputNodes.empty())
    Output = OutputNodes[0]->getDoubleValue();
 
  Input = Constrain(Detents.front(), Input, Detents.back());
 
  if (fcs->GetTrimStatus())
    // When trimming the output must be reached in one step
    Output = Input;
  else {
    // Process all detent intervals the movement traverses until either the
    // final value is reached or the time interval has finished.
    while ( dt0 > 0.0 && !EqualToRoundoff(Input, Output) ) {
 
      // Find the area where Output is in
      unsigned int ind;
      for (ind = 1; (Input < Output) ? Detents[ind] < Output : Detents[ind] <= Output ; ++ind)
        if (ind >= Detents.size())
          break;
 
      // A transition time of 0.0 means an infinite rate.
      // The output is reached in one step
      if (TransitionTimes[ind] <= 0.0) {
        Output = Input;
        break;
      } else {
        // Compute the rate in this area
        double Rate = (Detents[ind] - Detents[ind-1])/TransitionTimes[ind];
        // Compute the maximum input value inside this area
        double ThisInput = Constrain(Detents[ind-1], Input, Detents[ind]);
        // Compute the time to reach the value in ThisInput
        double ThisDt = fabs((ThisInput-Output)/Rate);
 
        // and clip to the timestep size
        if (dt0 < ThisDt) {
          ThisDt = dt0;
          if (Output < Input)
            Output += ThisDt*Rate;
          else
            Output -= ThisDt*Rate;
        } else
          // Handle this case separate to make shure the termination condition
          // is met even in inexact arithmetics ...
          Output = ThisInput;
 
        dt0 -= ThisDt;
      }
    }
  }
 
  Clip();
  SetOutput();
 
  return true;
}

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

• FGKinemat.h
• FGKinemat.cpp