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JSBSim::FGFilter Class Reference

Encapsulates a filter for the flight control system. More...

#include <FGFilter.h>

Inherits JSBSim::FGFCSComponent.

Public Member Functions

 FGFilter (FGFCS *fcs, Element *element)
 
 ~FGFilter ()
 
bool Run (void) override
 
void ResetPastStates (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
 
- 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/(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 a filter for the flight control system.

The filter component can simulate any first or second order filter. The Tustin substitution is used to take filter definitions from LaPlace space to the time domain. The general format for a filter specification is:

<typename name="name">
<input> property </input>
<c1> value|property </c1>
[<c2> value|property </c2>]
[<c3> value|property </c3>]
[<c4> value|property </c4>]
[<c5> value|property </c5>]
[<c6> value|property </c6>]
[<clipto>
<min> {[-]property name | value} </min>
<max> {[-]property name | value} </max>
</clipto>]
[<output> property </output>]
</typename>
min
#define min(X, Y)
Definition FGOutputFG.cpp:60
name
const char * name
Definition fg_commands.cxx:1136

The numerical integration of filters is made by a Runge-Kutta scheme of order 2 except for the second order filter which uses an RK scheme of order 3.

For a lag filter of the form $\frac{C_1}{s+C_1}$, the corresponding filter definition is:

<lag_filter name="name">
<input> property </input>
<c1> value|property </c1>
[<clipto>
<min> {[-]property name | value} </min>
<max> {[-]property name | value} </max>
</clipto>]
[<output> property <output>]
</lag_filter>

As an example, for the specific filter $\frac{600}{s+600}$ the corresponding filter definition could be:

<lag_filter name="Heading Roll Error Lag">
<input> fcs/heading-command </input>
<c1> 600 </c1>
</lag_filter>
command
SGCommandMgr::command_t command
Definition fg_commands.cxx:1137

For a lead-lag filter of the form $\frac{C_1s+C_2}{C_3s+C_4}$, the corresponding filter definition is:

<lead_lag_filter name="name">
<input> property </input>
<c1> value|property <c/1>
<c2> value|property <c/2>
<c3> value|property <c/3>
<c4> value|property <c/4>
[<clipto>
<min> {[-]property name | value} </min>
<max> {[-]property name | value} </max>
</clipto>]
[<output> property </output>]
</lead_lag_filter>

For a washout filter of the form $\frac{s}{s+C_1}$, the corresponding filter definition is:

<washout_filter name="name">
<input> property </input>
<c1> value </c1>
[<clipto>
<min> {[-]property name | value} </min>
<max> {[-]property name | value} </max>
</clipto>]
[<output> property </output>]
</washout_filter>

For a second order filter of the form $\frac{C_1s^2+C_2s+C_3}{C_4s^2+C_5s+C_6}$, the corresponding filter definition is:

<second_order_filter name="name">
<input> property </input>
<c1> value|property </c1>
<c2> value|property </c2>
<c3> value|property </c3>
<c4> value|property </c4>
<c5> value|property </c5>
<c6> value|property </c6>
[<clipto>
<min> {[-]property name | value} </min>
<max> {[-]property name | value} </max>
</clipto>]
[<output> property </output>]
</second_order_filter>

For an integrator of the form $\frac{C_1}{s}$, the corresponding filter definition is:

<integrator name="{string}">
<input> {property} </input>
<c1 type="rect|trap|ab2|ab3"> {[-]property | number} </c1>
[<trigger> {property} </trigger>]
[<clipto>
<min> {[-]property | number} </min>
<max> {[-]property | number} </max>
</clipto>]
[<output> {property} </output>]
</integrator>

For the integrator, the trigger features the following behavior. If the trigger property value is:

  • 0: no action is taken - the output is calculated normally
  • not 0: (or simply greater than zero), all current and previous inputs will be set to 0.0

By default, the integration scheme is the trapezoidal scheme.

An integrator is equivalent to a PID with the following parameters:

<pid name="{string}">
<input> {[-]property} </input>
<kp> 0.0 </kp>
<ki type="rect|trap|ab2|ab3"> {number|[-]property} </ki>
<kd> 0.0 </kd>
<trigger> {property} </trigger>
[<clipto>
<min> {[-]property | value} </min>
<max> {[-]property | value} </max>
</clipto>]
[<output> {property} </output>]
</pid>

As a consequence, JSBSim internally uses PID controllers to simulate INTEGRATOR filters.

In all the filter specifications above, an <output> element is also seen. This is so that the last component in a "string" can copy its value to the appropriate output, such as the elevator, or speedbrake, etc.

Author
Jon S. Berndt

Definition at line 215 of file FGFilter.h.

Constructor & Destructor Documentation

◆ FGFilter()

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

Definition at line 51 of file FGFilter.cpp.

◆ ~FGFilter()

JSBSim::FGFilter::~FGFilter ( )

Definition at line 76 of file FGFilter.cpp.

Member Function Documentation

◆ ResetPastStates()

void JSBSim::FGFilter::ResetPastStates ( void )
overridevirtual

Reimplemented from JSBSim::FGFCSComponent.

Definition at line 83 of file FGFilter.cpp.

◆ Run()

bool JSBSim::FGFilter::Run ( void )
overridevirtual

Reimplemented from JSBSim::FGFCSComponent.

Definition at line 147 of file FGFilter.cpp.

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