FlightGear: JSBSim::FGLinearActuator Class Reference

Models a flight control system summing component. More...

#include <FGLinearActuator.h>

Public Member Functions
	FGLinearActuator (FGFCS fcs, Element element)
	Constructor.

	~FGLinearActuator ()
	Destructor.

bool	Run (void) override
	The execution method for this FCS component.

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

Models a flight control system summing component.

Linear actuators typically operate by conversion of rotary motion into linear motion. The linear_actuator component is described in the Wikipedia link: https://en.wikipedia.org/wiki/Linear_actuator.

Linear actuators converts a rotation into a linear movement or a multiturn rotation. For the conversion it is necessary to declare a module that is defined by the difference of the maximum and minimum value Input.

List of parameters:

input: Value to be transformed
Output: Output value following the following rule it is the result of gain * (bias + Input + module*countSpin)
CountSpin is the number of complete rotations calculated by this device
gain: Apply a multiplication coefficient to the output value, the default value is 1.0
bias: Value that is added to the input value
module: Difference between the maximum and minimum value of Input. Default is 1.0.
hysteresis: Defines the sensitivity of the actuator according to the input.

For example, if the actuator has a module of 360 and if the hysteresis is 5.0, the actuator, with gain = 1, will output a value equal to: 5, 10...355, 360, 365, 370 etc. This parameter allows to simulate stepper motors. The default value is 0.1 It is not advisable to have this parameter too small (less than 0.1) as it could make the CPU load heavier.

versus: Direction of rotation if fixed. The versus allows to obtain a mechanism similar to the tick of a clock. The default value is 0.

If the value is zero, the verse is automatically obtained according to variation of the input data.

If set to a value > 0.5 the verse is increasing, i.e. the output changes only if the Input value is greater than the previous one.

If set to a value < -0.5 the output is changed only if the next value is lower than the previous one.

With this parameter allows to easily obtain a "step counter".

rate: To define when the rotation is complete, the differential criterion is used.

For example, if the rotation is clockwise and the module is 360, the revolution will be complete when the input value changes from 360 to 0.

When this happens a counter increases the output of the value of the module. As a way the system keeps track of the number of rotations. Rate defines the sensitivity of the system.

If a difficulty in determining the rotation is observed during the tests, this parameter must be modified with a positive value not exceeding 1. The default value is 0.3

set: If the absolute value is greater or equal 0.5, the output changes according to the input.

If its value is lower 0.5, the output remains constant (the system stores the data). The use of this parameter allows to simulate the behavior of a servomechanism that is blocked, for example due to a power failure.

Reset: if the absolute value is greater or equal 0.5, the output returns to zero and reset internal data.
lag: Activate a lag filter on exit if the value is greater 0.0 the lag is active.

Be very careful to use the lag filter in case you use two or more "linear_actuator" in cascade; it may happen that the smoothing effect due to the lag in the output value can mislead the rotation determination system. The effect is similar to that of a loose coupling of a rack and pinion. Therefore, with these types of coupling, place lag only at the last stage.

<linear_actuator name="{string}">
  <input> {property name} </input>
  <bias> {property name | value} </bias>
  <module> {value} </module>
  <hysteresis> {value} </hysteresis>
  <rate> {value} </rate>
  <versus> {property name | value} </versus>
  <gain> {value} </gain>
  <set> {property name | value} </set>
  <reset> {property name | value} </reset>
  <lag> {value} </lag>
  <output> {property name} </output>
</linear_actuator>

Mechanical counter:

It is the typical mechanism used to count the kilometers traveled by a car, for example the value of the digit changes quickly at the beginning of the km. Module 10 indicates that the count goes from 0 to 9 after one complete revolution.

<linear_actuator name="systems/gauges/PHI/indicator/digit3AW">
  <input>systems/gauges/PHI/indicator/digit3A</input>
  <module>10</module>
  <rate>0.2</rate>
  <lag>8.0</lag>
</linear_actuator>

The gyrocompass from a rotation with a value from 0 to 259 degrees. When it returns to zero, if it is made more realistic by means of an actuator, there is a jump of the disk which performs a complete rotation of 360 °. By activating a linear actuator followed by an actuator it is possible to obtain a very realistic result.

<linear_actuator name="gyrocompass-magnetic-deg-linear">
  <input>gyrocompass-magnetic-deg</input>
  <module>360</module>
</linear_actuator>
 
<actuator name="gyrocompass-magnetic-deg-linear-actuator">
  <input>gyrocompass-magnetic-deg-linear</input>
  <lag>2.0</lag>
  <rate_limit>100</rate_limit>
  <bias>0.1</bias>
  <deadband_width>1</deadband_width>
  <hysteresis_width>0.5</hysteresis_width>
</actuator>

Count steps with memory:

If you use a button or switch to advance a mechanism, we can build a step counter. In this case the module is 1 and the rate 1. The verse is positive (increasing). A pulse counter (for example the count of the switched-on states of a switch with values 1 and 0), the module must be 1 in that each step must advance its value by one unit. The verse is "1" because it has to accept only increasing values (as in a clock escapement). The gain is 0.5 because, in similitude to an escapement of a clock, the gear makes two steps for a complete rotation of the pendulum.

<linear_actuator name="systems/gauges/PHI/doppler/switch-increase-summer">
  <input>systems/gauges/PHI/doppler/switch-increase</input>
  <module>1</module>
  <rate>1</rate>
  <versus>1</versus>
  <gain>0.5</gain>
  <lag>0.0</lag>
  <reset>systems/gauges/PHI/doppler/test_reset_off</reset>
</linear_actuator>

Author: Adriano Bassignana

Definition at line 220 of file FGLinearActuator.h.

Constructor & Destructor Documentation

◆ FGLinearActuator()

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

Constructor.

Parameters

fcs	a pointer to the parent FGFCS object.
element	a pointer to the configuration file node.

Definition at line 51 of file FGLinearActuator.cpp.

◆ ~FGLinearActuator()

JSBSim::FGLinearActuator::~FGLinearActuator ( )

Destructor.

Definition at line 149 of file FGLinearActuator.cpp.

Member Function Documentation

◆ Run()

bool JSBSim::FGLinearActuator::Run ( void )

overridevirtual

The execution method for this FCS component.

Reimplemented from JSBSim::FGFCSComponent.

Definition at line 156 of file FGLinearActuator.cpp.

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