GNC App for performing the GPS measurement update step of an EKF when a GPS receiver is available to report the vehicle position in a known reference frame (e.g., ECEF, ECI, or NED). This app implements the EKF measurement correction step by comparing the measured GPS position (after necessary frame and lever-arm transformations) to the predicted position from the EKF state. More...

#include <GPSUpdate.h>

Inheritance diagram for warpos::GPSUpdate:

[legend]

Classes
struct	Params
struct	Inputs
struct	Outputs

Public Member Functions
	GPSUpdate (FlightExecutive &executive)
virtual	~GPSUpdate ()
int16	activate () override
	Activate the app. The app will step when active.
int16	deactivate () override
	Deactivate the app. The app will not step when deactivated.
int16	command (uint16 apid, uint8 *buffer, uint16 size) override
	Process commands issued to the app.
inertial_nav::MagMeasVector	getResidual ()
	Getter function to grab the internal residual.
Public Member Functions inherited from warpos::App
	App (FlightExecutive &executive, const char *name, uint16 apid, uint8 instance=0)
	Executive-based constructor for the task.
virtual	~App ()
	Destructor. Doesn't really do anything.
int16	startup ()
	Initialize the app. Should be called once before step.
int16	step ()
	Step the app by a single step. Maps params, inputs, etc. to outputs.
log_level_e	logLevel ()
	Get the log level set for the executive.
void	logLevel (log_level_e log_level)
	Set the executive log level.
bool	isStarted ()
	Return whether task startup has been run.
uint16	apid ()
	Get the apid for this app.
uint8 &	instance ()
	Get the instance of this app (used to differentiate between multiple instances of the same app).
Public Member Functions inherited from clockwerk::GraphTreeObject
	GraphTreeObject (const char gt_nme="", GraphTreeObject *storage_array=nullptr, uint32 storage_size=0)
	Name-based constructor for GraphTreeObject which will have no children by default.
virtual	~GraphTreeObject ()
	Destructor.
GraphTreeObject *	parent ()
	Functions to get object's parent/children.
GraphTreeObject **	children ()
GraphTreeObject *	childAtIndex (uint8 i) const
int16	parent (GraphTreeObject *new_parent)
	Function to assign the node's parent via pointer.
int16	parent (GraphTreeObject &new_parent)
	Function to assign the node's parent via reference.
uint8	nChildren () const
	Getters for number of children and descendants.
uint16	nDescendants () const
uint8	capacity () const
const char *	name () const
	Getter and setter for object name.
int16	name (const char *new_name)
uint8	rank ()
	Getter for the object rank.
int8	type ()
	Function to indicate type – -1 by default unless implemented downstream.
bool	loggable ()
	Getter for object logability flag – note no setter because should only be set by this or a derived class in its definition.
GraphTreeObject *	getRootDataPointer ()
	Get the pointer to the highest object in the graph tree.
virtual int16	str (char *output, size_t size) const
	Get object represented as string.
virtual int16	fromStr (const char *val)
	Set value of graphtreeobject from string.

Public Attributes
Params	params = Params(this, "params")
Inputs	inputs = Inputs(this, "inputs")
Outputs	outputs = Outputs(this, "outputs")
Public Attributes inherited from warpos::App
clockwerk::DataIO< bool >	active = clockwerk::DataIO<bool>(this, "active", true)
	The active flag for the task – set to true by default.

Protected Member Functions
int16	start () override
int16	execute () override
Protected Member Functions inherited from clockwerk::GraphTreeObject
int16	_setStorage (GraphTreeObject **storage_array, uint8 storage_size)
	Getter for object's string address.
void	_recalculateDescendants ()
	Function to recursively re-calculate the number of descendants of a given node on the tree.
void	_recalculateRank ()
	Function to recursively re-calculate the rank of a given node on the tree.
int16	_addChild (GraphTreeObject *child)
	Function to decompose a string into a series of substrings via indexing.
int16	_removeChild (GraphTreeObject *child)
	Function to remove a child from the graph node's children.

Protected Attributes
GPSMeasurements< inertial_nav::STATE_SIZE >	_measurements
	Reference variable to the internal Measurements.
EkfMeasurementUpdate< inertial_nav::STATE_SIZE, GPS_MEASUREMENT_VECTOR_ELEMENTS, GPS_MEASUREMENT_OBSERVER_VECTOR_ELEMENTS >	_measUpdate
	Reference variable to the internal EkfMeasurementsUpdate.
std::array< floating_point, 3 >	_dummy3
	Dummy temporary array for swapping between std::array and clockwerk::CartesianVector.
std::array< floating_point, 4 >	_dummy4
inertial_nav::MagObsVector	_dummyObs
inertial_nav::StateVector	_state_input_array
	Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.
inertial_nav::StateVector	_state_output_array
inertial_nav::GpsObsVector	_state_observer_array
	Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.
inertial_nav::GpsMeasVector	_measurement_array
	Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.
inertial_nav::GpsMeasVector	_residual
clockwerk::CartesianVector< 3 >	_gps_meas_vec_B_pI__pI
	Internal variables for the transformed measurements.
clockwerk::Quaternion	_unit_quat
	Temporary variable for unitizing a quaternion.
tlm_gnc_gps_update_state	_tlm_a_posteriori_state
	Packet to hold state after measurement incorporation.
clockwerk::Time	_repeat_check_time
	Variables to verify we are not processing stale measurements.
clockwerk::CartesianVector< 3 >	_repeat_check_meas
Protected Attributes inherited from warpos::App
FlightExecutive &	exc
	Override our executive to include the FlightExecutive instead.
int16	_error = 0
	Internal variable to track and return error on app step through.
uint16	_apid = 0
	Internal variable to hold the APID for this app.
bool	_is_started = false
	Flag indicating whether app has been started or not.
log_level_e	_local_log_level = log_level_e::LOG_WARNING
	The log level for this particular app.
GraphTreeObject *	_app_children [MAXIMUM_APP_CHILDREN]
	Local storage for App children so it can live on the graph tree.
uint8	_instance
	Instance number of this app. Used to differentiate between multiple instances of the same app.
Protected Attributes inherited from clockwerk::GraphTreeObject
GraphTreeObject *	_parent = nullptr
GraphTreeObject **	_children_ptr = nullptr
uint32	_max_num_children = 0
uint16	_num_descendants = 0
char	_name [MAXIMUM_NAME_CHARS] = ""
	String name for object.
uint8	_num_children = 0
	Number of direct children of the tree (not including the tree itself).
uint8	_rank = 0
int8	_graph_tree_type = BASE_GRAPH_TREE
	Variable to store graph tree object type.
bool	_loggable = false
	Variable to indicate whether the selected object is loggable. Set to false by default.
uint32	_index = 0
	Index pointing to the next write location for the graph tree children.

Detailed Description

GNC App for performing the GPS measurement update step of an EKF when a GPS receiver is available to report the vehicle position in a known reference frame (e.g., ECEF, ECI, or NED). This app implements the EKF measurement correction step by comparing the measured GPS position (after necessary frame and lever-arm transformations) to the predicted position from the EKF state.

This update step is primarily used to correct drift in position and velocity estimates that accumulate during IMU-only dead-reckoning propagation. By incorporating absolute GPS position fixes, the EKF can bound long-term error growth in navigation states.

The method assumes that the GPS receiver outputs position in a global reference frame (commonly ECEF or ECI) and that the transformation between the GPS antenna phase center, the body frame, and the EKF state reference frame is known. Corrections account for lever-arm offsets between the GPS sensor and the body center of gravity as well as orientation differences between the reporting frame and the pseudo-inertial frame used by the EKF.

Attention: See InertialNavigationDefinition.hpp for an in-depth description of the state vector and frame conventions used in this measurement update.

Author: James Tabony james.nosp@m..tab.nosp@m.ony@a.nosp@m.ttx..nosp@m.tech

Constructor & Destructor Documentation

◆ GPSUpdate()

warpos::GPSUpdate::GPSUpdate ( FlightExecutive & executive )

◆ ~GPSUpdate()

virtual warpos::GPSUpdate::~GPSUpdate ( )

inlinevirtual

Member Function Documentation

◆ activate()

int16 warpos::GPSUpdate::activate ( )

overridevirtual

Activate the app. The app will step when active.

Returns: Flag indicating success/failure

Reimplemented from warpos::App.

◆ command()

int16 warpos::GPSUpdate::command	(	uint16	apid,
		uint8 *	buffer,
		uint16	size )

overridevirtual

Process commands issued to the app.

Parameters

apid	The APID of the command sent
buffer	Pointer to the location of the buffer holding the command
size	The size of the command being sent

Returns: Flag indicating success/failure

Reimplemented from warpos::App.

◆ deactivate()

int16 warpos::GPSUpdate::deactivate ( )

overridevirtual

Deactivate the app. The app will not step when deactivated.

Returns: Flag indicating success/failure

Reimplemented from warpos::App.

◆ execute()

int16 warpos::GPSUpdate::execute ( )

overrideprotectedvirtual

Reimplemented from warpos::App.

◆ getResidual()

inertial_nav::MagMeasVector warpos::GPSUpdate::getResidual ( )

inline

Getter function to grab the internal residual.

Returns: Measurement residual

◆ start()

int16 warpos::GPSUpdate::start ( )

overrideprotectedvirtual

Reimplemented from warpos::App.

Member Data Documentation

◆ _dummy3

std::array<floating_point, 3> warpos::GPSUpdate::_dummy3

protected

Dummy temporary array for swapping between std::array and clockwerk::CartesianVector.

◆ _dummy4

std::array<floating_point, 4> warpos::GPSUpdate::_dummy4

protected

◆ _dummyObs

inertial_nav::MagObsVector warpos::GPSUpdate::_dummyObs

protected

◆ _gps_meas_vec_B_pI__pI

clockwerk::CartesianVector<3> warpos::GPSUpdate::_gps_meas_vec_B_pI__pI

protected

Internal variables for the transformed measurements.

◆ _measUpdate

EkfMeasurementUpdate<inertial_nav::STATE_SIZE, GPS_MEASUREMENT_VECTOR_ELEMENTS, GPS_MEASUREMENT_OBSERVER_VECTOR_ELEMENTS> warpos::GPSUpdate::_measUpdate

protected

Reference variable to the internal EkfMeasurementsUpdate.

◆ _measurement_array

inertial_nav::GpsMeasVector warpos::GPSUpdate::_measurement_array

protected

Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.

◆ _measurements

GPSMeasurements<inertial_nav::STATE_SIZE> warpos::GPSUpdate::_measurements

protected

Reference variable to the internal Measurements.

◆ _repeat_check_meas

clockwerk::CartesianVector<3> warpos::GPSUpdate::_repeat_check_meas

protected

◆ _repeat_check_time

clockwerk::Time warpos::GPSUpdate::_repeat_check_time

protected

Variables to verify we are not processing stale measurements.

◆ _residual

inertial_nav::GpsMeasVector warpos::GPSUpdate::_residual

protected

◆ _state_input_array

inertial_nav::StateVector warpos::GPSUpdate::_state_input_array

protected

Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.

◆ _state_observer_array

inertial_nav::GpsObsVector warpos::GPSUpdate::_state_observer_array

protected

Temporary variables for the array input/outputs passed into the EkfMeasurementUpdate object.

◆ _state_output_array

inertial_nav::StateVector warpos::GPSUpdate::_state_output_array

protected

◆ _tlm_a_posteriori_state

tlm_gnc_gps_update_state warpos::GPSUpdate::_tlm_a_posteriori_state

protected

Packet to hold state after measurement incorporation.

◆ _unit_quat

clockwerk::Quaternion warpos::GPSUpdate::_unit_quat

protected

Temporary variable for unitizing a quaternion.

◆ inputs

Inputs warpos::GPSUpdate::inputs = Inputs(this, "inputs")

◆ outputs

Outputs warpos::GPSUpdate::outputs = Outputs(this, "outputs")

◆ params

Params warpos::GPSUpdate::params = Params(this, "params")

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

/Users/mickey/Documents/Projects/warptwin/warpos/src/apps/gnc/InertialNavigationEKF/GPSUpdate.h
/Users/mickey/Documents/Projects/warptwin/warpos/src/apps/gnc/InertialNavigationEKF/GPSUpdate.cpp

Classes

Public Member Functions

Public Attributes

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ GPSUpdate()

◆ ~GPSUpdate()

Member Function Documentation

◆ activate()

◆ command()

◆ deactivate()

◆ execute()

◆ getResidual()

◆ start()

Member Data Documentation

◆ _dummy3

◆ _dummy4

◆ _dummyObs

◆ _gps_meas_vec_B_pI__pI

◆ _measUpdate

◆ _measurement_array

◆ _measurements

◆ _repeat_check_meas

◆ _repeat_check_time

◆ _residual

◆ _state_input_array

◆ _state_observer_array

◆ _state_output_array

◆ _tlm_a_posteriori_state

◆ _unit_quat

◆ inputs

◆ outputs

◆ params