Module: sunlineSuKF¶

This module implements and tests a Switch Unscented Kalman Filter in order to estimate the sunline direction. The theory used in this module can be found in this paper.

More information can be found in the PDF Description

Functions

void SelfInit_sunlineSuKF(SunlineSuKFConfig *configData, int64_t moduleID)¶

This method initializes the configData for theCSS WLS estimator.

Return

void

Parameters

configData: The configuration data associated with the CSS WLS estimator

void CrossInit_sunlineSuKF(SunlineSuKFConfig *configData, int64_t moduleID)¶

This method performs the second stage of initialization for the CSS sensor interface. It’s primary function is to link the input messages that were created elsewhere.

Return

void

Parameters

configData: The configuration data associated with the CSS interface

void Update_sunlineSuKF(SunlineSuKFConfig *configData, uint64_t callTime, int64_t moduleID)¶

This method takes the parsed CSS sensor data and outputs an estimate of the sun vector in the ADCS body frame

Return

void

Parameters

configData: The configuration data associated with the CSS estimator
callTime: The clock time at which the function was called (nanoseconds)

void Reset_sunlineSuKF(SunlineSuKFConfig *configData, uint64_t callTime, int64_t moduleID)¶

This method resets the sunline attitude filter to an initial state and initializes the internal estimation matrices.

Return

void

Parameters

configData: The configuration data associated with the CSS estimator
callTime: The clock time at which the function was called (nanoseconds)

int sunlineSuKFTimeUpdate(SunlineSuKFConfig *configData, double updateTime)¶

This method performs the time update for the sunline kalman filter. It propagates the sigma points forward in time and then gets the current covariance and state estimates.

Return

void

Parameters

configData: The configuration data associated with the CSS estimator
updateTime: The time that we need to fix the filter to (seconds)

int sunlineSuKFMeasUpdate(SunlineSuKFConfig *configData, double updateTime)¶

This method performs the measurement update for the sunline kalman filter. It applies the observations in the obs vectors to the current state estimate and updates the state/covariance with that information.

Return

void

Parameters

configData: The configuration data associated with the CSS estimator
updateTime: The time that we need to fix the filter to (seconds)

void sunlineStateProp(double *stateInOut, double *b_vec, double dt)¶

This method propagates a sunline state vector forward in time. Note that the calling parameter is updated in place to save on data copies.

Return

void

Parameters

stateInOut: The state that is propagated

void sunlineSuKFMeasModel(SunlineSuKFConfig *configData)¶

This method computes what the expected measurement vector is for each CSS that is present on the spacecraft. All data is transacted from the main data structure for the model because there are many variables that would have to be updated otherwise.

Return

void

Parameters

configData: The configuration data associated with the CSS estimator

void sunlineSuKFComputeDCM_BS(double sunheading[SKF_N_STATES_HALF], double bVec[SKF_N_STATES_HALF], double *dcm)¶

void sunlineSuKFSwitch(double *bVec_B, double *states, double *covar)¶

This method computes the dcms necessary for the switch between the two frames. It the switches the states and the covariance, and sets s2 to be the new, different vector of the body frame.

Return

void

Parameters

covarBar: The time updated covariance
hObs: The H matrix filled with the observations
s2_B: Pointer to the second frame vector
states: Pointer to the states
covar: Pointer to the covariance

void sunlineSuKFCleanUpdate(SunlineSuKFConfig *configData)¶

This method cleans the filter states after a bad upadate on the fly. It removes the potentially corrupted previous estimates and puts the filter back to a working state.

Return

void

Parameters

configData: The configuration data associated with the CSS estimator

struct SunlineSuKFCFit¶

Public Members

double cssRelScale¶: Relative scale factor for this CSS.

double cssKellPow¶: CSS kelly estimate power.

double cssKellFact¶: CSS kelly scale factor.

struct SunlineSuKFConfig¶

#include <sunlineSuKF.h>

Data structure for CSS Switch unscented kalman filter estimator.

Public Members

char navStateOutMsgName[MAX_STAT_MSG_LENGTH]¶: The name of the output message.

char filtDataOutMsgName[MAX_STAT_MSG_LENGTH]¶: The name of the output filter data message.

char cssDataInMsgName[MAX_STAT_MSG_LENGTH]¶: The name of the Input message.

char cssConfigInMsgName[MAX_STAT_MSG_LENGTH]¶: [-] The name of the CSS configuration message

size_t numStates¶: [-] Number of states for this filter

size_t countHalfSPs¶: [-] Number of sigma points over 2

size_t numObs¶: [-] Number of measurements this cycle

double beta¶: [-] Beta parameter for filter

double alpha¶: [-] Alpha parameter for filter

double kappa¶: [-] Kappa parameter for filter

double lambdaVal¶: [-] Lambda parameter for filter

double gamma¶: [-] Gamma parameter for filter

double qObsVal¶: [-] CSS instrument noise parameter

double dt¶: [s] seconds since last data epoch

double timeTag¶: [s] Time tag for statecovar/etc

double bVec_B[SKF_N_STATES_HALF]¶: [-] current vector of the b frame used to make frame

double switchTresh¶: [-] Threshold for switching frames

double stateInit[SKF_N_STATES_SWITCH]¶: [-] State to initialize filter to

double state[SKF_N_STATES_SWITCH]¶: [-] State estimate for time TimeTag

double statePrev[SKF_N_STATES_SWITCH]¶: [-] Previous state logged for clean

double wM[2 * SKF_N_STATES_SWITCH + 1]¶: [-] Weighting vector for sigma points

double wC[2 * SKF_N_STATES_SWITCH + 1]¶: [-] Weighting vector for sigma points

double sBar[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] Time updated covariance

double sBarPrev[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] Time updated covariance logged for clean

double covarInit[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] covariance to init to

double covar[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] covariance

double covarPrev[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] Covariance logged for clean

double xBar[SKF_N_STATES_SWITCH]¶: [-] Current mean state estimate

double obs[MAX_N_CSS_MEAS]¶: [-] Observation vector for frame

double yMeas[MAX_N_CSS_MEAS * (2 * SKF_N_STATES_SWITCH + 1)]¶: [-] Measurement model data

double postFits[MAX_N_CSS_MEAS]¶: [-] PostFit residuals

double SP[(2 * SKF_N_STATES_SWITCH + 1) * SKF_N_STATES_SWITCH]¶: [-] sigma point matrix

double qNoise[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] process noise matrix

double sQnoise[SKF_N_STATES_SWITCH * SKF_N_STATES_SWITCH]¶: [-] cholesky of Qnoise

double qObs[MAX_N_CSS_MEAS * MAX_N_CSS_MEAS]¶: [-] Maximally sized obs noise matrix

double cssNHat_B[MAX_NUM_CSS_SENSORS * 3]¶: [-] CSS normal vectors converted over to body

double CBias[MAX_NUM_CSS_SENSORS]¶: [-] CSS individual calibration coefficients

SunlineSuKFCFit kellFits[MAX_NUM_CSS_SENSORS]¶: [-] Curve fit components for CSS sensors

uint32_t numActiveCss¶: Number of currently active CSS sensors

uint32_t numCSSTotal¶: [-] Count on the number of CSS we have on the spacecraft

double sensorUseThresh¶: Threshold below which we discount sensors

NavAttIntMsg outputSunline¶: Output sunline estimate data

CSSArraySensorIntMsg cssSensorInBuffer¶: [-] CSS sensor data read in from message bus

int32_t navStateOutMsgId¶: ID for the outgoing body estimate message

int32_t filtDataOutMsgId¶: [-] ID for the filter data output message

int32_t cssDataInMsgId¶: ID for the incoming CSS sensor message

int32_t cssConfigInMsgId¶: [-] ID associated with the CSS configuration data

uint32_t filterInitialized¶: [-] Flag indicating if filter has been init or not

BSKLogger *bskLogger¶: BSK Logging.