Module: cssWlsEst¶
Executive Summary¶
A weighted least-squares minimum-norm algorithm is used to estimate the body-relative sun heading using a cluster of coarse sun sensors. Using two successive sun heading evaluation the module also computes the inertial angular velocity vector. As rotations about the sun-heading vector are not observable, this angular velocity vector only contains body rates orthogonal to this sun heading vector. More information on can be found in the
PDF Description
Message Connection Descriptions¶
The following table lists all the module input and output messages. The module msg connection is set by the user from python. The msg type contains a link to the message structure definition, while the description provides information on what this message is used for.
Msg Variable Name |
Msg Type |
Description |
---|---|---|
cssDataInMsg |
name of the CSS sensor input message |
|
cssConfigInMsg |
name of the CSS configuration input message |
|
navStateOutMsg |
name of the navigation output message containing the estimated states |
|
cssWLSFiltResOutMsg |
name of the CSS filter state data out message |
Functions
-
void SelfInit_cssWlsEst(CSSWLSConfig *configData, int64_t moduleID)¶
This method initializes the configData for theCSS WLS estimator.
- Parameters
configData – The configuration data associated with the CSS WLS estimator
moduleID – The module identifier
- Returns
void
-
void Update_cssWlsEst(CSSWLSConfig *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
- Parameters
configData – The configuration data associated with the CSS estimator
callTime – The clock time at which the function was called (nanoseconds)
moduleID – The module identifier
- Returns
void
-
void Reset_cssWlsEst(CSSWLSConfig *configData, uint64_t callTime, int64_t moduleID)¶
This method performs a complete reset of the module. Local module variables that retain time varying states between function calls are reset to their default values.
- Parameters
configData – The configuration data associated with the guidance module
callTime – The clock time at which the function was called (nanoseconds)
moduleID – The module identifier
- Returns
void
-
int computeWlsmn(int numActiveCss, double *H, double *W, double *y, double x[3])¶
This method computes a least squares fit with the given parameters. It treats the inputs as though they were double dimensioned arrays but they are all singly dimensioned for ease of use
- Parameters
numActiveCss – The count on input measurements
H – The predicted pointing vector for each measurement
W – the weighting matrix for the set of measurements
y – the observation vector for the valid sensors
x – The output least squares fit for the observations
- Returns
success indicator (0 for good, 1 for fail)
-
void computeWlsResiduals(double *cssMeas, CSSConfigMsgPayload *cssConfig, double *wlsEst, double *cssResiduals)¶
This method computes the post-fit residuals for the WLS estimate. Note that everything has to have been allocated appropriately as this function operates directly on the arrays.
- Parameters
cssMeas – The measured values for the CSS sensors
cssConfig – The CSS configuration information
wlsEst – The WLS estimate computed for the CSS measurements
cssResiduals – The measurement residuals output by this function
- Returns
void
-
struct CSSWLSConfig¶
- #include <cssWlsEst.h>
Top level structure for the CSS weighted least squares estimator. Used to estimate the sun state in the vehicle body frame.
Public Members
-
CSSArraySensorMsg_C cssDataInMsg¶
The name of the CSS sensor input message.
-
CSSConfigMsg_C cssConfigInMsg¶
The name of the CSS configuration input message.
The name of the navigation output message containing the estimated states.
-
SunlineFilterMsg_C cssWLSFiltResOutMsg¶
The name of the CSS filter data out message.
-
uint32_t numActiveCss¶
[-] Number of currently active CSS sensors
-
uint32_t useWeights¶
Flag indicating whether or not to use weights for least squares.
-
uint32_t priorSignalAvailable¶
Flag indicating if a recent prior heading estimate is available.
-
double dOld[3]¶
The prior sun heading estimate.
-
double sensorUseThresh¶
Threshold below which we discount sensors.
-
uint64_t priorTime¶
[ns] Last time the attitude control is called
-
CSSConfigMsgPayload cssConfigInBuffer¶
CSS constellation configuration message buffer.
-
SunlineFilterMsgPayload filtStatus¶
Filter message.
-
BSKLogger *bskLogger¶
BSK Logging.
-
CSSArraySensorMsg_C cssDataInMsg¶