attRefCorrection

Executive Summary

This module reads in the attitude reference message and adjusts it by a fixed rotation. This allows a general body-fixed frame \(B\) to align with this corrected reference frame \(R_c\).

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.

Module I/O Messages

Msg Variable Name	Msg Type	Description
attRefInMsg	AttRefMsgPayload	attitude reference input message
attRefOutMsg	AttRefMsgPayload	corrected attitude reference input message

Detailed Module Description

This module is an attitude reference message feed-through module where a fixed orientation offset can be applied to the output attitude sigma_RN. In not all cases do we wish to drive a body-fixed frame \(\cal B\) to a reference frame \(\cal R\). Rather, maybe it is desired to align the first \(\cal R\) frame axis with the 2nd body axis. Thus, a corrected body frame \({\cal B}_c\) must align with R. The can also be achieved by aligning \(\cal B\) with a corrected attitude reference frame \({\cal R}_c\).

Let the rotation between \(\cal B\) and \({\cal B}_c\) be given by the MRP set \(\sigma_{B/B_c}\). Using DCMs, thus we need

\[[BN] = [R_cN]\]

The original reference frame relates to the body frame through

\[[RN] = [B_cN][BN]\]

which leads to

\[[BN] = [B_cN]^T [RN]\]

Substituting this into the first equatino leads to the desired corrected reference frame:

\[[R_cN] = [B_cN]^T [RN]\]

The orientation of \([R_cN]\) is then translated to a MRP set for the output message.

User Guide

The only variable that is set with this module is the sigma_BcB MRP to rotate from the original body frame and the corrected frame.

Class AttRefCorrection

class AttRefCorrection : public SysModel

This module reads in the attitude reference message and adjusts it by a fixed rotation. This allows a general body-fixed frame B to align with this corrected reference frame Rc.

Public Functions

void reset(uint64_t callTime) override

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. Check if required input messages are connected.

Parameters:

callTime – [ns] time the method is called

Returns:

void

void updateState(uint64_t callTime) override

Corrects the reference attitude message by a fixed rotation

Parameters:

callTime – The clock time at which the function was called (nanoseconds)

Returns:

void

Public Members

ReadFunctor<AttRefMsgPayload> attRefInMsg

attitude reference input message

Message<AttRefMsgPayload> attRefOutMsg

corrected attitude reference input message

double sigma_BcB[3]

MRP from from body frame B to the corrected body frame Bc.

BSKLogger bskLogger = {}

BSK Logging.