Module: prvSteering

Executive Summary

This module implements a PRV steering attitude control routine.

The module PDF Description contains further information on this module’s function, how to run it, as well as testing.

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

guidInMsg

AttGuidMsgPayload

Attitude guidance input message.

rateCmdOutMsg

RateCmdMsgPayload

Rate command output message.

Functions

void SelfInit_prvSteering(PrvSteeringConfig *configData, int64_t moduleID)

This method initializes the configData for this module. It checks to ensure that the inputs are sane and then creates the output message

Parameters

  • configData – The configuration data associated with this module

  • moduleID – The module identifier

Returns

void

void Update_prvSteering(PrvSteeringConfig *configData, uint64_t callTime, int64_t moduleID)

This method takes the attitude and rate errors relative to the Reference frame, as well as the reference frame angular rates and acceleration, and computes the required control torque Lr.

Parameters

  • configData – The configuration data associated with the MRP Steering attitude control

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

  • moduleID – The module identifier

Returns

void

void Reset_prvSteering(PrvSteeringConfig *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 MRP steering control

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

  • moduleID – The module identifier

Returns

void

void PRVSteeringLaw(PrvSteeringConfig *configData, double sigma_BR[3], double omega_ast[3], double omega_ast_p[3])

This method computes the PRV Steering law. A commanded body rate is returned given the PRV attitude error measure of the body relative to a reference frame. The function returns the commanded body rate, as well as the body frame derivative of this rate command.

Parameters

  • configData – The configuration data associated with this module

  • sigma_BR – MRP attitude error of B relative to R

  • omega_ast – Commanded body rates

  • omega_ast_p – Body frame derivative of the commanded body rates

Returns

void

struct PrvSteeringConfig
#include <prvSteering.h>

module configuration message definition

Public Members

double K1

[rad/sec] Proportional gain applied to principal rotation angle error

double K3

[rad/sec] Cubic gain applied to principal rotation angle error in steering saturation function

double omega_max

[rad/sec] Maximum rate command of steering control

RateCmdMsg_C rateCmdOutMsg

rate command output message

AttGuidMsg_C guidInMsg

attitude guidance input message

BSKLogger *bskLogger

BSK Logging.