Module: sunSafePoint¶
This module provides the attitude guidance output for a sun pointing mode. This could be used for safe mode, or a power generation mode. The input is the sun direction vector which doesn’t have to be normalized, as well as the body rate information. The output is the standard BSK attitude reference state message. The sun direction measurement is cross with the desired body axis that is to point at the sun to create a principle rotation vector. The dot product between these two vectors is used to extract the principal rotation angle. With these a tracking error MRP state is computer. The body rate tracking errors relative to the reference frame are set equal to the measured body rates to bring the vehicle to rest when pointing at the sun. Thus, the reference angular rate and acceleration vectors relative to the inertial frame are nominally set to zero. If the sun vector is not available, then the reference rate is set to a body-fixed value while the attitude tracking error is set to zero.
The file
PDF Description.
contains further information on this module’s function, how to run it, as well as testing.
Functions
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void
SelfInit_sunSafePoint(sunSafePointConfig *configData, int64_t moduleID)¶ This method initializes the configData for the sun safe attitude guidance. It checks to ensure that the inputs are sane and then creates the output message
- Return
void
- Parameters
configData: The configuration data associated with the sun safe guidance
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void
CrossInit_sunSafePoint(sunSafePointConfig *configData, int64_t moduleID)¶ This method performs the second stage of initialization for the sun safe attitude 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 sun safe attitude guidance
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void
Update_sunSafePoint(sunSafePointConfig *configData, uint64_t callTime, int64_t moduleID)¶ This method takes the estimated body-observed sun vector and computes the current attitude/attitude rate errors to pass on to control.
- Return
void
- Parameters
configData: The configuration data associated with the sun safe attitude guidancecallTime: The clock time at which the function was called (nanoseconds)
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void
Reset_sunSafePoint(sunSafePointConfig *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.
- Return
void
- Parameters
configData: The configuration data associated with the guidance module
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struct
sunSafePointConfig¶ - #include <sunSafePoint.h>
Top level structure for the sun-safe attitude guidance routine.
Public Members
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char
attGuidanceOutMsgName[MAX_STAT_MSG_LENGTH]¶ The name of the output message
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char
sunDirectionInMsgName[MAX_STAT_MSG_LENGTH]¶ The name of the Input message
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char
imuInMsgName[MAX_STAT_MSG_LENGTH]¶ The name of the incoming IMU message
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double
minUnitMag¶ The minimally acceptable norm of sun body vector
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double
sunAngleErr¶ rad The current error between cmd and obs sun angle
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double
smallAngle¶ rad An angle value that specifies what is near 0 or 180 degrees
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double
eHat180_B[3]¶ Eigen axis to use if commanded axis is 180 from sun axis
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double
sunMnvrVec[3]¶ The eigen axis that we want to rotate on to get sun
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double
sHatBdyCmd[3]¶ Desired body vector to point at the sun
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double
omega_RN_B[3]¶ Desired body rate vector if no sun direction is available
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double
sunAxisSpinRate¶ r/s Desired constant spin rate about sun heading vector
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int32_t
attGuidanceOutMsgID¶ ID for the outgoing body estimate message
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int32_t
sunDirectionInMsgID¶ ID for the incoming CSS sensor message
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int32_t
imuInMsgID¶ ID for the incoming IMU sensor message
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AttGuidFswMsg
attGuidanceOutBuffer¶ The output data that we compute
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char