Module: spinningBodyOneDOFStateEffector
Executive Summary
The spinning body class is an instantiation of the state effector abstract class. The integrated test is validating the interaction between the spinning body module and the rigid body hub that it is attached to. In this case, a 1-DoF spinning body has an inertia tensor and is attached to the hub by a single degree of freedom axis. This module can represent multiple different effectors, such as a hinged solar panel, a reaction wheel or a single-gimbal. The spinning axis is fixed in the body frame and the effector is rigid, which means that its center of mass location does not move in the spinning frame S. An optional motor torque can be applied on the spinning axis, and the user can also lock the axis through a command.
Message Connection Descriptions
The following table lists all the module input and output messages. The module msg variable name 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 |
|---|---|---|
spinningBodyOutMsg |
Output message containing the spinning body state angle and angle rate |
|
motorTorqueInMsg |
(Optional) Input message of the motor torque value |
|
motorLockInMsg |
(Optional) Input message for locking the axis |
|
spinningBodyRefInMsg |
(Optional) Input message for prescribing the angle and angle rate |
|
spinningBodyConfigLogOutMsg |
Output message containing the spinning body inertial position and attitude states |
Detailed Module Description
A 1 DoF spinning body has 2 states: theta and thetaDot. The angle and angle rate can change due to the interaction with the hub, but also because of applied torques (control, spring and damper). The angle remains fixed and the angle rate is set to zero when the axis is locked.
Mathematical Modeling
See the following conference paper for a detailed description of this model.
Note
J. Vaz Carneiro, C. Allard and H. Schaub, “Rotating Rigid Body Dynamics Architecture for Spacecraft Simulation Software Implementation”, AAS Rocky Mountain GN&C Conference, Breckenridge, CO, Feb. 2–8, 2023
User Guide
This section is to outline the steps needed to setup a Spinning Body State Effector in Python using Basilisk.
Import the spinningBodyOneDOFStateEffector class:
from Basilisk.simulation import spinningBodyOneDOFStateEffector
Create an instantiation of a Spinning body:
spinningBody = spinningBodyOneDOFStateEffector.SpinningBodyOneDOFStateEffector()
Define all physical parameters for a Spinning Body. For example:
spinningBody.mass = 100.0 spinningBody.IPntSc_S = [[100.0, 0.0, 0.0], [0.0, 50.0, 0.0], [0.0, 0.0, 50.0]] spinningBody.dcm_S0B = [[-1.0, 0.0, 0.0], [0.0, -1.0, 0.0], [0.0, 0.0, 1.0]] spinningBody.r_ScS_S = [[0.5], [0.0], [1.0]] spinningBody.r_SB_B = [[1.5], [-0.5], [2.0]] spinningBody.sHat_S = [[0], [0], [1]]
(Optional) Define initial conditions of the effector. Default values are zero states:
spinningBody.thetaInit = 5 * macros.D2R spinningBody.thetaDotInit = 1 * macros.D2R
(Optional) Define spring and damper coefficients. Default values are zero states:
spinningBody.k = 1.0 spinningBody.c = 0.5
(Optional) Define a unique name for each state. If you have multiple spinning bodies, they each must have a unique name. If these names are not specified, then the default names are used which are incremented by the effector number:
spinningBody.nameOfThetaState = "spinningBodyTheta" spinningBody.nameOfThetaDotState = "spinningBodyThetaDot"
(Optional) Connect a command torque message:
cmdArray = messaging.ArrayMotorTorqueMsgPayload() cmdArray.motorTorque = [cmdTorque] # [Nm] cmdMsg = messaging.ArrayMotorTorqueMsg().write(cmdArray) spinningBody.motorTorqueInMsg.subscribeTo(cmdMsg)
(Optional) Connect an axis-locking message (0 means the axis is free to rotate and 1 locks the axis):
lockArray = messaging.ArrayEffectorLockMsgPayload() lockArray.motorTorque = [1] lockMsg = messaging.ArrayEffectorLockMsg().write(lockArray) spinningBody.motorLockInMsg.subscribeTo(lockMsg)
(Optional) Connect an angle and angle rate reference message:
angleRef = messaging.HingedRigidBodyMsgPayload() angleRef.theta = thetaRef angleRef.thetaDot = thetaDotRef angleRefMsg = messaging.HingedRigidBodyMsg().write(angleRef) spinningBody.spinningBodyRefInMsg.subscribeTo(angleRefMsg)
The angular states of the body are created using an output message
spinningBodyOutMsg.The spinning body config log state output message is
spinningBodyConfigLogOutMsg.Add the effector to your spacecraft:
scObject.addStateEffector(spinningBody)
See Module: spacecraft documentation on how to set up a spacecraft object.
Add the module to the task list:
unitTestSim.AddModelToTask(unitTaskName, spinningBody)
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class SpinningBodyOneDOFStateEffector : public StateEffector, public SysModel
- #include <spinningBodyOneDOFStateEffector.h>
spinning body state effector class
Public Functions
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SpinningBodyOneDOFStateEffector()
— Contructor
This is the constructor, setting variables to default values
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~SpinningBodyOneDOFStateEffector() override
— Destructor
This is the destructor, nothing to report here
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void Reset(uint64_t CurrentClock) override
— Method for reset
This method is used to reset the module.
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void writeOutputStateMessages(uint64_t CurrentClock) override
— Method for writing the output messages
This method takes the computed theta states and outputs them to the messaging system.
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void UpdateState(uint64_t CurrentSimNanos) override
— Method for updating information
This method is used so that the simulation will ask SB to update messages
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void registerStates(DynParamManager &statesIn) override
— Method for registering the SB states
This method allows the SB state effector to register its states: theta and thetaDot with the dynamic parameter manager
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void linkInStates(DynParamManager &states) override
— Method for getting access to other states
This method allows the SB state effector to have access to the hub states and gravity
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void updateContributions(double integTime, BackSubMatrices &backSubContr, Eigen::Vector3d sigma_BN, Eigen::Vector3d omega_BN_B, Eigen::Vector3d g_N) override
— Method for back-substitution contributions
This method allows the SB state effector to give its contributions to the matrices needed for the back-sub method
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void computeDerivatives(double integTime, Eigen::Vector3d rDDot_BN_N, Eigen::Vector3d omegaDot_BN_B, Eigen::Vector3d sigma_BN) override
— Method for SB to compute its derivatives
This method is used to find the derivatives for the SB stateEffector: thetaDDot and the kinematic derivative
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void updateEffectorMassProps(double integTime) override
— Method for giving the s/c the HRB mass props and prop rates
This method allows the SB state effector to provide its contributions to the mass props and mass prop rates of the spacecraft
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void updateEnergyMomContributions(double integTime, Eigen::Vector3d &rotAngMomPntCContr_B, double &rotEnergyContr, Eigen::Vector3d omega_BN_B) override
— Method for computing energy and momentum for SBs
This method is for calculating the contributions of the SB state effector to the energy and momentum of the spacecraft
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void prependSpacecraftNameToStates() override
Method used for multiple spacecraft.
This method prepends the name of the spacecraft for multi-spacecraft simulations.
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void computeSpinningBodyInertialStates()
Method for computing the SB’s states.
This method computes the spinning body states relative to the inertial frame
Public Members
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double mass = 1.0
[kg] mass of spinning body
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double k = 0.0
[N-m/rad] torsional spring constant
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double c = 0.0
[N-m-s/rad] rotational damping coefficient
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double thetaInit = 0.0
[rad] initial spinning body angle
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double thetaDotInit = 0.0
[rad/s] initial spinning body angle rate
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std::string nameOfThetaState
— identifier for the theta state data container
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std::string nameOfThetaDotState
— identifier for the thetaDot state data container
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Eigen::Vector3d r_SB_B = {0.0, 0.0, 0.0}
[m] vector pointing from body frame B origin to spinning frame S origin in B frame components
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Eigen::Vector3d r_ScS_S = {0.0, 0.0, 0.0}
[m] vector pointing from spinning frame S origin to point Sc (center of mass of the spinner) in S frame components
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Eigen::Vector3d sHat_S = {1.0, 0.0, 0.0}
— spinning axis in S frame components.
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Eigen::Matrix3d IPntSc_S
[kg-m^2] Inertia of spinning body about point Sc in S frame components
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Eigen::Matrix3d dcm_S0B
— DCM from the body frame to the S0 frame (S frame for theta=0)
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Message<HingedRigidBodyMsgPayload> spinningBodyOutMsg
state output message
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Message<SCStatesMsgPayload> spinningBodyConfigLogOutMsg
spinning body state config log message
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ReadFunctor<ArrayMotorTorqueMsgPayload> motorTorqueInMsg
— (optional) motor torque input message
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ReadFunctor<ArrayEffectorLockMsgPayload> motorLockInMsg
— (optional) motor lock flag input message
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ReadFunctor<HingedRigidBodyMsgPayload> spinningBodyRefInMsg
— (optional) spinning body reference input message name
Private Members
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double u = 0.0
[N-m] optional motor torque
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int lockFlag = 0
[] flag for locking the rotation axis
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double thetaRef = 0.0
[rad] spinning body reference angle
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double thetaDotRef = 0.0
[rad] spinning body reference angle rate
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Eigen::Vector3d aTheta = {0.0, 0.0, 0.0}
— rDDot_BN term for back substitution
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Eigen::Vector3d bTheta = {0.0, 0.0, 0.0}
— omegaDot_BN term for back substitution
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double cTheta = 0.0
— scalar term for back substitution
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double mTheta = 0.0
— auxiliary term for back substitution
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Eigen::Vector3d sHat_B = {1.0, 0.0, 0.0}
— spinning axis in B frame components
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Eigen::Vector3d r_ScS_B = {0.0, 0.0, 0.0}
[m] vector pointing from spinning frame S origin to point Sc in B frame components
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Eigen::Vector3d r_ScB_B = {0.0, 0.0, 0.0}
[m] vector pointing from body frame B origin to point Sc in B frame components.
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Eigen::Vector3d rPrime_ScS_B = {0.0, 0.0, 0.0}
[m/s] body frame time derivative of r_ScS_B
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Eigen::Vector3d rPrime_ScB_B = {0.0, 0.0, 0.0}
[m/s] body frame time derivative of r_ScB_B
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Eigen::Vector3d rDot_ScB_B = {0.0, 0.0, 0.0}
[m/s] inertial frame time derivative of r_ScB_B
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Eigen::Vector3d omega_SB_B = {0.0, 0.0, 0.0}
[rad/s] angular velocity of the S frame wrt the B frame in B frame components.
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Eigen::Vector3d omega_BN_B = {0.0, 0.0, 0.0}
[rad/s] angular velocity of the B frame wrt the N frame in B frame components.
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Eigen::Vector3d omega_SN_B = {0.0, 0.0, 0.0}
[rad/s] angular velocity of the S frame wrt the N frame in B frame components.
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Eigen::MRPd sigma_BN = {0.0, 0.0, 0.0}
— body frame attitude wrt to the N frame in MRPs
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Eigen::Matrix3d rTilde_ScB_B
[m] tilde matrix of r_ScB_B
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Eigen::Matrix3d omegaTilde_SB_B
[rad/s] tilde matrix of omega_SB_B
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Eigen::Matrix3d omegaTilde_BN_B
[rad/s] tilde matrix of omega_BN_B
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Eigen::Matrix3d dcm_BS
— DCM from spinner frame to body frame
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Eigen::Matrix3d dcm_BN
— DCM from inertial frame to body frame
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Eigen::Matrix3d IPntSc_B
[kg-m^2] inertia of spinning body about point Sc in B frame components
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Eigen::Vector3d r_ScN_N = {0.0, 0.0, 0.0}
[m] position vector of spinning body center of mass Sc relative to the inertial frame origin N
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Eigen::Vector3d v_ScN_N = {0.0, 0.0, 0.0}
[m/s] inertial velocity vector of Sc relative to inertial frame
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Eigen::Vector3d sigma_SN = {0.0, 0.0, 0.0}
— MRP attitude of frame S relative to inertial frame
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Eigen::Vector3d omega_SN_S = {0.0, 0.0, 0.0}
[rad/s] inertial spinning body frame angular velocity vector
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double theta = 0.0
[rad] spinning body angle
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double thetaDot = 0.0
[rad/s] spinning body angle rate
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Eigen::MatrixXd *inertialPositionProperty = nullptr
[m] r_N inertial position relative to system spice zeroBase/refBase
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Eigen::MatrixXd *inertialVelocityProperty = nullptr
[m] v_N inertial velocity relative to system spice zeroBase/refBase
Private Static Attributes
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static uint64_t effectorID = 1
[] ID number of this panel
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SpinningBodyOneDOFStateEffector()