C++ Module: linearSpringMassDamper

Auxiliary Files

• Unit tests

Example usage

• scenarioConstrainedDynamicsComponentAnalysis

• scenarioFuelSlosh

• scenarioCompareVariableMass

Executive Summary

This class in an instantiation of the state effector class and implements an effector representing a oscillating particle

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

Message Connection Descriptions

This state effector does not have any input or output messages.

Initialization and Reset

massInit must be finite and non-negative. Zero initial mass and depletion to zero during integration remain supported. The initial-mass check runs before state registration during spacecraft initialization, including when the effector is attached without being added to a task. Invalid input raises BasiliskError.

Reset() repeats this configuration check without accessing parent states or changing integrated displacement, velocity, or mass. In particular, it does not restore depleted mass from massInit. Initial values are applied during state registration. See Initialization and Configuration Validation.

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class LinearSpringMassDamper : public StateEffector, public SysModel, public FuelSlosh

#include <linearSpringMassDamper.h>

linear spring mass damper state effector class

Public Functions

LinearSpringMassDamper()

Constructor.

This is the constructor, setting variables to default values

~LinearSpringMassDamper()

Destructor.

This is the destructor, nothing to report here

void Reset(uint64_t CurrentSimNanos) override

Validate configuration without restoring depleted mass or changing integrated states.

Parameters:

CurrentSimNanos – [ns] Current simulation time.

void registerStates(DynParamManager &states) override

Method for SMD to register its states.

This is the method for the spring mass damper particle to register its states: rho and rhoDot

Parameters:

states – [inout] Dynamic parameter manager used to register states or properties.

void linkInStates(DynParamManager &states) override

Method for SMD to get access of other states.

Method for spring mass damper particle to access the states that it needs. It needs gravity and the hub states

Parameters:

states – [in] Dynamic parameter manager containing the required states.

void retrieveMassValue(double integTime) override

This method is used to pass mass properties information to the fuel tank

Parameters:

integTime – [in] [s] Current integration time.

void calcForceTorqueOnBody(double integTime, Eigen::Vector3d omega_BN_B) override

Force and torque on s/c due to linear spring mass damper.

Calculate the force and torque exerted on the attached body.

Parameters:

• integTime – [in] [s] Current integration time.

• omega_BN_B – [in] [rad/s] Hub angular velocity expressed in body-frame components.

void updateEffectorMassProps(double integTime) override

Method for stateEffector to give mass contributions.

This is the method for the SMD to add its contributions to the mass props and mass prop rates of the vehicle

Parameters:

integTime – [in] [s] Current integration time.

void updateContributions(double integTime, BackSubMatrices &backSubContr, Eigen::MRPd sigma_BN, Eigen::Vector3d omega_BN_B, Eigen::Vector3d g_N) override

Back-sub contributions.

This method is for the SMD to add its contributions to the back-sub method

Parameters:

• integTime – [in] [s] Current integration time.

• backSubContr – [inout] Backsubstitution contributions.

• sigma_BN – [in] Hub attitude relative to the inertial frame.

• omega_BN_B – [in] [rad/s] Hub angular velocity expressed in body-frame components.

• g_N – [in] [m/s^2] Gravitational acceleration expressed in inertial-frame components.

void updateEnergyMomContributions(double integTime, Eigen::Vector3d &rotAngMomPntCContr_B, double &rotEnergyContr, Eigen::Vector3d omega_BN_B) override

Energy and momentum calculations.

This method is for the SMD to add its contributions to energy and momentum

Parameters:

• integTime – [in] [s] Current integration time.

• rotAngMomPntCContr_B – [inout] [kg*m^2/s] Rotational angular momentum contribution.

• rotEnergyContr – [inout] [J] Rotational energy contribution.

• omega_BN_B – [in] [rad/s] Hub angular velocity expressed in body-frame components.

void computeDerivatives(double integTime, Eigen::Vector3d rDDot_BN_N, Eigen::Vector3d omegaDot_BN_B, Eigen::MRPd sigma_BN) override

Method for each stateEffector to calculate derivatives.

This method is used to define the derivatives of the SMD. One is the trivial kinematic derivative and the other is derived using the back-sub method

Parameters:

• integTime – [in] [s] Current integration time.

• rDDot_BN_N – [in] [m/s^2] Hub translational acceleration expressed in inertial-frame components.

• omegaDot_BN_B – [in] [rad/s^2] Hub angular acceleration expressed in body-frame components.

• sigma_BN – [in] Hub attitude relative to the inertial frame.

Public Members

double k

[N/m] linear spring constant for spring mass damper

double c

[N-s/m] linear damping term for spring mass damper

double rhoInit

[m] Initial value for spring mass damper particle offset

double rhoDotInit

[m/s] Initial value for spring mass damper particle offset derivative

double massInit

[kg] Initial value for spring mass damper particle mass

std::string nameOfRhoState

[-] Identifier for the rho state data container

std::string nameOfRhoDotState

[-] Identifier for the rhoDot state data container

std::string nameOfMassState

[-] Identifier for the mass state data container

Eigen::Vector3d r_PB_B

[m] position vector from B point to particle equilibrium, P, in body frame

Eigen::Vector3d pHat_B

[-] particle direction unit vector, in body frame

StateData *massState = nullptr

state data for the particles mass

BSKLogger bskLogger

BSK Logging.

Private Functions

void validateConfiguration()

Validate the initial particle mass without changing its current state.

Validate the initial particle mass, retaining the supported empty-particle case.

Private Members

double cRho

Term needed for back-sub method.

double rho

[m] spring mass damper displacement from equilibrium

double rhoDot

[m/s] time derivative of displacement from equilibrium

double massSMD

[kg] mass of spring mass damper particle

Eigen::Vector3d r_PcB_B

[m] position vector form B to center of mass location of particle

Eigen::Matrix3d rTilde_PcB_B

[m] tilde matrix of r_Pc_B

Eigen::Vector3d rPrime_PcB_B

[m/s] Body time derivative of r_Pc_B

Eigen::Matrix3d rPrimeTilde_PcB_B

[m/s] Tilde matrix of rPrime_PcB_B

Eigen::Vector3d aRho

Term needed for back-sub method.

Eigen::Vector3d bRho

Term needed for back-sub method.

Eigen::MatrixXd *g_N

[m/s^2] Gravitational acceleration in N frame components

StateData *rhoState

state data for spring mass damper displacement from equilibrium

Eigen::MatrixXd *c_B

[m] Vector from point B to CoM of s/c in B frame components

Eigen::MatrixXd *cPrime_B

[m/s] Body time derivative of vector c_B in B frame components

StateData *rhoDotState

state data for time derivative of rho;

Private Static Attributes

static uint64_t effectorID = 1

[] ID number of this panel