Description

Base class for loads.

This class can be inherited to implement applied loads to bodies, finite elements, etc. A load is an object that might wrap one or more ChLoader objects, whose value is dependent. It implements functionalities to perform automatic differentiation of the load so it optionally can compute the Jacobian (the tangent stiffness matrix of the load) that can be used in implicit integrators, statics, etc.

#include <ChLoad.h>

Inheritance diagram for chrono::ChLoadBase:

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Collaboration diagram for chrono::ChLoadBase:

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Public Member Functions
virtual int	LoadGetNumCoordsPosLevel ()=0
	Gets the number of DOFs affected by this load (position part).

virtual int	LoadGetNumCoordsVelLevel ()=0
	Gets the number of DOFs affected by this load (speed part).

virtual void	LoadGetStateBlock_x (ChState &mD)=0
	Gets all the current DOFs packed in a single vector (position part).

virtual void	LoadGetStateBlock_w (ChStateDelta &mD)=0
	Gets all the current DOFs packed in a single vector (speed part).

virtual void	LoadStateIncrement (const ChState &x, const ChStateDelta &dw, ChState &x_new)=0
	Increment a packed state (e.g., as obtained by LoadGetStateBlock_x()) by a given packed state-delta. More...

virtual int	LoadGetNumFieldCoords ()=0
	Number of coordinates in the interpolated field. More...

virtual void	ComputeQ (ChState state_x, ChStateDelta state_w)=0
	Compute the generalized load(s). More...

virtual void	ComputeJacobian (ChState state_x, ChStateDelta state_w)=0
	Compute the K=-dQ/dx, R=-dQ/dv, M=-dQ/da Jacobians. More...

ChLoadJacobians *	GetJacobians ()
	Access the Jacobians (if any, i.e. if this is a stiff load).

virtual void	CreateJacobianMatrices ()=0
	Create the Jacobian loads if needed and set the ChVariables referenced by the sparse KRM block.

virtual void	Update (double time)
	Update, called at least at each time step. More...

virtual bool	IsStiff ()=0
	Report if this is load is stiff. More...

virtual void	LoadIntLoadResidual_F (ChVectorDynamic<> &R, double c)=0
	Add the internal loads Q (pasted at global offsets) into a global vector R, multiplied by a scaling factor c. More...

virtual void	LoadIntLoadResidual_Mv (ChVectorDynamic<> &R, const ChVectorDynamic<> &w, double c)=0
	Increment a vector R with the matrix-vector product M*w, scaled by the factor c. More...

virtual void	LoadIntLoadLumpedMass_Md (ChVectorDynamic<> &Md, double &err, const double c)=0
	Add the lumped mass to an Md vector, representing a mass diagonal matrix. More...

virtual void	InjectKRMMatrices (ChSystemDescriptor &descriptor)
	Register with the given system descriptor any ChKRMBlock objects associated with this item.

virtual void	LoadKRMMatrices (double Kfactor, double Rfactor, double Mfactor)
	Compute and load current stiffnes (K), damping (R), and mass (M) matrices in encapsulated ChKRMBlock objects. More...

Public Member Functions inherited from chrono::ChObj
	ChObj (const ChObj &other)

virtual ChObj *	Clone () const =0
	"Virtual" copy constructor.

int	GetIdentifier () const
	Get the unique integer identifier of this object. More...

void	SetTag (int tag)
	Set an object integer tag (default: -1). More...

int	GetTag () const
	Get the tag of this object.

void	SetName (const std::string &myname)
	Set the name of this object.

const std::string &	GetName () const
	Get the name of this object.

double	GetChTime () const
	Gets the simulation time of this object.

void	SetChTime (double m_time)
	Sets the simulation time of this object.

virtual void	ArchiveOut (ChArchiveOut &archive_out)
	Method to allow serialization of transient data to archives.

virtual void	ArchiveIn (ChArchiveIn &archive_in)
	Method to allow de-serialization of transient data from archives.

virtual std::string &	ArchiveContainerName ()

Protected Attributes
ChLoadJacobians *	m_jacobians

Protected Attributes inherited from chrono::ChObj
double	ChTime
	object simulation time

std::string	m_name
	object name

int	m_identifier
	object unique identifier

int	m_tag
	user-supplied tag

Additional Inherited Members
Protected Member Functions inherited from chrono::ChObj
int	GenerateUniqueIdentifier ()

Member Function Documentation

◆ ComputeJacobian()

virtual void chrono::ChLoadBase::ComputeJacobian	(	ChState *	state_x,
		ChStateDelta *	state_w
	)

pure virtual

Compute the K=-dQ/dx, R=-dQ/dv, M=-dQ/da Jacobians.

Implementation in a derived class should load the Jacobian matrices K, R, M in the structure 'm_jacobians'. Note the sign that is flipped because we assume equations are written with Q moved to left-hand side.

Parameters

state_x	state position to evaluate Jacobians
state_w	state speed to evaluate Jacobians

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoadBodyInertia, chrono::ChLoad, and chrono::ChLoadBodyMesh.

◆ ComputeQ()

virtual void chrono::ChLoadBase::ComputeQ	(	ChState *	state_x,
		ChStateDelta *	state_w
	)

pure virtual

Compute the generalized load(s).

A derived class should cache the resulting Q which is then used in LoadIntLoadResidual_F.

Parameters

state_x	state position to evaluate Q
state_w	state speed to evaluate Q

Implemented in chrono::fea::ChLoadNodeXYZRotBody, chrono::ChLoadNodeXYZBody, chrono::ChLoadBodyBody, chrono::ChLoadBodyInertia, chrono::ChLoad, chrono::ChLoadNodeXYZNodeXYZ, chrono::ChShaftsElasticGear, chrono::fea::ChLoadNodeXYZRotNodeXYZRot, chrono::ChLoadBodyTorque, chrono::ChLoadNodeXYZForce, chrono::ChLoadBodyForce, chrono::ChLoadBodyMesh, chrono::fea::ChLoadNodeXYZRot, and chrono::ChShaftsLoad.

◆ IsStiff()

virtual bool chrono::ChLoadBase::IsStiff ( )

pure virtual

Report if this is load is stiff.

If so, InjectKRMMatrices will provide the Jacobians of the load.

Implemented in chrono::fea::ChLoadNodeXYZRotBodyBushingGeneric, chrono::ChLoadBodyBodyBushingGeneric, chrono::fea::ChLoadNodeXYZRotBodyBushingSpherical, chrono::ChLoadNodeXYZBodyBushing, chrono::ChLoadBodyBodyBushingSpherical, chrono::ChLoadNodeXYZBodySpring, chrono::fea::ChLoadNodeXYZRotNodeXYZRotBushingGeneric, chrono::ChLoadNodeXYZNodeXYZBushing, chrono::ChLoadNodeXYZNodeXYZSpring, chrono::fea::ChLoadNodeXYZRotNodeXYZRotBushingSpherical, chrono::ChLoad, chrono::ChLoadNodeXYZNodeXYZ, chrono::ChShaftsElasticGear, chrono::ChLoadNodeXYZForceAbs, chrono::fea::ChLoadNodeXYZRotForceAbs, chrono::ChLoadNodeXYZForce, chrono::ChShaftsTorsionSpringDamper, chrono::ChLoadBodyMesh, and chrono::fea::ChLoadNodeXYZRot.

◆ LoadGetNumFieldCoords()

virtual int chrono::ChLoadBase::LoadGetNumFieldCoords ( )

pure virtual

Number of coordinates in the interpolated field.

For example, 3 for a tetrahedron finite element or a cable, 1 for a thermal problem, etc.

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad, and chrono::ChLoadBodyMesh.

◆ LoadIntLoadLumpedMass_Md()

virtual void chrono::ChLoadBase::LoadIntLoadLumpedMass_Md	(	ChVectorDynamic<> &	Md,
		double &	err,
		const double	c
	)

pure virtual

Add the lumped mass to an Md vector, representing a mass diagonal matrix.

In other words, perform the operation: Md += c*diag(M). Used by lumped explicit integrators. If mass lumping is impossible or approximate, adds scalar error to "err" parameter. If no mass matrix M is present (i.e., no inertial effects), implement as no-op.

Parameters

Md	result: Md vector, diagonal of the lumped mass matrix
err	result: not touched if lumping does not introduce errors
c	a scaling factor

Implemented in chrono::ChLoadBodyMesh, chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, and chrono::ChLoad.

◆ LoadIntLoadResidual_F()

virtual void chrono::ChLoadBase::LoadIntLoadResidual_F	(	ChVectorDynamic<> &	R,
		double	c
	)

pure virtual

Add the internal loads Q (pasted at global offsets) into a global vector R, multiplied by a scaling factor c.

In other words, perform the operation: R += forces * c

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad, and chrono::ChLoadBodyMesh.

◆ LoadIntLoadResidual_Mv()

virtual void chrono::ChLoadBase::LoadIntLoadResidual_Mv	(	ChVectorDynamic<> &	R,
		const ChVectorDynamic<> &	w,
		double	c
	)

pure virtual

Increment a vector R with the matrix-vector product M*w, scaled by the factor c.

In other words, perform the operation: R += c*M*w (i.e., R += c*(-dQ/da)*w). If no mass matrix M is present (i.e., no inertial effects), implement as no-op.

Parameters

R	result: the R residual, R += cMv
w	the w vector
c	scaling factor

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad, chrono::ChLoadBodyMesh, and chrono::ChLoadBodyInertia.

◆ LoadKRMMatrices()

void chrono::ChLoadBase::LoadKRMMatrices	(	double	Kfactor,
		double	Rfactor,
		double	Mfactor
	)

virtual

Compute and load current stiffnes (K), damping (R), and mass (M) matrices in encapsulated ChKRMBlock objects.

The resulting KRM blocks represent linear combinations of the K, R, and M matrices, with the specified coefficients Kfactor, Rfactor,and Mfactor, respectively.

Reimplemented in chrono::ChLoadBodyMesh.

◆ LoadStateIncrement()

virtual void chrono::ChLoadBase::LoadStateIncrement	(	const ChState &	x,
		const ChStateDelta &	dw,
		ChState &	x_new
	)

pure virtual

Increment a packed state (e.g., as obtained by LoadGetStateBlock_x()) by a given packed state-delta.

Compute: x_new = x + dw. This method is used in calculating Jacobians with finite difference approximations (default implementations of ComputeJacobian).

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad, and chrono::ChLoadBodyMesh.

◆ Update()

void chrono::ChLoadBase::Update ( double time )

virtual

Update, called at least at each time step.

It recomputes the generalized load Q vector(s)
It recomputes the Jacobian matrices K,R,M in case of stiff load Q and Jacobians assumed evaluated at the current state. Jacobians are automatically allocated if needed.

Reimplemented in chrono::ChLoadNodeXYZNodeXYZ, chrono::ChLoadNodeXYZForceAbs, chrono::fea::ChLoadNodeXYZRotForceAbs, chrono::ChLoadNodeXYZForce, and chrono::fea::ChLoadNodeXYZRot.

The documentation for this class was generated from the following files:

/builds/uwsbel/chrono/src/chrono/physics/ChLoad.h
/builds/uwsbel/chrono/src/chrono/physics/ChLoad.cpp

Description

Public Member Functions

Protected Attributes

Additional Inherited Members

Member Function Documentation

◆ ComputeJacobian()

◆ ComputeQ()

◆ IsStiff()

◆ LoadGetNumFieldCoords()

◆ LoadIntLoadLumpedMass_Md()

◆ LoadIntLoadResidual_F()

◆ LoadIntLoadResidual_Mv()

◆ LoadKRMMatrices()

◆ LoadStateIncrement()

◆ Update()