chrono::ChLoadBase Class Referenceabstract

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:
Collaboration diagram for chrono::ChLoadBase:

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...
 
ChLoadJacobiansGetJacobians ()
 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 ChObjClone () 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

ChLoadJacobiansm_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_xstate position to evaluate Jacobians
state_wstate 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_xstate position to evaluate Q
state_wstate 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()

◆ 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
Mdresult: Md vector, diagonal of the lumped mass matrix
errresult: not touched if lumping does not introduce errors
ca 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
Rresult: the R residual, R += c*M*v
wthe w vector
cscaling 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