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 LoadGet_ndof_x ()=0
 Gets the number of DOFs affected by this load (position part)
 
virtual int LoadGet_ndof_w ()=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 (ex. More...
 
virtual int LoadGet_field_ncoords ()=0
 Number of coordinates in the interpolated field, ex=3 for a tetrahedron finite element or a cable, = 1 for a thermal problem, etc. More...
 
virtual void ComputeQ (ChState *state_x, ChStateDelta *state_w)=0
 Compute Q, the generalized load(s). More...
 
virtual void ComputeJacobian (ChState *state_x, ChStateDelta *state_w, ChMatrix<> &mK, ChMatrix<> &mR, ChMatrix<> &mM)=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 also set the ChVariables referenced by the sparse KRM block. More...
 
virtual void Update ()
 Update: this is 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, const double c)=0
 Adds the internal loads Q (pasted at global nodes offsets) into a global vector R, multiplied by a scaling factor c, as R += forces * c.
 
virtual void InjectKRMmatrices (ChSystemDescriptor &mdescriptor)
 Tell to a system descriptor that there are item(s) of type ChKblock in this object (for further passing it to a solver) Basically does nothing, but inherited classes must specialize this. More...
 
virtual void KRMmatricesLoad (double Kfactor, double Rfactor, double Mfactor)
 Adds the current stiffness K and damping R and mass M matrices in encapsulated ChKblock item(s), if any. More...
 

Protected Attributes

ChLoadJacobiansjacobians
 

Member Function Documentation

virtual void chrono::ChLoadBase::ComputeJacobian ( ChState state_x,
ChStateDelta state_w,
ChMatrix<> &  mK,
ChMatrix<> &  mR,
ChMatrix<> &  mM 
)
pure virtual

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

Called automatically at each Update().

Parameters
state_xstate position to evaluate jacobians
state_wstate speed to evaluate jacobians
mKresult dQ/dx
mRresult dQ/dv
mMresult dQ/da

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad< Tloader >, chrono::ChLoad< ChLoaderBeamWrench >, chrono::ChLoad< ChLoaderXYZnode >, chrono::ChLoad< ChLoaderBeamWrenchDistributed >, chrono::fea::ChLoadContactSurfaceMesh, and chrono::ChLoadBodyMesh.

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

Compute Q, the generalized load(s).

Where Q is stored depends on children classes. Called automatically at each Update().

Parameters
state_xstate position to evaluate Q
state_wstate speed to evaluate Q

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoadBodyBody, chrono::ChLoad< Tloader >, chrono::ChLoad< ChLoaderBeamWrench >, chrono::ChLoad< ChLoaderXYZnode >, chrono::ChLoad< ChLoaderBeamWrenchDistributed >, chrono::fea::ChLoadContactSurfaceMesh, chrono::ChLoadBodyMesh, chrono::ChLoadBodyTorque, and chrono::ChLoadBodyForce.

virtual void chrono::ChLoadBase::CreateJacobianMatrices ( )
pure virtual
virtual void chrono::ChLoadBase::InjectKRMmatrices ( ChSystemDescriptor mdescriptor)
virtual

Tell to a system descriptor that there are item(s) of type ChKblock in this object (for further passing it to a solver) Basically does nothing, but inherited classes must specialize this.

Reimplemented in chrono::fea::ChLoadContactSurfaceMesh, and chrono::ChLoadBodyMesh.

virtual void chrono::ChLoadBase::KRMmatricesLoad ( double  Kfactor,
double  Rfactor,
double  Mfactor 
)
virtual

Adds the current stiffness K and damping R and mass M matrices in encapsulated ChKblock item(s), if any.

The K, R, M matrices are added with scaling values Kfactor, Rfactor, Mfactor.

Reimplemented in chrono::fea::ChLoadContactSurfaceMesh, and chrono::ChLoadBodyMesh.

virtual int chrono::ChLoadBase::LoadGet_field_ncoords ( )
pure virtual

Number of coordinates in the interpolated field, ex=3 for a tetrahedron finite element or a cable, = 1 for a thermal problem, etc.

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad< Tloader >, chrono::ChLoad< ChLoaderBeamWrench >, chrono::ChLoad< ChLoaderXYZnode >, chrono::ChLoad< ChLoaderBeamWrenchDistributed >, chrono::fea::ChLoadContactSurfaceMesh, and chrono::ChLoadBodyMesh.

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

Increment a packed state (ex.

as obtained by LoadGetStateBlock_x()) by a given packed state-delta. Compute: x_new = x + dw. Ex. this is called by the BDF numerical differentiation routine that computes jacobian in the default ComputeJacobian() fallback, if not overriding ComputeJacobian() with an analytical form.

Implemented in chrono::ChLoadCustomMultiple, chrono::ChLoadCustom, chrono::ChLoad< Tloader >, chrono::ChLoad< ChLoaderBeamWrench >, chrono::ChLoad< ChLoaderXYZnode >, chrono::ChLoad< ChLoaderBeamWrenchDistributed >, chrono::fea::ChLoadContactSurfaceMesh, and chrono::ChLoadBodyMesh.

virtual void chrono::ChLoadBase::Update ( )
virtual

Update: this is called at least at each time step.

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