Description

Physics element that carries its own dynamics, described as a system of ODEs.

The internal states are integrated simultaneous with the containing system and they can be accessed and used coupled with other physics elements.

#include <ChExternalDynamics.h>

Inheritance diagram for chrono::ChExternalDynamics:

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Collaboration diagram for chrono::ChExternalDynamics:

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Public Member Functions
virtual ChExternalDynamics *	Clone () const override
	"Virtual" copy constructor (covariant return type).

void	Initialize ()
	Initialize the physics item.

ChVectorDynamic	GetInitialStates ()
	Get the initial values (state at initial time).

const ChVectorDynamic &	GetStates () const
	Get current states.

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

ChSystem *	GetSystem () const
	Get the pointer to the parent ChSystem().

virtual void	SetSystem (ChSystem *m_system)
	Set the pointer to the parent ChSystem(). More...

void	AddVisualModel (std::shared_ptr< ChVisualModel > model)
	Add an (optional) visualization model. More...

std::shared_ptr< ChVisualModel >	GetVisualModel () const
	Access the visualization model (if any). More...

void	AddVisualShape (std::shared_ptr< ChVisualShape > shape, const ChFrame<> &frame=ChFrame<>())
	Add the specified visual shape to the visualization model. More...

std::shared_ptr< ChVisualShape >	GetVisualShape (unsigned int i) const
	Access the specified visualization shape in the visualization model (if any). More...

void	AddVisualShapeFEA (std::shared_ptr< ChVisualShapeFEA > shapeFEA)
	Add the specified FEA visualization object to the visualization model. More...

std::shared_ptr< ChVisualShapeFEA >	GetVisualShapeFEA (unsigned int i) const
	Access the specified FEA visualization object in the visualization model (if any). More...

virtual ChFrame	GetVisualModelFrame (unsigned int nclone=0) const
	Get the reference frame (expressed in and relative to the absolute frame) of the visual model. More...

virtual unsigned int	GetNumVisualModelClones () const
	Return the number of clones of the visual model associated with this physics item. More...

void	AddCamera (std::shared_ptr< ChCamera > camera)
	Attach a ChCamera to this physical item. More...

std::vector< std::shared_ptr< ChCamera > >	GetCameras () const
	Get the set of cameras attached to this physics item.

virtual bool	IsActive () const
	Return true if the object is active and included in dynamics.

virtual bool	IsCollisionEnabled () const
	Tell if the object is subject to collision. More...

virtual void	AddCollisionModelsToSystem (ChCollisionSystem *coll_sys) const
	Add to the provided collision system any collision models managed by this physics item. More...

virtual void	RemoveCollisionModelsFromSystem (ChCollisionSystem *coll_sys) const
	Remove from the provided collision system any collision models managed by this physics item. More...

virtual void	SyncCollisionModels ()
	Synchronize the position and bounding box of any collsion models managed by this physics item.

virtual ChAABB	GetTotalAABB ()
	Get the entire AABB axis-aligned bounding box of the object. More...

virtual void	GetCenter (ChVector3d &mcenter)
	Get a symbolic 'center' of the object. More...

virtual void	Setup ()
	This might recompute the number of coordinates, DOFs, constraints, in case this might change (ex in ChAssembly), as well as state offsets of contained items (ex in ChMesh)

virtual void	Update (bool update_assets=true)
	As above, but does not require updating of time-dependent data. More...

virtual void	ForceToRest ()
	Set zero speed (and zero accelerations) in state, without changing the position. More...

virtual unsigned int	GetNumCoordsVelLevel ()
	Get the number of coordinates at the velocity level. More...

virtual unsigned int	GetNumConstraints ()
	Get the number of scalar constraints.

virtual unsigned int	GetNumConstraintsBilateral ()
	Get the number of bilateral scalar constraints.

virtual unsigned int	GetNumConstraintsUnilateral ()
	Get the number of unilateral scalar constraints.

unsigned int	GetOffset_x ()
	Get offset in the state vector (position part)

unsigned int	GetOffset_w ()
	Get offset in the state vector (speed part)

unsigned int	GetOffset_L ()
	Get offset in the lagrangian multipliers.

void	SetOffset_x (const unsigned int moff)
	Set offset in the state vector (position part) Note: only the ChSystem::Setup function should use this.

void	SetOffset_w (const unsigned int moff)
	Set offset in the state vector (speed part) Note: only the ChSystem::Setup function should use this.

void	SetOffset_L (const unsigned int moff)
	Set offset in the lagrangian multipliers Note: only the ChSystem::Setup function should use this.

virtual void	IntStateGatherReactions (const unsigned int off_L, ChVectorDynamic<> &L)
	From item's reaction forces to global reaction vector. More...

virtual void	IntStateScatterReactions (const unsigned int off_L, const ChVectorDynamic<> &L)
	From global reaction vector to item's reaction forces. More...

virtual void	IntStateIncrement (const unsigned int off_x, ChState &x_new, const ChState &x, const unsigned int off_v, const ChStateDelta &Dv)
	Computes x_new = x + Dt , using vectors at specified offsets. More...

virtual void	IntStateGetIncrement (const unsigned int off_x, const ChState &x_new, const ChState &x, const unsigned int off_v, ChStateDelta &Dv)
	Computes Dt = x_new - x, using vectors at specified offsets. More...

virtual void	IntLoadResidual_CqL (const unsigned int off_L, ChVectorDynamic<> &R, const ChVectorDynamic<> &L, const double c)
	Takes the term Cq'L, scale and adds to R at given offset: R += cCq'*L. More...

virtual void	IntLoadConstraint_C (const unsigned int off, ChVectorDynamic<> &Qc, const double c, bool do_clamp, double recovery_clamp)
	Takes the term C, scale and adds to Qc at given offset: Qc += c*C. More...

virtual void	IntLoadConstraint_Ct (const unsigned int off, ChVectorDynamic<> &Qc, const double c)
	Takes the term Ct, scale and adds to Qc at given offset: Qc += c*Ct. More...

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

virtual void	LoadConstraintJacobians ()
	Compute and load current Jacobians in encapsulated ChConstraint objects.

virtual void	ConstraintsBiReset ()
	Sets to zero the known term (b_i) of encapsulated ChConstraints.

virtual void	ConstraintsBiLoad_C (double factor=1, double recovery_clamp=0.1, bool do_clamp=false)
	Adds the current C (constraint violation) to the known term (b_i) of encapsulated ChConstraints.

virtual void	ConstraintsBiLoad_Ct (double factor=1)
	Adds the current Ct (partial t-derivative, as in C_dt=0-> [Cq]*q_dt=-Ct) to the known term (b_i) of encapsulated ChConstraints.

virtual void	ConstraintsBiLoad_Qc (double factor=1)
	Adds the current Qc (the vector of C_dtdt=0 -> [Cq]*q_dtdt=Qc ) to the known term (b_i) of encapsulated ChConstraints.

virtual void	ConstraintsFetch_react (double factor=1)
	Fetches the reactions from the lagrangian multiplier (l_i) of encapsulated ChConstraints. More...

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

virtual void	ArchiveIn (ChArchiveIn &archive_in) override
	Method to allow deserialization of transient data from archives. More...

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

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 std::string &	ArchiveContainerName ()

Protected Member Functions
virtual bool	IsStiff () const
	Declare as stiff (default: false). More...

virtual unsigned int	GetNumStates () const
	Specify number of states (dimension of y).

virtual void	SetInitialConditions (ChVectorDynamic<> &y0)
	Set initial conditions. More...

virtual void	CalculateRHS (double time, const ChVectorDynamic<> &y, ChVectorDynamic<> &rhs)
	Calculate and return the ODE right-hand side at the provided time and states. More...

virtual bool	CalculateJac (double time, const ChVectorDynamic<> &y, const ChVectorDynamic<> &rhs, ChMatrixDynamic<> &J)
	Calculate the Jacobian of the ODE right-hand side with respect to the ODE states. More...

virtual void	Update (double time, bool update_assets=true) override
	This is an important function, which is called by the owner ChSystem at least once per integration step. More...

virtual unsigned int	GetNumCoordsPosLevel () override
	Get the number of coordinates at the position level. More...

ChVariables &	Variables ()

virtual void	InjectVariables (ChSystemDescriptor &descriptor) override
	Register with the given system descriptor any ChVariable objects associated with this item.

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

virtual void	IntStateGather (const unsigned int off_x, ChState &x, const unsigned int off_v, ChStateDelta &v, double &T) override
	From item's state to global state vectors y={x,v} pasting the states at the specified offsets. More...

virtual void	IntStateScatter (const unsigned int off_x, const ChState &x, const unsigned int off_v, const ChStateDelta &v, const double T, bool full_update) override
	From global state vectors y={x,v} to item's state (and update) fetching the states at the specified offsets. More...

virtual void	IntStateGatherAcceleration (const unsigned int off_a, ChStateDelta &a) override
	From item's state acceleration to global acceleration vector. More...

virtual void	IntStateScatterAcceleration (const unsigned int off_a, const ChStateDelta &a) override
	From global acceleration vector to item's state acceleration. More...

virtual void	IntLoadResidual_F (const unsigned int off, ChVectorDynamic<> &R, const double c) override
	Takes the F force term, scale and adds to R at given offset: R += c*F. More...

virtual void	IntLoadResidual_Mv (const unsigned int off, ChVectorDynamic<> &R, const ChVectorDynamic<> &v, const double c) override
	Takes the Mv term, multiplying mass by a vector, scale and adds to R at given offset: R += cM*w. More...

virtual void	IntLoadLumpedMass_Md (const unsigned int off, ChVectorDynamic<> &Md, double &err, const double c) override
	Adds the lumped mass to a Md vector, representing a mass diagonal matrix. More...

virtual void	IntToDescriptor (const unsigned int off_v, const ChStateDelta &v, const ChVectorDynamic<> &R, const unsigned int off_L, const ChVectorDynamic<> &L, const ChVectorDynamic<> &Qc) override
	Prepare variables and constraints to accommodate a solution: More...

virtual void	IntFromDescriptor (const unsigned int off_v, ChStateDelta &v, const unsigned int off_L, ChVectorDynamic<> &L) override
	After a solver solution, fetch values from variables and constraints into vectors: More...

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

virtual void	VariablesFbReset () override
	Sets the 'fb' part (the known term) of the encapsulated ChVariables to zero.

virtual void	VariablesFbLoadForces (double factor=1) override
	Adds the current forces (applied to item) into the encapsulated ChVariables, in the 'fb' part: qf+=forces*factor.

virtual void	VariablesQbLoadSpeed () override
	Initialize the 'qb' part of the ChVariables with the current value of speeds. More...

virtual void	VariablesQbSetSpeed (double step=0) override
	Fetches the item speed (ex. More...

virtual void	VariablesFbIncrementMq () override
	Adds M*q (masses multiplied current 'qb') to Fb, ex. More...

virtual void	VariablesQbIncrementPosition (double step) override
	Increment item positions by the 'qb' part of the ChVariables, multiplied by a 'step' factor. More...

virtual void	ConstraintsFbLoadForces (double factor=1) override
	Adds the current link-forces, if any, (caused by springs, etc.) to the 'fb' vectors of the ChVariables referenced by encapsulated ChConstraints.

void	ComputeJac (double time)
	Compute the Jacobian at the current time and state.

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

Additional Inherited Members
Protected Attributes inherited from chrono::ChPhysicsItem
ChSystem *	system
	parent system

std::shared_ptr< ChVisualModelInstance >	vis_model_instance
	instantiated visualization model

std::vector< std::shared_ptr< ChCamera > >	cameras
	set of cameras

unsigned int	offset_x
	offset in vector of state (position part)

unsigned int	offset_w
	offset in vector of state (speed part)

unsigned int	offset_L
	offset in vector of lagrangian multipliers

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

Member Function Documentation

◆ CalculateJac()

virtual bool chrono::ChExternalDynamics::CalculateJac	(	double	time,
		const ChVectorDynamic<> &	y,
		const ChVectorDynamic<> &	rhs,
		ChMatrixDynamic<> &	J
	)

inlineprotectedvirtual

Calculate the Jacobian of the ODE right-hand side with respect to the ODE states.

Must load J = df/dy. Only used if the physics item is declared as stiff. If provided, load df/dy into the provided matrix 'jac' (already set to zero before the call) and return 'true'. In that case, the user-provided Jacobian will overwrite the default finite-difference approximation.

Parameters

time	current time
y	current ODE states
rhs	current ODE right-hand side vector
J	output Jacobian matrix

◆ CalculateRHS()

virtual void chrono::ChExternalDynamics::CalculateRHS	(	double	time,
		const ChVectorDynamic<> &	y,
		ChVectorDynamic<> &	rhs
	)

inlineprotectedvirtual

Calculate and return the ODE right-hand side at the provided time and states.

Must load rhs = f(t,y).

Parameters

time	current time
y	current ODE states
rhs	output ODE right-hand side vector

◆ GetNumCoordsPosLevel()

virtual unsigned int chrono::ChExternalDynamics::GetNumCoordsPosLevel ( )

inlineoverrideprotectedvirtual

Get the number of coordinates at the position level.

Might differ from coordinates at velocity level if quaternions are used for rotations.

Reimplemented from chrono::ChPhysicsItem.

◆ IntFromDescriptor()

void chrono::ChExternalDynamics::IntFromDescriptor	(	const unsigned int	off_v,
		ChStateDelta &	v,
		const unsigned int	off_L,
		ChVectorDynamic<> &	L
	)

overrideprotectedvirtual

After a solver solution, fetch values from variables and constraints into vectors:

Parameters

off_v	offset for v
v	vector to where the q 'unknowns' term of the variables will be copied
off_L	offset for L
L	vector to where L 'lagrangian ' term of the constraints will be copied

Reimplemented from chrono::ChPhysicsItem.

◆ IntLoadLumpedMass_Md()

void chrono::ChExternalDynamics::IntLoadLumpedMass_Md	(	const unsigned int	off,
		ChVectorDynamic<> &	Md,
		double &	err,
		const double	c
	)

overrideprotectedvirtual

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

Used by lumped explicit integrators. If mass lumping is impossible or approximate, adds scalar error to "error" parameter. Md += c*diag(M)

Parameters

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

Reimplemented from chrono::ChPhysicsItem.

◆ IntLoadResidual_F()

void chrono::ChExternalDynamics::IntLoadResidual_F	(	const unsigned int	off,
		ChVectorDynamic<> &	R,
		const double	c
	)

overrideprotectedvirtual

Takes the F force term, scale and adds to R at given offset: R += c*F.

Parameters

off	offset in R residual
R	result: the R residual, R += c*F
c	a scaling factor

Reimplemented from chrono::ChPhysicsItem.

Reimplemented in chrono::ChHydraulicActuatorBase.

◆ IntLoadResidual_Mv()

void chrono::ChExternalDynamics::IntLoadResidual_Mv	(	const unsigned int	off,
		ChVectorDynamic<> &	R,
		const ChVectorDynamic<> &	w,
		const double	c
	)

overrideprotectedvirtual

Takes the M*v term, multiplying mass by a vector, scale and adds to R at given offset: R += c*M*w.

Parameters

off	offset in R residual
R	result: the R residual, R += cMv
w	the w vector
c	a scaling factor

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateGather()

void chrono::ChExternalDynamics::IntStateGather	(	const unsigned int	off_x,
		ChState &	x,
		const unsigned int	off_v,
		ChStateDelta &	v,
		double &	T
	)

overrideprotectedvirtual

From item's state to global state vectors y={x,v} pasting the states at the specified offsets.

Parameters

off_x	offset in x state vector
x	state vector, position part
off_v	offset in v state vector
v	state vector, speed part
T	time

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateGatherAcceleration()

void chrono::ChExternalDynamics::IntStateGatherAcceleration	(	const unsigned int	off_a,
		ChStateDelta &	a
	)

overrideprotectedvirtual

From item's state acceleration to global acceleration vector.

Parameters

off_a	offset in a accel. vector
a	acceleration part of state vector derivative

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateScatter()

void chrono::ChExternalDynamics::IntStateScatter	(	const unsigned int	off_x,
		const ChState &	x,
		const unsigned int	off_v,
		const ChStateDelta &	v,
		const double	T,
		bool	full_update
	)

overrideprotectedvirtual

From global state vectors y={x,v} to item's state (and update) fetching the states at the specified offsets.

Parameters

off_x	offset in x state vector
x	state vector, position part
off_v	offset in v state vector
v	state vector, speed part
T	time
full_update	perform complete update

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateScatterAcceleration()

void chrono::ChExternalDynamics::IntStateScatterAcceleration	(	const unsigned int	off_a,
		const ChStateDelta &	a
	)

overrideprotectedvirtual

From global acceleration vector to item's state acceleration.

Parameters

off_a	offset in a accel. vector
a	acceleration part of state vector derivative

Reimplemented from chrono::ChPhysicsItem.

◆ IntToDescriptor()

void chrono::ChExternalDynamics::IntToDescriptor	(	const unsigned int	off_v,
		const ChStateDelta &	v,
		const ChVectorDynamic<> &	R,
		const unsigned int	off_L,
		const ChVectorDynamic<> &	L,
		const ChVectorDynamic<> &	Qc
	)

overrideprotectedvirtual

Prepare variables and constraints to accommodate a solution:

Parameters

off_v	offset for v and R
v	vector copied into the q 'unknowns' term of the variables
R	vector copied into the F 'force' term of the variables
off_L	offset for L and Qc
L	vector copied into the L 'lagrangian ' term of the constraints
Qc	vector copied into the Qb 'constraint' term of the constraints

Reimplemented from chrono::ChPhysicsItem.

◆ IsStiff()

virtual bool chrono::ChExternalDynamics::IsStiff ( ) const

inlineprotectedvirtual

Declare as stiff (default: false).

If stiff, Jacobian information will be generated.

Reimplemented in chrono::ChHydraulicActuatorBase.

◆ LoadKRMMatrices()

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

overrideprotectedvirtual

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. Note: signs are flipped from the term dF/dx in the integrator: K = -dF/dq and R = -dF/dv.

Reimplemented from chrono::ChPhysicsItem.

◆ SetInitialConditions()

virtual void chrono::ChExternalDynamics::SetInitialConditions ( ChVectorDynamic<> & y0 )

inlineprotectedvirtual

Set initial conditions.

Must load y0 = y(0).

◆ Update()

void chrono::ChExternalDynamics::Update	(	double	mytime,
		bool	update_assets = `true`
	)

overrideprotectedvirtual

This is an important function, which is called by the owner ChSystem at least once per integration step.

It may update all auxiliary data of the item, such as matrices if any, etc., depending on the current coordinates. The inherited classes, for example the ChLinkMask, often implement specialized versions of this Update(time) function, because they might need to update inner states, forces, springs, etc. This base version, by default, simply updates the item's time, and update the asset tree, if any.

Reimplemented from chrono::ChPhysicsItem.

Reimplemented in chrono::ChHydraulicActuatorBase.

◆ VariablesFbIncrementMq()

void chrono::ChExternalDynamics::VariablesFbIncrementMq ( )

overrideprotectedvirtual

Adds M*q (masses multiplied current 'qb') to Fb, ex.

if qb is initialized with v_old using VariablesQbLoadSpeed, this method can be used in timestepping schemes that do: M*v_new = M*v_old + forces*dt

Reimplemented from chrono::ChPhysicsItem.

◆ VariablesQbIncrementPosition()

void chrono::ChExternalDynamics::VariablesQbIncrementPosition ( double step )

overrideprotectedvirtual

Increment item positions by the 'qb' part of the ChVariables, multiplied by a 'step' factor.

pos+=qb*step If qb is a speed, this behaves like a single step of 1-st order numerical integration (Euler integration).

Reimplemented from chrono::ChPhysicsItem.

◆ VariablesQbLoadSpeed()

void chrono::ChExternalDynamics::VariablesQbLoadSpeed ( )

overrideprotectedvirtual

Initialize the 'qb' part of the ChVariables with the current value of speeds.

Note: since 'qb' is the unknown, this function seems unnecessary, unless used before VariablesFbIncrementMq()

Reimplemented from chrono::ChPhysicsItem.

◆ VariablesQbSetSpeed()

void chrono::ChExternalDynamics::VariablesQbSetSpeed ( double step = 0 )

overrideprotectedvirtual

Fetches the item speed (ex.

linear and angular vel.in rigid bodies) from the 'qb' part of the ChVariables and sets it as the current item speed. If 'step' is not 0, also should compute the approximate acceleration of the item using backward differences, that is accel=(new_speed-old_speed)/step. Mostly used after the solver provided the solution in ChVariables.

Reimplemented from chrono::ChPhysicsItem.

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

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

Description

Public Member Functions

Protected Member Functions

Additional Inherited Members

Member Function Documentation

◆ CalculateJac()

◆ CalculateRHS()

◆ GetNumCoordsPosLevel()

◆ IntFromDescriptor()

◆ IntLoadLumpedMass_Md()

◆ IntLoadResidual_F()

◆ IntLoadResidual_Mv()

◆ IntStateGather()

◆ IntStateGatherAcceleration()

◆ IntStateScatter()

◆ IntStateScatterAcceleration()

◆ IntToDescriptor()

◆ IsStiff()

◆ LoadKRMMatrices()

◆ SetInitialConditions()

◆ Update()

◆ VariablesFbIncrementMq()

◆ VariablesQbIncrementPosition()

◆ VariablesQbLoadSpeed()

◆ VariablesQbSetSpeed()