Description

Class for links which connect two 'markers'.

The markers are two ChMarker objects each belonging to the two linked ChBody parts. Many specialized classes are based on this ChLinkMarkers class, for example the family of ChLinkLock classes. ChLinkMarkers class allows an optional force vector and torque vector to be set between the two connected markers.

#include <ChLinkMarkers.h>

Inheritance diagram for chrono::ChLinkMarkers:

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Collaboration diagram for chrono::ChLinkMarkers:

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

ChMarker *	GetMarker1 ()
	Return the 1st referenced marker (the 'slave' marker, owned by 1st body)

ChMarker *	GetMarker2 ()
	Return the 2nd referenced marker (the 'master' marker, owned by 2nd body)

virtual void	SetUpMarkers (ChMarker mark1, ChMarker mark2)
	set the two markers associated with this link

void	SetMarkID1 (int mid)

void	SetMarkID2 (int mid)

int	GetMarkID1 ()

int	GetMarkID2 ()

bool	ReferenceMarkers (ChMarker mark1, ChMarker mark2)
	Shortcut: set markers and marker IDs at once.

virtual void	Initialize (std::shared_ptr< ChMarker > mark1, std::shared_ptr< ChMarker > mark2)
	Use this function after link creation, to initialize the link from two markers to join. More...

virtual void	Initialize (std::shared_ptr< ChBody > mbody1, std::shared_ptr< ChBody > mbody2, const ChCoordsys<> &mpos)
	Use this function after link creation, to initialize the link from two joined rigid bodies. More...

virtual void	Initialize (std::shared_ptr< ChBody > mbody1, std::shared_ptr< ChBody > mbody2, bool pos_are_relative, const ChCoordsys<> &mpos1, const ChCoordsys<> &mpos2)
	Use this function after link creation, to initialize the link from two joined rigid bodies. More...

virtual ChCoordsys	GetLinkRelativeCoords () override
	Get the link coordinate system, expressed relative to Body2 (the 'master' body). More...

virtual ChFrame	GetAssetsFrame (unsigned int nclone=0) override
	Get the master coordinate system for the assets (this will return the absolute coordinate system of the 'master' marker2)

virtual void	UpdateRelMarkerCoords ()
	Updates auxiliary quantities for all relative degrees of freedom of the two markers.

virtual void	UpdateForces (double mytime)
	Updates auxiliary forces caused by springs/dampers/etc. More...

virtual void	Update (double mytime, bool update_assets=true) override
	Complete link update: UpdateTime -> UpdateRelMarkerCoords -> UpdateForces.

virtual void	IntLoadResidual_F (const unsigned int off, ChVectorDynamic<> &R, const double c) override
	Adds force to residual R, as R= Fc NOTE: here the off offset in R is NOT used because add F at the TWO offsets of the two connected bodies, so it is assumed that offsets for Body1 and Body2 variables have been already set properly!

virtual void	ConstraintsFbLoadForces (double factor=1) override
	Overrides the empty behaviour of the parent ChLink implementation, which does not consider any user-imposed force between the two bodies. More...

const Coordsys &	GetRelM () const
	Relative position of marker 1 respect to marker 2.

const Coordsys &	GetRelM_dt () const
	Relative speed of marker 1 respect to marker 2.

const Coordsys &	GetRelM_dtdt () const
	Relative acceleration of marker 1 respect to marker 2.

double	GetRelAngle () const
	Relative rotation angle of marker 1 respect to marker 2 (best with revolute joints..).

const ChVector &	GetRelAxis () const
	Relative finite rotation axis of marker 1 respect to marker 2.

const ChVector &	GetRelRotaxis () const

const ChVector &	GetRelWvel () const
	Relative angular speed of marker 1 respect to marker 2.

const ChVector &	GetRelWacc () const
	Relative angular acceleration of marker 1 respect to marker 2.

double	GetDist () const
	Relative 'polar' distance of marker 1 respect to marker 2.

double	GetDist_dt () const
	Relative speed of marker 1 respect to marker 2, along the polar distance vector.

const ChVector &	GetC_force () const
	Get the total applied force accumulators (force, momentum) in link coords. More...

const ChVector &	GetC_torque () const

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

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

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

int	GetLeftDOF ()
	Get the number of free degrees of freedom left by this link, between two bodies.

virtual int	GetNumCoords () override
	Get the number of scalar variables affected by constraints in this link.

ChBodyFrame *	GetBody1 ()
	Get the constrained body '1', the 'slave' body.

ChBodyFrame *	GetBody2 ()
	Get the constrained body '2', the 'master' body.

virtual ChCoordsys	GetLinkAbsoluteCoords () override
	Get the link coordinate system in absolute reference. More...

virtual ChVector	Get_react_force () override
	Get reaction force, expressed in link coordinate system.

virtual ChVector	Get_react_torque () override
	Get reaction torque, expressed in link coordinate system.

virtual int	RestoreRedundant ()
	If some constraint is redundant, return to normal state //*OBSOLETE*.

virtual void	UpdateTime (double mytime)
	Given new time, current body state, update time-dependent quantities in link state, for example motion laws, moving markers, etc. More...

virtual void	Update (bool update_assets=true) override
	As above, but with current time.

virtual void	UpdatedExternalTime (double prevtime, double time)
	Called from a external package (i.e. a plugin, a CAD app.) to report that time has changed.

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

bool	IsValid ()
	Tells if the link data is currently valid. More...

void	SetValid (bool mon)
	Set the status of link validity.

bool	IsDisabled ()
	Tells if all constraints of this link are currently turned on or off by the user.

virtual void	SetDisabled (bool mdis)
	User can use this to enable/disable all the constraint of the link as desired.

bool	IsBroken ()
	Tells if the link is broken, for excess of pulling/pushing.

virtual void	SetBroken (bool mon)
	Set the 'broken' status vof this link.

bool	IsActive ()
	An important function! Tells if the link is currently active, in general, that is tells if it must be included into the system solver or not. More...

virtual ChVectorDynamic	GetConstraintViolation () const
	Get the current constraint violations.

virtual bool	IsRequiringWaking ()
	Tells if this link requires that the connected ChBody objects must be waken if they are sleeping. More...

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() and also add to new collision system / remove from old coll.system.

void	AddAsset (std::shared_ptr< ChAsset > masset)
	Add an optional asset (it can be used to define visualization shapes, es ChSphereShape, or textures, or custom attached properties that the user can define by creating his class inherited from ChAsset)

std::vector< std::shared_ptr< ChAsset > > &	GetAssets ()
	Access to the list of optional assets.

std::shared_ptr< ChAsset >	GetAssetN (unsigned int num)
	Access the Nth asset in the list of optional assets.

virtual unsigned int	GetAssetsFrameNclones ()
	Optionally, a ChPhysicsItem can return multiple asset coordinate systems; this can be helpful if, for example, when a ChPhysicsItem contains 'clones' with the same assets (ex. More...

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

virtual void	SyncCollisionModels ()
	If this physical item contains one or more collision models, synchronize their coordinates and bounding boxes to the state of the item.

virtual void	AddCollisionModelsToSystem ()
	If this physical item contains one or more collision models, add them to the system's collision engine.

virtual void	RemoveCollisionModelsFromSystem ()
	If this physical item contains one or more collision models, remove them from the system's collision engine.

virtual void	GetTotalAABB (ChVector<> &bbmin, ChVector<> &bbmax)
	Get the entire AABB axis-aligned bounding box of the object. More...

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

virtual void	StreamINstate (ChStreamInBinary &mstream)
	Method to deserialize only the state (position, speed) Must be implemented by child classes.

virtual void	StreamOUTstate (ChStreamOutBinary &mstream)
	Method to serialize only the state (position, speed) Must be implemented by child classes.

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

virtual int	GetDOF ()
	Get the number of scalar coordinates (variables), if any, in this item. More...

virtual int	GetDOF_w ()
	Get the number of scalar coordinates of variables derivatives (usually = DOF, but might be different than DOF, ex. More...

virtual int	GetDOC ()
	Get the number of scalar constraints, if any, in this item.

virtual int	GetDOC_c ()
	Get the number of scalar constraints, if any, in this item (only bilateral constr.) Children classes might override this.

virtual int	GetDOC_d ()
	Get the number of scalar constraints, if any, in this item (only unilateral constr.) Children classes might override this.

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	IntStateGather (const unsigned int off_x, ChState &x, const unsigned int off_v, ChStateDelta &v, double &T)
	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)
	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)
	From item's state acceleration to global acceleration vector. More...

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

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	IntLoadResidual_Mv (const unsigned int off, ChVectorDynamic<> &R, const ChVectorDynamic<> &w, const double c)
	Takes the Mv term, multiplying mass by a vector, scale and adds to R at given offset: R += cM*w. 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	IntToDescriptor (const unsigned int off_v, const ChStateDelta &v, const ChVectorDynamic<> &R, const unsigned int off_L, const ChVectorDynamic<> &L, const ChVectorDynamic<> &Qc)
	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)
	After a solver solution, fetch values from variables and constraints into vectors: More...

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

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

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

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

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

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

virtual void	InjectVariables (ChSystemDescriptor &mdescriptor)
	Tell to a system descriptor that there are variables of type ChVariables in this object (for further passing it to a solver) Basically does nothing, but maybe that inherited classes may specialize this.

virtual void	InjectConstraints (ChSystemDescriptor &mdescriptor)
	Tell to a system descriptor that there are constraints of type ChConstraint in this object (for further passing it to a solver) Basically does nothing, but maybe that inherited classes may specialize this.

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	ConstraintsLoadJacobians ()
	Adds the current jacobians in encapsulated ChConstraints.

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

virtual void	InjectKRMmatrices (ChSystemDescriptor &mdescriptor)
	Tell to a system descriptor that there are items of type ChKblock in this object (for further passing it to a solver) Basically does nothing, but maybe that inherited classes may specialize this.

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...

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

int	GetIdentifier () const
	Gets the numerical identifier of the object.

void	SetIdentifier (int id)
	Sets the numerical identifier of the object.

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

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

const char *	GetName () const
	Gets the name of the object as C Ascii null-terminated string -for reading only!

void	SetName (const char myname[])
	Sets the name of this object, as ascii string.

std::string	GetNameString () const
	Gets the name of the object as C Ascii null-terminated string.

void	SetNameString (const std::string &myname)
	Sets the name of this object, as std::string.

void	MFlagsSetAllOFF (int &mflag)

void	MFlagsSetAllON (int &mflag)

void	MFlagSetON (int &mflag, int mask)

void	MFlagSetOFF (int &mflag, int mask)

int	MFlagGet (int &mflag, int mask)

virtual std::string &	ArchiveContainerName ()

Protected Member Functions
	ChLinkMarkers (const ChLinkMarkers &other)

Protected Attributes
ChMarker *	marker1
	slave coordsys

ChMarker *	marker2
	master coordsys, =0 if liked to ground

int	markID1
	unique identifier for markers 1 & 2,

int	markID2
	when using plugin dynamic hierarchies

Coordsys	relM
	relative marker position 2-1

Coordsys	relM_dt
	relative marker speed

Coordsys	relM_dtdt
	relative marker acceleration

double	relAngle
	relative angle of rotation

ChVector	relAxis
	relative axis of rotation

ChVector	relRotaxis
	relative rotaion vector =angle*axis

ChVector	relWvel
	relative angular speed

ChVector	relWacc
	relative angular acceleration

double	dist
	the distance between the two origins of markers,

double	dist_dt
	the speed between the two origins of markers

ChVector	C_force
	internal force applied by springs/dampers/actuators

ChVector	C_torque
	internal torque applied by springs/dampers/actuators

ChVector	PQw

ChVector	PQw_dt

ChVector	PQw_dtdt

ChQuaternion	q_AD

ChQuaternion	q_BC

ChQuaternion	q_8

ChVector	q_4

Protected Attributes inherited from chrono::ChLink
ChBodyFrame *	Body1
	first connected body

ChBodyFrame *	Body2
	second connected body

ChVector	react_force
	store the xyz reactions, expressed in local coordinate system of link;

ChVector	react_torque
	store the torque reactions, expressed in local coordinate system of link;

Protected Attributes inherited from chrono::ChLinkBase
bool	disabled
	all constraints of link disabled because of user needs

bool	valid
	link data is valid

bool	broken
	link is broken because of excessive pulling/pushing.

Protected Attributes inherited from chrono::ChPhysicsItem
ChSystem *	system
	parent system

std::vector< std::shared_ptr< ChAsset > >	assets
	set of assets

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
	the time of simulation for the object

Member Function Documentation

◆ ArchiveIN()

void chrono::ChLinkMarkers::ArchiveIN ( ChArchiveIn & marchive )

overridevirtual

Method to allow deserialization of transient data from archives.

Method to allow de serialization of transient data from archives.

Reimplemented from chrono::ChLink.

Reimplemented in chrono::ChLinkLockLock, chrono::ChLinkLock, chrono::ChLinkPulley, chrono::ChLinkGear, chrono::ChLinkSpringCB, chrono::ChLinkSpring, chrono::ChLinkLinActuator, chrono::ChLinkClearance, chrono::ChLinkTrajectory, chrono::ChLinkRotSpringCB, chrono::ChLinkBrake, chrono::ChLinkBushing, chrono::ChLinkPointSpline, and chrono::ChLinkScrew.

◆ ConstraintsFbLoadForces()

void chrono::ChLinkMarkers::ConstraintsFbLoadForces ( double factor = 1 )

overridevirtual

Overrides the empty behaviour of the parent ChLink implementation, which does not consider any user-imposed force between the two bodies.

It adds the current link-forces, if any, (caused by springs, etc.) to the 'fb' vectors of the ChVariables referenced by encapsulated ChConstraints. In details, it adds the effect caused by C_force and C_torque. Both C_force and C_torque these forces are considered expressed in the reference coordsystem of marker2 (the MAIN marker), and their application point is the origin of marker1 (the SLAVE marker).

Reimplemented from chrono::ChPhysicsItem.

◆ GetC_force()

const ChVector& chrono::ChLinkMarkers::GetC_force ( ) const

inline

Get the total applied force accumulators (force, momentum) in link coords.

These forces might be affected by additional springs, dampers, etc. but they do not include the reaction forces.

◆ GetLinkRelativeCoords()

virtual ChCoordsys chrono::ChLinkMarkers::GetLinkRelativeCoords ( )

inlineoverridevirtual

Get the link coordinate system, expressed relative to Body2 (the 'master' body).

This represents the 'main' reference of the link: reaction forces and torques are expressed in this coordinate system. (It is the coordinate system of the 'master' marker2 relative to Body2)

Reimplemented from chrono::ChLink.

◆ Initialize() [1/3]

void chrono::ChLinkMarkers::Initialize	(	std::shared_ptr< ChBody >	mbody1,
		std::shared_ptr< ChBody >	mbody2,
		bool	pos_are_relative,
		const ChCoordsys<> &	mpos1,
		const ChCoordsys<> &	mpos2
	)

virtual

Use this function after link creation, to initialize the link from two joined rigid bodies.

Both rigid bodies must belong to the same ChSystem. Two markers will be created and added to the rigid bodies (later, you can use GetMarker1() and GetMarker2() to access them. To specify the (absolute) position of link and markers, use 'mpos'.

Parameters

mbody1	first body to join
mbody2	second body to join
pos_are_relative	if =true, following two positions are relative to bodies. If false, are absolute.
mpos1	the position & alignment of 1st marker (relative to body1 cords, or absolute)
mpos2	the position & alignment of 2nd marker (relative to body2 cords, or absolute)

◆ Initialize() [2/3]

void chrono::ChLinkMarkers::Initialize	(	std::shared_ptr< ChBody >	mbody1,
		std::shared_ptr< ChBody >	mbody2,
		const ChCoordsys<> &	mpos
	)

virtual

Use this function after link creation, to initialize the link from two joined rigid bodies.

Both rigid bodies must belong to the same ChSystem. Two markers will be created and added to the rigid bodies (later, you can use GetMarker1() and GetMarker2() to access them. To specify the (absolute) position of link and markers, use 'mpos'.

Parameters

mbody1	first body to join
mbody2	second body to join
mpos	the current absolute pos.& alignment.

◆ Initialize() [3/3]

void chrono::ChLinkMarkers::Initialize	(	std::shared_ptr< ChMarker >	mark1,
		std::shared_ptr< ChMarker >	mark2
	)

virtual

Use this function after link creation, to initialize the link from two markers to join.

Each marker must belong to a rigid body, and both rigid bodies must belong to the same ChSystem. The position of mark2 is used as link's position and main reference.

Parameters

mark1	first marker to join
mark2	second marker to join (master)

◆ UpdateForces()

void chrono::ChLinkMarkers::UpdateForces ( double mytime )

virtual

Updates auxiliary forces caused by springs/dampers/etc.

which may be connected between the two bodies of the link. By default, it adds the forces which might have been added by the user using Set_Scr_force() and Set_Scr_torque(). Note, these forces are considered in the reference coordsystem of marker2 (the MAIN marker), and their application point is the origin of marker1 (the SLAVE marker).

Reimplemented in chrono::ChLinkSpringCB, chrono::ChLinkRotSpringCB, chrono::ChLinkLock, chrono::ChLinkSpring, chrono::ChLinkClearance, and chrono::ChLinkBrake.

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

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

Description

Public Member Functions

Protected Member Functions

Protected Attributes

Member Function Documentation

◆ ArchiveIN()

◆ ConstraintsFbLoadForces()

◆ GetC_force()

◆ GetLinkRelativeCoords()

◆ Initialize() [1/3]

◆ Initialize() [2/3]

◆ Initialize() [3/3]

◆ UpdateForces()