## Description

Base class for joints implemented using the "lock formulation".

Derived classes provide models for revolute, prismatic, spherical, etc. Note that certain kinematic joints (e.g., Universal) cannot be modeled using the lock formulation. Joints of this type can optionally specify 'limits' over upper-lower motions of their respective degrees of freedom, using the ChLinkLimit objects.

#include <ChLinkLock.h>

Inheritance diagram for chrono::ChLinkLock:
Collaboration diagram for chrono::ChLinkLock:

## Public Member Functions

Default constructor. Builds a ChLinkLockSpherical.

Copy constructor.

virtual ChLinkLockClone () const override
"Virtual" copy constructor (covariant return type).

Must be called after whatever change the mask of the link, in order to update auxiliary matrices sizes. More...

Must be called after whatever change the mask of the link, in order to update auxiliary matrices sizes. More...

int RestoreRedundant () override
If some constraint is redundant, return to normal state.

virtual void SetDisabled (bool mdis) override
Enable/disable all constraints of the link.

virtual void SetBroken (bool mon) override
For example, a 3rd party software can set the 'broken' status via this method.

Get the pointer to the link mask, ie. More...

virtual void SetUpMarkers (ChMarker *mark1, ChMarker *mark2) override
overwrites inherited implementation of this method

virtual int GetDOC () override
Get the number of scalar constraints for this link.

virtual int GetDOC_c () override
Get the number of bilateral constraints for this link.

virtual int GetDOC_d () override
Get the number of unilateral constraints for this link.

ChMatrixGetC ()
Link violation (residuals of the link constraint equations).

ChMatrixGetC_dt ()
Time derivatives of link violations.

ChMatrixGetC_dtdt ()
Double time derivatives of link violations.

ChMatrixGetCq1 ()
The jacobian (body n.1 part, i.e. columns= 7 , rows= ndoc)

ChMatrixGetCq2 ()
The jacobian (body n.2 part, i.e. columns= 7 , rows= ndoc)

ChMatrixGetCqw1 ()
The jacobian for Wl (col 6, rows= ndoc), as [Cqw1_rot]=[Cq_rot]*[Gl_1]'.

ChMatrixGetCqw2 ()
The jacobian for Wl (col 6, rows= ndoc) as [Cqw2_rot]=[Cq_rot]*[Gl_2]'.

ChMatrixGetQc ()
The gamma vector used in dynamics, [Cq]x''=Qc.

ChMatrixGetCt ()
The Ct vector used in kinematics, [Cq]x'=Ct.

ChMatrixGetReact ()
Access the reaction vector, after dynamics computations.

virtual void UpdateState ()
Given current time and body state, computes the constraint differentiation to get the the state matrices Cq1, Cq2, Qc, Ct , and also C, C_dt, C_dtd. More...

virtual void UpdateForces (double mytime) override
Updates the local F, M forces adding penalties from ChLinkLimit objects, if any.

void UpdateCqw ()
Updates Cqw1 and Cqw2 given updated Cq1 and Cq2, i.e. More...

virtual void Update (double mytime, bool update_assets=true) override
Full update. More...

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.

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for internal forces on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

Accessors for limits on free degrees of freedom. More...

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

ChSystemGetSystem () 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< ChAssetGetAssetN (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. More...

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

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

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. More...

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

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

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 Types

LOCK, SPHERICAL, POINTPLANE, POINTLINE,
CYLINDRICAL, PRISMATIC, PLANEPLANE, OLDHAM,
REVOLUTE, FREE, ALIGN, PARALLEL,
PERPEND, TRAJECTORY, CLEARANCE, REVOLUTEPRISMATIC
}

## Protected Member Functions

Allocates matrices and initializes all mask-dependent quantities. More...

Allocates matrices and initializes all mask-dependent quantities. More...

Frees matrices allocated by BuildLink.

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

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

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

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

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

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:

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:

virtual void InjectConstraints (ChSystemDescriptor &mdescriptor) override
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. More...

virtual void ConstraintsBiReset () override
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) override
Adds the current C (constraint violation) to the known term (b_i) of encapsulated ChConstraints.

virtual void ConstraintsBiLoad_Ct (double factor=1) override
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) override
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 () override
Adds the current jacobians in encapsulated ChConstraints.

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

## Protected Attributes

type of link_lock joint

scalar constraints

int ndoc
number of degrees of constraint

int ndoc_c
number of degrees of constraint (bilateral constraintss)

int ndoc_d
number of degrees of constraint (unilateral constraints, excluding joint limits)

the force acting on the straight line m1-m2 (distance)

the torque acting about rotation axis

the force acting along X dof

the force acting along Y dof

the force acting along Z dof

the torque acting about Rx dof

the torque acting about Ry dof

the torque acting about Rz dof

double d_restlength
the rest length of the "d_spring" spring

the upper/lower limits for X dof

the upper/lower limits for Y dof

the upper/lower limits for Z dof

the upper/lower limits for Rx dof

the upper/lower limits for Ry dof

the upper/lower limits for Rz dof

the polar (conical) limit for "shoulder"rotation

the polar (conical) limit for "shoulder"rotation

ChMatrixC
C(q,q_dt,t), the constraint violations.

ChMatrixC_dt
Speed constraint violations.

ChMatrixC_dtdt
Acceleration constraint violations.

ChMatrixCq1
[Cq1], the jacobian of the constraint, for coords1, [ndoc,7]

ChMatrixCq2
[Cq2], the jacobian of the constraint, for coords2. [ndoc,7]

ChMatrixCqw1
[Cqw1], the jacobian [ndoc,6] for 3 Wl rot.coordinates instead of quaternions

ChMatrixCqw2
[Cqw2], the jacobian [ndoc,6] for 3 Wl rot.coordinates instead of quaternions

ChMatrixQc
{Qc}, the known part, {Qc}=-{C_dtdt}-([Cq]{q_dt})q-2[Cq_dt]{q_dt}

ChMatrixCt
partial derivative of the link kin. equation wrt to time

ChMatrixreact
{l}, the lagrangians forces in the constraints

ChMatrixCq1_temp

ChMatrixCq2_temp

ChMatrixQc_temp

Coordsys Ct_temp

Protected Attributes inherited from chrono::ChPhysicsItem
ChSystemsystem
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

class ChConveyor

## Member Function Documentation

protected

Allocates matrices and initializes all mask-dependent quantities.

Sets number of DOF and number DOC. Copies the mask from new_mask.

protected

Allocates matrices and initializes all mask-dependent quantities.

Sets number of DOF and number DOC. Uses the current mask.

Must be called after whatever change the mask of the link, in order to update auxiliary matrices sizes.

Must be called after whatever change the mask of the link, in order to update auxiliary matrices sizes.

 void chrono::ChLinkLock::ConstraintsFetch_react ( double factor = 1 )
overrideprotectedvirtual

Fetches the reactions from the lagrangian multiplier (l_i) of encapsulated ChConstraints.

Mostly used after the solver provided the solution in ChConstraints. Also, should convert the reactions obtained from dynamical simulation, from link space to intuitive react_force and react_torque.

Reimplemented from chrono::ChPhysicsItem.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for internal forces on free degrees of freedom.

These functions provide access to initialize and set parameters for link forces acting on different degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link force object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Accessors for limits on free degrees of freedom.

These functions provide access to initialize and set parameters for link limits on different free degrees of freedom of the joint. Note that they use "lazy initialization"; an internal link limit object is created on the first invocation of the corresponding accessor function.

Get the pointer to the link mask, ie.

a ChLinkMask (sort of array containing a set of ChConstraint items).

 void chrono::ChLinkLock::InjectConstraints ( ChSystemDescriptor & mdescriptor )
overrideprotectedvirtual

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.

Reimplemented from chrono::ChPhysicsItem.

 void chrono::ChLinkLock::Update ( double mytime, bool update_assets = true )
overridevirtual

Full update.

Fills-in all the matrices of the link, and does all required calculations by calling specific Update functions in sequence:

    UpdateTime;
UpdateRelMarkerCoords;
UpdateCqw
UpdateForces;


 void chrono::ChLinkLock::UpdateCqw ( )

Updates Cqw1 and Cqw2 given updated Cq1 and Cq2, i.e.

computes the jacobians with 'Wl' rotational coordinates knowing the jacobians for body rotations in quaternion coordinates.

virtual

Given current time and body state, computes the constraint differentiation to get the the state matrices Cq1, Cq2, Qc, Ct , and also C, C_dt, C_dtd.