## Description

Gear link between two rigid bodies.

This can also be used to represent spur and bevel gears, and it correctly handles the direction of transmitted force given the teeth pressure angle.

#include <ChLinkGear.h>

## Public Member Functions

"Virtual" copy constructor (covariant return type).

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

double Get_tau () const
Get the transmission ratio. More...

void Set_tau (double mset)
Set the transmission ratio. More...

void Set_tau (double mz1, double mz2)
Set the transmission ratio given the number of teeth (or radius) of 1st gear and the number of teeth (or radius) of 2nd gear.

double Get_alpha () const
Get the pressure angle (usually 20° for typical gears)

void Set_alpha (double mset)
Set the pressure angle (usually 20° for typical gears)

double Get_beta () const
Get the angle of teeth in bevel gears (0° for spur gears)

void Set_beta (double mset)
Set the angle of teeth in bevel gears (0° for spur gears)

double Get_phase () const
Get the initial phase of rotation of gear A respect to gear B.

void Set_phase (double mset)
Set the initial phase of rotation of gear A respect to gear B.

bool Get_epicyclic () const
If true, the bigger wheel has inner (internal) teeth.

void Set_epicyclic (bool mset)
If true, the bigger wheel has inner (internal) teeth.

void Set_checkphase (bool mset)
If true, enforce check on exact phase between gears (otherwise after many simulation steps the phasing may be affected by numerical error accumulation). More...

bool Get_checkphase () const

double Get_a1 () const
Get total rotation of 1st gear, respect to interaxis, in radians.

double Get_a2 () const
Get total rotation of 1st gear, respect to interaxis, in radians.

void Reset_a1a2 ()
Reset the total rotations of a1 and a2.

double Get_r1 () const
Get radius of 1st gear (depends on axis position and t.ratio)

double Get_r2 () const
Get radius of 2nd gear (depends on axis position and t.ratio)

const ChFrame< double > & Get_local_shaft1 () const
Get shaft position and direction, for 1st gear, in body1-relative reference. More...

void Set_local_shaft1 (ChFrame< double > mf)
Set shaft position and direction, for 1st gear, in body1-relative reference. More...

const ChFrame< double > & Get_local_shaft2 () const
Get shaft position and direction, for 2nd gear, in body2-relative reference. More...

void Set_local_shaft2 (ChFrame< double > mf)
Set shaft position and direction, for 2nd gear, in body2-relative reference. More...

ChVector Get_shaft_dir1 () const
Get shaft direction, for 1st gear, in absolute reference.

ChVector Get_shaft_dir2 () const
Get shaft direction, for 2nd gear, in absolute reference.

ChVector Get_shaft_pos1 () const
Get shaft position, for 1st gear, in absolute reference.

ChVector Get_shaft_pos2 () const
Get shaft position, for 2nd gear, in absolute reference.

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::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 ()

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.

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...

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 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.

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

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 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 Attributes

double tau
transmission coeff.

double alpha
inclination of action line

double beta
helix angle

double phase
mounting phase angle

bool checkphase
keep gear always on phase

bool epicyclic
epiciclyc (gear 1 is internal to gear2) if true.

double a1
auxiliary

double a2
auxiliary

double r1
auxiliary

double r2
auxiliary

ChVector contact_pt

ChFrame< double > local_shaft1
shaft1 pos & dir (as Z axis), relative to body1

ChFrame< double > local_shaft2
shaft2 pos & dir (as Z axis), relative to body2

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

## ◆ ArchiveIN()

 void chrono::ChLinkGear::ArchiveIN ( ChArchiveIn & marchive )
overridevirtual

Method to allow deserialization of transient data from archives.

Method to allow de serialization of transient data from archives.

## ◆ Get_local_shaft1()

 const ChFrame& chrono::ChLinkGear::Get_local_shaft1 ( ) const
inline

Get shaft position and direction, for 1st gear, in body1-relative reference.

The shaft direction is the Z axis of that frame.

## ◆ Get_local_shaft2()

 const ChFrame& chrono::ChLinkGear::Get_local_shaft2 ( ) const
inline

Get shaft position and direction, for 2nd gear, in body2-relative reference.

The shaft direction is the Z axis of that frame.

## ◆ Get_tau()

inline

Get the transmission ratio.

Its value is assumed always positive, both for inner and outer gears (so use Get_epicyclic() to distinguish)

## ◆ Set_checkphase()

 void chrono::ChLinkGear::Set_checkphase ( bool mset )
inline

If true, enforce check on exact phase between gears (otherwise after many simulation steps the phasing may be affected by numerical error accumulation).

By default, it is turned off. Note that, to ensure the correct phasing during the many rotations, an algorithm will use the a1 and a2 total rotation values, which might be affected by loss of numerical precision after few thousands of revolutions, so this is NOT suited to real-time simulators which must run for many hours.

## ◆ Set_local_shaft1()

 void chrono::ChLinkGear::Set_local_shaft1 ( ChFrame< double > mf )
inline

Set shaft position and direction, for 1st gear, in body1-relative reference.

The shaft direction is the Z axis of that frame. Note that the origin of shaft position may be automatically shifted along shaft direction in order to have both wheels on same plane (for spur gears) - same sphere (for bevel gears).

## ◆ Set_local_shaft2()

 void chrono::ChLinkGear::Set_local_shaft2 ( ChFrame< double > mf )
inline

Set shaft position and direction, for 2nd gear, in body2-relative reference.

The shaft direction is the Z axis of that frame.

## ◆ Set_tau()

 void chrono::ChLinkGear::Set_tau ( double mset )
inline

Set the transmission ratio.

Its value is assumed always positive, both for inner and outer gears (so use Set_epicyclic() to distinguish)

## ◆ UpdateTime()

 void chrono::ChLinkGear::UpdateTime ( double mytime )
overridevirtual

Given new time, current body state, update time-dependent quantities in link state, for example motion laws, moving markers, etc.

Default: do nothing except setting new time.