Description

Class for defining a planetary gear between three one-degree-of-freedom parts.

Planetary gears can be used to make, for instance, the differentials of cars. While traditional gear reducers have one input and one output, the planetary gear have two inputs and one output (or, if you prefer, one input and two outputs). Note that you can use this class also to make a gearbox if you are interested in knowing the reaction torque transmitted to the truss (whereas the basic ChLinkLockGear cannot do this because it has only in and out); in this case you just use the shaft n.1 as truss and fix it.

#include <ChShaftsPlanetary.h>

Inheritance diagram for chrono::ChShaftsPlanetary:

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Collaboration diagram for chrono::ChShaftsPlanetary:

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Public Member Functions
	ChShaftsPlanetary (const ChShaftsPlanetary &other)

virtual ChShaftsPlanetary *	Clone () const override
	"Virtual" copy constructor (covariant return type).

bool	Initialize (std::shared_ptr< ChShaft > shaft_1, std::shared_ptr< ChShaft > shaft_2, std::shared_ptr< ChShaft > shaft_3)
	Initialize this planetary gear, given three shafts to join. More...

void	SetDisabled (bool val)
	Disable this element (disable constraints).

ChShaft *	GetShaft1 () const
	Get the first shaft (carrier wheel).

ChShaft *	GetShaft2 () const
	Get the second shaft.

ChShaft *	GetShaft3 () const
	Get the third shaft.

double	GetSpeedShaft1 () const
	Return the speed of the first shaft (carrier wheel).

double	GetSpeedShaft2 () const
	Return the speed of the second shaft.

double	GetSpeedShaft3 () const
	Return the speed of the third shaft.

void	SetTransmissionRatios (double r_1, double r_2, double r_3)
	Set the transmission ratios r1 r2 r3 as in r1w1 + r2w2 + r3*w3 = 0. More...

void	SetTransmissionRatioOrdinary (double t0)
	Setting the transmission ratios r1 r2 r3 for r1w1 + r2w2 + r3*w3 = 0 may be cumbersome, but when you deal with typical planetary devices, this function provides a shortcut to setting them for you, given a single parameter t0, that is the speed ratio t'=w3'/w2' of the inverted planetary. More...

double	GetTransmissionRatioOrdinary () const
	Get the t0 transmission ratio of the equivalent ordinary gearbox (i.e., the inverted planetary). More...

double	GetTransmissionR1 () const
	Get the transmission ratio r1, as in r1w1+r2w2+r3*w3 = 0.

double	GetTransmissionR2 () const
	Get the transmission ratio r1, as in r1w1+r2w2+r3*w3 = 0.

double	GetTransmissionR3 () const
	Get the transmission ratio r1, as in r1w1+r2w2+r3*w3 = 0.

void	AvoidPhaseDrift (bool avoid)
	Enable phase drift avoidance (default: true). More...

double	GetReaction1 () const
	Get the reaction torque considered as applied to the 1st axis.

double	GetReaction2 () const
	Get the reaction torque considered as applied to the 2nd axis.

double	GetTorqueReactionOn3 () const
	Get the reaction torque considered as applied to the 3rd axis.

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.

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	GetNumCoordsPosLevel ()
	Get the number of coordinates at the position level. 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	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	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	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_F (const unsigned int off, ChVectorDynamic<> &R, const double c)
	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<> &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	IntLoadLumpedMass_Md (const unsigned int off, ChVectorDynamic<> &Md, double &err, const double c)
	Adds the lumped mass to a Md vector, representing a mass diagonal matrix. 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	InjectVariables (ChSystemDescriptor &descriptor)
	Register with the given system descriptor any ChVariable objects associated with this item.

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

virtual void	LoadKRMMatrices (double Kfactor, double Rfactor, double Mfactor)
	Compute and load current stiffnes (K), damping (R), and mass (M) matrices in encapsulated ChKRMBlock objects. 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	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	ConstraintsFbLoadForces (double factor=1)
	Adds the current link-forces, if any, (caused by springs, etc.) to the 'fb' vectors of the ChVariables referenced by encapsulated ChConstraints.

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 ()

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

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

◆ AvoidPhaseDrift()

void chrono::ChShaftsPlanetary::AvoidPhaseDrift ( bool avoid )

inline

Enable phase drift avoidance (default: true).

If true, phasing is always tracked and the constraint is satisfied also at the position level. If false, microslipping can accumulate (as in friction wheels).

◆ GetTransmissionRatioOrdinary()

double chrono::ChShaftsPlanetary::GetTransmissionRatioOrdinary ( ) const

inline

Get the t0 transmission ratio of the equivalent ordinary gearbox (i.e., the inverted planetary).

This is the ratio t0=w3'/w2' assuming that the carrier (shaft 1) is held fixed.

◆ Initialize()

bool chrono::ChShaftsPlanetary::Initialize	(	std::shared_ptr< ChShaft >	shaft_1,
		std::shared_ptr< ChShaft >	shaft_2,
		std::shared_ptr< ChShaft >	shaft_3
	)

Initialize this planetary gear, given three shafts to join.

Although there's no special requirement, you may think of the three typical moving parts of an epicycloidal reducer: the carrier, the input gear, and the gear with inner teeth that usually is kept fixed (but the ChShaftsPlanetary does not require that one shaft is fixed - it's up to you) Both shafts must belong to the same ChSystem.

Parameters

shaft_1	first shaft to join (carrier wheel)
shaft_2	second shaft to join (wheel)
shaft_3	third shaft to join (wheel)

◆ SetTransmissionRatioOrdinary()

void chrono::ChShaftsPlanetary::SetTransmissionRatioOrdinary ( double t0 )

inline

Setting the transmission ratios r1 r2 r3 for r1*w1 + r2*w2 + r3*w3 = 0 may be cumbersome, but when you deal with typical planetary devices, this function provides a shortcut to setting them for you, given a single parameter t0, that is the speed ratio t'=w3'/w2' of the inverted planetary.

That ratio is simple to get: to invert the planetary, imagine to hold fixed the carrier of shaft 1 (that is w1' =0), move the shaft 2 and see which is the speed of shaft 3, to get the ratio t0=w3'/w2'. Generally, shaft 1 is called the 'carrier'. For example, in normal operation of an epicycloidal reducer, the carrier (shaft 1) is used as output, shaft 2 is the input, and shaft 3 is hold fixed to get one degree of freedom only; but in 'inverted' operation imagine the carrier is fixed, so t0 can be easily got as t0=-z2/z3, with z=n.of teeth. In a car differential, again with shaft 1 as carrier, one can see that t0=w3'/w2' so t0=-1. See the Willis theory for more details on these formulas. Note that t0 should be different from 1 (singularity). Once you get t0, simply use this function and it will set r1 r2 r3 automatically.

◆ SetTransmissionRatios()

void chrono::ChShaftsPlanetary::SetTransmissionRatios	(	double	r_1,
		double	r_2,
		double	r_3
	)

inline

Set the transmission ratios r1 r2 r3 as in r1*w1 + r2*w2 + r3*w3 = 0.

For example, for the car differential, if you assume that shaft 1 is the carrier and shafts 2 and 3 go to the wheel hubs, you must use r1=-2, r2=1, r3=1 to satisfy the kinematics -2*w1+w2+w3=0 of the differential; equivalently, you may use r1=1, r2=-0.5, r3=-0.5 (the equation would hold the same).

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

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

Description

Public Member Functions

Additional Inherited Members

Member Function Documentation

◆ AvoidPhaseDrift()

◆ GetTransmissionRatioOrdinary()

◆ Initialize()

◆ SetTransmissionRatioOrdinary()

◆ SetTransmissionRatios()