Description

Class for defining a planetary gear between three one-degree-of-freedom parts; i.e., shafts that can be used to build 1D models of powertrains; this is more efficient than simulating power trains modeled full 3D ChBody objects).

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 ChLinkGear 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).

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

virtual int	GetDOC_c () override
	Number of scalar constraints.

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

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

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 += cCq'*L. More...

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. 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	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.

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	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...

bool	Initialize (std::shared_ptr< ChShaft > mshaft1, std::shared_ptr< ChShaft > mshaft2, std::shared_ptr< ChShaft > mshaft3)
	Use this function after planetary gear creation, to initialize it, given three shafts to join. More...

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

ChShaft *	GetShaft2 ()
	Get the second shaft.

ChShaft *	GetShaft3 ()
	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 mr1, double mr2, double mr3)
	Set the transmission ratios r1 r2 r3 as in r1w1 + r2w2 + r3w3 = 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 -2w1+w2+w3=0 of the differential; equivalently, you may use r1=1, r2=-0.5, r3=-0.5 (the equation would hold the same).

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, ie. 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	SetAvoidPhaseDrift (bool mb)
	Set if the constraint must avoid phase drift. More...

bool	GetAvoidPhaseDrift ()
	Set if the constraint is in "avoid phase drift" mode.

double	GetTorqueReactionOn1 () const
	Get the reaction torque considered as applied to the 1st axis.

double	GetTorqueReactionOn2 () 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	Update (double mytime, bool update_assets=true) override
	Update all auxiliary data of the gear transmission at given time.

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)

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 ChFrame	GetAssetsFrame (unsigned int nclone=0)
	Get the master coordinate system for assets that have some geometric meaning. More...

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

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_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	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_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	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	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	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.

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 ()

Additional Inherited Members
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::ChShaftsPlanetary::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::ChPhysicsItem.

◆ ConstraintsFetch_react()

void chrono::ChShaftsPlanetary::ConstraintsFetch_react ( double factor = 1 )

overridevirtual

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.

◆ GetTransmissionRatioOrdinary()

double chrono::ChShaftsPlanetary::GetTransmissionRatioOrdinary ( ) const

inline

Get the t0 transmission ratio of the equivalent ordinary gearbox, ie.

the inverted planetary, that is the ratio t0=w3'/w2' assuming that the carrier (shaft 1) is hold fixed.

◆ Initialize()

bool chrono::ChShaftsPlanetary::Initialize	(	std::shared_ptr< ChShaft >	mshaft1,
		std::shared_ptr< ChShaft >	mshaft2,
		std::shared_ptr< ChShaft >	mshaft3
	)

Use this function after planetary gear creation, to initialize it, 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) Each shaft must belong to the same ChSystem.

Parameters

mshaft1	first shaft to join (carrier wheel)
mshaft2	second shaft to join (wheel)
mshaft3	third shaft to join (wheel)

◆ IntFromDescriptor()

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

overridevirtual

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.

◆ IntLoadConstraint_C()

void chrono::ChShaftsPlanetary::IntLoadConstraint_C	(	const unsigned int	off,
		ChVectorDynamic<> &	Qc,
		const double	c,
		bool	do_clamp,
		double	recovery_clamp
	)

overridevirtual

Takes the term C, scale and adds to Qc at given offset: Qc += c*C.

Parameters

off	offset in Qc residual
Qc	result: the Qc residual, Qc += c*C
c	a scaling factor
do_clamp	apply clamping to c*C?
recovery_clamp	value for min/max clamping of c*C

Reimplemented from chrono::ChPhysicsItem.

◆ IntLoadResidual_CqL()

void chrono::ChShaftsPlanetary::IntLoadResidual_CqL	(	const unsigned int	off_L,
		ChVectorDynamic<> &	R,
		const ChVectorDynamic<> &	L,
		const double	c
	)

overridevirtual

Takes the term Cq'*L, scale and adds to R at given offset: R += c*Cq'*L.

Parameters

off_L	offset in L multipliers
R	result: the R residual, R += cCq'L
L	the L vector
c	a scaling factor

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateGatherReactions()

void chrono::ChShaftsPlanetary::IntStateGatherReactions	(	const unsigned int	off_L,
		ChVectorDynamic<> &	L
	)

overridevirtual

From item's reaction forces to global reaction vector.

Parameters

off_L	offset in L vector
L	L vector of reaction forces

Reimplemented from chrono::ChPhysicsItem.

◆ IntStateScatterReactions()

void chrono::ChShaftsPlanetary::IntStateScatterReactions	(	const unsigned int	off_L,
		const ChVectorDynamic<> &	L
	)

overridevirtual

From global reaction vector to item's reaction forces.

Parameters

off_L	offset in L vector
L	L vector of reaction forces

Reimplemented from chrono::ChPhysicsItem.

◆ IntToDescriptor()

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

overridevirtual

Prepare variables and constraints to accommodate a solution:

Parameters

off_v	offset for v and R
v	vector that will be copied into the q 'unknowns' term of the variables (for warm starting)
R	vector that will be copied into the F 'force' term of the variables
off_L	offset for L and Qc
L	vector that will be copied into the L 'lagrangian ' term of the constraints (for warm starting)
Qc	vector that will be copied into the Qb 'constraint' term of the constraints

Reimplemented from chrono::ChPhysicsItem.

◆ SetAvoidPhaseDrift()

void chrono::ChShaftsPlanetary::SetAvoidPhaseDrift ( bool mb )

inline

Set if the constraint must avoid phase drift.

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). Default is enabled.

◆ 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.

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

◆ ArchiveIN()

◆ ConstraintsFetch_react()

◆ GetTransmissionRatioOrdinary()

◆ Initialize()

◆ IntFromDescriptor()

◆ IntLoadConstraint_C()

◆ IntLoadResidual_CqL()

◆ IntStateGatherReactions()

◆ IntStateScatterReactions()

◆ IntToDescriptor()

◆ SetAvoidPhaseDrift()

◆ SetTransmissionRatioOrdinary()