chrono::ChShaftsPlanetary Class Reference

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:
Collaboration diagram for chrono::ChShaftsPlanetary:

Public Member Functions

ChShaftsPlanetary (const ChShaftsPlanetary &other)

virtual ChShaftsPlanetaryClone () 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 += c*Cq'*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.

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...

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

ChShaftGetShaft1 ()
Get the first shaft (carrier wheel)

ChShaftGetShaft2 ()
Get the second shaft.

ChShaftGetShaft3 ()
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 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).

void SetTransmissionRatioOrdinary (double t0)
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. 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 r1*w1+r2*w2+r3*w3 = 0.

double GetTransmissionR2 () const
Get the transmission ratio r1, as in r1*w1+r2*w2+r3*w3 = 0.

double GetTransmissionR3 () const
Get the transmission ratio r1, as in r1*w1+r2*w2+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)

ChSystemGetSystem () 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< ChVisualModelGetVisualModel () 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< ChVisualShapeGetVisualShape (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< ChVisualShapeFEAGetVisualShapeFEA (unsigned int i) const
Access the specified FEA visualization object in the visualization model (if any). More...

virtual ChFrame GetVisualModelFrame (unsigned int nclone=0)
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 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 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 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 M*v term, multiplying mass by a vector, scale and adds to R at given offset: R += c*M*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.

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.

Adds the current Qc (the vector of C_dtdt=0 -> [Cq]*q_dtdt=Qc ) to the known term (b_i) of encapsulated ChConstraints.

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 ()

Protected Attributes inherited from chrono::ChPhysicsItem
ChSystemsystem
parent system

std::shared_ptr< ChVisualModelInstancevis_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
the time of simulation for the object

◆ 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.

 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.

 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 += c*Cq'*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 copied into the q 'unknowns' term of the variables R vector copied into the F 'force' term of the variables off_L offset for L and Qc L vector copied into the L 'lagrangian ' term of the constraints Qc vector 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