chrono::ChShaftsPlanetary Class Reference

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:
Collaboration diagram for chrono::ChShaftsPlanetary:

Public Member Functions

 ChShaftsPlanetary (const ChShaftsPlanetary &other)
 
virtual ChShaftsPlanetaryClone () 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).
 
ChShaftGetShaft1 () const
 Get the first shaft (carrier wheel).
 
ChShaftGetShaft2 () const
 Get the second shaft.
 
ChShaftGetShaft3 () 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 r1*w1 + r2*w2 + r3*w3 = 0. More...
 
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 (i.e., the inverted planetary). 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 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)
 
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 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 M*v term, multiplying mass by a vector, scale and adds to R at given offset: R += c*M*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.
 
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
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
 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_1first shaft to join (carrier wheel)
shaft_2second shaft to join (wheel)
shaft_3third 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