Description
Class for defining a planetary gear between three onedegreeoffreedom 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>
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 costraints.  
virtual void  IntStateGatherReactions (const unsigned int off_L, ChVectorDynamic<> &L) override 
From item's reaction forces to global reaction vector.  
virtual void  IntStateScatterReactions (const unsigned int off_L, const ChVectorDynamic<> &L) override 
From global reaction vector to item's reaction forces.  
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.  
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.  
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 for a solution: From a vector R into the F 'force' term of the variables From a vector Qc into the Qb 'constraint' term of the constraints From a vector v into the q 'unknowns' term of the variables (for warm starting) From a vector L into the L 'lagrangian ' term of the constraints (for warm starting)  
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: To a vector v from the q 'unknowns' term of the variables To a vector L from the L 'lagrangian ' term of the constraints.  
virtual void  InjectConstraints (ChSystemDescriptor &mdescriptor) override 
Tell to a system descriptor that there are contraints of type ChConstraint in this object (for further passing it to a solver) Basically does nothing, but maybe that inherited classes may specialize this. More...  
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 tderivative, 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 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). 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, 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.  
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, sinchronize their coordinates and bounding boxes to the state of the item. More...  
virtual void  AddCollisionModelsToSystem () 
If this physical item contains one or more collision models, add them to the system's collision engine. More...  
virtual void  RemoveCollisionModelsFromSystem () 
If this physical item contains one or more collision models, remove them from the system's collision engine. More...  
virtual void  GetTotalAABB (ChVector<> &bbmin, ChVector<> &bbmax) 
Get the entire AABB axisaligned 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. More...  
virtual void  StreamOUTstate (ChStreamOutBinary &mstream) 
Method to serialize only the state (position, speed) Must be implemented by child classes. 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 timedependent 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. 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) 
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 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.  
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. 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 linkforces, 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. More...  
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 nullterminated 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 nullterminated 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) 
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

overridevirtual 
Method to allow deserialization of transient data from archives.
Method to allow de serialization of transient data from archives.
Reimplemented from chrono::ChPhysicsItem.

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.
double chrono::ChShaftsPlanetary::GetTransmissionRatioOrdinary  (  )  const 
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.
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 apycycloidal 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)

overridevirtual 
Tell to a system descriptor that there are contraints of type ChConstraint in this object (for further passing it to a solver) Basically does nothing, but maybe that inherited classes may specialize this.
Reimplemented from chrono::ChPhysicsItem.
void chrono::ChShaftsPlanetary::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.
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.
void chrono::ChShaftsPlanetary::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).