Description

Class for defining a torsional spring-damper between two 1D parts; i.e., shafts that can be used to build 1D models of powertrains.

This is more efficient than simulating power trains modeled with full 3D ChBody objects. This supersedes the old ChShaftsTorsionSpring (which cannot handle extremely stiff spring values)

#include <ChShaftsLoads.h>

Inheritance diagram for chrono::ChShaftsElasticGear:
Collaboration diagram for chrono::ChShaftsElasticGear:

Public Member Functions

 ChShaftsElasticGear (std::shared_ptr< ChShaft > mbodyA, std::shared_ptr< ChShaft > mbodyB, const double mstiffness, const double mdamping, const double mRa, const double mratio=-1)
 
virtual ChShaftsElasticGearClone () const override
 "Virtual" copy constructor (covariant return type).
 
void SetTeethStiffness (const double mstiffness)
 Set teeth stiffness, at contact point, in tangent direction to the two primitives. Es. [N/m].
 
double GetTeethStiffness () const
 
void SetTeethDamping (const double mdamping)
 Set teeth damping, at contact point, in tangent direction to the two primitives. Es. [Ns/m].
 
double GetTeethDamping () const
 
void SetRestPhase (const double mphase)
 Set the phase shaftA-tau*shaftB for zero compression of the spring (default = 0 [rad])
 
double GetRestPhase () const
 
void SetTransmissionRatioAndRadiusA (double mt, double mRa)
 Set the transmission ratio t, as in w2=t*w1, or t=w2/w1 , or t*w1 - w2 = 0. More...
 
void SetTransmissionRatioFromRadii (double mRa, double mRb, bool minternal=false)
 Set the transmission ratio t, as in w2=t*w1, using the two primitive radii Ra and Rb. More...
 
double GetTransmissionRatio () const
 Get the transmission ratio t, as in w2=t*w1, or t=w2/w1.
 
double GetGearRadiusA () const
 Get the primitive radius of the gear wheel of shaftA.
 
double GetGearRadiusB () const
 Get the primitive radius of the gear wheel of shaftB.
 
double GetContactForce () const
 Get the last computed contact force, for diagnostics. More...
 
- Public Member Functions inherited from chrono::ChLoadCustomMultiple
 ChLoadCustomMultiple (std::vector< std::shared_ptr< ChLoadable >> &mloadables)
 
 ChLoadCustomMultiple (std::shared_ptr< ChLoadable > mloadableA, std::shared_ptr< ChLoadable > mloadableB)
 
 ChLoadCustomMultiple (std::shared_ptr< ChLoadable > mloadableA, std::shared_ptr< ChLoadable > mloadableB, std::shared_ptr< ChLoadable > mloadableC)
 
virtual int LoadGet_ndof_x () override
 Gets the number of DOFs affected by this load (position part)
 
virtual int LoadGet_ndof_w () override
 Gets the number of DOFs affected by this load (speed part)
 
virtual void LoadGetStateBlock_x (ChState &mD) override
 Gets all the current DOFs packed in a single vector (position part)
 
virtual void LoadGetStateBlock_w (ChStateDelta &mD) override
 Gets all the current DOFs packed in a single vector (speed part)
 
virtual void LoadStateIncrement (const ChState &x, const ChStateDelta &dw, ChState &x_new) override
 Increment a packed state (ex. More...
 
virtual int LoadGet_field_ncoords () override
 Number of coordinates in the interpolated field, ex=3 for a tetrahedron finite element or a cable, = 1 for a thermal problem, etc. More...
 
virtual void ComputeJacobian (ChState *state_x, ChStateDelta *state_w, ChMatrix<> &mK, ChMatrix<> &mR, ChMatrix<> &mM) override
 Compute jacobians (default fallback). More...
 
virtual void LoadIntLoadResidual_F (ChVectorDynamic<> &R, const double c) override
 Adds the internal loads Q (pasted at global nodes offsets) into a global vector R, multiplied by a scaling factor c, as R += forces * c.
 
virtual void CreateJacobianMatrices () override
 Create the jacobian loads if needed, and also set the ChVariables referenced by the sparse KRM block. More...
 
virtual ChVectorDynamicGetQ ()
 Access the generalized load vector Q.
 
- Public Member Functions inherited from chrono::ChLoadBase
ChLoadJacobiansGetJacobians ()
 Access the jacobians (if any, i.e. if this is a stiff load)
 
virtual void Update (double time)
 Update: this is called at least at each time step. More...
 
virtual void InjectKRMmatrices (ChSystemDescriptor &mdescriptor)
 Tell to a system descriptor that there are item(s) of type ChKblock in this object (for further passing it to a solver) Basically does nothing, but inherited classes must 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 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 void ArchiveOUT (ChArchiveOut &marchive)
 Method to allow serialization of transient data to archives.
 
virtual void ArchiveIN (ChArchiveIn &marchive)
 Method to allow de-serialization of transient data from archives.
 
virtual std::string & ArchiveContainerName ()
 

Protected Member Functions

virtual bool IsStiff () override
 Report if this is load is stiff. More...
 
virtual void ComputeQ (ChState *state_x, ChStateDelta *state_w) override
 Compute Q, the generalized load. More...
 

Protected Attributes

double stiffness
 
double damping
 
double rest_phase
 
double Ra
 
double ratio
 
double contact_force
 
- Protected Attributes inherited from chrono::ChLoadBase
ChLoadJacobiansjacobians
 
- Protected Attributes inherited from chrono::ChObj
double ChTime
 the time of simulation for the object
 

Additional Inherited Members

- Public Attributes inherited from chrono::ChLoadCustomMultiple
std::vector< std::shared_ptr< ChLoadable > > loadables
 
ChVectorDynamic load_Q
 

Constructor & Destructor Documentation

chrono::ChShaftsElasticGear::ChShaftsElasticGear ( std::shared_ptr< ChShaft mbodyA,
std::shared_ptr< ChShaft mbodyB,
const double  mstiffness,
const double  mdamping,
const double  mRa,
const double  mratio = -1 
)
Parameters
mbodyAshaft A
mbodyBshaft B
mstiffnessnormal stiffness at teeth contact, tangent direction to primitive
mdampingnormal damping at teeth contact, tangent direction to primitive
mRaprimitive radius of the gear on shaft A (the radius of B is not needed)
mratiotransmission ratio (negative for outer gear, positive for inner gears)

Member Function Documentation

void chrono::ChShaftsElasticGear::ComputeQ ( ChState state_x,
ChStateDelta state_w 
)
overrideprotectedvirtual

Compute Q, the generalized load.

Called automatically at each Update().

Parameters
state_xstate position to evaluate Q
state_wstate speed to evaluate Q

Implements chrono::ChLoadBase.

double chrono::ChShaftsElasticGear::GetContactForce ( ) const

Get the last computed contact force, for diagnostics.

The force is assumed tangent to the primitives of the gear wheels, it can be positive or negative depending on clock/counterclock effect.

virtual bool chrono::ChShaftsElasticGear::IsStiff ( )
overrideprotectedvirtual

Report if this is load is stiff.

If so, InjectKRMmatrices will provide the jacobians of the load.

Implements chrono::ChLoadBase.

void chrono::ChShaftsElasticGear::SetTransmissionRatioAndRadiusA ( double  mt,
double  mRa 
)

Set the transmission ratio t, as in w2=t*w1, or t=w2/w1 , or t*w1 - w2 = 0.

For example, t=1 for a rigid joint; t=-0.5 for representing a couple of spur gears with teeth z1=20 & z2=40; t=0.1 for a gear with inner teeth (or epicycloidal reducer), etc. Differently from the ideal ChShaftsGear constraint, this model includes elasticity, so at least the radius of one of the two gear wheels is needed, namely Ra.

void chrono::ChShaftsElasticGear::SetTransmissionRatioFromRadii ( double  mRa,
double  mRb,
bool  minternal = false 
)

Set the transmission ratio t, as in w2=t*w1, using the two primitive radii Ra and Rb.

It will be computed as t=Ra/Rb by default, otherwise t=-Ra/Rb if the bigger wheel has inner teeth.