chrono::ChShaftsMotorPosition Class Reference

Description

Motor to enforce the relative position r(t) between two shafts, using a rheonomic constraint.

The position of shaft A with respect to shaft B is set trhough a function of time f(t) and an optional offset: r(t) = f(t) + offset The relative position represents an angle for rotational motor and a displacement for linear motors. Note: no compliance is allowed, so if the actuator hits an undeformable obstacle it hits a pathological situation and the solver result can be unstable/unpredictable. Think at it as a servo drive with "infinitely stiff" control. This type of motor is very easy to use, stable and efficient and should be used if the 'infinitely stiff' control assumption is a good approximation of what you simulate (e.g., very good and reactive controllers). By default it is initialized with linear ramp: df/dt = 1. Use SetPositionFunction() to change to other motion functions.

#include <ChShaftsMotorPosition.h>

Inheritance diagram for chrono::ChShaftsMotorPosition:
Collaboration diagram for chrono::ChShaftsMotorPosition:

Public Member Functions

ChShaftsMotorPosition (const ChShaftsMotorPosition &other)

virtual ChShaftsMotorPositionClone () const override
"Virtual" copy constructor (covariant return type).

void SetPositionFunction (const std::shared_ptr< ChFunction > function)
Set the motor function, f(t). More...

std::shared_ptr< ChFunctionGetPositionFunction () const
Gets the motor function f(t).

void SetOffset (double offset)
Set the initial offset for f(t)=0 (default: 0). More...

double GetOffset () const
Get the initial offset for f(t) = 0.

bool Initialize (std::shared_ptr< ChShaft > shaft_1, std::shared_ptr< ChShaft > shaft_2) override
Initialize the motor, given two shafts to join. More...

virtual double GetMotorLoad () const override
Get the current motor load between shaft2 and shaft1, expressed as applied to shaft1.

double GetConstraintViolation () const
Return current constraint violation.

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. More...

Public Member Functions inherited from chrono::ChShaftsMotor
ChShaftsMotor (const ChShaftsMotor &other)

virtual double GetMotorPos () const
Get the position of the motor, as position of shaft 1 with respect to 2. More...

virtual double GetMotorPosDt () const
Get the motor speed, as speed of shaft 1 with respect to 2.

virtual double GetMotorPosDt2 () const
Get the motor acceleration, as accelerations of shaft 1 with respect to 2.

virtual int GetMotorNumTurns () const
Get number of full rotations for this shafts rotational motor. More...

virtual double GetMotorAngleWrapped () const
Get the motor angle in the range [-pi, +pi]. More...

virtual double GetReaction1 () const override
Get the reaction torque exchanged between the two shafts, considered as applied to the 1st axis.

virtual double GetReaction2 () const override
Get the reaction torque exchanged between the two shafts, considered as applied to the 2nd axis.

Public Member Functions inherited from chrono::ChShaftsCouple
ChShaftsCouple (const ChShaftsCouple &other)

virtual unsigned int GetNumAffectedCoords ()
Get the number of scalar variables affected by constraints in this couple.

ChShaftGetShaft1 () const
Get the first (input) shaft.

ChShaftGetShaft2 () const
Get the second (output) shaft.

double GetRelativePos () const
Get the actual relative position (angle or displacement) in terms of phase of shaft 1 with respect to 2.

double GetRelativePosDt () const
Get the actual relative speed (angle or displacement) of shaft 1 with respect to 2.

double GetRelativePosDt2 () const
Get the actual relative acceleration (angle or displacement) of shaft 1 with respect to 2.

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) const
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 () const
Get the axis-aligned bounding box (AABB) of this object. More...

virtual ChVector3d GetCenter () const
Get a symbolic 'center' of the object. More...

virtual void Setup ()
Perform setup operations. More...

virtual void Update (bool update_assets=true)
Perform an update using the current time.

void UpdateVisualModel ()
Utility function to update only the associated visual assets (if any).

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 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.

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...

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.

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.

const 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 ()

Protected Member Functions inherited from chrono::ChObj
int GenerateUniqueIdentifier ()

Protected Attributes inherited from chrono::ChShaftsCouple
ChShaftshaft1
first shaft

ChShaftshaft2
second shaft

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

◆ ArchiveIn()

 void chrono::ChShaftsMotorPosition::ArchiveIn ( ChArchiveIn & archive_in )
overridevirtual

Method to allow deserialization of transient data from archives.

Method to allow de serialization of transient data from archives.

Reimplemented from chrono::ChShaftsMotor.

◆ Initialize()

 bool chrono::ChShaftsMotorPosition::Initialize ( std::shared_ptr< ChShaft > shaft_1, std::shared_ptr< ChShaft > shaft_2 )
overridevirtual

Initialize the motor, given two shafts to join.

The first shaft is the 'output' shaft of the motor, the second is the 'truss', often fixed and not moving. The load is applied to the output shaft, while the truss shafts gets the same load but with opposite sign. Both shafts must belong to the same ChSystem.

Parameters
 shaft_1 first shaft to join (motor output shaft) shaft_2 second shaft to join (motor truss)

Reimplemented from chrono::ChShaftsCouple.

◆ SetOffset()

 void chrono::ChShaftsMotorPosition::SetOffset ( double offset )
inline

Set the initial offset for f(t)=0 (default: 0).

Relative position of the two shafts will be r(t) = f(t) + offset.

◆ SetPositionFunction()

 void chrono::ChShaftsMotorPosition::SetPositionFunction ( const std::shared_ptr< ChFunction > function )
inline

Set the motor function, f(t).

This function outputs an angle for a rotational motor and a displacement for a linear motor. Note that is must be at least C0 continuous. Ideally, f is C1, otherwise it produces spikes in accelerations.

The documentation for this class was generated from the following files:
• /builds/uwsbel/chrono/src/chrono/physics/ChShaftsMotorPosition.h
• /builds/uwsbel/chrono/src/chrono/physics/ChShaftsMotorPosition.cpp