Description

Implementation of the HHT implicit integrator for II order systems.

This timestepper allows use of an adaptive time-step, as well as optional use of a modified Newton scheme for the solution of the resulting nonlinear problem.

#include <ChTimestepperHHT.h>

Inheritance diagram for chrono::ChTimestepperHHT:

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Collaboration diagram for chrono::ChTimestepperHHT:

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Public Types
enum	HHT_Mode { ACCELERATION, POSITION }

Public Types inherited from chrono::ChTimestepper
enum	Type { EULER_IMPLICIT_LINEARIZED = 0, EULER_IMPLICIT_PROJECTED = 1, EULER_IMPLICIT = 2, TRAPEZOIDAL = 3, TRAPEZOIDAL_LINEARIZED = 4, HHT = 5, HEUN = 6, RUNGEKUTTA45 = 7, EULER_EXPLICIT = 8, LEAPFROG = 9, NEWMARK = 10, CUSTOM = 20 }
	Available methods for time integration (time steppers).

Public Member Functions
	ChTimestepperHHT (ChIntegrableIIorder *intgr=nullptr)

virtual Type	GetType () const override
	Return type of the integration method. More...

void	SetAlpha (double malpha)
	Set the numerical damping parameter. More...

double	GetAlpha ()
	Return the current value of the method parameter alpha.

void	SetMode (HHT_Mode mmode)
	Set the HHT formulation.

void	SetScaling (bool mscaling)
	Turn scaling on/off.

void	SetStepControl (bool val)
	Turn step size control on/off. More...

void	SetMinStepSize (double min_step)
	Set the minimum step size. More...

void	SetMaxItersSuccess (int iters)
	Set the maximum allowable number of iterations for counting a step towards a stepsize increase.

void	SetRequiredSuccessfulSteps (int num_steps)
	Set the minimum number of (internal) steps that require at most maxiters_success before considering a stepsize increase.

void	SetStepIncreaseFactor (double factor)
	Set the multiplicative factor for a stepsize increase. More...

void	SetStepDecreaseFactor (double factor)
	Set the multiplicative factor for a stepsize decrease. More...

void	SetModifiedNewton (bool val)
	Enable/disable modified Newton. More...

virtual void	Advance (const double dt) override
	Perform an integration timestep. More...

bool	GetConvergenceFlag () const
	Get an indicator to tell whether the iteration in current step tends to convergence or divergence. More...

void	SetThreshold_R (double mv)
	Set the threshold of norm of R, which is used to judge the trend of convergency. More...

double	GetThreshold_R () const
	Get the threshold of norm of R, which is used to judge the trend of convergency.

virtual void	ArchiveOUT (ChArchiveOut &archive) override
	Method to allow serialization of transient data to archives.

virtual void	ArchiveIN (ChArchiveIn &archive) override
	Method to allow de-serialization of transient data from archives.

Public Member Functions inherited from chrono::ChTimestepperIIorder
	ChTimestepperIIorder (ChIntegrableIIorder *intgr=nullptr)
	Constructor.

virtual	~ChTimestepperIIorder ()
	Destructor.

virtual ChState &	get_X ()
	Access the state, position part, at current time.

virtual ChStateDelta &	get_V ()
	Access the state, speed part, at current time.

virtual ChStateDelta &	get_A ()
	Access the acceleration, at current time.

virtual void	SetIntegrable (ChIntegrableIIorder *intgr)
	Set the integrable object.

Public Member Functions inherited from chrono::ChTimestepper
	ChTimestepper (ChIntegrable *intgr=nullptr)
	Constructor.

virtual	~ChTimestepper ()
	Destructor.

virtual ChVectorDynamic &	get_L ()
	Access the lagrangian multipliers, if any.

virtual void	SetIntegrable (ChIntegrable *intgr)
	Set the integrable object.

ChIntegrable *	GetIntegrable ()
	Get the integrable object.

virtual double	GetTime () const
	Get the current time.

virtual void	SetTime (double mt)
	Set the current time.

void	SetVerbose (bool verb)
	Turn on/off logging of messages.

void	SetQcDoClamp (bool dc)
	Turn on/off clamping on the Qcterm.

void	SetQcClamping (double cl)
	Turn on/off clamping on the Qcterm.

Public Member Functions inherited from chrono::ChImplicitIterativeTimestepper
void	SetMaxiters (int iters)
	Set the max number of iterations using the Newton Raphson procedure.

double	GetMaxiters ()
	Get the max number of iterations using the Newton Raphson procedure.

void	SetRelTolerance (double rel_tol)
	Set the relative tolerance. More...

void	SetAbsTolerances (double abs_tolS, double abs_tolL)
	Set the absolute tolerances. More...

void	SetAbsTolerances (double abs_tol)
	Set the absolute tolerances. More...

int	GetNumIterations () const
	Return the number of iterations.

int	GetNumSetupCalls () const
	Return the number of calls to the solver's Setup function.

int	GetNumSolveCalls () const
	Return the number of calls to the solver's Solve function.

Additional Inherited Members
Protected Attributes inherited from chrono::ChTimestepperIIorder
ChState	X

ChStateDelta	V

ChStateDelta	A

Protected Attributes inherited from chrono::ChTimestepper
ChIntegrable *	integrable

double	T

ChVectorDynamic	L

bool	verbose

bool	Qc_do_clamp

double	Qc_clamping

Protected Attributes inherited from chrono::ChImplicitIterativeTimestepper
int	maxiters
	maximum number of iterations

double	reltol
	relative tolerance

double	abstolS
	absolute tolerance (states)

double	abstolL
	absolute tolerance (Lagrange multipliers)

int	numiters
	number of iterations

int	numsetups
	number of calls to the solver's Setup function

int	numsolves
	number of calls to the solver's Solve function

Member Function Documentation

◆ Advance()

void chrono::ChTimestepperHHT::Advance ( const double dt )

overridevirtual

Perform an integration timestep.

Parameters

dt	timestep to advance

Implements chrono::ChTimestepper.

◆ GetConvergenceFlag()

bool chrono::ChTimestepperHHT::GetConvergenceFlag ( ) const

inline

Get an indicator to tell whether the iteration in current step tends to convergence or divergence.

This could be helpful if you want to fall back to iterate again via using more rigorous stepper settings, such as smaller fixed time stepper, turning off ModifiedNerton,etc, WHEN you are not satisfied by current iteration result.

◆ GetType()

virtual Type chrono::ChTimestepperHHT::GetType ( ) const

inlineoverridevirtual

Return type of the integration method.

Default is CUSTOM. Derived classes should override this function.

Reimplemented from chrono::ChTimestepper.

◆ SetAlpha()

void chrono::ChTimestepperHHT::SetAlpha ( double malpha )

Set the numerical damping parameter.

It must be in the [-1/3, 0] interval. The closer to -1/3, the more damping. The closer to 0, the less damping (for 0, it is the trapezoidal method). The method coefficients gamma and beta are set automatically, based on alpha.

◆ SetMinStepSize()

void chrono::ChTimestepperHHT::SetMinStepSize ( double min_step )

inline

Set the minimum step size.

An exception is thrown if the internal step size decreases below this limit.

◆ SetModifiedNewton()

void chrono::ChTimestepperHHT::SetModifiedNewton ( bool val )

inline

Enable/disable modified Newton.

If enabled, the Newton matrix is evaluated, assembled, and factorized only once per step or if the Newton iteration does not converge with an out-of-date matrix. If disabled, the Newton matrix is evaluated at every iteration of the nonlinear solver. Modified Newton iteration is enabled by default.

◆ SetStepControl()

void chrono::ChTimestepperHHT::SetStepControl ( bool val )

inline

Turn step size control on/off.

Step size control is enabled by default.

◆ SetStepDecreaseFactor()

void chrono::ChTimestepperHHT::SetStepDecreaseFactor ( double factor )

inline

Set the multiplicative factor for a stepsize decrease.

Must be a value smaller than 1.

◆ SetStepIncreaseFactor()

void chrono::ChTimestepperHHT::SetStepIncreaseFactor ( double factor )

inline

Set the multiplicative factor for a stepsize increase.

Must be a value larger than 1.

◆ SetThreshold_R()

void chrono::ChTimestepperHHT::SetThreshold_R ( double mv )

inline

Set the threshold of norm of R, which is used to judge the trend of convergency.

For different systems, this threshold may be much different, such as a mini robot and a huge wind turbine. You could turn on 'verbose' of HHT stepper and look at the norm of R for your system firstly, and then set a suitable threshold of norm of R. This threshold should always be larger than the normal norm of R for your system.

The documentation for this class was generated from the following files:

/builds/uwsbel/chrono/src/chrono/timestepper/ChTimestepperHHT.h
/builds/uwsbel/chrono/src/chrono/timestepper/ChTimestepperHHT.cpp

Description

Public Types

Public Member Functions

Additional Inherited Members

Member Function Documentation

◆ Advance()

◆ GetConvergenceFlag()

◆ GetType()

◆ SetAlpha()

◆ SetMinStepSize()

◆ SetModifiedNewton()

◆ SetStepControl()

◆ SetStepDecreaseFactor()

◆ SetStepIncreaseFactor()

◆ SetThreshold_R()