Description

Granular terrain model.

This class implements a rectangular patch of granular terrain with spherical particles. Boundary conditions (model of a container bin) are imposed through a custom collision detection object.

#include <GranularTerrain.h>

Inheritance diagram for chrono::vehicle::GranularTerrain:

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Collaboration diagram for chrono::vehicle::GranularTerrain:

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Public Member Functions
	GranularTerrain (ChSystem *system)
	Construct a default GranularTerrain. More...

void	SetContactFrictionCoefficient (float friction_coefficient)
	Set coefficient of friction. More...

void	SetContactRestitutionCoefficient (float restitution_coefficient)
	Set coefficient of restitution. More...

void	SetContactCohesion (float cohesion)
	Set the cohesion constant. More...

void	SetContactMaterialProperties (float young_modulus, float poisson_ratio)
	Set contact material properties. More...

void	SetContactMaterialCoefficients (float kn, float gn, float kt, float gt)
	Set contact material coefficients. More...

void	SetContactMaterialSMC (std::shared_ptr< ChMaterialSurfaceSMC > mat)
	Set contact material for SMC method.

void	SetContactMaterialNSC (std::shared_ptr< ChMaterialSurfaceNSC > mat)
	Set contact material for NSC method.

void	SetCollisionEnvelope (double envelope)
	Set outward collision envelope. More...

void	SetMinNumParticles (unsigned int min_num_particles)
	Set the minimum number of particles to be generated (default: 0).

void	EnableVerbose (bool val)
	Enable/disable verbose output (default: false).

void	EnableRoughSurface (int num_spheres_x, int num_spheres_y)
	Enable creation of particles fixed to bottom container. More...

void	EnableMovingPatch (std::shared_ptr< ChBody > body, double buffer_distance, double shift_distance, const ChVector<> &init_vel=ChVector<>())
	Enable moving patch and set parameters. More...

void	SetStartIdentifier (int id)
	Set start value for body identifiers of generated particles (default: 1000000). More...

float	GetCoefficientFriction () const
	Get coefficient of friction for contact material.

float	GetCoefficientRestitution () const
	Get coefficient of restitution for contact material.

float	GetCohesion () const
	Get cohesion constant.

float	GetYoungModulus () const
	Get Young's modulus of elasticity for contact material.

float	GetPoissonRatio () const
	Get Poisson ratio for contact material.

float	GetKn () const
	Get normal stiffness coefficient for contact material.

float	GetKt () const
	Get tangential stiffness coefficient for contact material.

float	GetGn () const
	Get normal viscous damping coefficient for contact material.

float	GetGt () const
	Get tangential viscous damping coefficient for contact material.

void	EnableVisualization (bool val)
	Enable/disable visualization of boundaries (default: false).

bool	IsVisualizationEnabled () const

void	SetColor (ChColor color)
	Set boundary visualization color.

std::shared_ptr< ChBody >	GetGroundBody ()
	Return a handle to the ground body.

void	Initialize (const ChVector<> &center, double length, double width, unsigned int num_layers, double radius, double density, const ChVector<> &init_vel=ChVector<>())
	Initialize the granular terrain system. More...

virtual void	Synchronize (double time) override
	Update the state of the terrain system at the specified time.

double	GetPatchFront () const
	Get current front boundary location (in positive X direction).

double	GetPatchRear () const
	Get current rear boundary location (in negative X direction).

double	GetPatchLeft () const
	Get left boundary location (in positive Y direction).

double	GetPatchRight () const
	Get right boundary location (in negative Y direction).

double	GetPatchBottom () const
	Get bottom boundary location.

bool	PatchMoved () const
	Report if the patch was moved during the last call to Synchronize().

unsigned int	GetNumParticles () const
	Get the number of particles.

virtual double	GetHeight (double x, double y) const override
	Get the terrain height at the specified (x,y) location. More...

virtual chrono::ChVector	GetNormal (double x, double y) const override
	Get the terrain normal at the specified (x,y) location.

virtual float	GetCoefficientFriction (double x, double y) const override
	Get the terrain coefficient of friction at the specified (x,y) location. More...

Public Member Functions inherited from chrono::vehicle::ChTerrain
virtual void	Advance (double step)
	Advance the state of the terrain system by the specified duration.

void	RegisterFrictionFunctor (FrictionFunctor *functor)
	Specify the functor object to provide the coefficient of friction at given (x,y) locations.

Friends
class	BoundaryContact

Additional Inherited Members
Protected Attributes inherited from chrono::vehicle::ChTerrain
FrictionFunctor *	m_friction_fun
	functor for location-dependent coefficient of friction

Constructor & Destructor Documentation

◆ GranularTerrain()

chrono::vehicle::GranularTerrain::GranularTerrain ( ChSystem * system )

Construct a default GranularTerrain.

The user is responsible for calling various Set methods before Initialize.

Parameters

[in] system pointer to the containing multibody system

Member Function Documentation

◆ EnableMovingPatch()

void chrono::vehicle::GranularTerrain::EnableMovingPatch	(	std::shared_ptr< ChBody >	body,
		double	buffer_distance,
		double	shift_distance,
		const ChVector<> &	init_vel = `ChVector<>()`
	)

Enable moving patch and set parameters.

Parameters

body	monitored body
buffer_distance	look-ahead distance
shift_distance	chunk size of relocated particles
init_vel	initial particle velocity

◆ EnableRoughSurface()

void chrono::vehicle::GranularTerrain::EnableRoughSurface	(	int	num_spheres_x,
		int	num_spheres_y
	)

Enable creation of particles fixed to bottom container.

Parameters

num_spheres_x	number of fixed spheres in X direction
num_spheres_y	number of fixed spheres in Y direction

◆ GetCoefficientFriction()

float chrono::vehicle::GranularTerrain::GetCoefficientFriction	(	double	x,
		double	y
	)		const

overridevirtual

Get the terrain coefficient of friction at the specified (x,y) location.

This coefficient of friction value may be used by certain tire models to modify the tire characteristics, but it will have no effect on the interaction of the terrain with other objects (including tire models that do not explicitly use it). For GranularTerrain, this function defers to the user-provided functor object of type ChTerrain::FrictionFunctor, if one was specified. Otherwise, it returns the constant value specified through SetContactFrictionCoefficient.

Implements chrono::vehicle::ChTerrain.

◆ GetHeight()

double chrono::vehicle::GranularTerrain::GetHeight	(	double	x,
		double	y
	)		const

overridevirtual

Get the terrain height at the specified (x,y) location.

This function returns the highest point over all granular particles.

Implements chrono::vehicle::ChTerrain.

◆ Initialize()

void chrono::vehicle::GranularTerrain::Initialize	(	const ChVector<> &	center,
		double	length,
		double	width,
		unsigned int	num_layers,
		double	radius,
		double	density,
		const ChVector<> &	init_vel = `ChVector<>()`
	)

Initialize the granular terrain system.

The granular material is created in successive layers within the specified volume, using the specified generator, until the number of particles exceeds the specified minimum value (see SetMinNumParticles). The initial particle locations are obtained with Poisson Disk sampling, using the given minimum separation distance.

Parameters

[in]	center	center of bottom
[in]	length	patch dimension in X direction
[in]	width	patch dimension in Y direction
[in]	num_layers	number of layers
[in]	radius	particle radius
[in]	density	particle density
[in]	init_vel	particle initial velocity

◆ SetCollisionEnvelope()

void chrono::vehicle::GranularTerrain::SetCollisionEnvelope ( double envelope )

inline

Set outward collision envelope.

This value is used for the internal custom collision detection for imposing boundary conditions. Note that if the underlying system is of SMC type (i.e., using a penalty-based contact method), the envelope is automatically set to 0. For NSC systems (i.e., when using a complementarity-based contact method), if the envelope is not specified, the default value is 5% of the particle radius.

◆ SetContactCohesion()

void chrono::vehicle::GranularTerrain::SetContactCohesion ( float cohesion )

Set the cohesion constant.

The default value is 0.

◆ SetContactFrictionCoefficient()

void chrono::vehicle::GranularTerrain::SetContactFrictionCoefficient ( float friction_coefficient )

Set coefficient of friction.

The default value is 0.9

◆ SetContactMaterialCoefficients()

void chrono::vehicle::GranularTerrain::SetContactMaterialCoefficients	(	float	kn,
		float	gn,
		float	kt,
		float	gt
	)

Set contact material coefficients.

These values are used directly to compute contact forces (if the containing system is so configured and if the SMC contact method is being used). The default values are: kn=2e5, gn=40, kt=2e5, gt=20

Parameters

[in]	kn	normal contact stiffness
[in]	gn	normal contact damping
[in]	kt	tangential contact stiffness
[in]	gt	tangential contact damping

◆ SetContactMaterialProperties()

void chrono::vehicle::GranularTerrain::SetContactMaterialProperties	(	float	young_modulus,
		float	poisson_ratio
	)

Set contact material properties.

These values are used to calculate contact material coefficients (if the containing system is so configured and if the SMC contact method is being used). The default values are: Y = 2e5 and nu = 0.3

Parameters

[in]	young_modulus	Young's modulus of elasticity
[in]	poisson_ratio	Poisson ratio

◆ SetContactRestitutionCoefficient()

void chrono::vehicle::GranularTerrain::SetContactRestitutionCoefficient ( float restitution_coefficient )

Set coefficient of restitution.

The default value is 0.

◆ SetStartIdentifier()

void chrono::vehicle::GranularTerrain::SetStartIdentifier ( int id )

inline

Set start value for body identifiers of generated particles (default: 1000000).

It is assumed that all bodies with a larger identifier are granular material particles.

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

/builds/uwsbel/chrono/src/chrono_vehicle/terrain/GranularTerrain.h
/builds/uwsbel/chrono/src/chrono_vehicle/terrain/GranularTerrain.cpp

Description

Public Member Functions

Friends

Additional Inherited Members

Constructor & Destructor Documentation

◆ GranularTerrain()

Member Function Documentation

◆ EnableMovingPatch()

◆ EnableRoughSurface()

◆ GetCoefficientFriction()

◆ GetHeight()

◆ Initialize()

◆ SetCollisionEnvelope()

◆ SetContactCohesion()

◆ SetContactFrictionCoefficient()

◆ SetContactMaterialCoefficients()

◆ SetContactMaterialProperties()

◆ SetContactRestitutionCoefficient()

◆ SetStartIdentifier()