Description

Deformable terrain model.

This class implements a deformable terrain based on the Soil Contact Model. Unlike RigidTerrain, the vertical coordinates of this terrain mesh can be deformed due to interaction with ground vehicles or other collision shapes.

#include <SCMDeformableTerrain.h>

Inheritance diagram for chrono::vehicle::SCMDeformableTerrain:

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Collaboration diagram for chrono::vehicle::SCMDeformableTerrain:

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Classes
class	SoilParametersCallback
	Class to be used as a callback interface for location-dependent soil parameters. More...

Public Types
enum	DataPlotType { PLOT_NONE, PLOT_LEVEL, PLOT_LEVEL_INITIAL, PLOT_SINKAGE, PLOT_SINKAGE_ELASTIC, PLOT_SINKAGE_PLASTIC, PLOT_STEP_PLASTIC_FLOW, PLOT_PRESSURE, PLOT_PRESSURE_YELD, PLOT_SHEAR, PLOT_K_JANOSI, PLOT_IS_TOUCHED, PLOT_ISLAND_ID, PLOT_MASSREMAINDER }

typedef std::pair< ChVector2< int >, double >	NodeLevel
	Node height level at a given grid location.

Public Member Functions
	SCMDeformableTerrain (ChSystem *system, bool visualization_mesh=true)
	Construct a default SCM deformable terrain. More...

void	SetPlane (const ChCoordsys<> &plane)
	Set the plane reference. More...

const ChCoordsys &	GetPlane () const
	Get the current reference plane. More...

void	SetSoilParameters (double Bekker_Kphi, double Bekker_Kc, double Bekker_n, double Mohr_cohesion, double Mohr_friction, double Janosi_shear, double elastic_K, double damping_R)
	Set the properties of the SCM soil model. More...

void	EnableBulldozing (bool mb)
	Enable/disable the creation of soil inflation at the side of the ruts (bulldozing effects).

void	SetBulldozingParameters (double erosion_angle, double flow_factor=1.0, int erosion_iterations=3, int erosion_propagations=10)
	Set parameters controlling the creation of side ruts (bulldozing effects). More...

void	SetTestHeight (double offset)
	Set the vertical level up to which collision is tested (relative to the reference level at the sample point). More...

double	GetTestHeight () const
	Return the current test height level.

void	SetPlotType (DataPlotType plot_type, double min_val, double max_val)
	Set the color plot type for the soil mesh. More...

void	SetColor (const ChColor &color)
	Set visualization color.

void	SetTexture (const std::string tex_file, float tex_scale_x=1, float tex_scale_y=1)
	Set texture properties. More...

void	AddMovingPatch (std::shared_ptr< ChBody > body, const ChVector<> &OOBB_center, const ChVector<> &OOBB_dims)
	Add a new moving patch. More...

void	RegisterSoilParametersCallback (std::shared_ptr< SoilParametersCallback > cb)
	Specify the callback object to set the soil parameters at given (x,y) locations. More...

double	GetInitHeight (const ChVector<> &loc) const
	Get the initial (undeformed) terrain height below the specified location.

ChVector	GetInitNormal (const ChVector<> &loc) const
	Get the initial (undeformed) terrain normal at the point below the specified location.

virtual double	GetHeight (const ChVector<> &loc) const override
	Get the terrain height below the specified location.

virtual ChVector	GetNormal (const ChVector<> &loc) const override
	Get the terrain normal at the point below the specified location.

virtual float	GetCoefficientFriction (const ChVector<> &loc) const override
	Get the terrain coefficient of friction at the point below the specified location. More...

std::shared_ptr< ChTriangleMeshShape >	GetMesh () const
	Get the visualization triangular mesh.

void	SetMeshWireframe (bool val)
	Set the visualization mesh as wireframe or as solid (default: wireframe). More...

void	WriteMesh (const std::string &filename) const
	Save the visualization mesh as a Wavefront OBJ file.

void	Initialize (double sizeX, double sizeY, double delta)
	Initialize the terrain system (flat). More...

void	Initialize (const std::string &heightmap_file, double sizeX, double sizeY, double hMin, double hMax, double delta)
	Initialize the terrain system (height map). More...

std::vector< NodeLevel >	GetModifiedNodes (bool all_nodes=false) const
	Get the heights of all modified grid nodes. More...

void	SetModifiedNodes (const std::vector< NodeLevel > &nodes)
	Modify the level of grid nodes from the given list.

TerrainForce	GetContactForce (std::shared_ptr< ChBody > body) const
	Return the current cumulative contact force on the specified body (due to interaction with the SCM terrain).

int	GetNumRayCasts () const
	Return the number of rays cast at last step.

int	GetNumRayHits () const
	Return the number of ray hits at last step.

int	GetNumContactPatches () const
	Return the number of contact patches at last step.

int	GetNumErosionNodes () const
	Return the number of nodes in the erosion domain at last step (bulldosing effects).

double	GetTimerMovingPatches () const
	Return time for updating moving patches at last step (ms).

double	GetTimerRayTesting () const
	Return time for geometric ray intersection tests at last step (ms).

double	GetTimerRayCasting () const
	Return time for ray casting at last step (ms). Includes time for ray intersectin testing.

double	GetTimerContactPatches () const
	Return time for computing contact patches at last step (ms).

double	GetTimerContactForces () const
	Return time for computing contact forces at last step (ms).

double	GetTimerBulldozing () const
	Return time for computing bulldozing effects at last step (ms).

double	GetTimerVisUpdate () const
	Return time for visualization assets update at last step (ms).

void	PrintStepStatistics (std::ostream &os) const
	Print timing and counter information for last step.

Public Member Functions inherited from chrono::vehicle::ChTerrain
virtual void	Synchronize (double time)
	Update the state of the terrain system at the specified time.

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.

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

Constructor & Destructor Documentation

◆ SCMDeformableTerrain()

chrono::vehicle::SCMDeformableTerrain::SCMDeformableTerrain	(	ChSystem *	system,
		bool	visualization_mesh = `true`
	)

Construct a default SCM deformable terrain.

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

Parameters

[in]	system	pointer to the containing multibody system
[in]	visualization_mesh	enable/disable visualization asset

Member Function Documentation

◆ AddMovingPatch()

void chrono::vehicle::SCMDeformableTerrain::AddMovingPatch	(	std::shared_ptr< ChBody >	body,
		const ChVector<> &	OOBB_center,
		const ChVector<> &	OOBB_dims
	)

Add a new moving patch.

Multiple calls to this function can be made, each of them adding a new active patch area. If no patches are defined, ray-casting is performed for every single node of the underlying SCM grid. If at least one patch is defined, ray-casting is performed only for mesh nodes within the AABB of the body OOBB projection onto the SCM plane.

Parameters

[in]	body	monitored body
[in]	OOBB_center	OOBB center, relative to body
[in]	OOBB_dims	OOBB dimensions

◆ GetCoefficientFriction()

float chrono::vehicle::SCMDeformableTerrain::GetCoefficientFriction ( const ChVector<> & loc ) const

overridevirtual

Get the terrain coefficient of friction at the point below the specified 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 SCMDeformableTerrain, this function defers to the user-provided functor object of type ChTerrain::FrictionFunctor, if one was specified. Otherwise, it returns the constant value of 0.8.

Reimplemented from chrono::vehicle::ChTerrain.

◆ GetModifiedNodes()

std::vector< SCMDeformableTerrain::NodeLevel > chrono::vehicle::SCMDeformableTerrain::GetModifiedNodes ( bool all_nodes = false ) const

Get the heights of all modified grid nodes.

If 'all_nodes = true', return modified nodes from the start of simulation. Otherwise, return only the nodes modified over the last step.

◆ GetPlane()

const ChCoordsys & chrono::vehicle::SCMDeformableTerrain::GetPlane ( ) const

Get the current reference plane.

The SCM terrain patch is in the (x,y) plane with normal along the Z axis.

◆ Initialize() [1/2]

void chrono::vehicle::SCMDeformableTerrain::Initialize	(	const std::string &	heightmap_file,
		double	sizeX,
		double	sizeY,
		double	hMin,
		double	hMax,
		double	delta
	)

Initialize the terrain system (height map).

The initial undeformed mesh is provided via the specified image file as a height map. By default, a mesh vertex is created for each pixel in the image. If divX and divY are non-zero, the image will be sampled at the specified resolution with linear interpolation as needed.

Parameters

[in]	heightmap_file	filename for the height map (image file)
[in]	sizeX	terrain dimension in the X direction
[in]	sizeY	terrain dimension in the Y direction
[in]	hMin	minimum height (black level)
[in]	hMax	maximum height (white level)
[in]	delta	grid spacing (may be slightly decreased)

◆ Initialize() [2/2]

void chrono::vehicle::SCMDeformableTerrain::Initialize	(	double	sizeX,
		double	sizeY,
		double	delta
	)

Initialize the terrain system (flat).

This version creates a flat array of points.

Parameters

[in]	sizeX	terrain dimension in the X direction
[in]	sizeY	terrain dimension in the Y direction
[in]	delta	grid spacing (may be slightly decreased)

◆ RegisterSoilParametersCallback()

void chrono::vehicle::SCMDeformableTerrain::RegisterSoilParametersCallback ( std::shared_ptr< SoilParametersCallback > cb )

Specify the callback object to set the soil parameters at given (x,y) locations.

To use constant soil parameters throughout the entire patch, use SetSoilParameters.

◆ SetBulldozingParameters()

void chrono::vehicle::SCMDeformableTerrain::SetBulldozingParameters	(	double	erosion_angle,
		double	flow_factor = `1.0`,
		int	erosion_iterations = `3`,
		int	erosion_propagations = `10`
	)

Set parameters controlling the creation of side ruts (bulldozing effects).

Parameters

erosion_angle	angle of erosion of the displaced material [degrees]
flow_factor	growth of lateral volume relative to pressed volume
erosion_iterations	number of erosion refinements per timestep
erosion_propagations	number of concentric vertex selections subject to erosion

◆ SetMeshWireframe()

void chrono::vehicle::SCMDeformableTerrain::SetMeshWireframe ( bool val )

Set the visualization mesh as wireframe or as solid (default: wireframe).

Note: in wireframe mode, normals for the visualization mesh are not calculated.

◆ SetPlane()

void chrono::vehicle::SCMDeformableTerrain::SetPlane ( const ChCoordsys<> & plane )

Set the plane reference.

By default, the reference plane is horizontal with Z up (ISO vehicle reference frame). To set as Y up, call SetPlane(ChCoordys(VNULL, Q_from_AngX(-CH_C_PI_2)));

◆ SetPlotType()

void chrono::vehicle::SCMDeformableTerrain::SetPlotType	(	DataPlotType	plot_type,
		double	min_val,
		double	max_val
	)

Set the color plot type for the soil mesh.

When a scalar plot is used, also define the range in the pseudo-color colormap.

◆ SetSoilParameters()

void chrono::vehicle::SCMDeformableTerrain::SetSoilParameters	(	double	Bekker_Kphi,
		double	Bekker_Kc,
		double	Bekker_n,
		double	Mohr_cohesion,
		double	Mohr_friction,
		double	Janosi_shear,
		double	elastic_K,
		double	damping_R
	)

Set the properties of the SCM soil model.

These parameters are described in: "Parameter Identification of a Planetary Rover Wheel-Soil Contact Model via a Bayesian Approach", A.Gallina, R. Krenn et al. Note that the original SCM model does not include the K and R coefficients. A very large value of K and R=0 reproduce the original SCM.

Parameters

Bekker_Kphi	Kphi, frictional modulus in Bekker model
Bekker_Kc	Kc, cohesive modulus in Bekker model
Bekker_n	n, exponent of sinkage in Bekker model (usually 0.6...1.8)
Mohr_cohesion	Cohesion for shear failure [Pa]
Mohr_friction	Friction angle for shear failure [degree]
Janosi_shear	Shear parameter in Janosi-Hanamoto formula [m]
elastic_K	elastic stiffness K per unit area, [Pa/m] (must be larger than Kphi)
damping_R	vertical damping R per unit area [Pa.s/m] (proportional to vertical speed)

◆ SetTestHeight()

void chrono::vehicle::SCMDeformableTerrain::SetTestHeight ( double offset )

Set the vertical level up to which collision is tested (relative to the reference level at the sample point).

Since the contact is unilateral, this could be zero. However, when computing bulldozing flow, one might also need to know if in the surrounding there is some potential future contact: so it might be better to use a positive value (but not higher than the max. expected height of the bulldozed rubble, to avoid slowdown of collision tests). Default: 0.1 m.

◆ SetTexture()

void chrono::vehicle::SCMDeformableTerrain::SetTexture	(	const std::string	tex_file,
		float	tex_scale_x = `1`,
		float	tex_scale_y = `1`
	)

Set texture properties.

Parameters

[in]	tex_file	texture filename
[in]	tex_scale_x	texture scale in X
[in]	tex_scale_y	texture scale in Y

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

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

Description

Classes

Public Types

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ SCMDeformableTerrain()

Member Function Documentation

◆ AddMovingPatch()

◆ GetCoefficientFriction()

◆ GetModifiedNodes()

◆ GetPlane()

◆ Initialize() [1/2]

◆ Initialize() [2/2]

◆ RegisterSoilParametersCallback()

◆ SetBulldozingParameters()

◆ SetMeshWireframe()

◆ SetPlane()

◆ SetPlotType()

◆ SetSoilParameters()

◆ SetTestHeight()

◆ SetTexture()