Description

Base class definition of a single-wheel test rig.

Accepts an arbitrary wheel assembly (derived from ChWheelTestRig::WheelAssembly)
Works with Rigid, SCM, DEM granular, or CRM terrain
Allows variation of longitudinal speed, wheel angular speed, and wheel slip angle as functions of time
Provides support for automatic selection of longitudinal and angular speeds in order to enforce a specified longitudinal slip value
Allows specification of camber angle (kept constant through the simulation)

#include <ChWheelTestRig.h>

Inheritance diagram for chrono::vehicle::ChWheelTestRigBase:

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Collaboration diagram for chrono::vehicle::ChWheelTestRigBase:

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Classes
class	SuspensionAssembly
	Definition of a suspension assembly for rig testing. More...

struct	TerrainParamsGranular
	Granular terrain patch parameters. More...

struct	TerrainParamsRigid
	Rigid terrain patch parameters. More...

struct	TerrainParamsSCM
	SCM terrain patch parameters. More...

struct	TerrainPatchSize
	Terrain patch dimensions. More...

class	WheelAssembly
	Definition of a wheel assembly for rig testing. More...

Public Types
enum	Mode { Mode::SUSPEND, Mode::DROP, Mode::TEST }
	Tire test rig operation mode. More...

enum	TerrainType { SCM, RIGID, CRG, GRANULAR, CRM, NONE }
	Terrain type.

Public Member Functions
void	SetGravitationalAcceleration (double grav)
	Set gravitational acceleration (default: 9.81 m/s2).

void	SetNormalLoad (double load)
	Set desired normal load (default: 1000 N).

void	SetLongSpeedFunction (std::shared_ptr< ChFunction > funct)
	Specify rig carrier longitudinal speed as function of time (default: none). More...

void	SetAngSpeedFunction (std::shared_ptr< ChFunction > funct)
	Specify wheel angular speed as function of time (default: none). More...

void	SetConstantLongitudinalSlip (double long_slip, double base_speed=1)
	Specify a constant given longitudinal slip. More...

void	SetStepsize (double step)
	Set the time step for advancing wheel assembly dynamics (default: 1e-3 s).

void	SetVisualizationType (VisualizationType vis)
	Set visualization type for the wheel assembly (default: PRIMITIVES).

void	SetTerrainRigid (const TerrainPatchSize &size, const TerrainParamsRigid &params)
	Enable use of rigid terrain.

void	SetTerrainRigid (const TerrainPatchSize &size, float mu, float cr, float Y)
	Enable use of rigid terrain. More...

void	SetTerrainSCM (const TerrainPatchSize &size, const TerrainParamsSCM &params)
	Enable use of SCM terrain.

void	SetTerrainSCM (const TerrainPatchSize &size, double Bekker_Kphi, double Bekker_Kc, double Bekker_n, double Mohr_cohesion, double Mohr_friction, double Janosi_shear, double grid_spacing=0.125)
	Enable use of SCM terrain. More...

void	SetTerrainGranular (const TerrainPatchSize &size, const TerrainParamsGranular &params)
	Enable use of granular terrain. More...

void	SetTerrainGranular (const TerrainPatchSize &size, double radius, double density, double friction, double cohesion, double Young_modulus)
	Enable use of granular terrain. More...

void	SetTimeDelay (double delay)
	Set time delay before applying motion functions (default: 0 s). More...

double	GetTimeDelay () const
	Get time delay after which measurements are calculated. More...

bool	OutputEnabled () const
	Check if kinematic and kinetic quantities are collected. More...

void	Initialize (Mode mode, double drop_speed=0.1)
	Initialize the rig system. More...

void	Advance (double step)
	Advance system state by the specified time step.

void	GetSuggestedCollisionSettings (double &collision_envelope, ChVector3i &collision_bins) const
	Get suggested collision settings. More...

double	GetNormalLoad () const
	Get the normal load.

double	GetMass () const
	Get total rig mass.

std::shared_ptr< ChTerrain >	GetTerrain () const
	Get a handle to the underlying terrain subsystem.

const ChVector3d &	GetPos () const
	Get current carrier body position.

ChVector3d	GetWheelPos () const
	Get current wheel position.

TerrainForce	ReportWheelForce () const
	Get the current terrain forces acting on the wheel as applied to the wheel hub.

double	GetDBP () const
	Return current drawbar-pull value. More...

double	GetLongitudinalSlip () const
	Get current wheel longitudinal slip. More...

double	GetSlipAngle () const
	Get current wheel slip angle. More...

double	GetCamberAngle () const
	Get current wheel camber angle. More...

std::shared_ptr< ChLinkMotorLinearSpeed >	GetMotorCarrier () const
	Get the linear motor used to actuate the carrier.

std::shared_ptr< ChShaftsMotorSpeed >	GetMotorWheel () const
	Get the rotation motor used to actuate the wheel.

Protected Member Functions
	ChWheelTestRigBase (ChSystem &system, std::shared_ptr< WheelAssembly > wheel)
	Construct a test rig within the specified system using the given custom wheel.

virtual void	CreateMechanism ()
	Create the single-wheel test rig mechanism.

void	CreateTerrain ()
	Create the terrain patch of specified type.

void	CreateTerrainSCM ()

void	CreateTerrainRigid ()

void	CreateTerrainGranular ()

virtual void	OnCreateMechanism (double dim)=0
	Additional operations to be performed during rig construction. More...

virtual void	OnInitialize (Mode mode)
	Additional operations to be performed on rig initialization.

virtual void	OnAdvance (double step)
	Additional operations to be performed on rig advance.

virtual void	OnStartActuation ()
	Additional operations to be performed when actuation is enabled. More...

Protected Attributes
ChSystem &	m_system
	containing Chrono system

Mode	m_mode
	testing mode

bool	m_output
	if false, report default measurements (typically 0)

std::shared_ptr< ChTerrain >	m_terrain
	handle to underlying terrain subsystem

std::shared_ptr< WheelAssembly >	m_wheel_assembly
	wheel assembly

VisualizationType	m_vis_type
	visualization type for wheel assembly

double	m_step_size
	step size for wheel assembly integration

double	m_grav
	gravitational acceleration

double	m_normal_load
	desired normal load

double	m_total_mass
	total sprung mass

double	m_time_delay
	time delay before applying external load

TerrainType	m_terrain_type
	terrain type

double	m_terrain_offset
	Y coordinate of wheel center.

double	m_terrain_height
	height coordinate for terrain subsystem

TerrainPatchSize	m_terrain_size
	terrain patch dimensions

TerrainParamsSCM	m_params_SCM
	SCM soil parameters.

TerrainParamsRigid	m_params_rigid
	rigid terrain contact material properties

TerrainParamsGranular	m_params_granular
	granular terrain parameters

ChAABB	m_wheel_AABB
	AABB for the entire wheel assembly (estimated or user-provided)

std::shared_ptr< ChBody >	m_ground_body
	ground body

std::shared_ptr< ChBodyAuxRef >	m_carrier_body
	rig carrier body

std::shared_ptr< ChBodyAuxRef >	m_chassis_body
	"chassis" body which carries normal load

bool	m_ls_actuated
	is linear speed actuated?

bool	m_rs_actuated
	is angular speed actuated?

bool	m_long_slip_constant
	true if constant longitudinal slip was specified

double	m_long_slip
	user-specified longitudinal slip

double	m_base_speed
	base speed for long slip calculation

std::shared_ptr< ChFunction >	m_ls_fun
	longitudinal speed function of time

std::shared_ptr< ChFunction >	m_rs_fun
	angular speed function of time

std::shared_ptr< ChLinkMotorLinearSpeed >	m_drop_motor
	actuator for controlled wheel drop

std::shared_ptr< ChLinkMotorLinearSpeed >	m_lin_motor
	carrier actuator

std::shared_ptr< ChShaftsMotorSpeed >	m_rot_motor
	wheel actuator

Member Enumeration Documentation

◆ Mode

enum chrono::vehicle::ChWheelTestRigBase::Mode

strong

Tire test rig operation mode.

Enumerator
SUSPEND	suspended wheel (locked spindle)
DROP	wheel drop test
TEST	normal wheel test

Member Function Documentation

◆ CreateTerrainGranular()

void chrono::vehicle::ChWheelTestRigBase::CreateTerrainGranular ( )

protected

< estimate for integration step size

◆ GetCamberAngle()

double chrono::vehicle::ChWheelTestRigBase::GetCamberAngle ( ) const

Get current wheel camber angle.

This value is calculated from the current hub normal direction.

◆ GetDBP()

double chrono::vehicle::ChWheelTestRigBase::GetDBP ( ) const

Return current drawbar-pull value.

This is the reaction force in the linear motor used to enforce the specified rig longitudinal speed.

◆ GetLongitudinalSlip()

double chrono::vehicle::ChWheelTestRigBase::GetLongitudinalSlip ( ) const

Get current wheel longitudinal slip.

This value is calculated from the horizontal speed of the hub body and its angular rotation speed.

◆ GetSlipAngle()

double chrono::vehicle::ChWheelTestRigBase::GetSlipAngle ( ) const

Get current wheel slip angle.

This value is calculated from the current hub normal direction.

◆ GetSuggestedCollisionSettings()

void chrono::vehicle::ChWheelTestRigBase::GetSuggestedCollisionSettings	(	double &	collision_envelope,
		ChVector3i &	collision_bins
	)		const

Get suggested collision settings.

These values are meaningful only when using granular terrain and Chrono::Multicore.

Parameters

collision_envelope	suggested envelope based on particle radius
collision_bins	suggested number of bins for broad-phase collision detection

◆ GetTimeDelay()

double chrono::vehicle::ChWheelTestRigBase::GetTimeDelay ( ) const

inline

Get time delay after which measurements are calculated.

After the drop phase (TEST mode only), this value is set to the input time delay increased by the wheel drop time. Before the drop phase is completed, this function returns the input time delay.

◆ Initialize()

void chrono::vehicle::ChWheelTestRigBase::Initialize	(	Mode	mode,
		double	drop_speed = `0.1`
	)

Initialize the rig system.

It is the user's responsibility to set the operation mode and motion functions in a consistent way. In TEST mode, the wheel is lowered onto the terrain with a speed equal to drop_speed.

◆ OnCreateMechanism()

virtual void chrono::vehicle::ChWheelTestRigBase::OnCreateMechanism ( double dim )

protectedpure virtual

Additional operations to be performed during rig construction.

A derived class must:

create any additional necessary bodies, links, and motors;
initialize the wheel assembly and connect it to the rig mechanism;
adjust mass properties of the rig bodies to be commensurate with those of the wheel assembly. 'dim' represents a characteristic length for the rig mechanism.

◆ OnStartActuation()

virtual void chrono::vehicle::ChWheelTestRigBase::OnStartActuation ( )

inlineprotectedvirtual

Additional operations to be performed when actuation is enabled.

This is called a single time and only in TEST mode at the end of the drop phase.

◆ OutputEnabled()

bool chrono::vehicle::ChWheelTestRigBase::OutputEnabled ( ) const

inline

Check if kinematic and kinetic quantities are collected.

This function returns true only in TEST mode once the motion functions are activated.

◆ SetAngSpeedFunction()

void chrono::vehicle::ChWheelTestRigBase::SetAngSpeedFunction ( std::shared_ptr< ChFunction > funct )

Specify wheel angular speed as function of time (default: none).

If a function is not specified, the wheel is not actuated.

◆ SetConstantLongitudinalSlip()

void chrono::vehicle::ChWheelTestRigBase::SetConstantLongitudinalSlip	(	double	long_slip,
		double	base_speed = `1`
	)

Specify a constant given longitudinal slip.

This version overrides the motion functions for the carrier longitudinal slip and for the wheel angular speed to enforce the specified longitudinal slip value. A positive slip value indicates that the wheel is spinning. A negative slip value indicates that the wheel is sliding (skidding); in particular, s=-1 indicates sliding without rotation.

◆ SetLongSpeedFunction()

void chrono::vehicle::ChWheelTestRigBase::SetLongSpeedFunction ( std::shared_ptr< ChFunction > funct )

Specify rig carrier longitudinal speed as function of time (default: none).

If a function is not specified, the carrier is not actuated.

◆ SetTerrainGranular() [1/2]

void chrono::vehicle::ChWheelTestRigBase::SetTerrainGranular	(	const TerrainPatchSize &	size,
		const TerrainParamsGranular &	params
	)

Enable use of granular terrain.

The terrain subsystem consists of identical spherical particles initialized in layers. A moving-patch option is used.

◆ SetTerrainGranular() [2/2]

void chrono::vehicle::ChWheelTestRigBase::SetTerrainGranular	(	const TerrainPatchSize &	size,
		double	radius,
		double	density,
		double	friction,
		double	cohesion,
		double	Young_modulus
	)

Enable use of granular terrain.

Specify contact material properties. The terrain subsystem consists of identical spherical particles initialized in layers. A moving-patch option is used.

Parameters

size	terrain patch size
radius	particle radius [m]
density	particle material density [kg/m3]
friction	inter-particle coefficient of friction
cohesion	inter-particle cohesion pressure [Pa]
Young_modulus	particle contact material Young's modulus [Pa]

◆ SetTerrainRigid()

void chrono::vehicle::ChWheelTestRigBase::SetTerrainRigid	(	const TerrainPatchSize &	size,
		float	mu,
		float	cr,
		float	Y
	)

Enable use of rigid terrain.

Specify contact material properties and patch dimensions.

Parameters

size	terrain patch size
mu	coefficient of friction
cr	coefficient of restitution
Y	contact material Young's modulus [Pa]

◆ SetTerrainSCM()

void chrono::vehicle::ChWheelTestRigBase::SetTerrainSCM	(	const TerrainPatchSize &	size,
		double	Bekker_Kphi,
		double	Bekker_Kc,
		double	Bekker_n,
		double	Mohr_cohesion,
		double	Mohr_friction,
		double	Janosi_shear,
		double	grid_spacing = `0.125`
	)

Enable use of SCM terrain.

Specify SCM soil parameters and patch dimensions.

Parameters

size	terrain patch size
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 [Pa], for shear failure
Mohr_friction	Friction angle [degrees], for shear failure
Janosi_shear	shear parameter J [m], (usually a few mm or cm)
grid_spacing	SCM grid spacing

◆ SetTimeDelay()

void chrono::vehicle::ChWheelTestRigBase::SetTimeDelay ( double delay )

inline

Set time delay before applying motion functions (default: 0 s).

In TEST mode, this delay is measured after the wheel bottom point reaches the terrain height.

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

/builds/uwsbel/chrono/src/chrono_vehicle/wheeled_vehicle/test_rig/ChWheelTestRig.h
/builds/uwsbel/chrono/src/chrono_vehicle/wheeled_vehicle/test_rig/ChWheelTestRig.cpp

Description

Classes

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Member Enumeration Documentation

◆ Mode

Member Function Documentation

◆ CreateTerrainGranular()

◆ GetCamberAngle()

◆ GetDBP()

◆ GetLongitudinalSlip()

◆ GetSlipAngle()

◆ GetSuggestedCollisionSettings()

◆ GetTimeDelay()

◆ Initialize()

◆ OnCreateMechanism()

◆ OnStartActuation()

◆ OutputEnabled()

◆ SetAngSpeedFunction()

◆ SetConstantLongitudinalSlip()

◆ SetLongSpeedFunction()

◆ SetTerrainGranular() [1/2]

◆ SetTerrainGranular() [2/2]

◆ SetTerrainRigid()

◆ SetTerrainSCM()

◆ SetTimeDelay()