Detailed Description

These properties will be used as defaults when the geometry as added via API calls or parsed from model files doesn't say anything more specific.

See also: Modeling Compliant Contact, Hydroelastic Contact User Guide, Modeling of Dry Friction and subsections therein.

#include <drake/geometry/scene_graph_config.h>

Public Member Functions
template<typename Archive >
void	Serialize (Archive *a)
	Passes this object to an Archive. More...

void	ValidateOrThrow () const
	Throws if the values are inconsistent. More...

Public Attributes
Hydroelastic Contact Properties
These properties affect hydroelastic contact only. For more detail, including limits of the numeric parameters, See also geometry::AddRigidHydroelasticProperties, geometry::AddCompliantHydroelasticProperties, geometry::AddCompliantHydroelasticPropertiesForHalfSpace. For more context, See also Properties for hydroelastic contact.
std::string	compliance_type {"undefined"}
	There are three valid options for `compliance_type`: More...

std::optional< double >	hydroelastic_modulus {1e7}
	A measure of material stiffness, in units of Pascals. More...

std::optional< double >	resolution_hint {0.02}
	Controls how finely primitive geometries are tessellated, units of meters. More...

std::optional< double >	slab_thickness
	For a halfspace, the thickness of compliant material to model, in units of meters. More...

std::optional< double >	margin
	(Advanced) Specifies a thin layer of thickness "margin" (in meters) around each geometry. More...

General Contact Properties
These properties affect contact in general. For more detail, including limits of the numeric parameters, See also geometry::AddContactMaterial, multibody::CoulombFriction, mbp_contact_modeling, Modeling Dissipation.
std::optional< double >	dynamic_friction {0.5}
	To be valid, either both friction values must be populated, or neither. More...

std::optional< double >	static_friction {0.5}

std::optional< double >	hunt_crossley_dissipation {50.0}
	Controls energy dissipation from contact, for contact approximations other than* multibody::DiscreteContactApproximation::kSap. More...

std::optional< double >	relaxation_time {0.1}
	Controls energy damping from contact, only for multibody::DiscreteContactApproximation::kSap. More...

Point Contact Properties
These properties affect point contact only. For complete descriptions of the numeric parameters, See Compliant Point Contact Forces, geometry::AddContactMaterial.
std::optional< double >	point_stiffness {1e6}
	A measure of material stiffness, in units of Newtons per meter. More...

Member Function Documentation

◆ Serialize()

void Serialize ( Archive * a )

Passes this object to an Archive.

Refer to YAML Serialization for background.

◆ ValidateOrThrow()

void ValidateOrThrow ( ) const

Throws if the values are inconsistent.

Member Data Documentation

◆ compliance_type

std::string compliance_type {"undefined"}

There are three valid options for compliance_type:

"undefined": hydroelastic contact will not be used.
"rigid": the default hydroelastic compliance type will be rigid; note that rigid-rigid contact is not supported by the hydroelastic contact model, but is supported by point contact (multibody::ContactModel::kPoint or multibody::ContactModel::kHydroelasticWithFallback).
"compliant": the default hydroelastic compliance type will be compliant.

◆ dynamic_friction

std::optional<double> dynamic_friction {0.5}

To be valid, either both friction values must be populated, or neither.

Friction quantities are unitless.

◆ hunt_crossley_dissipation

std::optional<double> hunt_crossley_dissipation {50.0}

Controls energy dissipation from contact, for contact approximations other than* multibody::DiscreteContactApproximation::kSap.

Units are seconds per meter.

If a non-deformable geometry is missing a value for dissipation, MultibodyPlant will generate a default value (based on multibody::MultibodyPlantConfig::penetration_allowance). However, this behavior will be going away. Therefore, we recommend guaranteeing that every geometry has a dissipation value either by assigning the property directly to the geometry or by providing a non-null value here.

Please refer to Default Contact Parameters for more details on Drake's defaults along with guidelines on how to estimate parameters specific to your model.

◆ hydroelastic_modulus

std::optional<double> hydroelastic_modulus {1e7}

A measure of material stiffness, in units of Pascals.

◆ margin

std::optional<double> margin

(Advanced) Specifies a thin layer of thickness "margin" (in meters) around each geometry.

Two bodies with margins δ₁ and δ₂ are considered for contact resolution whenever their distance is within δ₁ + δ₂. That is, (speculative) contact constraints are added for objects at a distance smaller than δ₁+δ₂.

Refer to Margin for Hydroelastic Contact for further details, including theory, examples, recommended margin values and limitations.

There will only be contact if the two zero level sets intersect. Unless the zero level sets of both geometries overlap, there is no contact and no contact force. However, (speculative) contact constraints will be added allowing our discrete contact solvers to predict if a contact "will" occur at the next time step. This leads to additional time coherence and stability. Analytical studies of stability show that a value of 0.1 mm to 1.0 mm is more than enough for most robotics applications. This is not an "action-at-a-distance" trick, there is no contact when the thin margin layers of two objects overlap. The margin is simply a "cheap" mechanism to avoid significantly more complex and costly strategies such as Continuous Collision Detection.

Note: Inflating the geometries does not appreciably change the domain of contact. In the original mesh, the contact pressure is zero on the mesh's boundary surface. When inflating the meshes, we redefine the pressure field so that its zero level set field is a good approximation to the surface of the original geometry. When visualizing hydroelastic proximity geometry, the rendered geometry will include the inflation.; Currently margin only applies to compliant hydroelastic contact and it does not affect point contact.

◆ point_stiffness

std::optional<double> point_stiffness {1e6}

A measure of material stiffness, in units of Newtons per meter.

If a non-deformable geometry is missing a value for stiffness, MultibodyPlant will generate a default value (based on multibody::MultibodyPlantConfig::penetration_allowance). However, this behavior will be going away. Therefore, we recommend guaranteeing that every geometry has a stiffness value either by assigning the property directly to the geometry or by providing a non-null value here.

Please refer to Default Contact Parameters for more details on Drake's defaults along with guidelines on how to estimate parameters specific to your model.

◆ relaxation_time

std::optional<double> relaxation_time {0.1}

Controls energy damping from contact, only for multibody::DiscreteContactApproximation::kSap.

Units are seconds.

◆ resolution_hint

std::optional<double> resolution_hint {0.02}

Controls how finely primitive geometries are tessellated, units of meters.

While no single value is universally appropriate, this value was selected based on the following idea. We're attempting to make introducing novel manipulands as easy as possible. Considering a simple soup can as a representative manipuland, we've picked a value that would result in a tessellated cylinder with enough faces to be appropriate for contact with a compliant gripper.

◆ slab_thickness

std::optional<double> slab_thickness

For a halfspace, the thickness of compliant material to model, in units of meters.

◆ static_friction

std::optional<double> static_friction {0.5}

See also: dynamic_friction.

The documentation for this struct was generated from the following file:

drake/geometry/scene_graph_config.h