MultibodyPlantConfig Struct Reference

Detailed Description

The set of configurable properties on a MultibodyPlant.

The field names and defaults here match MultibodyPlant's defaults exactly, with the exception of time_step.

#include <drake/multibody/plant/multibody_plant_config.h>

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

Public Attributes
double	time_step {0.001}
	Configures the MultibodyPlant::MultibodyPlant() constructor time_step. More...
double	penetration_allowance {0.001}
	Configures the MultibodyPlant::set_penetration_allowance(). More...
double	stiction_tolerance {0.001}
	Configures the MultibodyPlant::set_stiction_tolerance(). More...
std::string	contact_model {"hydroelastic_with_fallback"}
	Configures the MultibodyPlant::set_contact_model(). More...
std::string	discrete_contact_solver {""}
	Configures the MultibodyPlant::set_discrete_contact_solver(). More...
std::string	discrete_contact_approximation {""}
	Configures the MultibodyPlant::set_discrete_contact_approximation(). More...
double	sap_near_rigid_threshold {1.0}
	Non-negative dimensionless number typically in the range [0.0, 1.0], though larger values are allowed even if uncommon. More...
std::string	contact_surface_representation {"polygon"}
	Configures the MultibodyPlant::set_contact_surface_representation(). More...
bool	adjacent_bodies_collision_filters {true}
	Configures the MultibodyPlant::set_adjacent_bodies_collision_filters(). More...

Member Function Documentation

Serialize()

void Serialize

(

Archive *

a

)

Passes this object to an Archive.

Refer to YAML Serialization for background.

Member Data Documentation

adjacent_bodies_collision_filters

bool adjacent_bodies_collision_filters {true}

Configures the MultibodyPlant::set_adjacent_bodies_collision_filters().

contact_model

std::string contact_model {"hydroelastic_with_fallback"}

Configures the MultibodyPlant::set_contact_model().

Refer to drake::multibody::ContactModel for details. Valid strings are:

• "point"
• "hydroelastic"
• "hydroelastic_with_fallback"

contact_surface_representation

std::string contact_surface_representation {"polygon"}

Configures the MultibodyPlant::set_contact_surface_representation().

Refer to drake::geometry::HydroelasticContactRepresentation for details. Valid strings are:

• "triangle"
• "polygon"

The default value used here is consistent with the default time_step chosen above; keep this consistent with MultibodyPlant::GetDefaultContactSurfaceRepresentation().

discrete_contact_approximation

std::string discrete_contact_approximation {""}

Configures the MultibodyPlant::set_discrete_contact_approximation().

Refer to drake::multibody::DiscreteContactApproximation for details. Valid strings are:

• "tamsi"
• "sap"
• "similar"
• "lagged"

Refer to MultibodyPlant::set_discrete_contact_approximation() and the references therein for further details.

Note

If empty, the contact approximation is determined by discrete_contact_solver, see set_discrete_contact_solver(). If both discrete_contact_solver and discrete_contact_approximation are empty, the default model (and solver) is TAMSI.

discrete_contact_solver

std::string discrete_contact_solver {""}

Configures the MultibodyPlant::set_discrete_contact_solver().

Refer to drake::multibody::DiscreteContactSolver for details. Valid strings are:

• "tamsi", uses the TAMSI model approximation.
• "sap" , uses the SAP model approximation.

Note

If empty, the contact solver is determined by discrete_contact_approximation, see MultibodyPlant::set_discrete_contact_approximation(). If both discrete_contact_solver and discrete_contact_approximation are empty, the default model (and solver) is TAMSI.

Warning

discrete_contact_solver is deprecated. Use discrete_contact_approximation to set the contact model approximation. The underlying solver will be inferred automatically. The deprecated code will be removed from Drake on or after 2024-04-01.

penetration_allowance

double penetration_allowance {0.001}

Configures the MultibodyPlant::set_penetration_allowance().

sap_near_rigid_threshold

double sap_near_rigid_threshold {1.0}

Non-negative dimensionless number typically in the range [0.0, 1.0], though larger values are allowed even if uncommon.

This parameter controls the "near rigid" regime of the SAP solver, β in section V.B of [Castro et al., 2021]. It essentially controls a threshold value for the maximum amount of stiffness SAP can handle robustly. Beyond this value, stiffness saturates as explained in [Castro et al., 2021]. A value of 1.0 is a conservative choice to avoid numerical ill-conditioning. However, this might introduce artificial softening of the contact constraints. If this is your case try:

1. Set this parameter to zero.
2. For difficult problems (hundreds of contacts for instance), you might need to use a low value if the solver fails to converge. For instance, set values in the range (1e-3, 1e-2).

stiction_tolerance

double stiction_tolerance {0.001}

Configures the MultibodyPlant::set_stiction_tolerance().

time_step

double time_step {0.001}

Configures the MultibodyPlant::MultibodyPlant() constructor time_step.

There is no default value for this within MultibodyPlant itself, so here we choose a nominal value (a discrete system, with a 1ms periodic update) as a reasonably conservative estimate that works in many cases.

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

• drake/multibody/plant/multibody_plant_config.h