Implementation:ARISE Initiative Robosuite DynamicsModder

Metadata:

Overview

Concrete class for randomizing physics dynamics parameters in MuJoCo simulations provided by the robosuite modding utilities.

Description

DynamicsModder modifies MjModel physical parameters including: global (density, viscosity), body (position, quaternion, inertia, mass), geom (friction, solref, solimp), and joint (stiffness, frictionloss, damping, armature). Requires modder.update() after modifications to propagate changes. Inherits from BaseModder.

Usage

Used internally by DomainRandomizationWrapper. Can be used standalone for custom dynamics randomization.

Code Reference

Source: robosuite
File: robosuite/utils/mjmod.py
Lines: L1405-1997
Signature:

class DynamicsModder(BaseModder):
    def __init__(self, sim, random_state=None,
                 randomize_density=True, randomize_viscosity=True,
                 density_perturbation_ratio=0.1, viscosity_perturbation_ratio=0.1,
                 body_names=None, randomize_position=True, randomize_quaternion=True,
                 randomize_inertia=True, randomize_mass=True,
                 position_perturbation_size=0.02, quaternion_perturbation_size=0.02,
                 inertia_perturbation_ratio=0.02, mass_perturbation_ratio=0.02,
                 geom_names=None, randomize_friction=True, randomize_solref=True,
                 randomize_solimp=True, friction_perturbation_ratio=0.1,
                 solref_perturbation_ratio=0.1, solimp_perturbation_ratio=0.1,
                 joint_names=None, randomize_stiffness=True, randomize_frictionloss=True,
                 randomize_damping=True, randomize_armature=True,
                 stiffness_perturbation_ratio=0.1, frictionloss_perturbation_size=0.05,
                 damping_perturbation_size=0.01, armature_perturbation_size=0.01):

Import: from robosuite.utils.mjmod import DynamicsModder

I/O Contract

Inputs:

sim (MjSim, Required): MuJoCo simulation instance to modify
random_state (RandomState, Optional): Random state for reproducibility
body_names (list, Optional, Default: all elements): Body names to randomize
geom_names (list, Optional, Default: all elements): Geometry names to randomize
joint_names (list, Optional, Default: all elements): Joint names to randomize
All randomize_* parameters (bool, Optional, Default: True): Enable/disable specific randomizations
All *_perturbation_* parameters (float, Optional): Perturbation magnitudes (see defaults in signature)

Methods:

randomize(): Apply random perturbations to configured parameters
save_defaults(): Store current parameter values as defaults
restore_defaults(): Reset parameters to saved defaults
update(): Must call after modifications to propagate changes to simulation

Usage Examples

The DynamicsModder is typically used through the DomainRandomizationWrapper by specifying dynamics_randomization_args:

from robosuite.wrappers import DomainRandomizationWrapper

# Configure dynamics randomization parameters
dynamics_args = {
    'randomize_density': True,
    'density_perturbation_ratio': 0.15,
    'randomize_friction': True,
    'friction_perturbation_ratio': 0.2,
    'randomize_mass': True,
    'mass_perturbation_ratio': 0.1,
}

# Wrap environment with domain randomization
env = DomainRandomizationWrapper(
    env,
    dynamics_randomization_args=dynamics_args
)

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