Implementation:ARISE Initiative Robosuite LegBaseModel

Knowledge Sources	ARISE_Initiative_Robosuite
Domains	Robotics, Simulation, MJCF_Modeling
Last Updated	2026-02-15 07:00 GMT

Overview

LegBaseModel is the abstract base class for all mobile leg base models in robosuite, providing methods for converting robot bases into floating (mobile) configurations.

Description

The LegBaseModel class extends RobotBaseModel to define the interface and common functionality for legged robot bases. It provides core methods for manipulating the MJCF XML model of a leg base, including removing joint actuation for specific body parts, removing free joints, and programmatically adding mobile joints (forward, side, and yaw) that convert a stationary leg base into a floating mobile platform.

The _add_mobile_joint method is particularly notable, as it dynamically creates three joints (forward slide, side slide, and yaw hinge) along with corresponding velocity actuators. These joints enable planar motion with configurable friction loss (250 N) and force limits (600 N). The yaw actuator has a higher velocity gain (kv=1500) compared to the translational actuators (kv=1000) and a wider control range of [-1.5, 1.5] versus [-1.0, 1.0] for the slide joints.

The _remove_joint_actuation method provides a way to strip joints, motors, and associated sensors (position, velocity, actuator force) from specific body parts by name matching. This is useful when certain parts of the leg base model need to be fixed or simplified. The naming prefix follows the pattern leg{idn}_ for proper namespace isolation in multi-robot scenarios.

Usage

Use LegBaseModel as a base class when implementing new legged robot base models. Subclasses must implement the init_qpos property to define the default joint positions. The default_base property returns "NullMobileBase", indicating that by default no mobile base is attached.

Code Reference

Source Location

• Repository: ARISE_Initiative_Robosuite
• File: robosuite/models/bases/leg_base_model.py

Signature

class LegBaseModel(RobotBaseModel):
    # Inherits __init__ from RobotBaseModel
    # def __init__(self, fname: str, idn=0):

Import

from robosuite.models.bases.leg_base_model import LegBaseModel

I/O Contract

Inputs

Name	Type	Required	Description
fname	str	Yes	Path to relevant XML file to create this leg base instance (inherited from RobotBaseModel)
idn	int or str	No	Unique identification number or string for this base instance. Default: 0

Outputs

Name	Type	Description
LegBaseModel instance	LegBaseModel	Abstract leg base model with mobile joint support
naming_prefix	str	Returns "leg{idn}_" prefix for namespace isolation
default_base	str	Returns "NullMobileBase"
init_qpos	np.array	Default joint positions (must be defined by subclasses)

Usage Examples

from robosuite.models.bases.leg_base_model import LegBaseModel

# LegBaseModel is abstract; typically used via a concrete subclass.
# Example subclass usage pattern:
class MyLegBase(LegBaseModel):
    @property
    def init_qpos(self):
        return np.zeros(6)

    @property
    def naming_prefix(self):
        return "leg{}_".format(self.idn)

    @property
    def top_offset(self):
        return np.array([0, 0, 0.5])

    @property
    def horizontal_radius(self):
        return 0.3

# Programmatically add mobile joints to make the leg base floating
# leg_base._add_mobile_joint()

# Remove actuation from a specific part
# leg_base._remove_joint_actuation("knee")

Related Pages

• Environment:ARISE_Initiative_Robosuite_MuJoCo_Python