robot_models

Robot models of the MAB Robotics Honey Badger quadrupeds, in one ROS 2 package:

• xacro / URDF for ROS 2, RViz and Gazebo Sim (with ros2_control)
• MuJoCo MJCF with flat, ramp and room scenes
• RBDL Lua models
• visual meshes (STL)
• an Isaac Lab articulation config (hb50)

Robot documentation: https://mabrobotics.github.io/hb-docs/intro.html

Robot	Type	Actuated joints	Mass
hb40	quadruped	12	12.60 kg
hb50	quadruped	12	17.11 kg
hb50w	wheeled quadruped	16 (12 + 4 wheels)	25.46 kg

The models in MuJoCo:

hb40	hb50	hb50w

Installation

Tested with ROS 2 Jazzy, Gazebo Harmonic and MuJoCo 3.4. Clone the repository into the src/ folder of a colcon workspace, then from the workspace root:

rosdep install --from-paths src --ignore-src -y
colcon build --packages-select robot_models
source install/setup.bash

Usage

RViz

ros2 launch robot_models view.launch.py robot:=hb50

Shows the robot with joint sliders. The fixed frame is body.

Gazebo Sim

ros2 launch robot_models gazebo.launch.py robot:=hb50

Spawns the robot in an empty world with ros2_control (gz_ros2_control) and starts:

• joint_state_broadcaster
• forward_position_controller: position commands for the 12 leg joints on /forward_position_controller/commands (std_msgs/Float64MultiArray, joint order as in config/<robot>/ros2_control.yaml)
• wheel_velocity_controller (hb50w only): velocity commands for the wheels
• a bridge for /clock and the body IMU on /imu (sensor_msgs/Imu)

MuJoCo

pip install mujoco
python3 -m mujoco.viewer --mjcf mujoco/hb50/scene.xml

The MJCF follows the MuJoCo Menagerie standards. mujoco/<robot>/<robot>.xml is the robot alone. scene.xml adds a flat floor; scene_ramp.xml and scene_room.xml combine the robot with the terrains in mujoco/scenes/, which all robots share. The home keyframe is the standing pose.

Actuators are torque motors named after their joint. Sensors: <joint>_pos, <joint>_vel and <joint>_trq for every joint, plus torso-orientation, torso-angular-velocity, torso-linear-acceleration and torso-magnetometer on the imu site.

RBDL

rbdl/<robot>/<robot>.lua loads with RBDL's LuaModel addon. The root body base has a 6-DoF free-flyer joint; every other body is named after the joint that moves it (fr_j0, fr_j1, ...), and <leg>_foot is a fixed frame at the foot (at the wheel centre for hb50w).

Isaac Sim / Isaac Lab

Convert the URDF to USD with Isaac Sim's URDF Importer. This package provides:

• urdf/hb50/hb50.urdf: the URDF to convert
• usd/hb50/isaaclab/hb50_cfg.py: an Isaac Lab articulation config (HB50_CFG) that loads the converted model from usd/hb50/hb50.usd and sets the joint armature, which URDF cannot express

Model conventions

• SI units, angles in radians; x forward, y left, z up.
• Legs: fr, fl, rl, rr. Joints: <leg>_j0 hip abduction, <leg>_j1 hip flexion, <leg>_j2 knee, <leg>_j3 wheel (hb50w).
• Links: root body (free-floating, no base_link), <leg>_l0, <leg>_l1, <leg>_l2, and <leg>_foot, or <leg>_w for the hb50w wheels.
• URDF, MJCF and the ros2_control configs use the same names.

xacro arguments

urdf/<robot>/<robot>.urdf.xacro takes a sim argument:

• none (default): plain URDF, identical to the committed <robot>.urdf
• mock: adds a ros2_control block with mock_components/GenericSystem
• gazebo: adds a ros2_control block with gz_ros2_control, the Gazebo plugins and an IMU sensor

Any other value stops xacro with an error.

Repository layout

<robot> is hb40, hb50 or hb50w.

robot_models
│
└───urdf
│   └───common          shared xacro macros: materials, ros2_control, Gazebo
│   └───<robot>         xacro robot description and the generated plain URDF
│
└───meshes
│   └───<robot>/visual  visual STL meshes
│
└───mujoco
│   └───scenes          ramp and room terrains shared by all robots
│   └───planes          height maps for the terrains
│   └───<robot>         MJCF robot model and its scenes
│
└───rbdl
│   └───<robot>         RBDL Lua model
│
└───config
│   └───<robot>         ros2_control and joint limit configs
│
└───usd
│   └───hb50            Isaac Lab articulation config
│
└───launch              RViz and Gazebo Sim launch files
└───media               README images
└───rviz                RViz config
└───scripts             URDF generation script
└───test                consistency tests

Development

The MJCF is the numeric reference. When you change a model, update the MJCF, the xacro, the Lua model and config/<robot>/joint_limits.yaml together, then regenerate the plain URDFs and run the tests:

scripts/generate_urdf.sh
python3 -m pytest test/

Commit the regenerated .urdf files. Both the script and the tests need xacro on PATH; the tests do not need the package to be built or sourced. They check:

• URDF vs MJCF: inertials, joint frames, axes, limits and effort, visual and collision geometry, the Gazebo IMU pose against the MJCF imu site, and the <joint>, <joint>_pos, <joint>_vel and <joint>_trq names
• URDF vs RBDL: inertials, joint frames and axes, total mass (skipped without lua5.1)
• config/<robot>/*.yaml joint names and limits vs URDF
• that every xacro variant expands and the committed URDFs are up to date
• that every MuJoCo scene runs without warnings under random controls, and the home keyframe stands on the floor (skipped without the mujoco Python package)
• that each mujoco/<robot>/ folder has its README, CHANGELOG, LICENSE and preview image, and the <compiler> line and mesh paths its derivation steps change

colcon test --packages-select robot_models runs the same tests plus the ament linters.

Known limitations

• The Isaac Lab config exists for hb50 only, and its default pose is a placeholder.
• config/<robot>/joint_limits.yaml lists the URDF joint limits for reference; the launch files do not load it.
• robot_state_publisher warns that the root link body has an inertia (a KDL limitation); the warning is harmless.

License

Apache-2.0, see LICENSE.