Table of Contents

[Last generated: Thu 07 Dec 2023 02:38:20 PM EST]

• Mujoco Simulation Packages
  • 1. Preview:
    • 1.1 Custom Library to support with MuJoCo 2.2.x
    • 1.2 Waterloo Steel Mobile Playground (engine & viewer):
  • 2. ToDo:
  • 3. Note:
  • 4. Installation
  • 5. Launch:
    • 5.1 Cart Manipulation:
      • Variables of simulation:
  • 6. File Hierarchy:
  • A*. Appendix:
    • A.1 Note:
    • A.2 Waterloo Steel Mobile Manipulator Simulation:
      • A.2.1 AJoints and MOI:
    • A.2.2 Installation Guide Extra
      • A.2.3 Tested Platforms:
      • A.2.4 M1 Macbook Instructions:
      • A.2.5 Unity module:
    • A.3 MuJoCo-ROS integration

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# Mujoco Simulation Packages

Mujoco Physics Simulation Package for Waterloo Steel Robot

1. Preview:

1.1 Custom Library to support with MuJoCo 2.2.x

• Launch Package (includes models) (This Package)
• Graphical User Interface / Direct OnOff-screen Render: uwarl-mujoco-python-viewer
  • branching from jx-mujoco-python-viewer
• Main Engine Code uwarl-mujoco-python-engine
  • branching from jx-mujoco-python-engine (similar to deepmind/dm_control)
• MuJoCo 2.2.x locking variants jx-mujoco
• [TODO: ROS Integration] for bridging SIL and HIL
• [TODO: Unity Integration] for rendering and realistic camera views
• [TODO: Migration to MuJoCo 3] for rendering higher simulation speeds

1.2 Waterloo Steel Mobile Playground (engine & viewer):

2. ToDo:

• Full Assembly
• Simulation setup
• Contact Physics [Last Edit: 15/Jun/2022]
• [WAM] Ensure Mechanical Params are Verified
• [BHAND] Ensure Mechanical Params are Verified
• [?] [SUMMIT] Ensure Mechanical Params are Verified
• Control Descriptors
• PID control for base
• ROS integration
• Real-time simulation synchronization
• Find solution for convex hull of wagon handle
• Passing all variables in highest level launch file
• ....

3. Note:

:announcement: Starting version 2.1.2, MuJoCo comes with python bindings, no need to look into mujoco_py package (which only works for 210) Migration notes: https://mujoco.readthedocs.io/en/latest/python.html#migration-notes-for-mujoco-py Right now, we will use mujoco-viewer based on https://github.com/rohanpsingh/mujoco-python-viewer TODO: We will migrate to the official viewer in python bindings later: Watch PR: google-deepmind/mujoco#201

4. Installation

1. Submodule Update

   $ cd submodules
   $ git submodule update

2. Install editable python viewer:

   $ cd uwarl-mujoco-python-viewer
   $ pip install -e .

3. Install editable python engine:

   $ cd uwarl-mujoco-python-engine
   $ pip install -e .

5. Launch:

5.1 Cart Manipulation:

Launches the cart manipulation simulation with ROS integration. The launch file will launch:

• Clock publisher for simulation time
• Mujoco Engine and Viewer based on submodules
• ROS controllers which are used for trajectory control of the WAM
• Hardware simulation interface node to connect MuJoCo to ROS controllers
• Trajectory following action server for mobile base
• Rosbag recorder action server
• Demo_V09_mujoco.py node

$ roslaunch waterloo_steel_sim_bringup waterloo_steel_complete_cart_mujoco.launch

Variables of simulation:

These variables can be changed depending on the simulation.

• In launch/mujocolaunch.launch param sim_frequency_mujoco. This changes the frequency of the node which updates the engine. It is synched to the simulation Hardware Simulation Interface for control of the WAM.
• In components/include_common.xml param timestep for changing the engines stepsize.

Important

Make sure 1/frequency of the ROS node updating the engine is equal to a multiple of the engine stepsize for real-time simulation.

• In playground/playground_mobile_wagon_manipulation.xml comment out the world body and the contact exclusions to simulate without a world. This increases the rendering performance.
  • You might want to compress the mesh to increase rendering performance, by using MeshLab for example.
• In components/include_e7_3rd_floor_Dependencies.xml, the world .stl file is defined. Change to simulate different world.
• In src/main.py the MuJoCo viewer rate can be defined.
• In src/main.py the onboard cameras of the Summit and WAM can be enabled. This can be done by passing True in the Engine _update function. Default value equals False.

6. File Hierarchy:

.
├── CITATION.cff
├── LICENSE
├── README.md
├── components
│   ├── meshes
│   │   ├── bases
│   │   ├── meshes_bhand
│   │   └── ...
│   ├── robots
│   │   ├── wam_7dof_wam_bhand.urdf.xacro
│   │   └── waterloo_steel_mujoco.urdf.xacro
│   ├── urdf
│   │   ├── bases
│   │   ├── wagon
│   │   ├── wam
│   │   └── wheels
│   ├── include_common.xml
│   ├── include_{assembly-name}_Chain.xml
│   ├── include_{assembly-name}_Dependencies.xml
│   ├── include_{assembly-name}_actuators.xml
│   └── ...
├── documentation
│   └── ...
├── include
│   └── mujoco_ros_control
│   │   ├── mujoco_ros_control.h
│   │   ├── robot_hw_sim_plugin.h
│   │   └── robot_hw_sim.h
├── meshes
│   ├── maps_thirdfloor
│   │   ├── map_e7_3_v6.stl
│   │   └── ...
│   ├── meshes_{module-name}
│   │   ├── {3D-model-component-name}.stl
│   │   └── ...
│   └── ...
├── playground
│   ├── playground_{playground-name}.xml
│   └── ...
├── src
│   ├── {scripts}.py # [launch files]
│   └── ...
├── submodules
│   ├── uwarl-mujoco-python-viewer # [Mujoco Render/Interaction GUI]
│   └── uwarl-mujoco-python-engine # [Main engine code]
└── textures
│   └── ...
x

[ 5 directories, # files ]

A*. Appendix:

A.1 Note:

• WAM sim file is a CORRECTED and MODIFIED version based on the official archived MuJoCo model made by Vikash kumar
  • Findings: The original model has collision disabled, and parameters are incorrectly populated
  • Note: We have modified the original model based on the given stl files completely, and configured MoI based on the Official Barrett WAM Specification.
    • Specifically, we made exactly the same as described in the document, and removed incorrect quaternion parameters for inertial , and populated the inertial purely based on the centre of the mass and translated the coordinate frames to the stl model frame (manually)
• Shall you have any concern with the parameters, kindly open an issue.

A.2 Waterloo Steel Mobile Manipulator Simulation:

A.2.1 AJoints and MOI:

Joints	MOI

A.2.2 Installation Guide Extra

• Install MuJoCo 2.2.x via $ sudo pip install mujoco
• Download MuJoCo 2.2.x release package from https://github.com/deepmind/mujoco/releases

A.2.3 Tested Platforms:

• M1 Macbook Pro 14"
• Ubuntu 20.04
• [TBD] WINDOWS ---x

A.2.4 M1 Macbook Instructions:

• Make directory MuJoCo_v2.2 under /Applications
• Copy all files from MuJoCo 2.2.x release dmg into /Applications/MuJoCo_v2.2

A.2.5 Unity module:

• The directory for the .dylib has been modified to /Applications/MuJoCo_v2.2/MuJoCo.app/Contents/Frameworks under this submodules/jx-mujoco

A.3 MuJoCo-ROS integration

The current MuJoCo-ROS integration is shown below:

In detail, zoomed in on the Hardware Simulation Interface:

To find more details on the ROS integration of the MuJoCo simulator, see the pdf file in the documentation folder.

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