OnShape to URDF

Overview

We will be using the onshape-to-robot plugin to read robot model from Onshape, and export them to a urdf file.

GitHub - Rhoban/onshape-to-robot: Converting Onshape assembly to robot definition (URDF, SDF, MuJoCo) through Onshape APIGitHub

Installation

sudo apt install openscad meshlab

pip install onshape-to-robot

Also install ROS2 environment following this guide:

Setting up ROS 2 Humble Hawksbill on Ubuntu

Set up Onshape API access key

Set up an API access key at OnShape developer portal.

Store the API keys in ./scripts/onshape_api_key.sh

# Obtained at https://dev-portal.onshape.com/keys
export ONSHAPE_API=https://cad.onshape.com
export ONSHAPE_ACCESS_KEY=Your_Access_Key
export ONSHAPE_SECRET_KEY=Your_Secret_Key

On every new terminal opened, run

source ./scripts/onshape_api_key.sh

Set up the ROS2 workspace

This procedure only needs to be performed when initially setting up a new workspace and package.

Create the package

mkdir -p ~/Desktop/humanoid-urdf/src
cd ~/Desktop/humanoid-urdf/src
ros2 pkg create --build-type ament_cmake humanoid_v1

Create additional folders

cd ~/Desktop/humanoid-urdf/src/humanoid_v1
mkdir -p config launch maps meshes models params rviz urdf worlds

Test build

cd ~/Desktop/humanoid-urdf
colcon build

If the package is built without error, try the following command.

colcon_cd humanoid_v1

colcon_cd should navigate to our package directory ~/Desktop/humanoid-urdf/src/humanoid_v1

Create Config Files

We need to create these files in the ROS package.

touch ~/Desktop/humanoid-urdf/src/humanoid_v1/launch/humanoid_v1.launch.py

touch ~/Desktop/humanoid-urdf/src/humanoid_v1/rviz/rviz_basic_settings.rviz

touch ~/Desktop/humanoid-urdf/src/humanoid_v1/urdf/robot.urdf.xacro

humanoid_v1.launch.py:

# Author: Addison Sears-Collins
# Date: September 14, 2021
# Description: Launch a robot URDF file using Rviz.
# https://automaticaddison.com

import os
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.conditions import IfCondition, UnlessCondition
from launch.substitutions import Command, LaunchConfiguration
from launch_ros.actions import Node
from launch_ros.substitutions import FindPackageShare

def generate_launch_description():

  # Set the path to this package.
  pkg_share = FindPackageShare(package="humanoid_v1").find("humanoid_v1")

  # Set the path to the RViz configuration settings
  default_rviz_config_path = os.path.join(pkg_share, "rviz/rviz_basic_settings.rviz")

  # Set the path to the URDF file
  default_urdf_model_path = os.path.join(pkg_share, "urdf/robot.urdf.xacro")

  ########### YOU DO NOT NEED TO CHANGE ANYTHING BELOW THIS LINE ##############  
  # Launch configuration variables specific to simulation
  gui = LaunchConfiguration("gui")
  urdf_model = LaunchConfiguration("urdf_model")
  rviz_config_file = LaunchConfiguration("rviz_config_file")
  use_robot_state_pub = LaunchConfiguration("use_robot_state_pub")
  use_rviz = LaunchConfiguration("use_rviz")
  use_sim_time = LaunchConfiguration("use_sim_time")

  # Declare the launch arguments  
  declare_urdf_model_path_cmd = DeclareLaunchArgument(
    name="urdf_model", 
    default_value=default_urdf_model_path, 
    description="Absolute path to robot urdf file")
    
  declare_rviz_config_file_cmd = DeclareLaunchArgument(
    name="rviz_config_file",
    default_value=default_rviz_config_path,
    description="Full path to the RVIZ config file to use")
    
  declare_use_joint_state_publisher_cmd = DeclareLaunchArgument(
    name="gui",
    default_value="True",
    description="Flag to enable joint_state_publisher_gui")
  
  declare_use_robot_state_pub_cmd = DeclareLaunchArgument(
    name="use_robot_state_pub",
    default_value="True",
    description="Whether to start the robot state publisher")

  declare_use_rviz_cmd = DeclareLaunchArgument(
    name="use_rviz",
    default_value="True",
    description="Whether to start RVIZ")
    
  declare_use_sim_time_cmd = DeclareLaunchArgument(
    name="use_sim_time",
    default_value="True",
    description="Use simulation (Gazebo) clock if true")
   
  # Specify the actions

  # Publish the joint state values for the non-fixed joints in the URDF file.
  start_joint_state_publisher_cmd = Node(
    condition=UnlessCondition(gui),
    package="joint_state_publisher",
    executable="joint_state_publisher",
    name="joint_state_publisher")

  # A GUI to manipulate the joint state values
  start_joint_state_publisher_gui_node = Node(
    condition=IfCondition(gui),
    package="joint_state_publisher_gui",
    executable="joint_state_publisher_gui",
    name="joint_state_publisher_gui")

  # Subscribe to the joint states of the robot, and publish the 3D pose of each link.
  start_robot_state_publisher_cmd = Node(
    condition=IfCondition(use_robot_state_pub),
    package="robot_state_publisher",
    executable="robot_state_publisher",
    parameters=[{"use_sim_time": use_sim_time, 
    "robot_description": Command(["xacro ", urdf_model])}],
    arguments=[default_urdf_model_path])

  # Launch RViz
  start_rviz_cmd = Node(
    condition=IfCondition(use_rviz),
    package="rviz2",
    executable="rviz2",
    name="rviz2",
    output="screen",
    arguments=["-d", rviz_config_file])
  
  # Create the launch description and populate
  ld = LaunchDescription()

  # Declare the launch options
  ld.add_action(declare_urdf_model_path_cmd)
  ld.add_action(declare_rviz_config_file_cmd)
  ld.add_action(declare_use_joint_state_publisher_cmd)
  ld.add_action(declare_use_robot_state_pub_cmd)  
  ld.add_action(declare_use_rviz_cmd) 
  ld.add_action(declare_use_sim_time_cmd)

  # Add any actions
  ld.add_action(start_joint_state_publisher_cmd)
  ld.add_action(start_joint_state_publisher_gui_node)
  ld.add_action(start_robot_state_publisher_cmd)
  ld.add_action(start_rviz_cmd)

  return ld

rviz

Panels:
  - Class: rviz_common/Displays
    Help Height: 78
    Name: Displays
    Property Tree Widget:
      Expanded:
        - /Global Options1
        - /Status1
        - /RobotModel1
        - /TF1
        - /TF1/Frames1
      Splitter Ratio: 0.5
    Tree Height: 617
  - Class: rviz_common/Selection
    Name: Selection
  - Class: rviz_common/Tool Properties
    Expanded:
      - /2D Goal Pose1
      - /Publish Point1
    Name: Tool Properties
    Splitter Ratio: 0.5886790156364441
  - Class: rviz_common/Views
    Expanded:
      - /Current View1
    Name: Views
    Splitter Ratio: 0.5
Visualization Manager:
  Class: ""
  Displays:
    - Alpha: 0.5
      Cell Size: 1
      Class: rviz_default_plugins/Grid
      Color: 160; 160; 164
      Enabled: true
      Line Style:
        Line Width: 0.029999999329447746
        Value: Lines
      Name: Grid
      Normal Cell Count: 0
      Offset:
        X: 0
        Y: 0
        Z: 0
      Plane: XY
      Plane Cell Count: 10
      Reference Frame: <Fixed Frame>
      Value: true
    - Alpha: 1
      Class: rviz_default_plugins/RobotModel
      Collision Enabled: false
      Description File: ""
      Description Source: Topic
      Description Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /robot_description
      Enabled: true
      Links:
        All Links Enabled: true
        Expand Joint Details: false
        Expand Link Details: false
        Expand Tree: false
        Link Tree Style: Links in Alphabetic Order
        base_footprint:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        base_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_x_l_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_x_r_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_y_l_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_y_r_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_z_l_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        hip_z_r_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        wheel_1_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        wheel_2:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        front_caster:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
        gps_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        imu_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
        lidar_link:
          Alpha: 1
          Show Axes: false
          Show Trail: false
          Value: true
      Name: RobotModel
      TF Prefix: ""
      Update Interval: 0
      Value: true
      Visual Enabled: true
    - Class: rviz_default_plugins/TF
      Enabled: true
      Frame Timeout: 15
      Frames:
        All Enabled: false
        base_link:
          Value: false
        hip_x_l_link:
          Value: true
        hip_x_r_link:
          Value: true
        front_caster:
          Value: false
        gps_link:
          Value: false
        imu_link:
          Value: false
        lidar_link:
          Value: false
      Marker Scale: 1
      Name: TF
      Show Arrows: false
      Show Axes: true
      Show Names: true
      Tree:
        base_footprint:
          base_link:
            drivewhl_l_link:
              {}
            drivewhl_r_link:
              {}
            front_caster:
              {}
            gps_link:
              {}
            imu_link:
              {}
            lidar_link:
              {}
      Update Interval: 0
      Value: true
  Enabled: true
  Global Options:
    Background Color: 48; 48; 48
    Fixed Frame: base_link
    Frame Rate: 30
  Name: root
  Tools:
    - Class: rviz_default_plugins/Interact
      Hide Inactive Objects: true
    - Class: rviz_default_plugins/MoveCamera
    - Class: rviz_default_plugins/Select
    - Class: rviz_default_plugins/FocusCamera
    - Class: rviz_default_plugins/Measure
      Line color: 128; 128; 0
    - Class: rviz_default_plugins/SetInitialPose
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /initialpose
    - Class: rviz_default_plugins/SetGoal
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /goal_pose
    - Class: rviz_default_plugins/PublishPoint
      Single click: true
      Topic:
        Depth: 5
        Durability Policy: Volatile
        History Policy: Keep Last
        Reliability Policy: Reliable
        Value: /clicked_point
  Transformation:
    Current:
      Class: rviz_default_plugins/TF
  Value: true
  Views:
    Current:
      Class: rviz_default_plugins/Orbit
      Distance: 4.434264183044434
      Enable Stereo Rendering:
        Stereo Eye Separation: 0.05999999865889549
        Stereo Focal Distance: 1
        Swap Stereo Eyes: false
        Value: false
      Focal Point:
        X: 0.31193429231643677
        Y: 0.11948385089635849
        Z: -0.4807402193546295
      Focal Shape Fixed Size: true
      Focal Shape Size: 0.05000000074505806
      Invert Z Axis: false
      Name: Current View
      Near Clip Distance: 0.009999999776482582
      Pitch: 0.490397572517395
      Target Frame: <Fixed Frame>
      Value: Orbit (rviz)
      Yaw: 1.0503965616226196
    Saved: ~
Window Geometry:
  Displays:
    collapsed: false
  Height: 846
  Hide Left Dock: false
  Hide Right Dock: false
  QMainWindow State: 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
  Selection:
    collapsed: false
  Tool Properties:
    collapsed: false
  Views:
    collapsed: false
  Width: 1200
  X: 246
  Y: 77

urdf

<robot name="onshape">

    <link name="base_link">
    </link>
    <joint name="base_anchor_joint" type="fixed">
      <parent link="base_link"/>
      <child link="body_1_link"/>
    </joint>
    <link name="body_1_link">
        <visual>
            <origin xyz="0 0 0" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/body.stl" />
            </geometry>
            <material name="body_material">
                <color rgba="0.8 0.8 0.8 1.0" />
            </material>
        </visual>
        <collision>
            <origin xyz="0 0 0" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/body.stl" />
            </geometry>
            <material name="body_material">
                <color rgba="0.8 0.8 0.8 1.0" />
            </material>
        </collision>
        <inertial>
            <origin xyz="0.0375 0.0253843 0.0225241" rpy="0 0 0" />
            <mass value="2.23874" />
            <inertia ixx="0.00206023" ixy="4.48497e-10" ixz="6.47006e-11" iyy="0.00150691"
                iyz="-0.00028761" izz="0.00254354" />
        </inertial>
    </link>

    <link name="wheel_1_link">
        <visual>
            <origin xyz="0.02 -0.0325 -0.025" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/wheel.stl" />
            </geometry>
            <material name="wheel_material">
                <color rgba="0.262745 0.282353 0.301961 1.0" />
            </material>
        </visual>
        <collision>
            <origin xyz="0.02 -0.0325 -0.025" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/wheel.stl" />
            </geometry>
            <material name="wheel_material">
                <color rgba="0.262745 0.282353 0.301961 1.0" />
            </material>
        </collision>
        <inertial>
            <origin xyz="0.004 0 -3.46945e-18" rpy="0 0 0" />
            <mass value="0.335419" />
            <inertia ixx="0.000345298" ixy="0" ixz="0" iyy="0.000174367" iyz="0" izz="0.000174367" />
        </inertial>
    </link>

    <joint name="wheel_1_joint" type="revolute">
        <origin xyz="-0.02 0.0325 0.025" rpy="0 -0 0" />
        <parent link="body_1_link" />
        <child link="wheel_1_link" />
        <axis xyz="-1 0 0" />
        <limit upper="1.0472" lower="-1.0472" effort="20" velocity="10.0"/>
    </joint>

    <link name="wheel_2">
        <visual>
            <origin xyz="0.012 -0.0325 -0.025" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/wheel.stl" />
            </geometry>
            <material name="wheel_material">
                <color rgba="0.262745 0.282353 0.301961 1.0" />
            </material>
        </visual>
        <collision>
            <origin xyz="0.012 -0.0325 -0.025" rpy="0 -0 0" />
            <geometry>
                <mesh filename="package://biped_v1/meshes/wheel.stl" />
            </geometry>
            <material name="wheel_material">
                <color rgba="0.262745 0.282353 0.301961 1.0" />
            </material>
        </collision>
        <inertial>
            <origin xyz="-0.004 6.93889e-18 -3.46945e-18" rpy="0 0 0" />
            <mass value="0.335419" />
            <inertia ixx="0.000345298" ixy="0" ixz="0" iyy="0.000174367" iyz="0" izz="0.000174367" />
        </inertial>
    </link>

    <joint name="wheel2_speed" type="revolute">
        <origin xyz="0.095 0.0325 0.025" rpy="0 -0 0" />
        <parent link="body_1_link" />
        <child link="wheel_2" />
        <axis xyz="-1 -0 -0" />
        <joint_properties friction="0.0" />
        <limit upper="1.0472" lower="-1.0472" effort="20" velocity="10.0"/>
    </joint>

    <link name="wheel3_link">
        <inertial>
          <mass value="0.9"/>
          <origin xyz="0 0 0"/>
          <inertia ixx=".004" ixy="1.445e-11" ixz="-1.922e-4" iyy="0.004" iyz="1.954e-11" izz="2.696e-4"/>
        </inertial>
      </link>
      <joint name="wheel3_joint" type="revolute">
        <parent link="body_1_link"/>
        <child link="wheel3_link"/>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <dynamics damping="0.01" friction="0.1"/>
        <limit upper="1.0472" lower="-1.0472" effort="20" velocity="10.0"/>
        <axis xyz="1 0 0"/>
      </joint>
</robot>
    

Change Files

Change package.xml by adding these lines:

  <buildtool_depend>ament_cmake</buildtool_depend>

<!-- insert the following lines -->
  <exec_depend>joint_state_publisher</exec_depend>
  <exec_depend>robot_state_publisher</exec_depend>
  <exec_depend>rviz</exec_depend>
  <exec_depend>xacro</exec_depend>
<!-- end of insertion -->

  <test_depend>ament_lint_auto</test_depend>
  <test_depend>ament_lint_common</test_depend>

Change CMakeLists.txt by adding these lines:

# find_package(<dependency> REQUIRED)

# insert the following lines
install(
  DIRECTORY config launch maps meshes models params rviz src urdf worlds
  DESTINATION share/${PROJECT_NAME}
)
# end of insertion

if(BUILD_TESTING)

Test Build

make ros-build

colcon build

source install/setup.sh

ros2 launch humanoid_v1 humanoid_v1.launch.py

If the following error is raised, we need to install the gui package separately, suggested here.

[ERROR] [launch]: Caught exception in launch (see debug for traceback): "package 'joint_state_publisher_gui' not found, searching: ['/home/tk/Desktop/humanoid-urdf/install/humanoid_v1', '/opt/ros/humble']"

sudo apt install ros-humble-joint-state-publisher-gui

might also need

sudo apt install ros-humble-xacro

if running into this error:

[rviz2-3] /opt/ros/humble/lib/rviz2/rviz2: symbol lookup error: /snap/core20/current/lib/x86_64-linux-gnu/libpthread.so.0: undefined symbol: __libc_pthread_init, version GLIBC_PRIVATE
[ERROR] [rviz2-3]: process has died [pid 8882, exit code 127, cmd '/opt/ros/humble/lib/rviz2/rviz2 -d /home/tk/Desktop/humanoid-urdf/install/humanoid_v1/share/humanoid_v1/rviz/rviz_basic_settings.rviz --ros-args -r __node:=rviz2'].
[joint_state_publisher_gui-1] /usr/bin/python3: symbol lookup error: /snap/core20/current/lib/x86_64-linux-gnu/libpthread.so.0: undefined symbol: __libc_pthread_init, version GLIBC_PRIVATE
[ERROR] [joint_state_publisher_gui-1]: process has died [pid 8878, exit code 127, cmd '/opt/ros/humble/lib/joint_state_publisher_gui/joint_state_publisher_gui --ros-args -r __node:=joint_state_publisher_gui'].

highly possible that this is a VSCode terminal issue. Do

unset GTK_PATH

Onshape Modeling Considerations

When making mate connections, always click child component first, and then parent. (bind child to parent).

By doing so, the order of the mate connectors should look like the one shown in the following diagram.

Export Onshape robot

make urdf-build

This command will dump the urdf and related asset files in ./onshape/humanoid_v1 directory, and automatically copy the necessary files to the ROS2 package.

To clear the previous build, run

make urdf-clean

onshape-to-robot humanoid_v1

Change the exported urdf

For exported urdf, we need to make several changes

1. Add base_link

<link name="base_link">
</link>
<joint name="base_anchor_joint" type="fixed">
<parent link="base_link"/>
<child link="body_1"/>
</joint>

2. Change mesh path setting

package://mesh.stl -> package://humanoid_v1/meshes/mesh.stl

3. Add position limit

4. Collision

% scale(1000) import("extrusion_100mm.stl");

translate([65, 0, 0])
cube([20, 100, 20], center=true);

Build

To force refresh the static files, do

rm -rf ~/Desktop/humanoid-urdf/install/humanoid_v1/share/

and then

colcon build && ros2 launch humanoid_v1 humanoid_v1.launch.py

sudo apt install openscad

onshape-to-robot-edit-shape