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Pose-Estimation-Demo Tutorial: Troubleshooting

Table of Contents

Part 1: Create a Unity Scene with an Imported URDF

Package Installation

  • If you are receiving a [Package Manager Window] Unable to add package ... xcrun: error: invalid developer path..., you may need to install the Command Line Tools package for macOS via xcode-select --install.
  • If receiving [Package Manager] Done resolving packages in ... seconds ... An error occurred while resolving packages: Project has invalid dependencies: ... Error when executing git command. fatal: update_ref failed for ref 'HEAD': cannot update ref 'refs/heads/master' or similar git-related Package Manger errors, please note that this is a known issue that is being tracked on the Issue Tracker. The current workaround is to use a lightweight tag for the git URLs, i.e. https://github.com/...#v0.2.0-light. This workaround is reflected in the current version of the tutorial.

Assets, Materials

  • Upon import, the cube and floor materials may appear to be bright pink (i.e. missing texture).

    • Cube: Go to Assets/TutorialAssets/Materials. Select the AlphabetCubeMaterial. There is a section called Surface Inputs. If the Base Map is not assigned, select the circle next to this field. Click on it and start typing NonsymmetricCubeTexture and select it when it appears. Apply this updated AlphabetCubeMaterial to the Cube. Your Inspector view of the Material should look like the following:
    • Floor: Assign the NavyFloor material to the Floor object.

  • If all of the project materials appear to have missing textures, ensure you have created the project using the Universal Render Pipeline.

  • If the UR3 arm's base has some missing textures (e.g. pink ovals), in the Project window, navigate to Assets/TutorialAssets/URDFs/ur3_with_gripper/ur_description/meshes/ur3/visual >base.dae. Select the base, and in the Inspector window, open the Materials tab. If the Material_001 and _002 fields are blank, assign them to Assets/TutorialAssets/URDFs/ ur3_with_gripper/ur_description/Materials/Material_001 and _002, respectively.

URDF Importer

  • If you are not seeing Import Robot from URDF in the Assets menu, check the Console for compile errors. The project must compile correctly before the editor tools become available.

  • If the robot appears loose/wiggly or is not moving with no console errors, ensure on the Controller script of the ur3_with_gripper that the Stiffness is 10000, the Damping is 1000 and the Force Limit is 1000.

  • Note that the world-space origin of the robot is defined in its URDF file. In this sample, we have assigned it to sit on top of the table, which is at (0, 0.77, 0) in Unity coordinates. Moving the robot from its root position in Unity will require a change to its URDF definition.

    <joint name="joint_world" type="fixed">
    <parent link="world" />
        <child link="base_link" />
    <origin rpy="0.0 0.0 0.0" xyz="0.0 0.0 0.77"/>
</joint>

    Note: Going from Unity world space to ROS world space requires a conversion. Unity's (x,y,z) is equivalent to the ROS (z,-x,y) coordinate.

Part 3: Data Collection and model training

Docker, Environment

  • If you are using a Docker container to train your model but it is killed shortly after starting, you may need to increase the memory allocated to Docker. In the Docker Dashboard, navigate to Settings (via the gear icon) > Resources. The suggested minimum memory is 4.00 GB, but you may need to modify this for your particular needs.
  • If you encounter errors installing Pytorch via the instructed pip3 command, try the following instead: 
    sudo pip3 install rospkg numpy jsonpickle scipy easydict torch==1.7.1 torchvision==0.8.2 torchaudio==0.7.2 -f https://download.pytorch.org/whl/torch_stable.html

Part 4: Pick-and-Place

Running the Pick-and-Place task

  • Error processing request: invalid load key... This has most likely occurred due to the downloaded model's .tar file being corrupted, e.g. caused by an unstable connection, or otherwise interrupted download process. Please try redownloading the UR3_single_cube_model.tar file and try the process again.

Unity Scene

  • The buttons might appear oversized compared to the rest of the objects in the scene view, this is a normal behavior. If you zoom out from the table you should see something similar to the following:

Docker, ROS-TCP Connection

  • Building the Docker image may throw an Could not find a package configuration file provided by... exception if one or more of the directories in ROS/ appears empty. This project uses Git Submodules to grab the ROS package dependencies. If you cloned the project and forgot to use --recurse-submodules, or if any submodule in this directory doesn't have content, you can run the git submodule update --init --recursive to grab the Git submodules.
  • ...failed because unknown error handler name 'rosmsg' This is due to a bug in an outdated package version. Try running sudo apt-get update && sudo apt-get upgrade to upgrade packages.
  • Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running? The system-independent docker info command can verify whether or not Docker is running. This command will throw a Server: ERROR if the Docker daemon is not currently running, and will print the appropriate system-wide information otherwise.
  • Occasionally, not having enough memory allocated to the Docker container can cause the server_endpoint to fail. This may cause unexpected behavior during the pick-and-place task, such as constantly predicting the same pose. If this occurs, check your Docker settings. You may need to increase the Memory to 8GB.
    • This can be found in Docker Desktop settings, under the gear icon.
  • Exception Raised: unpack requires a buffer of 4 bytes: This may be caused by a mismatch in the expected Service Request formatting. Ensure that the srv definition matches the generated C# script, and that you have not modified these files since the last push to your ROS workspace.

ROS Workspace

  • If the catkin_make command is failing, ensure you are specifying which packages to build (i.e. catkin_make -DCATKIN_WHITELIST_PACKAGES="moveit_msgs;ros_tcp_endpoint;ur3_moveit;robotiq_2f_140_gripper_visualization;ur_description;ur_gazebo").
    • If the problem persists, add the -j1 flag to the catkin_make command.

Ubuntu

  • Running Unity and Docker on Ubuntu may throw a System.Net.SocketException: Address already in use error when using the loopback address. If this is the case, in your Unity Editor, under Robotics > ROS Settings, leave the Override Unity IP Address blank to let Unity automatically determine the address. Change the ROS IP Address to the IP of your Docker container, most likely 172.17.0.X. You may need to modify these settings based on your unique network setup.