Introduction to OptiTrack

Welcome to the world of OptiTrack, where precision meets innovation. As a leading provider of motion capture technology, OptiTrack empowers robotics enthusiasts, researchers, and industry professionals with unparalleled tracking solutions. In today's rapidly evolving robotics landscape, the ability to accurately capture and analyze motion data is crucial for pushing the boundaries of robotic performance. With OptiTrack, users can achieve sub-millimeter accuracy, allowing for precise control and analysis of robotic systems. Our journey with OptiTrack begins here, as we explore the features and capabilities that make it the preferred choice for robotics applications. Join us as we delve into the world of high-precision motion capture and discover how OptiTrack is revolutionizing the field of robotics.

Key Features of OptiTrack

OptiTrack offers a wide range of features designed to meet the diverse needs of robotics professionals. Here are some of the key features that set OptiTrack apart:

• High-Precision Tracking: OptiTrack delivers sub-millimeter accuracy, allowing for precise measurement and analysis of robotic motion.
• Flexible Configurations: Whether indoor or outdoor tracking, OptiTrack offers flexible configurations to suit various environments and applications.
• Real-Time Data Streaming: With OptiTrack, users can stream motion capture data in real-time, enabling instant feedback and control of robotic systems.
• Easy Integration: OptiTrack seamlessly integrates with popular robotics platforms and software tools, making it easy to incorporate motion capture into existing workflows.
• Scalable Solutions: From small-scale research projects to large-scale industrial applications, OptiTrack offers scalable solutions to meet the needs of any project or budget.

Feature Spotlight: Real-Time Humanoid Robot Tracking

One of the standout features of OptiTrack is its capability to perform high-precision, real-time tracking of complex robotic systems, such as the H1 humanoid robot. This feature highlights the robustness and accuracy of the OptiTrack system in dynamic and intricate scenarios.

In this example, the H1 humanoid robot is outfitted with reflective markers on its left and right hands, showcasing OptiTrack's ability to capture detailed and precise movements. The system utilizes high-speed cameras to gather motion data, which is then processed in real-time by the Motive software. This data is streamed over the network to a ROS-enabled PC via the VRPN streaming engine, where it is transformed into ROS TFs, facilitating seamless integration with other ROS nodes and applications.

The accompanying GIFs below illustrate this feature in action. The first GIF shows the real-time movements of the H1 humanoid robot, demonstrating its agility and responsiveness. The second GIF highlights the precision of OptiTrack's motion capture as the robot's movements are tracked in the Motive software. The third GIF provides a visual representation of the robot's movements in RViz, emphasizing the integration capabilities of OptiTrack with ROS-enabled visualization tools.

H1 Humanoid Robot in Real

H1 Humanoid Robot being tracked by OptiTrack in Motive

H1 Humanoid Robot being tracked in RViz by subscribing to Motive data

This example underscores the comprehensive capabilities of OptiTrack in tracking and visualizing humanoid robots, making it an indispensable tool for researchers and developers in the field of robotics.

OptiTrack Setup

Required Equipment for OptiTrack Setup

Welcome to the OptiTrack Setup guide, your gateway to unlocking the full potential of motion capture technology. In this comprehensive walkthrough, we'll guide you through every crucial step to ensure your OptiTrack system is up and running smoothly, delivering unparalleled performance and accuracy.

Hardware Setup

Let's start with the hardware setup of your OptiTrack system, which is essential for optimal performance.

Preparing the Capture Area

For best tracking results, ensure that the capture environment is clean and free from obstructions. Remove unnecessary objects, cover reflective surfaces, and minimize ambient light sources, especially sunlight and other infrared light sources. Consider the layout of your capture area and position the cameras to provide adequate coverage. Pay attention to potential occlusion areas and adjust camera placement accordingly.

Cabling and Load Balancing

Connect your Ethernet camera system to the host PC using PoE switches and Ethernet cables. Ensure that the switches are powered and that the cameras are connected securely. Pay attention to cable quality and distance limitations to avoid data transmission issues. Proper load balancing ensures that data is distributed efficiently across the network to prevent bottlenecks and ensure smooth operation of the system. Consider the number of cameras in your setup and adjust the network configuration accordingly.

Placing and Aiming Cameras

Position your cameras around the capture volume to ensure optimal coverage. Securely mount the cameras onto stable structures such as tripods or truss systems. Ensure that the cameras are positioned at appropriate heights and angles to capture motion data accurately. Aim the cameras to overlap their views around the region where most of the capture will take place. Verify camera focus for accurate tracking results and adjust camera settings as needed. Consider the field of view of each camera and ensure that there are no blind spots or areas with limited coverage. Perform test captures to verify camera placement and adjust as necessary.

Software Setup

Finally, let's complete the software setup to ensure seamless operation of your OptiTrack system.

Host PC Requirements

Check that your host PC meets the minimum system requirements for running Motive. Ensure that the operating system, CPU, RAM, and GPU specifications are compatible with the size of your camera system. Consider the processing power required for real-time tracking and data processing. Optimize system performance by closing unnecessary applications and processes running in the background.

Motive Installation

If you haven't already done so, download and install Motive on your host PC. Follow the installation instructions provided by OptiTrack and ensure that Motive is activated using the USB Security Key. During installation, configure Motive settings according to your specific requirements. Customize user preferences, camera settings, and system configurations to optimize performance and usability.

System Calibration

Proper system calibration is crucial for accurate motion tracking. Follow these steps to ensure your system is calibrated correctly:

1. Masking: Remove or cover any extraneous reflections or unnecessary markers in the capture area. This step helps ensure that only the intended markers are tracked.
2. Wanding: Wave the calibration wand across the capture volume to provide reference points for the system. This step helps the software understand the spatial relationships within the capture area.
3. Solving: The software will use the reference points collected during wanding to calculate the position and orientation of each camera. This step finalizes the calibration process.

Capture Setup

With the system calibrated, you're ready to set up your capture session. Follow these steps to ensure a smooth capture process:

1. Prepare Session Folders: Organize your capture recordings by creating session folders. This practice helps keep your data organized and easily accessible.
2. Define Trackable Assets: In Motive, define the Rigid Bodies and Skeletons that will be tracked. Rigid Bodies represent objects or entities, while Skeletons represent human or animal subjects.
3. Attach Markers: Securely attach markers to the subjects. Proper marker placement is essential for accurate tracking.

OptiTrack (NatNet) Streaming Engine with mocap_optitrack ROS Package

Installation:

This section guides users through the installation process of the mocap_optitrack ROS package. It's essential to ensure that ROS is properly set up on the system before proceeding with package installation. Users are instructed to clone the mocap_optitrack repository from GitHub and then compile it using catkin_make.

  cd $ROS_WORKSPACE/src
  git clone https://github.com/ros-drivers/mocap_optitrack.git
  cd $ROS_WORKSPACE
  catkin_make
  source devel/setup.bash
  

Configuring Motive:

Here, users are walked through the configuration steps within OptiTrack's Motive software. They learn how to activate the NatNet streaming engine and configure the streaming settings to ensure data is properly streamed to the ROS PC. Specific attention is given to selecting the correct Network Interface, activating streaming for rigid bodies, and configuring advanced network settings such as multicast addressing.

1. Open the Data Streaming Pane in Motive by clicking on View -> Data Streaming.
2. Activate the OptiTrack streaming engine by checking the Broadcast Frame Data checkbox in the OptiTrack Streaming Engine group.
3. Select the proper Network Interface by setting the Local Interface to the PC's IP address of the network to which the ROS PC is connected.
4. Set Stream Rigid Bodies to True to activate streaming of rigid bodies.
5. Set Type in Advanced Network Settings to Multicast, specify the command and data ports if necessary, and set the Multicast Interface (default: 239.255.42.99).

Configuring mocap_optitrack:

This section explains how to configure the mocap_optitrack package to work seamlessly with Motive. Users are instructed to edit the configuration file (config/mocap.yaml) to define the rigid bodies to be tracked, their corresponding topics, and TFs. It's emphasized that these settings must match those in Motive, including the multicast address.

  rigid_bodies:
      '1':
          pose: Robot_1/pose
          pose2d: Robot_1/ground_pose
          child_frame_id: Robot_1/base_link
          parent_frame_id: world

  optitrack_config:
          multicast_address: 224.0.0.1
  

The section under rigid_bodies defines all the rigid bodies that will be tracked. Their ID needs to match the User ID defined in the project pane in Motive. pose and pose2d define the topics to which the streamed data will be published. child_frame_id and parent_frame_id define the TF that will be published.

In the optitrack_config section, all necessary information to communicate with Motive will be set. The multicast_address defined here needs to match the Multicast Interface defined in Motive.

Note that the default value for the multicast_address in mocap_optitrack is 224.0.0.1 whereas the default value in Motive for Multicast Interface is 239.255.42.99!

Results:

After completing the configuration, users can launch the mocap_optitrack package and visualize the streamed data in RViz. Use the following command to launch the package:

  roslaunch mocap_optitrack mocap.launch
  rosrun rviz rviz
  

They're informed that ROS nodes will publish topics and TFs containing the motion data received from the OptiTrack system, facilitating further integration into their ROS projects.

Bugs/Problems:

This section highlights a known issue where mocap_optitrack may crash when multiple objects are streamed from Motive. Users are advised to use the latest version of the package or apply any available fixes to resolve this issue.

VRPN Streaming Engine with vrpn-client-ros ROS Package

Installation:

Users are instructed to install the vrpn-client-ros ROS package using the apt-get command. This ensures that the necessary package dependencies are installed on the system. Use the following commands to install the required packages:

  sudo apt-get install ros-kinetic-vrpn

  sudo apt-get install ros-kinetic-vrpn-client-ros
  

Next, clone the repository into your catkin workspace, compile it, and source your setup file:

  cd $ROS_WORKSPACE
  git clone https://github.com/socrob/mocap.git
  catkin build
  source ~/.bashrc
  

Configuring Motive:

The configuration steps for the VRPN streaming engine in Motive are detailed below. Users learn how to activate the engine, set the VRPN broadcast port if necessary, and ensure that object names do not contain whitespaces, which could cause issues during streaming.

1. Turn on the switch and the mocap PC, open Motive, and click calibrate.
2. Start wanding, set the ground plane, and place a marker somewhere in the testbed.
3. Ensure the VRPN streaming engine is activated.
4. Set the VRPN broadcast port if necessary.
5. Ensure that object names do not contain whitespaces.

Configuring vrpn-client-ros:

This section provides guidance on creating a launch file to start the VRPN client for ROS. Users are shown how to specify the server's IP address and configure additional settings such as refresh frequency and TF broadcasting. Here are the commands to launch the VRPN client node:

  roslaunch mbot_mocap mocap.launch
  

Troubleshooting tips are provided for resolving coordinate system mismatches.

Results:

After launching the vrpn-client-ros package, users can visualize the streamed data in RViz. Open RViz, set the fixed frame to map, and add the tf topic. The section emphasizes the importance of noting any coordinate system mismatches and adjusting settings accordingly.

Bugs/Problems:

Potential issues with coordinate system mismatches in RViz when using vrpn-client-ros are addressed here. Users are encouraged to troubleshoot these issues by verifying settings and configurations to ensure smooth data visualization.