NatNet 4 ROS driver

This is a motion capture system with crazyflie robot.

Requirements

This package is only tested with the Natnet 4.0 and ROS noetic but probably will work with the older versions of both as well.

Crazyflie Mocap Pipeline

Natnet ROS was used as part of crazyflie drone position tracking & broadcasting in 3D. A lander was created whose position was also tracked by the mocap with sufficient accuracy. The Windows PC and the Ubuntu PC need to be connected to the same LAN, so, the Ubuntu PC needs a wired connection to the LAN to get the position stream from the Windows computer. Also, after the Wired connection, some settings of the wired connection need to be changed.

Setup Motiv

This package contains a ROS driver for the NatNet protocol used by the OptiTrack motion capture system. It supports NatNet versions 4.0 (Motive 2.2 and higher). The NatNet SDK provided by the optitrack can be found here. It will be downloaded under deps/NatnetSDK while building it for the first time. NatNet protocol is used for streaming live motion capture data (rigid bodies, skeletons etc) across the shared network.

Current Features:

• Stable and with more functionality than mocap_optitrack
• Rigid bodies are published as geometry_msgs/PoseStamped under name given in the Motive, i.e /natnet_ros/<body-name>/pose. Plus those are also broadcasting as tf frame for rviz
• Markers of the rigid bodies are published ad geometry_msgs/PointStamped unuder the name /natnet_ros/<body-name>/marker#/pose
• Unlabeled markers with the initial position and the name mentione in the /config/initiate.yamlare published as geometry_msgs/PoseStamped unuder the name /natnet_ros/<name-in-config-file>/pose. Plus those are also broadcasting as tf frame for rviz. The marker position is updated based on Iterative closest point (nearest neighbour)
• Unlabled markers can be also published as sensor_msgs/PointCloud
• Different options for publishing and logging the data

Build the package

Install the requirements:

sudo apt install -y ros-$ROS_DISTRO-tf2* wget

Build the package:

cd ~/catkin_ws/src
git clone https://github.com/L2S-lab/natnet_ros_cpp
cd ..
catkin_build  
source devel/setup.bash
roslaunch natnet_ros_cpp natnet_ros.launch

Setup the Motive for this package

• Disable the firewall for the network on which the data is being published.
• Open the Motive app.
• In the motive app, open the streaming panel.
• Disable the other streaming Engines like VRPN, Trackd etc.
• Under the OptiTrack Streaming Engine, turn on the Broadcast Frame.
• Select the correct IP address in the Local Interface.
• Select the Up Axis as Z.

Here is an example of how your streaming settings should look.

Understanding the launch file

Launch file natnet_ros.launch contains the several configurable arguments. The details are mentioned in the launch file. Following are several important argument for the connection and the data transfer. Other connection arguments are for the advanced option.

• serverIP : The IP address of the host PC. (The one selected in the Local Interface in Motive app)
• clientIP : The IP address of the PC on which the file will be launched
• serverType : Two possible options, multicast and unicast

Publishing the single marker

It is possible to track the single marker as a rigid body with constant orientation. Go to the config/initiate.yaml It is suggested to make a copy of the file and rename the new file. The file contains the details on what to modify.

The question might arise on how to check the position of the single marker. For that, you can log the frames of the incoming data in the terminal. To do so, enable the log_frames in the launch file.

After configuring the initiate.yaml, in the launch file, enable the pub_individual_marker. Change the name of the config file in the argument conf_file if needed and launch the file.

Replacing existing package

You can easily replace the current package with this package. In the natnet_ros.launch change the name of node to the node you currently using. For an example, If you are using the vrpn_client_node changes are following

<node pkg="natnet_ros_cpp" type="natnet_ros_cpp" name="vrpn_client_node" output="screen" >   

Resources

• Data Streaming [website]
• mocap4ros2-setup [website]