Introduction

This ros package is used to read mocap pose from vrpn and send the pose data to px4 flight controller through mavros at a frequency of 60Hz.

Note!!!

This package is default for motion capture vrpn system with distance unit 'm'. For systems with distance unit 'mm', you should change the mocap_unit into "mm" in mocap2px4.launch.

Build:

This ros package should be built on the onboard computer of the drone.

git clone https://gitee.com/shu-peixuan/px4mocap.git
cd px4mocap/
catkin_make
source devel/setup.bash

Please install or update vrpn client to the newest version like (melodic for ubuntu18 and noetic for ubuntu20):

sudo apt install ros-melodic-vrpn-client-ros

If you have not installed mavros, then you can follow the command in ./ROS-install-command to install mavros first (melodic for ubuntu18 and noetic for ubuntu20):

sudo apt install ros-melodic-mavros ros-melodic-mavros-extras -y

cd ROS-install-command

sudo chmod +x install_geographiclib_datasets.sh

sudo ./install_geographiclib_datasets.sh

Launch:

To launch the px4mocap, please connect to the same WIFI with mocap server. Change the fcu_url (onboard computer port), gcs_url (QGroundControl IP), server IP (motion capture system vrpn IP) and desired rigidpose_topic (vrpn rigid body pose topic) in mocap2px4.launch. Then

roslaunch px4mocap mocap2px4.launch

Then the xyz position and yaw angle (quaternion) will be sent to px4 flight controller(pixhawk).

Or you can use the shell script to launch quickly:

cd src/px4mocap/launch
# change the `source` path in mocap2px4.sh first
./mocap2px4.sh

Similarly, you can launch mavros.launch|mavros.sh and vrpn2mavros.launch|vrpn2mavros.sh separately in your need.

Result:

Remember to check that the mocap pose data were transferred to the pixhawk properly:

rostopic echo /mavros/vision_pose/pose
rostopic echo /mavros/local_position/pose

Note that rostopic echo is cpu and RAM consuming. Do not keep rostopic echo on resource-limited onboard computer like raspberrypi.

Attention:

Be sure to properly set EKF2_AID_MASK (EKF2_EV_CTRL in px4 v1.14.0 and newer version) and EKF2_HGT_REF parameters of PX4 on QgroundControl to receive these pose messages.

Be sure to align body x axis to the heading of the drone when creating rigid body in Seeker(mocap software). Otherwise, the yaw angle calculated by mocap system will not be the angle from world x to the heading of the drone(Mavros use ENU world frame and FLU body frame).

Auto Start:

Furthur more, you can set mavros or vrpn2mavros as auto-startup service on boot using systemctl. It is worth noting that these ROS nodes should be launched a few seconds after roscore.service has been launched. Otherwise, if the first ROS node which auto-start roscore by default is shut down occassionally, other ROS nodes will be shut down as well, which is unwanted.

cd px4mocap/src/px4mocap/launch
# change `ExecStart` path in **.service and **.sh first (must use absolute path).
# service文件中不要出现中文和注释！
sudo cp roscore.service /etc/systemd/system/roscore.service
sudo cp mavros.service /etc/systemd/system/mavros.service 
sudo cp vrpn2mavros.service /etc/systemd/system/vrpn2mavros.service 

sudo systemctl enable roscore.service mavros.service vrpn2mavros.service # enable service on boot
sudo systemctl daemon-reload # reload service

# other operations:
sudo systemctl status **.service # echo the output of the service
sudo systemctl disable **.service # disable service on boot
sudo systemctl start **.service # start service once
sudo systemctl stop **.service # stop the active service

Please feel free to ask questions in Issue.

附注

vncserver-command/中附有vnc远程桌面配置说明，ROS-install-command中附有安装ROS、mavros、vrpn等说明，详情请进入对应文件夹浏览。