airsim_ros_pkgs.md

airsim_ros_pkgs

A ROS wrapper over the AirSim C++ client library.

Setup

• Ubuntu 16.04

  • Install ROS kinetic

• Ubuntu 18.04

  • Install ROS melodic

Build

• Build AirSim

git clone https://github.com/Microsoft/AirSim.git;
cd AirSim;
./setup.sh;
./build.sh;

• Build ROS package

cd ros;
catkin_make; # or catkin build

Running

source devel/setup.bash;
roslaunch airsim_ros_pkgs airsim_node.launch;
roslaunch airsim_ros_pkgs rviz.launch;

Using AirSim ROS wrapper

The ROS wrapper is composed of two ROS nodes - the first is a wrapper over AirSim's multirotor C++ client library, and the second is a simple PD position controller.
Let's look at the ROS API for both nodes:

AirSim ROS Wrapper Node

Publishers:

• /airsim_node/origin_geo_point airsim_ros_pkgs/GPSYaw
  GPS coordinates corresponding to global NED frame. This is set in the airsim's settings.json file under the OriginGeopoint key.

• /airsim_node/VEHICLE_NAME/global_gps sensor_msgs/NavSatFix
  This the current GPS coordinates of the drone in airsim.

• /airsim_node/VEHICLE_NAME/odom_local_ned nav_msgs/Odometry
  Odometry in NED frame wrt take-off point.

• /airsim_node/VEHICLE_NAME/CAMERA_NAME/IMAGE_TYPE/camera_info sensor_msgs/CameraInfo

• /airsim_node/VEHICLE_NAME/CAMERA_NAME/IMAGE_TYPE sensor_msgs/Image
  RGB or float image depending on image type requested in settings.json.

• /tf tf2_msgs/TFMessage

Subscribers:

• /airsim_node/vel_cmd_body_frame airsim_ros_pkgs/VelCmd
  Ignore vehicle_name field, leave it to blank. We will use vehicle_name in future for multiple drones.

• /airsim_node/vel_cmd_world_frame airsim_ros_pkgs/VelCmd
  Ignore vehicle_name field, leave it to blank. We will use vehicle_name in future for multiple drones.

• /gimbal_angle_euler_cmd airsim_ros_pkgs/GimbalAngleEulerCmd
  Gimbal set point in euler angles.

• /gimbal_angle_quat_cmd airsim_ros_pkgs/GimbalAngleQuatCmd
  Gimbal set point in quaternion.

Services:

• /airsim_node/VEHICLE_NAME/land airsim_ros_pkgs/Takeoff

• /airsim_node/takeoff airsim_ros_pkgs/Takeoff

• /airsim_node/reset airsim_ros_pkgs/Reset Resets all drones

Parameters:

• /airsim_node/update_airsim_control_every_n_sec [double]
  Set in: $(airsim_ros_pkgs)/launch/airsim_node.launch
  Default: 0.01 seconds.
  Timer callback frequency for updating drone odom and state from airsim, and sending in control commands.
  The current RPClib interface to unreal engine maxes out at 50 Hz.
  Timer callbacks in ROS run at maximum rate possible, so it's best to not touch this parameter.

• /airsim_node/update_airsim_img_response_every_n_sec [double]
  Set in: $(airsim_ros_pkgs)/launch/airsim_node.launch
  Default: 0.01 seconds.
  Timer callback frequency for receiving images from all cameras in airsim.
  The speed will depend on number of images requested and their resolution.
  Timer callbacks in ROS run at maximum rate possible, so it's best to not touch this parameter.

Simple PID Position Controller Node

Parameters:

• PD controller parameters:

  • /pd_position_node/kd_x [double],
    /pd_position_node/kp_y [double],
    /pd_position_node/kp_z [double],
    /pd_position_node/kp_yaw [double]
    Proportional gains

  • /pd_position_node/kd_x [double],
    /pd_position_node/kd_y [double],
    /pd_position_node/kd_z [double],
    /pd_position_node/kd_yaw [double]
    Derivative gains

  • /pd_position_node/reached_thresh_xyz [double]
    Threshold euler distance (meters) from current position to setpoint position

  • /pd_position_node/reached_yaw_degrees [double]
    Threshold yaw distance (degrees) from current position to setpoint position

• /pd_position_node/update_control_every_n_sec [double]
  Default: 0.01 seconds

Services:

• /airsim_node/VEHICLE_NAME/gps_goal [Request: srv/SetGPSPosition]
  Target gps position + yaw.
  In absolute altitude.

• /airsim_node/VEHICLE_NAME/local_position_goal [Request: srv/SetLocalPosition
  Target local position + yaw in global NED frame.

Subscribers:

• /airsim_node/origin_geo_point airsim_ros_pkgs/GPSYaw
  Listens to home geo coordinates published by airsim_node.

• /airsim_node/VEHICLE_NAME/odom_local_ned nav_msgs/Odometry
  Listens to odometry published by airsim_node

Publishers:

• /vel_cmd_world_frame airsim_ros_pkgs/VelCmd
  Sends velocity command to airsim_node

Global params

• Dynamic constraints. These can be changed in dynamic_constraints.launch:

  • /max_vel_horz_abs [double]
    Maximum horizontal velocity of the drone (meters/second)

  • /max_vel_vert_abs [double]
    Maximum vertical velocity of the drone (meters/second)

  • /max_yaw_rate_degree [double]
    Maximum yaw rate (degrees/second)

Misc

Windows Subsytem for Linux on Windows 10

• WSL setup:

  • Get Windows Subsystem for Linux
  • Get Ubuntu 16.04 or Ubuntu 18.04
  • Go to Ubuntu 16 / 18 instructions!

• Setup for X apps (like RViz, rqt_image_view, terminator) in Windows + WSL

  • Install Xming X Server.
  • Find and run XLaunch from the Windows start menu.
    Select Multiple Windows in first popup, Start no client in second popup, only Clipboard in third popup. Do not select Native Opengl.
  • Open Ubuntu 16.04 / 18.04 session by typing Ubuntu 16.04 / Ubuntu 18.04 in Windows start menu.
  • Recommended: Install terminator : $ sudo apt-get install terminator.
    • You can open terminator in a new window by entering $ DISPLAY=:0 terminator -u.