WallFollow

This wall_follow package contains code for navigation around bridge structures using routines for flight alongside the bridge, flight along a bridge column, etc.

Pre-requisites

• Ubuntu 16.04 + ROS Kinetic + Gazebo 7
• Mavros: ROS node to communicate with PX4 firmware
• PX4 firmware : code for low level UAV flight control (on actual Pixhawk hardware or as software-in-the-loop (SITL) for Gazebo simulation)

The PX4 website contains information and instructions for installing PX4 firmware and Mavros. https://dev.px4.io/en/setup/dev_env_linux.html

The ubuntu_sim_ros_gazebo.sh script from the PX4 website may help install all the above pre-reqs conveniently. Works well on a clean Ubuntu installation on most conventional PCs. Have had issues getting it to work on NVIDIA Jetson, in which case manual installation of the pre-reqs had to be done.

Refer to this document for help regarding PX4 and Mavros and some clarity on software architecture: https://docs.google.com/document/d/1i-lWuEwOOzB-5ZloPOaRV5dGP6J1aeJemh8ISfB3lxE/edit?usp=sharing (Access restricted to those within Virginia Tech)

Dependencies

• Catkin_tools: http://catkin-tools.readthedocs.io/en/latest/installing.html (other catkin build tool will also likely work)
• PCL: http://wiki.ros.org/pcl (likely included in the standard ROS installation)
• Scanse Sweep ROS driver: https://github.com/scanse/sweep-ros.git (Reads data from the Scanse Sweep LIDAR and publishes it as a point cloud; not required for simulation)
• Gazebo models and worlds from this repository: https://github.com/raaslab/sitl_gazebo_wall_follow.git (only required for simulation)

Copy and replace the models and worlds folders under your ~/src/Firmware/Tools/sitl_gazebo with those from the sitl_gazebo_wall_follow repository

Edit ~/src/Firmware/launch/mavros_posix_sitl.launch and ensure the below line to launch the correct WORLD:

<arg name="world" default="$(find mavlink_sitl_gazebo)/worlds/2_wall_new.world"/>

Get Model Working:

Add "rplidar_vert" folder to the location Firmware/Tools/sitl_gazebo/models and replace "rplidar" with the one in this repository. By doing this you change the lidar from a GPU based lidar to a CPU based lidar. The GPU based lidar does not always work correctly and potentially sees through objects, giving incorrect data.

Launch files

Flight beside bridge girder

Simulation: roslaunch wall_follow besideWall_simulation.launch

Real World: roslaunch wall_follow besideWall_real.launch

Flight along a bridge column

Simulation: roslaunch wall_follow columnLoop_simulation.launch

Real World: roslaunch wall_follow columnLoop_real.launch

Nodes

/hor/pc_subscriber

Horizontal point cloud subscriber:

• Processes the horizontal lidar data (filtering + Hough Transform)
• Publishes line(s) that estimate bridge structure

Subscribed topic:

• /hor/pc2 (sensor_msgs/PointCloud2)

Published topic:

• /hor/ho/li (wall_follow/Lines)

/vert/pc_subscriber

Vertical point cloud subscriber:

• Processes the vertical lidar data (filtering + Hough Transform)
• Publishes line(s) that estimate bridge structure

Subscribed topic:

• /vert/pc2 (sensor_msgs/PointCloud2)

Published topic:

• /vert/ho/li (wall_follow/Lines)

/besideWall

Flight alongside the bridge girder:

• Maintains desired distance perpendicular to the girder
• Maintains desired altitude w.r.t the top of the girder
• Contanst fixed velocity parallel to the girder

Subscribed topics:

• /hor/ho/li (wall_follow/Lines)
• /vert/ho/li (wall_follow/Lines)

Published topic:

• /mavros/setpoint_raw/local (mavros_msgs/PositionTarget)

/columnLoop

Flight along a bridge column:

• Maintains desired distance to the column
• Maintains centering w.r.t the column
• Contanst fixed velocity in the vertical direction

Subscribed topics:

• /hor/ho/li (wall_follow/Lines)
• /vert/ho/li (wall_follow/Lines)

Published topic:

• /mavros/setpoint_raw/local (mavros_msgs/PositionTarget)

Parameters:

/besideWall

The parameters in the besideWall_params.yaml file control the flight beside the bridge girder. Please refer to the comments in the yaml file itself for documentation.

/columnLoop

The parameters in the columnLoop_params.yaml file control the flight along a bridge column. Please refer to the comments in the yaml file itself for documentation.

Supporting documentation

• ICRA paper:
• ISER paper:
• Video: https://www.youtube.com/watch?v=DtDk0OMeIXs