Obstacle Avoidance

Key features

• This code uses the RRT*-algorithm for collision avoidance at a fixed altitude
• 3D obstacle detection using the Intel D435 camera
• redirecting the UAV onto the predefined mission path (ideal for photogrammetry missions)
• paths smoothing
• uses octomap for obstacle mapping

Note: Collision prevention at a cruise velocity of 6 m/s.

Note: Collision avoidance at a cruise velocity of 6 m/s.

Blue line: followed path Green line: alternative suggested path

Instructions

Getting Started

See also:

• Paper: Utilizing the RRT*-Algorithm for Collision Avoidance in UAV Photogrammetry Missions
• Gazebo and ROS setup

Add to .bashrc:

Note: Your catkin workspace is assumed to be in ~/catkin_ws.

• export GAZEBO_MODEL_PATH=$GAZEBO_MODEL_PATH:~/catkin_ws/src/px4_rrt_avoidance/include/gazebo_models

QGC (QGroundControl): \

• set parameter COM_OBS_AVOID = 1
• select mission mode

Recommendations

• We recommend testing the code in the safe simulation software Gazebo

Run RRT-Star collision avoidance simulation

run the following commands:

• roslaunch px4_rrt_avoidance iris_depth.launch
• rosrun px4_rrt_avoidance Master_node.py

To-Do's:

• [ ] Some topics/msg can be changed into services
• [ ] Create ROS-parameters to adjust the basic variables
• [ ] Before take-off: obstacle must be visible otherwise /projected_map is not being published
• [ ] When altitude is not correct: mapping error (ground detected as obstacle)
• [ ] Obstacle avoidance below 5 meters ignored (ground mapping issue)
• [ ] Drone stops at the end of mission: changes yaw angle to zero (EAST)
• [ ] New ROS-parameter: change distance for incremental WP's
• [ ] Sequential start of the master node
• [ ] Solely allow flight direction to be within the visual field of view
• [ ] Huge obstacle (e.g., building): incremental WP lays within a free cell of the grid map, but can't be reached -- create a service when the map has reached the maximum number of iterations and RRT* still can't find a solution to skip this WP