B3RB ROS LINE FOLLOWER

INTRODUCTION

A line follower project for NXP MR-B3RB (Mobile Robotics Buggy 3 Rev B) for participants of AIM 2024.

• This project provides a framework for an autonomous driving application. (See description below)

HARDWARE

This software can run on the B3RB and Gazebo Simulator.

1. NXP MR-B3RB: The actual hardware rover made by NXP.
2. Gazebo Simulator: Development and testing environment used for B3RB.
   • It's used to simulate the B3RB with it's various sensors and capabilities.
   • It's used to simulate the track with it's various challenges and obstacles.

SOFTWARE

This project is based on the autopilot project - CogniPilot (AIRY Release for B3RB).

• Refer the CogniPilot AIRY Dev Guide for information about it's various components.
• Cranium: A ROS workspace that performs higher level computation for CogniPilot.
  • On the hardware B3RB, it runs on NavQPlus board (Mission Computer).
  • On the Gazebo Simulator, it runs on the Ubuntu Linux machine.
• This project includes a ROS2 Python package that integrates into the Cranium workspace.
  • This project (b3rb_ros_line_follower) should be moved to ~/cognipilot/cranium/src.
  • This is the only folder that participants would modify and submit for the regional finale.

DESCRIPTION

This project contains three python scripts which provide a framework for a line follower application.

• b3rb_ros_edge_vectors: It creates vectors on the edges of the road in front of the rover.
  • The image captured from the front camera is used for detecting edges of the road.
  • Cases based on number of vectors created:
    • 0: When neither left or right edge of the road is detected.
    • 1: When only 1 out of left or right edge of the road is detected.
    • 2: When both left and right edge of the road are detected.
      • Both the vectors's mid-point can't lie in either the left or right half.
      • One vector must lie in the left half and the other must lie in the right half.
  • The vectors are published to the topic "/edge_vectors".
    • Message type: "~/cognipilot/cranium/src/synapse_msgs/msg/EdgeVectors.msg".
  • We assume the part of road that is very close to the rover is relevant for decision making.
    • Hence, only the bottom 40% of the image is analyzed for edges of the road.
      • This threshold could be modified by changing the value of lower_image_height.
    • Hence, the y-coordinates of the vectors ∈ [40% of image height, image height].
  • Please feel free to modify this file if you feel that would improve the vector creation.
• b3rb_ros_line_follower: Contains framework for running the rover using edge vectors.
  • Write your code in the "edge_vectors_callback" function for line follower application.
    • This callback is called whenever a new set of vectors are published on "/edge_vectors".
  • Utilize "rover_move_manual_mode" for moving the rover. Refer its docstring for explanation.
  • Write your code in the "lidar_callback" function for obstacle avoidance and ramp detection.
    • This callback is called whenever a new set of data is published on "/scan".
  • Please note that this file contains a generic implementation of line follower functionality.
    • You are allowed to modify or implement a different method to improve performance.
• b3rb_ros_object_recog: Contains framework for recognizing objects on the track.
  • Write your code in the "camera_image_callback" function.

EXECUTION STEPS

Follow - https://airy.cognipilot.org/getting_started/install/.

Move "b3rb_ros_line_follower" to "~/cognipilot/cranium/src/".

Open a terminal and follow the following steps to setup Cranium.

cd ~/cognipilot/cranium/src/
rm -rf dream_world
rm -rf synapse_msgs

git clone git@github.com:NXPHoverGames/dream_world.git
git clone git@github.com:NXPHoverGames/synapse_msgs.git

cd ~/cognipilot/cranium/src/dream_world
git checkout aim_track

cd ~/cognipilot/cranium/src/synapse_msgs
git checkout b3rb_ros_line_follower

Open a terminal and follow the following steps for building Cranium and running Gazebo Simulation.

cd ~/cognipilot/cranium/
colcon build
ros2 launch b3rb_gz_bringup sil.launch.py world:=<track_name>

Open a terminal and follow the following steps for running b3rb_ros_edge_vectors.

source ~/cognipilot/cranium/install/setup.bash
ros2 run b3rb_ros_line_follower vectors

Open a terminal and follow the following steps for running b3rb_ros_object_recog.

source ~/cognipilot/cranium/install/setup.bash
ros2 run b3rb_ros_line_follower detect

Open a terminal and follow the following steps for running b3rb_ros_line_follower.

source ~/cognipilot/cranium/install/setup.bash
ros2 run b3rb_ros_line_follower runner

LIMITATIONS

• The track width should be 3.5 to 4.0 times that of the rover.
• At the start, the rover should be inside the road and in the middle.
• Intersections and forks should be detected using machine learning.
  • There should be road signs telling the rover which path to take.
• The rover should stop by detecting the STOP sign at the finish line.
  • The participants need to implement the ML model for detecting stop signs.
  • Alternatively, the rover could be stopped by terminating runner manually.
• Obstacles, bumps, ramps on the track need to be handled by the participants.
• TODO: This project needs to be tested on the hardware track when available.