Code Overview for AIM 2024 software stack
A line follower project for NXP MR-B3RB (Mobile Robotics Buggy 3 Rev B) for participants of AIM 2024.
HARDWARE
This software can run on the B3RB and Gazebo Simulator.
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.
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.
Understanding the B3RB ROS LINE FOLLOWER
_**~/congnipilot/cranium/src/b3rb_ros_line_follower**_ is the only folder that the participants have to modify an submit for the Regional Finale
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.
Communication between ROS-2 nodes
The below diagram depicts how various essential ROS-2 nodes are communicating with each other:
In above graph:
The ovals are the nodes.
The rectangles are the topics.
The outer rectangles are namespaces of the topics.
The arrows represent publishers and subscriptions of nodes.
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