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Code Overview

This is a run-down of what our code does. The project repo may look daunting, but half of it is just configurations and boilerplate. I promise its not as complicated as it looks!

ROS2

The core of our boat runs on ROS2. This is standard for most robotics applications in industry.

Why ROS?

ROS provides many benefits:

  • It handles the parallelization of code, which means you can utilize your entire CPU.
  • It makes code independent. This lets you test individual nodes and scale easier.
  • It standardizes how code communicates. This lets you swap out a sensor or rewrite code without causing bugs in other parts of the code.
  • And it provides a lot of supporting libraries

What is ROS?

The foundation of ROS relies on a network of independent Nodes. These often represent a physical sensor or motor, but they also apply to anything you would write a Class or Object for.

To communicate between nodes, ROS uses topics. This is essentially like a group chat where nodes can talk on or listen to messages from other nodes. To speak on a topic, you create a publisher. Then, you can write whatever messages you want to a topic. To listen to a topic, you create a subscriber. Any messages that are published onto a topic are broadcasted to ALL subscribers listening on that topic. It's important that each topic uses a single standard message type, like a String, Float32, or a custom message type you define.

Whenever a message is broadcasted, the subscribers will run a callback function. A callback function is just a function that is executed whenever a specific event happens. For example, pressing the 'A' key on a keyboard might run a_pressed_callback(), which would execute whatever code is defined in the function. ROS also uses callbacks for when a certain time has passed, called timers. This is useful for setting up sensors to publish data every so often.

Contextualizing ROS:

  • Each Node is like a user
  • All Nodes can join specfic 'group chats' called topics, which are identified by a topic name like "/sensors/windvane/angle"
  • Nodes can send and receive messages on that topic, following the same language as defined in the message type
  • Whenever a message is received by a Node, it executes a defined callback function

Sensors/Controls

Scripts which interface with the mechanical parts of the boat. Virtual versions of each sensor exist for debugging with fake values.

  • GPS - boat position
  • compass - boat heading
  • windvane - wind direction
  • camera - RGB optical camera
  • cameraServos - pitch and yaw servos controlling camera movement
  • boatMovement - rudder/sail controls and controlling the boat's movement
  • Odrive - motors used in rudder and sail control
  • transceiver - wireless communication to shore

Utils

Miscellaneous functions used by the boat

  • constants - config containing all static parameters used by the boat
  • utils - commonly used functions for anything
  • boatMath - common functions for working with coordinates and angles
  • eventUtils - common functions used in events
  • objectDetection - AI buoy detection from an image

Debug

Scripts used to test boat behavior

  • boatSim - simulates how the boat moves in a virtual environment