Pathing Architecture

Owned by R D
Last updated: 2024-10-01 by Aaron Wang
4 min read

Overview

The pathing system controls the drone’s movement at a high level from the ground station computer.

2023: The system converts a QR code into a waypoint path that the drone follows autonomously with no human intervention.

2024: The system makes the drone follow a predetermined waypoint path, with the possibility of early stop and return to launch (RTL).

MAVLink

MAVLink is a communication protocol used to communicate with the drone. More detail here: MAVLink

The pathing system uses the dronekit library to interface with MAVLink: https://dronekit-python.readthedocs.io/en/latest/

We are currently migrating to use the common repository to interface with MAVLink: The common Repository

Waypoints

Waypoints are named locations with latitude, longitude, (and optionally altitude), coordinates

Alpha

Bravo

Charlie

Delta

Echo

Foxtrot

Golf

Hotel

India

Juliette

Kilo

Lima

Mike

November

Oscar

Papa

Quebec

Point 18

Romeo

Sierra

Tango

Uniform

Victor

Whiskey

Xray

Yankee

Zulu

Waypoint file

The waypoint file stores the name, latitude, and longitude of each waypoint in a CSV.

There may be a header with name,latitude,longitude

Each row contains a waypoint.

Example:

name,latitude,longitude WARG,43.47323264522664,-80.54011639872981 University of Waterloo Station for 301 ION,43.4735247614021,-80.54144667502672

Modules

A pathing program is consisted of modules. Modules are reusable segments of code. Generally modules can be broken down into three types

  1. Command modules: These are modules that create or alter a list of mavlink commands to be sent to the drone

  2. Utility modules: Modules for “utilities”, for example a parser for a specific data format, or QR scanner

  3. Data structure modules: Modules for more advanced data structures that may be needed for certain scenarios (such as Waypoint class with altitude)

The main pathing script should be consisted of modules, and implement logic specific to a task on top of it.

Sample Modules

Load waypoints (Type 2)

Create a name to coordinate mapping of waypoints from the waypoint file.

Return:

  • True, [data] if successful

  • False, None on error (e.g. file doesn’t exist)

Function signature:

def load_waypoint_name_to_coordinates_map(waypoint_file_path: string) \ -> "tuple[bool, dict[string, tuple[float, float]] | None]":

Example:

WAYPOINT_FILE_PATH = "~/pathing/waypoints_example.csv" result, value = load_waypoints_name_to_coordinates_map(WAYPOINT_FILE_PATH) print(result) True print(value) {'WARG': (43.47323264522664, -80.54011639872981), 'University of Waterloo Station for 301 ION': (43.4735247614021, -80.54144667502672)}

Waypoint names to waypoints coordinates (Type 2)

Converts waypoint names to waypoint coordinates using the provided mapping.

Return:

  • True, [data] if successful

  • False, None on error (e.g. name has no entry in mapping)

Function signature:

Example:

Waypoints to commands (Type 1)

Converts the list of waypoint coordinates into a list of commands. Use the same altitude parameter for all commands.

  • Use MAV_FRAME_GLOBAL_RELATIVE_ALT and MAV_CMD_NAV_WAYPOINT (16)

Function signature:

Example:

Add takeoff and landing command (Type 1)

Prefixes a takeoff command and suffixes a landing command to the ends of the list of commands.

  • Use MAV_CMD_NAV_TAKEOFF (22)

    • With relative frame

    • All parameters 0 except altitude

  • Use MAV_CMD_NAV_RETURN_TO_LAUNCH (20)

    • With global frame: MAV_FRAME_GLOBAL

    • All parameters 0

Function signature:

Example:

Upload commands (Deprecated, this is now in flightcontroller class instead)

Adds the list of commands to the drone’s command sequence.

  • Download and clear the command sequence before adding the commands

Function signature:

Example:

 

2023

QR input

Uses the camera to convert a QR code into QR text. Displays the camera as it is being used. Can be aborted by pressing 'q' .

Return:

  • True, [data] if successful

  • False, None on error (e.g. user abort)

Function signature:

Example:

QR to waypoint names

Converts the QR text string into a list of waypoint names. The QR text string input is expected as:

where [waypoint name] is one of the waypoint names.

Return:

  • True, [data] if successful

  • False, None on error (e.g. bad QR string)

Function signature:

Example: