Aruco detector

ArUco marker detection and localisation.

Given a calibration setup this program will detect ArUco markers, log and broadcast its positions. By default, the program will shutdown the computer it is running in. If you want to disable this behaviour, please supply the flag --no-shutdown when running it.

1. Setup your Raspberry Pi

Install the rpi operating system by downloading the installer here: https://www.raspberrypi.com/software/

Install 'Raspberry Pi OS (Legacy, 32bit) Debian Bullseye port'

To access wifi, once logged on select your network (e.g., oplab-net), and from the rpi logo (top left) select Preferences -> Raspberry Pi Configuration -> Interfaces and enable VNC (click OK) Similarly, set display headless resolution to 1920 x 1080.

Add where the software will go to the path by typing in a terminal

nano .bashrc

and at the bottom adding this line

export PATH="/home/pi/.local/bin:$PATH"

Install chrony for time synchronisation

sudo apt-get update
sudo apt-get install chrony
sudo systemctl start chrony
sudo systemctl enable chrony

Install some base libraries

sudo apt-get update
sudo apt-get install libblas-dev liblapack-dev libatlas-base-dev libhdf5-dev

Setup crontab to autorun the software on boot

crontab -e

add this at bottom

@reboot DISPLAY=:0 /bin/bash /home/pi/autostart_aruco.sh > /home/pi/cron_usr.log 2>&1

and add the file autostart_aruco.sh from this repository to the /home/pi directory

Make it executable with

chmod +x autostart_aruco.sh

run the autostart_aruco.sh from the terminal,

./autostart_aruco.sh

It should install the software by itself and you can start using it.

How to install

To install this software manually, run the following in a terminal:

pip install git+https://github.com/ocean-perception/uos_aruco_detector.git

Usage

To run the program, connect a webcam to your computer and type uos_aruco_detector in a terminal.

If you don't want the program to shutdown your computer at the end, type uos_aruco_detector --no-shutdown instead.

uos_aruco_detector [-h] [--no-shutdown]

options:
  -h, --help     show this help message and exit
  --no-shutdown  Don't shutdown at the end of the program

Aruco IDs

Check the configuration in the configuration.yaml file

Tag	ID	Function
OK	12	Setting confirmation
SHUTDOWN	13	Shutdown RPi
FRAME_ENU	14	Publish in ENU
FRAME_NED	15	Publish in NED
CALIBRATION	17	Calibrate origin frame
BROADCAST_NEVER	22	Do not broadcast unless OK is shown
BROADCAST_FREQ_01_HZ	18	Limit broadcast at 0.1 Hz
BROADCAST_FREQ_02_HZ	19	Limit broadcast at 0.2 Hz
BROADCAST_FREQ_1_HZ	20	Limit broadcast at 1 Hz
BROADCAST_FREQ_5_HZ	21	Limit broadcast at 5 Hz
BROADCAST_ALWAYS	16	Broadcast continuously

Check reception

In a bash terminal, you can check the UDP broadcast using netcat. Type the following:

nc -ul 50000

where 50000 is the default port. Change this number if the port changes in your setup.

Message contents

The fields are

  "epoch [s]",
  "elapsed [s]",
  "x [m]",
  "y [m]",
  "z [m]",
  "roll [deg]",
  "pitch [deg]",
  "yaw [deg]",

Reference frames

Here are the defined reference frames:

TAG:
                A y
                |
                |
                |tag center
                O---------> x

CAMERA:


                X--------> x
                | frame center
                |
                |
                V y