Robot Localization Using Ceiling Fiducials

This code was developed to allow a robot to localize itself in an indoor environment where fiducial tags are located on the ceiling.

Installation

This code is destributed as a ROS package. The new ROS packaging format called catkin is used. We are currently testing against the “Groovy” release of ROS. ROS currently only installs on the various Ubuntu Linux distributions (e.g. Ubuntu, Kubuntu, etc.)

Install ROS Groovy

The first step is to install ROS Groovy.

Make sure that you have edited your ~/.bashrc file to have:

    source /opt/ros/groovy/setup.bash

in it. Then make sure you have run that script file:

    source ~/.bashrc

Now go to the ROS tutorials and play with catkin workspaces.

Install GCC 4.7 or Higher

The second step is to get to a version of the GCC compiler suite that is at revision of 4.7 or higher. The reason for this is because the Fiducials code is written in the newer C11 (for 2011) revision of the C programming language. The GCC revisions 4.6 and below do not support C11.

To figure out which version you have. Type:

    sudo apt-get install -y build-essential

to make sure that you have a compiler. Next, type:

    gcc --version

and you will get something that looks like:

    gcc (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2
    Copyright (C) 2012 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

In this particular example, GCC is at revision 4.7.2 which is what you need. If it says 4.6.x or less, you need to get a newer GCC compiler.

    sudo add-apt-repository ppa:ubuntu-toolchain-r/test
    sudo apt-get update
    sudo apt-get upgrade -y
    sudo apt-get dist-upgrade -y
    sudo apt-get install -y gcc-4.8
    sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 30

Install InkScape and Doxygen

InkScape is used to convert fiducial tags from .svg Scalable Vector Graphics format into .pdf Portable Document Format so that they can be printed out on a laser printer. To install InkScape:

    sudo apt-get install -y inkscape

Doxygen is the documentation generation program that reads the various source files an prints more readable documenation. To install Doxygen:

    sudo apt-get install -y doxygen

Install Pt. Grey SDK

There are a bunch of Pt. Gray Flycapture-MV cameras kicking around. These are 648 x 480 USB monochrome cameras with a global shutter. The global shutter makes them much less immune to motion blur. For now, we are standardizing on this camera for testing the fiducial software.

Evenutally, we will make the software build optionally with or without the Pt. Grey device drivers. However, until then, it is necessary to download the Pt. Grey Software Develoment Kit. Please follow the following steps:

• to go to the Point Grey Web Site

• go to [Support] => [Downloads] and click. The following downloads link will work until the site gets reorganized.

• You can not have the software until you create an account. Their passwords must consist of letters and digits only.

• If you are lucky you should get to the Product Support: Downloads page. As usual, the link will break when the web site is reorganized.

• Currently it brings you to a selection panel. Just click the on [Software (24)] item. It will expand into 24 possibilities.

• Scroll down until you get [FlyCapure 2.5 Release 4 - Linux]. The are four options – 1) 32-bit x86, 2) 64-bit x86, 3) ARM Hard Float, and 4) ARM Soft Float. Download the correct one for your platform.

• Untar the tarball:

  cd {somwhere} gunzip -c {name_of_tar.gz} | tar xvf -

• Read the “readme.txt” file and install as much as you can. These instructions only go up to Ubuntu 10.04, which is getting pretty old.

• Finally run the install script:

    sudo sh install_flycapture.sh
  

Now it should be possible to download and build the fiducials package.

Install and Build the Fiducials Code

We assume that you called your catkin workspace “catkin_ws” in the installation steps below.

First you fetch the fiducials and fiducials_rviz catkin package:

cd .../catkin_ws/src
git clone https://github.com/waynegramlich/fiducials.git
git clone https://github.com/waynegramlich/fiducials_rviz.git

Next you build it:

cd ..
catkin_make

Everything is now installed:

I only test on Linux/Ubuntu so you are on your own for other platforms.

Installation Issues

If the instructions above do not work for you, please drop us a line at Wayne@Gramlich.Net and let us know what when wrong.

Programs

The program should be present in your fiducials build directory:

    cd .../catkin_ws/build/fiducials

Tags

The Tags program is used to generate .svg files for tags. Runing Tags:

Tags 41 42

will generate tag41.svg and tag42.svg. To print:

inkscape --without-gui --export-pdf=tag41.pdf tag41.svg
lpr tag41.pdf

Video_Capture

The Video_Capture program capture is used to display video from a video camera and capture a sequence of images from the video stream. To use:

Video_Capture camera_number [capture_base_name]

If the image does not come up, try again. If comes up with the image rotated horizontally. If it keeps coming up screwy, unplug the camera and try again. Honest, it is unclear what the issue is.

To use image capture, first click on the image to shift the input focus to Video capture. To capture an image, type the [space] key. To exit, type the [Esc] key.

Fly_Capture

The Fly_Capture program capture is used to display video from a Pt. Grey video camera and capture a sequence of images from video stream. To use:

Fly_Capture camera_number [capture_base_name]

If the image does not come up, try again. If comes up with the image rotated horizontally. If it keeps coming up screwy, unplug the camera and try again. Honest, it is unclear what the issue is.

To use image capture, first click on the image to shift the input focus to Video capture. To capture an image, type the [space] key. To exit, type the [Esc] key.

Demo

The Demo program is used to debug and show what is going on under the covers with the Fiducials code:

Demo dojo_3.6mm_6Oct2013/pg_3_6mm.txt dojo_3.6mm_6Oct2013/dojo_3.6mm-15.pnm

will load the dojo_3.6mm-15.pnm file and do fiducial recognition on it. pg_3_6.txt is the lens correction coeeficients. Move the cursor over the window that pops up and click on the image. This moves the input focus to the Demo program. Click on ‘+’ to increment one step through processing and ‘-‘ to decrement one step through processing.

The steps are:

• Color to Gray
• Gaussian blur [‘b’ toggles the blur]
• Gray to Black and White
• Edge detect
• Edge simplify to polygons
• Select reasonable size quadralaterals
• Find corners to sub-pixel resolution
• Sample fiducial edges
• Sample fiducial bits
• Recognize fiducial id’s (nothing visible yet)