Simultaneous Localization and Mapping Using Fiducial Markers

Travis:

Jenkins:

Overview

This package implements a system that uses ceiling mounted fiducials (think QR Codes) to allow a robot to identify its location and orientation. It does this by constructing a map of the ceiling fiducials. Once the map has been constructed, the robot can identify its location by locating itself relative to one or more ceiling fiducials.

A more detailed document is available that describes the system in more detail.

In order to use this system you will need to do the following:

• Software Installation. You will have to install the appropriate software.

• Mount Ceiling Fiducials. You will need to print and install a number of fiduicals on your ceiling. The fiduicals have to be big enough that your camera can resolve them.

• Camera Installation. You will need to install and calibrate an upward pointing camera. On Ubiquity Robotics robots this has already been done.

Installing software

First you must install ROS (Robot Operating System), see install ROS for more details.

Currently you must install from source–binaries are not yet available. First, create a ROS catkin workspace, if you don’t already have one:

 $ mkdir -p ~/catkin_ws/src
 $ cd ~/catkin_ws/src
 $ catkin_init_workspace

Then get the source:

$ git clone https://github.com/UbiquityRobotics/fiducials 
$ git clone https://github.com/UbiquityRobotics/raspicam_node 
$ cd ..
$ catkin_make    

Install inkscape

 $ sudo apt-get install inkscape

Generating fiducials

The fiducials are typically generated from the laptop/desktop.

Fiduical tags are generated using the following commands:

cd /tmp
    rosrun fiducial_lib Tags num ...

Thus, the following command will generate tag42.svg and tag43.svg:

    rosrun fiducial_lib Tags 42 43

To generate a 100 at a time, use the following command:

    rosrun fiducial_lib Tags 17{0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9}

This will generate tag1700.svg through tag1799.svg.

To convert the .svg files to to .pdf files use theinkscape program and the following commands:

    # Convert a single .svg to a single .pdf
    inkscape --without-gui --export-pdf=tag42.pdf tag42.svg
    # Convert a bunch at a time:
    for n in 17{0,1,2,3,4,5,6,7,8,9}{0,1,2,3,4,5,6,7,8,9} ; do \
       inkscape --without-gui --export-pdf=tag$n.pdf tag$n.svg ; \
       done
    # Merge the pdf files:
    sudo apt-get install poppler-utils
    pdfunite tag17??.pdf tags17xx.pdf
	rm tag*.svg

You can print the .pdfs using using evince:

sudo apt-get install evince
evince tags17xx.pdf

Camera Installation:

On Ubiquity Robotics robots the camera in already installed and calibrated. For users of other robots, the process is described in an Appendix.

Map Creation

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