From Ants to Service Robots

212 Pages·2017·15.23 MB·English

by  Ali Abdul Khaliq

From Ants to Service Robots: an Exploration in Stigmergy-Based
Navigation Algorithms
یہر رگ تمدخ یريم تبحم یريت رهب رمع
یسب لچوت اوه بج لباقےک تمدخ یرت ںيم
)لابقا(

To my late parents
with love and eternal appreciation,
whom I lost during my PhD studies
Örebro Studies in Technology 79

ALI ABDUL KHALIQ

From Ants to Service Robots: an Exploration in
Stigmergy-Based Navigation Algorithms
© Ali Abdul Khaliq, 2018
Title: From Ants to Service Robots: an Exploration in
Stigmergy-Based Navigation Algorithms
Publisher: Örebro University 2018
www.publications.oru.se

Print: Örebro University, Repro 05/2018
ISSN 1650-8580
ISBN 978-91-7529-253-3
Abstract
Ali Abdul Khaliq (2018): From Ants to Service Robots: an Exploration in
Stigmergy-Based Navigation Algorithms.
Örebro Studies in Technology 79.

Navigation is a core functionality of mobile robots. To navigate autonomously, a
mobile robot typically relies on internal maps, self-localization, and path plan-
ning. Reliable navigation usually comes at the cost of expensive sensors and often
requires significant computational overhead.
Many insects in nature perform robust, close-to-optimal goal directed naviga-
tion without having the luxury of sophisticated sensors, powerful computational
resources, or even an internally stored map. They do so by exploiting a simple but
powerful principle called stigmergy: they use their environment as an external
memory to store, read and share information. In this thesis, we explore the use of
stigmergy as an alternative route to realize autonomous navigation in practical
robotic systems.
In our approach, we realize a stigmergic medium using RFID (Radio Frequency
Identification) technology by embedding a grid of read-write RFID tags in the
floor. A set of mobile robots, then, build and store maps used for navigation in
the stigmergic medium itself. These maps are of three types: (1) goal maps which
guide robots to known locations; (2) clearance maps which help robots avoid
obstacles; (3) feature maps which can be used to store observable properties, such
as light intensity or gas concentration. We show how these maps can be built both
in static and in dynamic environments and used for navigation of heterogeneous
robots. We also show that goal maps can be used for navigation to previously
unknown and/or dynamic locations, and that feature maps can be used to navi-
gate towards specific features, e.g., places with high gas concentration that are
beyond the sensor’s range. We address the issue of perceptual errors (e.g., broken
tags) during navigation. We further study the use of the built navigation maps to
enable different types of human-aware robot navigation on the RFID floor.
We define several stigmergic algorithms for building maps and navigating on
these maps. We formally analyse the properties of the main algorithms, and em-
pirically evaluate all the algorithms both in simulation and with multiple physical
robots. Results collected from tens of hours of real experiments and thousands of
simulated runs demonstrate the effectiveness of our approach.

Keywords: Stigmergy, Minimalistic Robots, Mobile robot navigation, RFID
technology, Multi-robot system, Path planning, Localization, Map building.

Ali Abdul Khaliq, School of Science and Technology
Örebro University, SE-70182 Örebro, Sweden,
[email protected]

Acknowledgement
Writing this part of the thesis has refreshen the memories of my PhD
years, starting all the way back to my initial days in the lab when Ales-
sandro gave me tiny robots to play with (of course I was given larger sized
robots to play with later as I progressed). And the journey began: reading
a lot of research articles, conducting exciting experiments, late night dead-
lines, early morning teaching assistance, and finally thesis writing. The
completion of this journey would not have been possible without some
wonderful people, hence, I would like to take this opportunity to express
my gratitude to all these wonderful people.
First and foremost, I would like to express my deepest gratitude to my
main supervisor Prof. Alessandro Saffiotti for believing in me and giving
me the opportunity to work under his guidance. His knowledge, expertise,
through feedback and support during the stressful moments have been
invaluable throughout my PhD studies. I would like to express my heart-
felt gratitude to my co-supervisor, Federico Pecora for detailed discus-
sions, constructive comments, and encouragement. Working with both of
my supervisors has not only helped producing this thesis, but also boosted
my self-confidence in dealing with scientific issues and shaped my way of
looking into problems. More supportive and considerate supervisors I
could not have asked for. Thank you, Alessandro and Federico.
Many thanks to Dr. Maurizio Di Rocco, who was my co-supervisor in
the first year of my PhD, for inspiring discussions and advises that helped
a lot in creating a better start for my PhD. I would like to thank my re-
viewer, opponent, and committee members that took the time to review
my work.
I would like to thank all AASS people for providing a friendly and great
working environment. Among the AASS people, special thanks go to
Marco Trincavelli, Sepideh Pashami and Victor Hernandez Bennetts for
their guidance before starting and in the initial phase of my PhD studies.
Thanks also go to our lab engineers Per Sporrong and Bo-Lennart
Silfverdal for providing technical support and customized building of the
RFID antennas. Many thanks to Chittaranjan, Hadi, Iran, Marjan, Ravi,
Sai, and Stevan with whom I not only had constructive discussions in the
lab but also a good time outside the lab. Thank you, Alberto, André, and
Neziha for nice chitchats during the coffee breaks.
I would like to extend my thanks to wonderful Pakistani circle of
friends (mini Pakistan in Örebro) for their moral support and making my
stay pleasant in Örebro during my PhD studies (in alphabetical order):
Abdullah, Ali, Idrees, Muneeb, M. Abdullah, Qasim, Shoaib, Taimur,
Umer, and Zulqarnain. Thank you, wonderful families, for making Öre-
bro feel like home and for the delicious food! (in alphabetical order):
Amin, Asif, Faisal, Farrukh, Humanyun, Mubashar, Naeem, and Naveed.
Last but not the least, my gratitude goes to those without whom none
of this would be possible in the first place: my wonderful family. I would
like to thank my sisters: Zaib, for being most encouraging and caring;
Sajeela, for being my strength and my best friend; Romana, for being most
supportive and loving; Uzma, for being caring and the heart of the family;
my brother Khuram, for being my childhood mentor. Despite being far
away, I can always count on them. I wish I could thank my late mother
Jamila and my late father Abdul khaliq for their unconditional support,
endless sacrifices, countless prayers, immense love throughout my life and,
believing in me. The void they left will never be filled again. People go, but
memories remain.
Contents
1 Introduction 1
1.1 Stigmergyinnature . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Stigmergicmedium . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Stigmergicagents . . . . . . . . . . . . . . . . . . . . . . 3
1.1.3 Stigmergicalgorithms . . . . . . . . . . . . . . . . . . . 3
1.1.4 Stigmergictasks. . . . . . . . . . . . . . . . . . . . . . . 3
1.1.5 Stigmergicmaps . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Realizationofstigmergyinrobots . . . . . . . . . . . . . . . . . 4
1.2.1 Thestigmergicmedium:RFIDfloor . . . . . . . . . . . . 4
1.2.2 Roboticagents . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.3 Humanagents . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Objectivesofthisthesis. . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 Researchquestions . . . . . . . . . . . . . . . . . . . . . 7
1.3.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.3 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.4 Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 MethodOverview 13
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Scopeofthethesis . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Systemoverview . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 Systemcomponents . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4.1 TheRFIDtechnology. . . . . . . . . . . . . . . . . . . . 16
2.4.2 Theenvironments. . . . . . . . . . . . . . . . . . . . . . 16
2.4.3 Therobots . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.4 RFIDslipper . . . . . . . . . . . . . . . . . . . . . . . . 19
2.4.5 Thesimulator . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5 Notationusedinthethesis . . . . . . . . . . . . . . . . . . . . . 21
2.6 Performancemetrics . . . . . . . . . . . . . . . . . . . . . . . . 21
2.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
v
vi CONTENTS
3 RelatedWork 25
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 Stigmergyincomputerscience . . . . . . . . . . . . . . . . . . . 25
3.3 Stigmergyinrobotics . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3.1 Stigmergyinroboticsusingphysicalmarkers . . . . . . . 27
3.3.2 Stigmergyinroboticswithoutphysicalmarkers . . . . . 28
3.3.3 StigmergyinroboticsusingRFIDtechnology. . . . . . . 31
3.4 OtherusesofRFIDtechnologyinrobotics . . . . . . . . . . . . 32
3.5 Alandscapeofstigmergyinrobotics . . . . . . . . . . . . . . . 33
3.6 Humanrobotinteraction . . . . . . . . . . . . . . . . . . . . . . 34
3.6.1 Navigationinthepresenceofhumans. . . . . . . . . . . 35
3.6.2 Humanfollowing . . . . . . . . . . . . . . . . . . . . . . 35
3.6.3 Interactionwithchildren . . . . . . . . . . . . . . . . . . 36
3.6.4 Comparisonwiththeworkinthisthesis . . . . . . . . . 36
3.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4 BuildingNavigationMaps 39
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2 Mapbuildingsystem . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3 Buildinggoalmaps . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.3.1 Ontheuseofmultipleseeds . . . . . . . . . . . . . . . . 43
4.4 Goalmapbuildingindynamicenvironments . . . . . . . . . . . 44
4.5 BuildingaclearanceMap . . . . . . . . . . . . . . . . . . . . . 46
4.6 Experimentsandresults . . . . . . . . . . . . . . . . . . . . . . 48
4.6.1 Goalmapbuilding . . . . . . . . . . . . . . . . . . . . . 49
4.6.2 Dealingwithdynamicenvironments . . . . . . . . . . . 58
4.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5 NavigationovertheBuiltMaps 63
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.2 Basicrequirementsfornavigation . . . . . . . . . . . . . . . . . 63
5.3 Navigationtowardsapredefinedseed . . . . . . . . . . . . . . . 64
5.4 Navigationstrategies . . . . . . . . . . . . . . . . . . . . . . . . 66
5.5 Experimentsandresults . . . . . . . . . . . . . . . . . . . . . . 67
5.5.1 Analysingthenavigationstrategies . . . . . . . . . . . . 68
5.5.2 Navigationwithaphysicalrobot . . . . . . . . . . . . . 69
5.5.3 Navigationonapartiallybuiltmap . . . . . . . . . . . . 70
5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6 BeyondtheLab:TowardsDeploymentintheRealWorld 73
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.2 Navigationtoanarbitraryposition . . . . . . . . . . . . . . . . 73
6.2.1 Distanceestimationtoanarbitraryposition . . . . . . . 74
6.2.2 Onlinedistanceestimationtoanarbitraryposition . . . 75