Dynamic Stabilisation of the Biped Lucy Powered by Actuators with Controllable Stiffness

252 Pages·2010·7.09 MB·English

by  Bram Vanderborght (auth.)

Springer Tracts in Advanced Robotics
Volume 63
Editors:BrunoSiciliano·OussamaKhatib·FransGroen
Bram Vanderborght
Dynamic Stabilisation of
the Biped Lucy Powered
by Actuators with
Controllable Stiffness
ABC
ProfessorBrunoSiciliano,DipartimentodiInformaticaeSistemistica,UniversitàdiNapoliFedericoII,
ViaClaudio21,80125Napoli,Italy,E-mail:[e-mail]
ProfessorOussamaKhatib,ArtificialIntelligenceLaboratory,DepartmentofComputerScience,
StanfordUniversity,Stanford,CA94305-9010,USA,E-mail:[e-mail]
ProfessorFransGroen,DepartmentofComputerScience,UniversiteitvanAmsterdam,Kruislaan403,
1098SJAmsterdam,TheNetherlands,E-mail:[e-mail]
Author
BramVanderborght
VrijeUniversiteitBrussel
Pleinlaan2
1050Brussel
Belgium
E-mail:[e-mail]
ISBN978-3-642-13416-6 e-ISBN978-3-642-13417-3
DOI 10.1007/978-3-642-13417-3
SpringerTractsinAdvancedRobotics ISSN1610-7438
LibraryofCongressControlNumber:2010928125
(cid:2)c 2010Springer-VerlagBerlinHeidelberg
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EditorialAdvisoryBoard
OliverBrock,TUBerlin,Germany
HermanBruyninckx,KULeuven,Belgium
RajaChatila,LAAS,France
HenrikChristensen,GeorgiaTech,USA
PeterCorke,QueenslandUniv.Technology,Australia
PaoloDario,ScuolaS.AnnaPisa,Italy
RüdigerDillmann,Univ.Karlsruhe,Germany
KenGoldberg,UCBerkeley,USA
JohnHollerbach,Univ.Utah,USA
MakotoKaneko,OsakaUniv.,Japan
LydiaKavraki,RiceUniv.,USA
VijayKumar,Univ.Pennsylvania,USA
SukhanLee,SungkyunkwanUniv.,Korea
FrankPark,SeoulNationalUniv.,Korea
TimSalcudean,Univ.BritishColumbia,Canada
RolandSiegwart,ETHZurich,Switzerland
GauravSukhatme,Univ.SouthernCalifornia,USA
SebastianThrun,StanfordUniv.,USA
YangshengXu,ChineseUniv.HongKong,PRC
Shin’ichiYuta,TsukubaUniv.,Japan
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Foreword
Roboticsisundergoingamajortransformationinscopeanddimension.From
alargelydominantindustrialfocus,roboticsisrapidlyexpandingintohuman
environmentsandvigorouslyengagedinits newchallenges.Interactingwith,
assisting, serving, and exploring with humans, the emerging robots will in-
creasingly touch people and their lives.
Beyondits impact onphysicalrobots,the body ofknowledge roboticshas
produced is revealing a much wider range of applications reaching across di-
verseresearchareasandscientific disciplines,suchas:biomechanics,haptics,
neurosciences, virtual simulation, animation, surgery, and sensor networks
among others. In return, the challenges of the new emerging areas are prov-
ing an abundant source of stimulation and insights for the field of robotics.
It is indeed at the intersection of disciplines that the most striking advances
happen.
The Springer Tracts in Advanced Robotics (STAR) is devoted to bringing
totheresearchcommunitythelatestadvancesintheroboticsfieldontheba-
sisoftheirsignificanceandquality.Throughawideandtimelydissemination
of critical researchdevelopments in robotics, our objective with this series is
to promote more exchanges and collaborations among the researchers in the
community and contribute to further advancements in this rapidly growing
field.
The monograph written by Bram Vanderborght is the third in the series
devotedtobipedrobots.Theworkspeculatesonthestudyofhumanwalking
toensureasuitablecompliantbehaviourforapneumaticallyactuatedbiped.
A complete hardware and software architecture is developed and different
planning and control techniques are tested for energy efficient walking.
The monographis expanded from the doctoral dissertation of the author,
whichwasafinalistfortheEightEditionoftheEURONGeorgesGiraltPhD
Award. A very fine addition to STAR!
Naples, Italy Bruno Siciliano
January 2010 STAR Editor
Preface
This book reports on the developments of the bipedal walking robot Lucy.
Special about it is that the biped is not actuatedwith the classicalelectrical
drivesbutwithpleatedpneumaticartificialmuscles.Inanantagonisticsetup
ofsuchmusclesboththetorqueandthecompliancearecontrollable.Fromhu-
man walking there is evidence that joint compliance plays an important role
in energy efficient walking and running. Moreover pneumatic artificial mus-
cles have a high power to weight ratio and can be coupled directly without
complex gearing mechanism, which can be beneficial towards legged mecha-
nisms.Additionally,theyhavethe capabilityofabsorbingimpactshocksand
store and release motion energy. This book gives a complete description of
Lucy: the hardware, the electronics and the software. A hybrid simulation
program,combining the robot dynamics and muscle/valve thermodynamics,
has been written to evaluate control strategies before implementing them in
the real biped.
The current control architecture consists of a trajectory generator and a
joint trajectory tracking controller.Two different trajectory generators have
been explored. The first is based on an inverted pendulum model where the
objective locomotion parameters can be changedfrom step to step. The sec-
ond is an implementation of the preview control of the zero moment point
developedby Kajita.The jointtrajectorytrackingunit controlsthe pressure
inside the muscles so the desired motion is followed. It is based on a com-
puted torque model and takes the torque-angle relation of the antagonistic
muscle setup into account. With this strategy the robot is able to walk up
to a speed of 0.15m/s.Higher walking speeds are difficult because the robot
has to walk flat-feet and the valve system is not fast enough to follow the
predescribed pressure courses.
On a single pendulum structure a strategy is developed to combine active
trajectory control with the exploitation of the natural dynamics to reduce
energy consumption.A mathematicalformulationwas found to find anopti-
mal compliance setting depending on the trajectory and physical properties
of the system. This strategy was not implemented on the real robot because
the walking speed of the robot is currently too slow.
Acknowledgements
First of all, I would like to thank my promotor Dirk Lefeber to let me walk
freely where I found the road ahead myself, but also for assisting me when
needed.
Robotics is a very multidisciplinary research domain, which demands for
themostvaryingcompetencies.Itisthusimmenselyimportanttoworkwithin
a team of enthusiastic people. This was for me one of the key factors for
deciding to do my masters thesis and afterwards my doctoral thesis in the
Robotics & Multibody Mechanics Research Group. Although a dissertation
hasonlyoneauthor,theworkwasonlypossiblebyaclosecollaborationwith
thegroupmembers.I’mespeciallygratefultoBj¨ornVerrelstandRonaldVan
Ham who started the research towards Lucy. Also Micha¨el Van Damme for
his help, particularly on programming issues, Joris Naudet and the other
members. Also the technicians Jean-Paul Schepens, Andr´e Plasschaert and
Gabri¨el Van den Nest for the crucial help in the construction of Lucy and
Thierry Lenoir for keeping the computers alive.
I also want to thank the people of the Vrije Universiteit Brussel, the Fac-
ulty of Engineering, the Polytechnische Kring, Liberaal Vlaams Studenten-
Verbond, HVI,... I am very grateful to the people that have been with me
to share this whole experience. They have stretched me academically and
personally. My best friends come out of this splendid period. Thanks Ken,
Rianne, Sophie VH, Niels, Sophie H, Jan, Daft, Xtel, Jean-Marc, Nathalie,
Nancy, David, Olivier, Rina, Laurent, Jean-Jacques, Eva, Peter, St´ephanie,
Emma... You have always been a great support for me.
Thanks to Kazuhito Yokoi I had the opportunity to work for 6 weeks on
the humanoid robot HRP-2 at the ISRI/AIST-CNRS Joint Japanese-French
Robotics Laboratory.It was a wonderful experience thanks to Olivier Stasse
and the other members of the lab.
I would also like to thank the jury members of my PhD: Jean-Paul Lau-
mond, Martijn Wisse, Yvan Baudoin, Rik Pintelon, Jacques Tiberghien,
Philippe Lataire and Patrick Kool for their comments and suggestions to
improve the dissertation.
XII Acknowledgements
Sidney Appelboom learnedme asswimmingcoachtopushmy boundaries
and helped me to overstepmy own limits. His training schedules were some-
times extremely hard, some said they were crazy. Although I never reached
the top, they were important lessons for me. So many thanks Sid!
Finally, my most profound thanks are to my parents and the other mem-
bersofthe family,especiallymy brother,oma,opaandbompafortheir love,
supportandunderstandingthroughouttheyears.Mymotherhasspentmany
hourstotinkerwithme;myfatherhelpedmealotbuildingmodelboatsand
airplanes.They bothwereconvincedonecannotstartexplainingscienceand
technology at an early enough stage. Probably these were the first steps to-
wards robotics. They showed that science and technology can be fun and I
hope the work done for Lucy and my efforts explaining it to children has
inspired many to start a career in exact or applied sciences.
Brussels Bram Vanderborght
January 2010
Fig. 0.1 Visit of His Majesty KingAlbert II of Belgium.
Contents
1 Introduction............................................. 1
1.1 Motivation ........................................... 1
1.2 Robotics ............................................. 3
1.2.1 Humanoid Robots ............................... 5
1.2.2 Overview of Humanoid Robots.................... 7
1.3 Focus on Legs......................................... 19
1.4 Compliant Actuation .................................. 22
1.4.1 Biological Aspects of Walking and Running......... 22
1.4.2 Passive Compliant Actuators ..................... 29
1.4.3 Use of Compliant Actuators in Robotics............ 31
1.5 Goal of the Lucy Project ............................... 38
1.6 Approach............................................. 38
1.7 Outline .............................................. 39
2 Description of Lucy...................................... 41
2.1 Introduction .......................................... 41
2.2 Pleated Pneumatic Artificial Muscle (PPAM) ............. 42
2.3 Concept.............................................. 44
2.4 Force Characteristic ................................... 45
2.5 Volume Characteristic.................................. 47
2.5.1 Antagonistic Muscle Setup ....................... 48
2.5.2 Compliance Characteristics of an Antagonistic
Muscle Setup ................................... 50
2.6 Modular Unit ......................................... 52
2.6.1 Complete Robot ................................ 61
2.7 Electronics ........................................... 63
2.7.1 Complete Electronic Hardware .................... 71
2.7.2 Safety Board.................................... 75
2.7.3 Control of Treadmill ............................. 76
XIV Contents
2.8 Interface Program ..................................... 77
2.9 Virtual “Lucy”........................................ 79
2.9.1 Mechanics...................................... 80
2.9.2 Thermodynamics................................ 85
2.9.3 Complete Simulation Model ...................... 86
2.9.4 Use of Middleware............................... 88
2.10 Conclusion ........................................... 90
3 Trajectory Generator .................................... 93
3.1 Dynamic Balance...................................... 94
3.2 Trajectory Generator .................................. 98
3.2.1 Natural Dynamics-Based Control.................. 99
3.2.2 Soft Computing ................................. 100
3.2.3 Model-Based Trajectory Generation ............... 101
3.3 Requirements ......................................... 102
3.4 Trajectory Generation Based on Inverted Pendulum
Mode ................................................ 103
3.4.1 Objective Locomotion Parameters Based Inverted
Pendulum Mode (OLPIPM) Trajectory Generator... 105
3.4.2 Calculation of the Joint Trajectories ............... 113
3.4.3 Influence of the Complete Multibody Model ........ 116
3.5 Implementation of a Preview Controller of the Zero
Moment Point to Generate Trajectories .................. 117
3.5.1 Introduction to Preview Controller ................ 118
3.5.2 Cart-Table Model ............................... 119
3.5.3 Trajectory Generation as Servo Tracking Control
of ZMP ........................................ 119
3.5.4 Trajectory Generation Using Preview Control....... 121
3.5.5 Methodology and Influence of Parameters .......... 123
3.5.6 Complete Multibody Model....................... 127
3.6 Comparison between OLPIPM en Preview Control
Method .............................................. 132
3.7 Dynamically Stepping over Large Obstacles by the
Humanoid Robot HRP-2 ............................... 133
3.7.1 Introduction to Stepping Over .................... 133
3.7.2 Feasibility Unit ................................. 134
3.7.3 Spline Foot Trajectories.......................... 135
3.7.4 Preview Control on ZMP......................... 136
3.7.5 Trajectory Adaptations for Higher Obstacles........ 137
3.7.6 Simulation Results .............................. 138
3.7.7 Experimental Results ............................ 138
3.8 Conclusion ........................................... 141