CURRICULUM VITÆ
June 2011
Abílio Joaquim Gomes de Oliveira Azenha
Biographical Data:
Name: Abílio Joaquim Gomes de Oliveira Azenha
Birth Place: Barca − Maia
Nacionality: Portuguese
Academic Background:
10TH/11TH/12TH YEARS OF SCHOOL
On 1985 he concluded the 10th/11th years of schoolarity: area B − Electrotecnics with
average of 15 in 20, at Escola Secundária da Maia.
On 1986 he concluded the 12th year of schoolarity with average 16.7 in 20, at Escola
Secundária da Maia, with attendance of classes of Mathematics, Physics and Chemistry.
FOREIGN LANGUAGE STUDIED: English.
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BSC. ELECTRICAL AND COMPUTER ENGINEERING DEGREE − FACULDADE DE
ENGENHARIA DA UNIVERSIDADE DO PORTO (FEUP):
Branch: Automation, Control and Instrumentation.
Final Average of the classes concluded on 1992: 16 in 20.
MSC. ELECTRICAL AND COMPUTER ENGINEERING DEGREE − FEUP:
Specialization Domain: INDUSTRIAL INFORMATICS.
Course started on October 1992 and concluded on 14 December 1994.
Dissertation Theme: Force Control of Robotic Manipulators:
The classical perspective of controlling robotic manipulators reports to their configuration (i.e.
the position) and to their time derivatives (i.e. the velocity and the acceleration). Nevertheless, many
of the required tasks to these types of systems are not compatible with this scheme. In fact, the
activities requiring a force/torque control are not possible of position control and vice versa, due to
the finite end-effector degrees-of-freedom. This situation led to the development of algorithms for
the control of position and force/torque according to the executing tasks requirements. So, the
concepts of impedance control, hybrid position/force control and, in general, force control were
established.
This work intended to study the various proposed algorithms and to analyse them. Several
simulations (and the corresponding analysis) of position control and hybrid position/force control of
robotic manipulators were undertaken.
Final Classification: Very Good.
PHD. ELECTRICAL AND COMPUTER ENGINEERING DEGREE − FEUP
Work started on 21 October 1994 and concluded on 22 February 1999.
Dissertation Theme:
Robotic manipulators are systems made from various links interconnected by prismatic or
rotational joints. These mechanical systems exhibit complex kinematic, static and dynamic
phenomena that lead to a difficult analysis and control. These facts lead to that till recently the use
of robots was restricted to tasks needing a reduced interaction with the environment (e.g. painting
and welding). Due to this reason, in the past years a considerable research has been done on the
area of manipulator modelling and control for tasks in which a contact force with the environment is
required (e.g. deburring and assembly). The classical perspective for manipulator control considers
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the configuration (i.e. the position) and the time derivatives (i.e. the velocity and the acceleration) of
the robot mechanical structure. Nevertheless, many of the tasks demanded to this type of systems
are not compatible with this philosophy. In fact, the actions that require a force/torque control are
not possible to control in position and vice versa. This situation motivated the development of
algorithms establishing a compromise between position and force/torque control according with the
task requirements. In this line of thought, impedance control, hybrid position/force control and, in a
more general form, force control concepts were evolved. In this perspective, this work studies the
hybrid position/force control (HC) technique with “second order dynamic effects” such as nonlinear
friction (in the joints and in the environment), backlash (in the mechanical structure) and flexibilities
at the joints. These dynamic phenomena reveal to be of fundamental importance for a precise and
stable control of the interaction forces. The nonlinear phenomena are analysed adopting a
describing function (DF) approach which leads to powerful results in terms of predicting system
oscillations and stability margins. These effects are analysed in terms of time and closed-loop
frequency responses for several position/force controllers and different robot/environment
parameters. Moreover, the behaviours of the standard (i.e. with the inverse Jacobian matrix) system
versus the pseudo-inverse modification are also compared. For all case studies, the system stability
locus in terms of the constraint surface parameters (for two distinct dynamical models) is studied
and the system responses, when a multirate control strategy is adopted, are calculated. In
particular, the HC performance during the occurrence of impacts for several transition schemes
(from position to force control) of the controller structure is studied. Briefly, the adoption of
fractional-order controllers, in the position and force loops, in alternative to the variable structure
controllers used throughout the work is also analysed. This work ends with a DF analysis of the HC
with respect to both stability and sampling rate issues.
Final Classification : Aproved by Unanimity.
On 1998 he attended a course from OMRON about Programable Logic Controllers.
Post Doctoral Project:
On July 2001 he started the Post-Doctoral Project at Departamento de Engenharia
Electrotécnica e de Computadores, Faculdade de Engenharia da Universidade do Porto (FEUP),
Instituto de Sistemas e Robótica (ISR), Portugal. The planned work “Autonomous Vehicles Control
and Instrumentation” can be summarized as follows:
An automated guided vehicle (AGV) is a device capable of being driven through the
corresponding control system within a given workspace. In many applications, the AGVs are
typically wheeled mobile robots (WMRs).
The navigation and path planning, with success, of an AGV in a given environment requires
the availability of a reliable estimation of the vehicle location and of an accurate workspace or
navigation map. A good localization and map generation scheme for AGVs should make the
following actions:
• to formulate consistently the representation and integration of sensorial information
collected by different sensors;
• to overcome the difficulties encountered in many design solutions with respect to
singularities in geometric properties representation;
• to implement a rigorous and complete resolution to localization and simultaneous map
generation for AGVs.
Also, an AGV is ruled by kinematic or geometric and dynamical (gravitational,
Coriolis/centripetal and inertial effects) physical laws. Frequently, the restrictions to its movement
are purely kinematic, because there is no interaction with the environment. Usually, an AGV is a
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nonholonomic system, and so the differential equation constraint variables that describe its physical
behaviour can not be integrated and therefore to be analytically solved.
For the AGV a path planning to reach the goal is needed. Some of the problems found in this
project aspect are the need for the AGV of not to pass between obstacles separated by small
spaces, oscillations in the obstacles neighbourhood and oscillations in narrow paths.
After the path planning, the AGV needs to follow it. By its nature, a nonholonomic system can
not be controlled through a state space feedback, because such systems representation is
impossible. Therefore, the linear control is not possible. In this line of thought, usually a sliding
mode or variable structure systems trajectory control based for AGVs are proposed.
Localization is a very important aspect in AGVs operation. If they do not know where they
are, it is not possible to efficiently plan movements, locate objects or achieve target final positions.
For an AGV to self-locating it needs to generate a workspace map in real-time. The map can be
built through information collected by the instrumentation systems that detect AGV external
properties, such as vision, sonar and laser scanning (lidar). The different sensor signals can be
fused through real-time digital signal processing technologies.
Therefore, vision systems have a fundamental role in the AGVs associated instrumentation.
In general, the video cameras are of CCD (Charge Coupled Device) type and may incorporate
stereo vision when recognizing 3D or 2D objects is required. These systems are very expensive
and demand a high software computational burden. Eventually, these systems can be fused with
other electronic instrumentation signals such as laser scanners. Because of their complexity these
systems become too expensive and process too much information than it is needed in localization
systems required for quasi-structured movement environments. In this proposed work, studying and
development of locating systems as AGVs control sub-systems moving in quasi-structured indoors
environments are the main goals.
In industrial environments, the solutions are yet expensive and based on some types of
vision. The methodological and technological improvement of such sub-system requires some of
this domain research, as explained in this work and the achieving success is strongly inductor of the
technological advance for the different Portuguese companies. These companies are
manufacturers of AGVs based materials handling automatic movement equipments, being a part of
the industrial tissue where ISR − Pólo do Porto is inserted.
Publications (1994-2011):
He has twenty six publications in International Conferences, three publications in Portuguese
Journals and three publications in International Journals.
He has two published Thesis:
Azenha, A., 1994, Controlo de Força de Manipuladores Robóticos, MSc Thesis (in Portuguese),
FEUP, Porto.
Azenha, A., 1998, Análise Dinâmica e Controlo de Forças em Manipuladores Robóticos, PhD
Thesis
(in
Portuguese),
FEUP,
Porto,
published
in
Internet
in
URL:
http://paginas.fe.up.pt/~azenha/TDAJA.pdf (in PDF).
He has two publications in Robotics International Journal Robotica:
Azenha, A., 2000, Iterative Learning in Variable Structure Position/Force Hybrid Control of
Manipulators,
http://www.journals.cup.org/owa_dba/owa/ISSUES_IN_JOURNAL?JID=ROB,
Robotica, 18, No. 2, pp. 213-217, Cambridge University Press.
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Azenha, A. and Carvalho, A., 2008, Dynamic Analysis of AGV Control under Dead-Reckoning
Algorithm, http://www.journals.cup.org/owa_dba/owa/ISSUES_IN_JOURNAL?JID=ROB, Robotica,
26, No. 5, pp. 635-641, Cambridge University Press.
He has one book chapter:
Peneda, L., Azenha, A. and Carvalho, A., 2011, Indoors Localization Using Mobile Communications
Radio Signal Strength, Advanced Trends in Wireless Communications, Mutamed Khatib (Ed.),
ISBN: 978-953-307-183-1, InTech, Available from:
http://www.intechopen.com/articles/show/title/indoors-localization-using-mobile-communicationsradio-signal-strength
He has seven publications in Internet:
Azenha, A. and Machado, J. A. T., 2000, Dynamic Analysis in Variable Structure Position/Force
Hybrid Control of Manipulators with Impact Phenomena, published in Internet in URL:
http://paginas.fe.up.pt/~azenha/Paper1.pdf.
Azenha, A., 2001, Pay-Load Influence Analysis in Variable Structure Position/Force Hybrid Control
of Manipulators, published in Internet in URL: http://paginas.fe.up.pt/~azenha/Paper4.pdf.
Azenha, A., 2002, Automatic PID Controller Tuning for Robots with Nonlinear Friction at the Joints,
published in Internet in URL: http://paginas.fe.up.pt/~azenha/Paper2.pdf.
Azenha, A., 2002, Environment Stiffness Analysis in Variable Structure Position/Force Hybrid
Control of Manipulators, published in Internet in URL: http://paginas.fe.up.pt/~azenha/Paper3.pdf.
Azenha, A., 2002, Autonomous Vehicles Control and Instrumentation, Report published in Internet
in URL: http://paginas.fe.up.pt/~azenha/FCT/WMR1.pdf.
Azenha, A., 2002, Technologies for AGVs Localisation, Report published in Internet in URL:
http://paginas.fe.up.pt/~azenha/FCT/WMR2.pdf.
Azenha, A. and Carvalho, A., 2002, Localisation in Quasi-Structured Environments Lessons from
Autonomous
Mobile
Robots
Positioning,
published
in
Internet
in
URL:
http://paginas.fe.up.pt/~azenha/FCT/WMR3.pdf.
Invited Lectures:
Machado, J. A. T. and Azenha, A., 26/February/1997, Hybrid Position/Force Control and Nonlinear
Phenomena in Mechanical Manipulators, ITA (Instituto Tecnológico de Aeronáutica), S. José
de Campos, Brasil.
Machado, J. A. T. and Azenha, A., 28/February/1997, Hybrid Position/Force Control and Nonlinear
Phenomena in Mechanical Manipulators, Workshop on Advanced Research Activities in
Dynamics and Robotics, Federal University of Rio de Janeiro/COPPE, Brasil.
International Conferences where he participated and
presented communications (1995-2011):
• At present he has fifteen participations in International Conferences where he presented one
and sometimes two communications at each.
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Coordination Activities in Conferences:
• Co-chair of the session “Robot Learning and Control” in IEEE International Conference on
Systems, Man, and Cybernetics, 12-15/October/1997, Orlando, Florida, USA.
Reviewer (2004-2011):
• International Journal IEEE Transactions on Automatic Control, 2004.
• International
Journal
Robotica,
Cambridge
University
Press,
2007,
2008,
http://www.journals.cup.org/owa_dba/owa/ISSUES_IN_JOURNAL?JID=ROB.
• International Conference IEEE Multi-conference on Systems and Control, 2010.
• International Journal of Modelling and Simulation (ActaPress), 2010.
• International Conference IEEE Industrial Electronics Conference, 2010.
• International Conference IEEE Conference on Decision and Control – European Control
Conference, 2011.
• International Conference IEEE Industrial Electronics Conference, 2011.
Works with his references published:
IEE INSPEC, Key Abstracts on CD-ROM, 1996, Register: INSPEC 5323140 C9608-3390-069,
Azenha, A. and Machado, J. A. T., 22-28/April/1996, Variable Structure Control of Robots with
Nonlinear Friction and Backlash at the Joints, 1996 IEEE International Conference on
Robotics and Automation, Minneapolis, USA, pp. 366-371.
IEE INSPEC, Key Abstracts on CD-ROM, 1996, Register: INSPEC 5425460 C9612-3390-048,
Azenha, A. and Machado, J. A. T., 13-16/May/1996, Control of Robots with Nonlinear
Phenomena in the Joints, 8th Mediterranean Electrotechnical Conference, melecon’96, Bari,
Italy, pp. 1123-1126.
Campilho, A., 1997, Controlo e Instrumentação. Resenha de Actividades Desenvolvidas em
Portugal (in Portuguese), ANAIS da Engenharia e Tecnologia Electrotécnica, Colégio de
Engenharia Electrotécnica da Ordem dos Engenheiros, Ano II, No. 3, pp. 5-8.
IEE INSPEC, Key Abstracts on CD-ROM, 1998, Register: INSPEC 5906405 C9806-1340B-015,
Azenha, A. and Machado, J. A. T., 30/June/1996-05/July/1996, Variable Structure Control of
Systems with Nonlinear Friction and Dynamic Backlash, IFAC 13th World Congress,
San Francisco, California, USA, vol. E, pp. 515-520.
IEE INSPEC, Key Abstracts on CD-ROM, 1998, Register: INSPEC 6060805 C9812-3390-008,
Azenha, A. and Machado, J. A. T., 06-08/October/1996, Limit Cycle Prediction of Robot
Systems with Nonlinear Phenomena in the Joints, 27th International Symposium on Industrial
Robots, Milan, Italy, pp. 1003-1008.
Nordin, M. and Gutman, P.-O., 2002, Controlling Mechanical Systems with Backlash − a Survey,
Automatica, 38, no. 10, pp. 1633-1649: refer paper of Azenha, A. and Machado, J. A. T.,
30/June/1996-05/July/1996, Variable Structure Control of Systems with Nonlinear Friction and
Dynamic Backlash, IFAC 13th World Congress, San Francisco, California, USA, vol. E, pp.
515-520.
Parlangeli, G. and Corradini, M.L., 2005, Output Zeroing of MIMO Plants in the Presence of Actuator
and Sensor Uncertain Hysteresis Nonlinearities, IEEE Transactions on Automatic Control, 50,
no. 9, pp. 1403-1407: refer paper of Azenha, A. and Machado, J. A. T., 22-28/April/1996,
Variable Structure Control of Robots with Nonlinear Friction and Backlash at the Joints, 1996
IEEE International Conference on Robotics and Automation, Minneapolis, USA, pp. 366-371.
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Memberships:
• Efective member of Ordem dos Engenheiros with cédula profissional number 36159 and with
the number 9169 of Região Norte;
• Founding member of APCA (Portuguese Association of Automatic Control);
• Member of IEEE (Institute of Electrical and Electronics Engineers), region: Portugal.
Other Projects:
He participated on 1994/95/96/97 in the preparation of the robotics tutorial computer program
WinRob from Departamento de Engenharia Electrotécnica e de Computadores of FEUP.
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