Tesis doctorales:

Atencia J., "Diseño, Modelización, Construcción y Control de Motor
Lineal de Inducción". Tesis Doctoral. San
Sebastián. Abril 2002.
Resumen de la tesis:
Design, Modelling,
Construction and Control of Linear Induction
Motor. 2002. F. Javier Atencia Fernández. Escuela
Superior de Ingenieros, University of Navarra
(Spain). Calificación: Sobresaliente Cum Laude.
The objective of this
Doctoral Thesis is to achieve a deep knowledge of
Linear Induction Motors, from the point of view of
the new possible applications due to the modern
control strategies of rotary machines. Thus, an
exhaustive bibliographical review has been made, a
laboratory prototype has been constructed, and new
ways of characterizing it have been explored.
After that, a
comparative study of modelling LIMs as actuators
has been performed. The importance of this study
has been recognised with a Price at the LDIA2001
(Linear Drives for Industry Applications). This
symposium has taken place in Nagano, Japan, and it
is the only international congress specific of
linear actuators.
In order to compare the
advantages and problems involved in controlling
LIMs, several control strategies have been
implemented with the prototype. The results of
speed and position control are presented, as well
as the criteria used in order to compare the
controls.
From all the information
obtained by modelling and controlling the
prototype, some design guides are proposed, and
also some criteria for setting the specifications
of LIMs.
Key words: Linear
Induction Motor. Linear Machines. Drives Control. 
Resumen de la tesis:
Design of a new
Vectorial Control Strategy for Linear Induction Motors.
2005. Miguel MartínezIturralde Maiza. Escuela
Superior de Ingenieros, University of Navarra
(Spain). Calificación: Sobresaliente Cum Laude.
The linear induction
motor (LIM) adds up all the advantages of being a
direct drive to the known characteristics of their
rotary counterparts, that is, robustness and low cost.
Traditionally,
this kind of motors has been used in conveyance and
transportation applications. However, in the last
years, the reduction of the cost of power electronics
and microprocessors, has made these motors suitable
for tasks which require high speed and accurate
positioning.
Dealing with speed and
position control of linear induction motors, most
strategies in bibliography are based on Secondary Flux
Oriented Control (SFOC) and Direct Thrust Control
(DTC). However, SFOC of linear induction motors needs
complex identification methods to compensate parameter
variation during operation, mainly due to local
heating and endeffects. On the other hand, DTC based
methods for LIMs introduce thrust ripple and have
problems at low and zero speed.
In this doctoral thesis,
a new speed and position control strategy for linear
induction motors that makes up for these drawbacks is
presented.
The primary flux control
algorithm is stated for normal and fullvoltage
operation. Moreover, the speed and position control
loops design methodology and the method for automatic
adjustment of compensators are presented.
Experimental results are
presented to evaluate the performance of the control
strategy and, also, its sensitivity to the variation
of the linear induction motor parameters.
Finally, some
conclusions are drawn about the applicability of the
new algorithm that demonstrate the main advantages
versus Secondary Flux Oriented Control and Direct
Thrust Control.
Key words: linear
motors, parameter identification, field oriented
control, position control. 
Resumen de la tesis:
Dynamic performance
optimization of permanent magnet linear synchronous
motors.
2005. Gonzalo Martínez Díez. Escuela
Superior de Ingenieros, University of Navarra
(Spain). Calificación: Sobresaliente Cum Laude.
Linear
synchronous motors are a very interesting option
when thinking about linear actuators. The
conventional linear systems consisting of a rotary
motor and mechanical devices used to convert
rotation to displacement are being replaced by
linear electric motors in many industrial
applications. Among linear synchronous motors,
permanent magnet motors are the most commonly used
in industry.
In
Permanent Magnet Linear Synchronous Motors, the
magnetic field of the secondary is produced by
permanent magnets instead of other methods such as
DC coils. This kind of motors presents some
characteristic forces that are usually undesired
because they produce disturbances in the motor
motion. These forces reduce the dynamic features
and the precision of the motor, and they are the
cogging force (or detent force) and the normal
forces between the primary and the secondary of
the motor. Normal forces also generate big
stresses in the structure.
Cogging
force has the same direction as the motor motion
and cause disturbances in the production of
thrust. Normal forces are perpendicular to the
motor motion and cause big stresses in the
structure, increase friction losses and audible
noise. They also can generate undesired mechanical
vibrations. First of all, cogging force was
analysed, and various methods to reduce it were
developed. Secondly, normal forces were studied,
and a control strategy to control these forces was
developed. All the tasks were validated by means
of the Finite Element Method and experimental
tests.
The
target of this thesis is to obtain a method of
designing, constructing and controlling Permanent
Magnet Linear Synchronous Motors that can achieve
the more and more demanding dynamic features that
industry requires for this kind of actuators.
Key words: linear
motors, cogging force, attraction forces, optimization. 
Listado de Publicaciones:
Desde la creación del grupo se han publicado
veinte papers, entre artículos y
comunicaciones a congresos, uno mereció el Premio
a la Excelencia en la conferencia sobre
accionamientos lineales, LDIA, en Nagano (Japón),
Octubre de 2001.

Atencia J., Martínez G.,
García Rico A., Flórez J., (2000) "Electrical
performance analysis of three different types of
linear machines", Proceedings of the IASTED
International Conference, Power and Energy Systems,
Marbella (Spain), September 2000.
ABSTRACT: In this paper we present a
Linear prototype Induction Motor (LIM), an
iron core armature Permanent Magnet Linear
Synchronous Motor (PMLSM), and an ironless
armature PMLSM, all of them with the same
primary parameters. The electromagnetic
properties of these three prototypes are
compared, and the thrust and dynamic
performance discussed.


García Rico A., Atencia
J., Martínez G., (2000) "Modelización y simulación
de máquinas lineales asíncronas, y síncronas de
imanes permanentes", III Conferencia anual
Elementos Finitos. Cosmos, Zamudio (Spain),
Septiembre 2000.
ABSTRACT: Se demuestra cómo el programa
COSMOS/M resulta de gran ayuda en la búsqueda de
diseños de máquinas lineales síncronas y asíncronas,
facilitando el conseguir correcciones que permiten
mejorar, a priori, el comportamiento que acabarán
teniendo los prototipos; ahorrándose así multitud de
recursos, tanto de tiempo como económicos. Los
prototipos diseñados están en funcionamiento como
herramienta experimental dentro de un proyecto global
a largo plazo que abarcará el diseño, construcción,
alimentación, control y análisis del comportamiento
electrodinámico de máquinas eléctricas lineales. 

Atencia J., García Rico
A., Flórez J., (2001) "A low cost linear induction
motor for laboratory experiments", Int. J. Electr.
Eng. Educ. (UK), vol. 38, nº 2, pp. 11734, April
2001.
ABSTRACT: In this paper we present a
Linear Induction Motor (LIM) prototype for
education. LIMs allow to easy identification
and study of the different concepts and
parameters of the electromagnetic circuit
that they have in common with any other
types of electrical machines. Some
experiments are presented that highlight the
proposed approach. 

Atencia J.,
MartínezIturralde M., García Rico A., Flórez J.,
(2001) "Modeling of linear induction motors as
linear drives", Proceedings of the IEEE Porto
Powertech Conference, Porto (Portugal), September
2001.
ABSTRACT: There is a large bibliography
in simulation models for Linear Induction
Motors (LIMs). However, most of them only
consider steady state performance. LIMs
working as Linear Drives generally operate
under transient conditions. The aim of this
paper is to investigate the suitability of
different mathematical models to simulate
LIMs as Linear Drives. An study of most
major techniques of calculating lumped
parameters is provided. The most
representative models capable of simulating
transient of LIMs are described and applied
to a laboratory prototype. Finally, the
results obtained are compared to
experimental data. 

MartínezIturralde M.,
Atencia J., García Rico A., Flórez J., (2001) "Analysis
of different models of linear induction drives",
Proceedings of the IEEJ LDIA Conference, Nagano (Japan),
October 2001. ISBN 8469932535, pp. 135139.
Esta publicación mereció el premio a
la excelencia por parte de la IJEE, organizadores
de la conferencia.
ABSTRACT: Many authors have developed
different models to simulate Linear
Induction Motors (LIMs). Nonetheless, these
models usually only focus on the steady
state performance of the machine. The
increasing demand for LIMs in industry,
working as linear drives, makes it necessary
to use models capable of simulating LIMs
under transient conditions. The objective of
this paper is to draw some conclusions about
the suitability of different mathematical
models to simulate LIMs as linear drives.
Three representative models are described
and applied to a laboratory prototype.
Finally, the results obtained are compared
to experimental data. 

Atencia J., Martínez G.,
García Rico A., Flórez J., (2001) "Minimization of
cogging force in flat permanent magnet linear motors",
Proceedings of the IEEJ LDIA Conference, Nagano (Japan),
October 2001. ISBN 8469932535, pp. 441444.
ABSTRACT: This paper proposes a
technique to reduce cogging force choosing
the optimal size of the magnets, and the
optimal geometry of the primary iron. The
feasibility of the proposed technique is
confirmed both by finite element analysis
and by the experimental results obtained
with laboratory prototypes. 

Atencia J., "Diseño, Modelización, Construcción y Control de Motor
Lineal de Inducción". Tesis Doctoral. San
Sebastián. Abril 2002. Codirectores de tesis:
Julián Flórez Esnal y Andrés García Rico.
Ver resumen.

Martínez G., Atencia J.,
García Rico A., Flórez J., (2002) "Electrical
performance of two different types of Permanent
Magnet Linear Machines with Vector Control", Proceedings of the 17th International Conference
on Magnetically Levitated Systems and Linear
Drives (MAGLEV2002), Lausanne (Switzerland),
September 2002.
ABSTRACT: There is a dilemma about
employing or not employing iron in the
primary core of synchronous linear actuators.
To give some guidance about the convenience
of using iron or ironless primary cores, two
prototypes of Permanent Magnet Linear
Machines (PMLSM) geometrically identical
were built. The prototypes were tested in
order to get reliable comparative
conclusions. The purpose of this paper is to
analyse the performance of two different
topologies of linear synchronous machines,
using vector control techniques. Several
tests were performed to determine the
electromagnetic properties and the static
forces of the prototypes involved. The paper
concludes with a discussion of their
performances and dynamics, and their
suitability for different applications. 

Martínez G., Atencia J.,
García Rico A., Flórez J., (2002) "Vector control of Permanent Magnet Linear Synchronous Machines
with detent force compensation", Proceedings of
the IEE MEDPower 2002 Conference, Athens (Greece)
November, 2002.
ABSTRACT: The aim of this paper is the
design and analysis of a control algorithm
for Permanent Magnet Linear Synchronous
Motors (PMLSM) which takes into account the
detent force characteristic of this kind of
machines. The control algorithm includes a
compensator that minimizes the negative
effects caused by detent force. This study
is part of a more extensive project that
seeks the complete cancellation of these
forces working simultaneously in two
separate fields: the constructive design of
the machine and the control system. A very
important reduction of detent force with a
constructive optimization of the machine has
been achieved. The next target is to
eliminate the forces completely by a
suitable control algorithm. The elimination
of detent force will increase the high
precision features of these actuators. Rotor
Flux Oriented Control (RFOC) strategy was
employed. Detent force was measured in a
PMLSM prototype, and a control algorithm
that minimizes the undesired effects has
been designed. Experimental tests were
performed to verify the effectiveness of the
method. The electrical and dynamic
performance of a prototype are compared
under two different conditions: firstly
including the force compensation in its
control algorithm, and secondly without
force compensation. The influence of the
force compensator alone is analysed in this
paper. The following step is to combine the
optimized constructive design and the
developed control algorithm in order to
supress completely the force and speed
ripple. 

MartínezIturralde M.,
Simón I., García Rico A., Flórez J., (2002) "Parameter
identification of vector controlled linear
induction motor", Proceedings of the IEE MEDPower
2002 Conference, Athens(Greece), November 2002.
ABSTRACT: The special geometry of Linear
Induction Motors (LIMs) produces some
specific effects (i.e. end effects and
asymmetric field distribution) that affect
the value of their lumped parameters.
Because of this, it is usual to control LIMs
by means of scalar control, instead of using
the more efficient vector control techniques.
The aim of this paper is to test the
influence of the LIMs specific effects in
the lumped parameters of the machine and,
therefore, in their vector control. A
parameter identification technique based on
the Least Squares method was developed and
applied to a LIM prototype under various
operating conditions. Moreover, the
influence of vector control parameters
variation in the LIM performance was
evaluated. Rotor Field Oriented Control (RFOC)
was applied to a laboratory prototype.
Different experimental tests were performed. 

Atencia J.,
MartínezIturralde M., Martínez G., García Rico A.,
Flórez J., (2003) "Control strategies for
positioning of Linear Induction Motors: tests and
discussion", Proceedings of the IEEE IEMDC 2003
Conference, Madison, Wisconsin (USA), June 2003. ISBN 0780378180, pp. 16511655.
ABSTRACT: The target of this paper is to
establish the main problems and goals of the
four most popular control strategies for
induction motor drives, applied to the
special case of Linear Motors: Scalar
Control, Direct fieldoriented control (direct
FOC), indirect Fieldoriented Control (indirect
FOC) and Direct Torque Control (DTC). We
introduce the peculiarities of the
implementation of the different strategies
for Linear Induction Motors, the results of
experimental tests of the speed controller
and position controller, and a discussion of
the experiments. 

Martínez G., Atencia J.,
MartínezIturralde M., García Rico A., Flórez J.,
(2003) "Reduction of detent force in flat Permanent
Magnet Linear Synchronous Machines by means of three
different methods", Proceedings of the IEEE IEMDC
2003 Conference, Madison, Wisconsin (USA), June 2003. ISBN 0780378180, pp. 11051110.
ABSTRACT: This paper proposes two
different techniques to reduce detent force
in flat Permanent Magnet Linear Synchronous
Motors (PMLSM). The first one is the choice
of an optimal constructive design, taking
into account the width and arrangement of
the magnets, and the length and shape of the
solid iron core. The second is the employ of
a force compensator in the control algorithm,
which counteracts the detent force effects.
Both methods are based on a Fourier analysis
of the detent force curve as a function of
the machine position. The curve is broken
down into harmonics. The constructive method
considers that each harmonic has its
peculiar source and is independent from the
others. The force compensator employs a
detent force model based on the Fourier
series of the curve. The two methods were
tested separately, and their results were
compared. Experimental tests were performed
to verify the effectiveness of the methods.
A very important reduction with a
constructive optimization of the machine was
achieved. The reduction by means of a
compensator in the control scheme also
reaches excellent results. In order to
achieve the maximum reduction of detent
force, both techniques can be combined. This
measure will increase the precision features
of this kind of machines. 

MartínezIturralde M.,
Martínez G., Atencia J., García Rico A., Flórez J.,
(2003) "Analysis of voltage measurement techniques
for Direct Torque Control of induction motors",
Proceedings of the IEEE IEMDC 2003 Conference, Madison,
Wisconsin (USA), June 2003. ISBN 0780378180, pp. 11511155.
ABSTRACT: The knowledge of the real
stator voltages is basic for a correct
estimation of stator flux and torque in
Direct Torque Controlled induction motors.
In this paper, two different lowcost and
effective techniques are presented for
stator voltage acquisition: one based on an
electronic circuit and the other based on
software programming. Both of them have been
developed and applied to a direct torque
control (DTC) scheme. Experimental tests
demonstrate their suitability when
controlling an induction motor. A
comparative of the two mentioned techniques
is presented. 

MartínezIturralde M.,
Martínez G., García Rico A., Flórez J., (2003) "Estrategias
de control para accionamientos eléctricos lineales",
Sección española de ISA (International Society for
Measurement and Control, Instrumentation, and
Automation), Ponencia Invitada para sesión especial,
Madrid, 17 de Junio de 2003.
RESUMEN: En este artículo se presentan
estrategias de control específicas para los
dos tipos de motores lineales más comunes en
la industria: el motor lineal de inducción (LIM)
y el motor lineal síncrono de imanes
permanentes (PMLSM). 

Martínez G., García Rico
A., Flórez J., (2003) "Simultaneous position and
levitation control of Permanent Magnet Linear
Synchronous Machines using vector control techniques",
Proceedings of the IEEJ LDIA 2003 Conference,
Birmingham (UK), September 2003. ISBN 0953522814, pp. 311315.
ABSTRACT: The aim of this paper is to
analyse the normal forces characteristic of
flat Permanent Magnet Linear Synchronous
Machines (PMLSMs). The results of this study
allow to take several conclusions and to
develop control strategies able to reach a
decoupled control of thrust and attraction /
repulsion forces in this kind of linear
machines. The control of the normal forces
can provide multiple advantages, such as the
reduction of friction forces, or even their
suppression. The main purposes of this study
are to achieve the simultaneous and
decoupled control of the thrust and the
normal forces in PMLSMs and draw some
conclusions.


MartínezIturralde M.,
García Rico A., Flórez J., (2003) "Control
strategies for linear induction motors",
Proceedings of the IEEJ LDIA 2003 Conference,
Birmingham (UK), September 2003. ISBN 0953522814, pp. 319323.
ABSTRACT: Rotor Flux Oriented Control (RFOC)
of linear induction motors needs complex
identification methods to compensate
parameter variation during operation, mainly
due to local heating and end effects. Direct
Torque Control (DTC) based methods for LIMs
introduce thrust ripple and have problems at
low and zero speed. In this paper, a new
control strategy for linear induction motors
that makes up for these drawbacks is
presented. The new algorithm for normal and
fullvoltage operation is described.
Simulation and experimental results
demonstrate the main advantages against RFOC
and DTC. The strategy is also applicable to
rotary motors.


G. Martínez, M.
MartínezIturralde, A. García Rico, J. Flórez, "Motores
lineales en Máquina – Herramienta. Tipología y
características electromagnéticas y dinámicas", XV
Congreso de Máquinas – Herramienta y Tecnologías de
Fabricación, vol. 1, pp. 381  400 San Sebastián,
20,21 y 22 de octubre de 2004, I.S.B.N. 93182877.
ABSTRACT: Los accionamientos lineales
empleados en máquinasherramienta basados en husillos
a bolas están siendo progresivamente reemplazados por
motores eléctricos lineales. Estos motores se pueden
clasificar según su principio de funcionamiento
(síncronos, asíncronos, paso a paso, de reluctancia,
de corriente continua,..) y según su estructura
(planos, tubulares...), resultando una gran cantidad
de configuraciones electromagnéticas diferentes. Sin
embargo, se ha constatado que el abanico de motores
lineales más ampliamente utilizados para
máquinaherramienta es muy reducido.
Este documento
pretende arrojar más luz sobre los diferentes tipos de
motores lineales que existen en el mercado y sus
sistemas de control. Por un lado se describirán las
características fundamentales de cada uno a la hora
del diseño de una máquina industrial: fuerza,
velocidad, aceleración, precisión, repetibilidad y
necesidad de refrigeración. Por otro lado, se
comentarán los diferentes problemas electromagnéticos
específicos de cada tipo de motor: fuerzas de
reluctancia y de atracción, variación de su
comportamiento con la velocidad, etc..., que pueden
afectar al comportamiento de la máquina industrial,
sobre todo a la hora de exigir gran precisión de
funcionamiento.
Se aportará
información relevante obtenida de publicaciones
científicas recientes, catálogos comerciales y, sobre
todo, de la experimentación realizada desde hace 6
años en el Laboratorio de Investigación en Máquinas
Eléctricas de TECNUN (Universidad de Navarra), donde
se han diseñado y construido varios prototipos de
motores lineales. 

Martínez, G.,
MartínezIturralde, M., Castelli, M., García Rico,
A., Flórez, J., "Simultaneous motion and
normal forces control of Flat Permanent Magnet Linear
Synchronous Motors employed as actuators ",
Proceedings of the IEEJ LDIA Conference, KobeAwaji
(Japan), September 2005.
ABSTRACT: This paper analyses the
dynamic performance of flat singlesided Permanent
Magnet Linear Synchronous Motors (PMLSMs) employed as
actuators, when the motion and the attractive or
repulsive forces between the primary and the secondary
are controlled simultaneously. The control of the
normal forces when the motor is in dynamic operation
provides multiples advantages, such as the reduction
of friction forces and audible noise, and the
minimization of mechanical stresses of guides and
supports. Two PMLSM prototypes, one with a
ferromagnetic primary core, and another with a
nonmagnetic armature, were tested under these special
operation conditions. A modified Rotor Flux Oriented
Control (RFOC) strategy was employed to carry out the
tests, and several conclusions were taken. The main
purposes of this study are to show the feasibility of
the simultaneous control of motion and normal forces
employing vector control techniques and to analyse the
dynamic response of the prototypes. 

MartínezIturralde,
M., Martínez, G., Castelli, M., García Rico, A.,
Flórez, J., "Simple and Robust Indirect
Thrust Control for Positioning of Linear Induction
Motors ", Proceedings of the IEEJ LDIA
Conference, KobeAwaji (Japan), September 2005.
ABSTRACT: Dealing with position control
of Linear Induction Motors (LIM), most strategies in
bibliography are based on Secondary Flux Oriented
Control (SFOC) and Direct Thrust Control (DTC).
However, SFOC of linear induction motors needs complex
identification methods to compensate parameter
variation during operation, mainly due to local
heating and endeects. On the other hand, DTC
based methods for LIMs present thrust ripple and have
problems at low and zero speeds.
In this paper, a
new Indirect Thrust Control (ITC) based strategy for
position control of linear induction motors that makes
up for these drawbacks is presented. The position
control loop design methodology and the method for
automatic adjustment of compensators are described.
Experimental results are presented to evaluate the
performance and sensitivity of the control strategy.
Finally, some conclusions are drawn about the
applicability of the new algorithm that demonstrate
the main advantages versus SFOC and DTC. 

Castelli, M.,
MartínezIturralde, M., Martínez, G., García Rico,
A., Flórez, J., "Design, Construction and
Control of a High Performance XY Positioner ",
Proceedings of the IEEJ LDIA Conference, KobeAwaji
(Japan), September 2005.
ABSTRACT: Linear motors offer several
advantages over their rotary counterparts in many
industrial applications requiring linear motion and
positioning accuracy (1); linear motors can achieve a
higher value of the position loop gain, and thus
higher accelerations and speeds, due to the
elimination of mechanical transmission devices.
However, dealing with precision machinery, it is not
possible to make simple replacement of conventional
systems to linear servomotors. Mechanical vibration,
thermal expansion, regenerative energy dissipation or
electromagnetic compatibility are only a few problems
that could appear if not taken into account through
the design process of the precision machine.
Interesting conclusions are drawn form the project
realized, as the fact of being able to use only one
linear scale to control two motors in one axis, or
need of using external regenerative resistors. 

Castelli, M.,
MartínezIturralde, M., Martínez, G., García Rico,
A., Flórez, J., "Linear Induction Motor
Control for Simultaneous Propulsion and Levitation of
an Aluminium Plate ", Proceedings of the IEEJ
LDIA Conference, KobeAwaji (Japan), September 2005.
ABSTRACT: This paper presents
interesting results about the aplication of an
innovative control strategy of an aluminium plate,
using both levitation and horizontal movements.
Construction simplicity and economy are among some of
its main advantages, since it only uses one AC source.
Another feature is the utilization of the same
algorithm to control both movements, propulsion and
levitation. The aluminium plate has a vectorial,
primary flux oriented control. The algorithm for
propulsion and levitation described in this article
was based in a new LIM control strategy developed in
TECNUN(1). Also simulation and experimental results
are presented in order to validate the new control
strategy. Finally some conclusions are drawn about the
advantages of the new control method and future works
are presented. 
