Neuronal assembly dynamics in supervised and unsupervised learning scenarios

The dynamic formation of groups of neurons—neuronal assemblies—is believed to mediate cognitive phenomena at many levels, but their detailed operation and mechanisms of interaction are still to be uncovered. One hypothesis suggests that synchronized oscillations underpin their formation and functioning, with a focus on the temporal structure of neuronal signals. In this context, we investigate neuronal assembly dynamics in two complementary scenarios: the first, a supervised spike pattern classification task, in which noisy variations of a collection of spikes have to be correctly labeled; the second, an unsupervised, minimally cognitive evolutionary robotics tasks, in which an evolved agent has to cope with multiple, possibly conflicting, objectives. In both cases, the more traditional dynamical analysis of the system’s variables is paired with information-theoretic techniques in order to get a broader picture of the ongoing interactions with and within the network. The neural network model is inspired by the Kuramoto model of coupled phase oscillators and allows one to fine-tune the network synchronization dynamics and assembly configuration. The experiments explore the computational power, redundancy, and generalization capability of neuronal circuits, demonstrating that performance depends nonlinearly on the number of assemblies and neurons in the network and showing that the framework can be exploited to generate minimally cognitive behaviors, with dynamic assembly formation accounting for varying degrees of stimuli modulation of the sensorimotor interactions

Fault-tolerant Synchronization of Autonomous Underwater Vehicles

The main objective of this thesis is to develop a fault-tolerant and reconfigurable synchronization scheme based on model-based control protocols for stern and sail hydroplanes that are employed as actuators in the attitude control subsystem (ACS) of an autonomous underwater vehicle (AUV). In this thesis two control approaches are considered for synchronization, namely i) state feedback synchronization, and ii) output feedback synchronization. Both problems are tackled by proposing a passive control approach as well as an active reconfiguration (re-designing the control gains). For the ”state feedback” synchronization scheme, to achieve consensus the relative/absolute measurements of the AUV’s states (position and attitude) are available. The states of a longitudinal model of an AUV are mainly heave, pitch, and their associated rates. For the state feedback problem we employ a static protocol, and it is shown that the multi-agent system will synchronize in the stochastic mean square sense in the presence of measurement noise. However, the resulting performance index defined as the accumulated sum of variations of control inputs and synchronization errors is high. To deal with this problem, Kalman filtering is used for states estimation that are used in synchronization protocol. Moreover, the e�ffects of parameter uncertainty of the agent’s dynamics are also investigated through simulation results. By employing the static protocol it is demonstrated that when a loss of e�ffectiveness (LOE) or float fault occurs the synchronization can still be achieved under some conditions. Finally, one of the main problems that is tackled in the state feedback scenario is our proposed proportional-integral (PI) control methodology to deal with the lock in place (LIP) fault. It is shown that if the LIP fault occurs, by employing a PI protocol the synchronization could still be achieved. Finally, our proposed dynamic synchronization protocol methodology is applied given that the fault (LOE/float) severity is known. Since after a fault occurrence the agents become heterogeneous, employing the dynamic scheme makes the task of reconfiguration (redesigning the gains) more e�ffective. For the ”output feedback” synchronization approach, to achieve consensus relative/absolute measurements of the AUV’s states except the pitch rate are available. For the output feedback problem a dynamic protocol through a Luenberger observer is first employed for state estimation and the synchronization achievement is demonstrated. Then, a system under state and measurement noise is considered, and it is shown that by employing a Kalman filter for the state estimation; the multi-agent system will synchronize in the stochastic mean square sense. Furthermore, by employing the static protocol, it is shown that when a LOE/float fault occurs the synchronization is still achieved under certain conditions. Finally, one of the main problems that is tackled in the output feedback scenario is our proposed dynamic controller methodology. The results of this scheme are compared with another approach that exploits both dynamic controller and dynamic observer. The former approach has less computational e�ort and results in more a robust control with respect to the actuator fault. The reason is that the later method employs an observer that uses the control input matrix information. When fault occurs, this information will not be correct any more. However, if there is a need to redesign the synchronization gains under faulty scenario, the later methodology is preferred. The reason is that the former approach becomes complicated when there is a fault even though its severity is known. In this thesis, fault-tolerant synchronization of autonomous underwater vehicles is considered. In the first chapter a brief introduction on the motivation, problem definition, objectives and the methodologies that are used in the dissertation are discussed. A literature review on research dedicated to synchronization, fault diagnosis, and fault-tolerant control is provided. In Chapter 2, a through literature review on unmanned underwater vehicles is covered. It also comprises a comprehensive background information and definitions including algebraic graph theory, matrix theory, and fault modeling. In the problem statement, the two main problems in this thesis, namely state feedback synchronization and output feedback synchronization are discussed. Chapters 3 and 4 will cover these two problems, their solutions, and the corresponding simulation results that are provided. Finally, Chapter 5 includes a discussion of conclusions and future work

Estimation and stability of nonlinear control systems under intermittent information with applications to multi-agent robotics

This dissertation investigates the role of intermittent information in estimation and control problems and applies the obtained results to multi-agent tasks in robotics. First, we develop a stochastic hybrid model of mobile networks able to capture a large variety of heterogeneous multi-agent problems and phenomena. This model is applied to a case study where a heterogeneous mobile sensor network cooperatively detects and tracks mobile targets based on intermittent observations. When these observations form a satisfactory target trajectory, a mobile sensor is switched to the pursuit mode and deployed to capture the target. The cost of operating the sensors is determined from the geometric properties of the network, environment and probability of target detection. The above case study is motivated by the Marco Polo game played by children in swimming pools. Second, we develop adaptive sampling of targets positions in order to minimize energy consumption, while satisfying performance guarantees such as increased probability of detection over time, and no-escape conditions. A parsimonious predictor-corrector tracking filter, that uses geometrical properties of targets\u27 tracks to estimate their positions using imperfect and intermittent measurements, is presented. It is shown that this filter requires substantially less information and processing power than the Unscented Kalman Filter and Sampling Importance Resampling Particle Filter, while providing comparable estimation performance in the presence of intermittent information. Third, we investigate stability of nonlinear control systems under intermittent information. We replace the traditional periodic paradigm, where the up-to-date information is transmitted and control laws are executed in a periodic fashion, with the event-triggered paradigm. Building on the small gain theorem, we develop input-output triggered control algorithms yielding stable closed-loop systems. In other words, based on the currently available (but outdated) measurements of the outputs and external inputs of a plant, a mechanism triggering when to obtain new measurements and update the control inputs is provided. Depending on the noise environment, the developed algorithm yields stable, asymptotically stable, and Lp-stable (with bias) closed-loop systems. Control loops are modeled as interconnections of hybrid systems for which novel results on Lp-stability are presented. Prediction of a triggering event is achieved by employing Lp-gains over a finite horizon in the small gain theorem. By resorting to convex programming, a method to compute Lp-gains over a finite horizon is devised. Next, we investigate optimal intermittent feedback for nonlinear control systems. Using the currently available measurements from a plant, we develop a methodology that outputs when to update the control law with new measurements such that a given cost function is minimized. Our cost function captures trade-offs between the performance and energy consumption of the control system. The optimization problem is formulated as a Dynamic Programming problem, and Approximate Dynamic Programming is employed to solve it. Instead of advocating a particular approximation architecture for Approximate Dynamic Programming, we formulate properties that successful approximation architectures satisfy. In addition, we consider problems with partially observable states, and propose Particle Filtering to deal with partially observable states and intermittent feedback. Finally, we investigate a decentralized output synchronization problem of heterogeneous linear systems. We develop a self-triggered output broadcasting policy for the interconnected systems. Broadcasting time instants adapt to the current communication topology. For a fixed topology, our broadcasting policy yields global exponential output synchronization, and Lp-stable output synchronization in the presence of disturbances. Employing a converse Lyapunov theorem for impulsive systems, we provide an average dwell time condition that yields disturbance-to-state stable output synchronization in case of switching topology. Our approach is applicable to directed and unbalanced communication topologies.\u2

Neuronal oscillations, information dynamics, and behaviour: an evolutionary robotics study

Oscillatory neural activity is closely related to cognition and behaviour, with synchronisation mechanisms playing a key role in the integration and functional organization of different cortical areas. Nevertheless, its informational content and relationship with behaviour - and hence cognition - are still to be fully understood. This thesis is concerned with better understanding the role of neuronal oscillations and information dynamics towards the generation of embodied cognitive behaviours and with investigating the efficacy of such systems as practical robot controllers. To this end, we develop a novel model based on the Kuramoto model of coupled phase oscillators and perform three minimally cognitive evolutionary robotics experiments. The analyses focus both on a behavioural level description, investigating the robot’s trajectories, and on a mechanism level description, exploring the variables’ dynamics and the information transfer properties within and between the agent’s body and the environment. The first experiment demonstrates that in an active categorical perception task under normal and inverted vision, networks with a definite, but not too strong, propensity for synchronisation are more able to reconfigure, to organise themselves functionally, and to adapt to different behavioural conditions. The second experiment relates assembly constitution and phase reorganisation dynamics to performance in supervised and unsupervised learning tasks. We demonstrate that assembly dynamics facilitate the evolutionary process, can account for varying degrees of stimuli modulation of the sensorimotor interactions, and can contribute to solving different tasks leaving aside other plasticity mechanisms. The third experiment explores an associative learning task considering a more realistic connectivity pattern between neurons. We demonstrate that networks with travelling waves as a default solution perform poorly compared to networks that are normally synchronised in the absence of stimuli. Overall, this thesis shows that neural synchronisation dynamics, when suitably flexible and reconfigurable, produce an asymmetric flow of information and can generate minimally cognitive embodied behaviours

Neuromonitoring during newborn transition

Background: Newborn infant neurological function can be measured by monitoring electrical activity (electroencephalography) or cerebral oxygenation via NIRS (near infrared spectroscopy). In practice the clinical applications of electroencephalography (EEG) are limited to monitoring infants following moderate to severe hypoxic ischemic injury (HIE), and for the detection of seizures in at risk infants. NIRS monitoring has been the focus of a number of research trials but has no clinical applications in the immediate newborn period to date, and is not routinely performed in neonatal units. Aim: To assess the feasibility of infant neuromonitoring in the immediate period in two important clinical scenarios. Firstly, to assess the feasibility of monitoring brain activity during the first minutes of life in healthy term infants. Secondly, to assess the feasibility and utility of monitoring newborn preterm infants’ brain activity and cerebral oxygenation in the context of an interventional randomized controlled trial. Methods: 1. Healthy term newborn infants had EEG monitoring performed for the first ten minutes of life. EEG was assessed both qualitatively and quantitatively. All infants had respiratory function monitoring performed simultaneously. 2. Forty-five infants (< 32 weeks gestation) were randomly assigned to different methods of newborn infant cord clamping. All infants had EEG and NIRS monitoring for the first 72 hours of life. Quantitative features of EEG and median NIRS values were compared between groups at 6 and 12 hours of life as a primary outcome measure. Results: 1. Forty-nine infants had EEG recordings. Median (IQR) age at time of initial EEG recording was 3.0 (2·5 to 3·8) minutes. End tidal CO2 and tidal volumes increased over the first 3 minutes of life and then stabilized. Good quality EEG, with continuous mixed frequency activity with a range of 25-50μV, was observed in all infants. The majority of EEG spectral power was within the delta band. 2. There were 45 infants included. One infant died in the delivery room. Median time (IQR) from birth until EEG application was 3.05 (1.85 to 5.38) hrs. For primary outcome measures, data was available for 42/44 (95%) at 6 hrs and 44/44 (100%) at 12 hours. There was no significant difference between groups for measures for EEG values or cerebral NIRS. Conclusion: Infant neuromonitoring in the immediate newborn period is feasible in the first minutes of life in healthy term infants and within the first hours of life in preterm infants. Normative quantitative data for electrical activity in healthy newborn term infants during the first minutes of life is described for the first time. Neuromonitoring during the first day of life as an outcome measure for preterm interventional trials is possible and the outcomes from this research is promising for further trials

Autonomous landing of fixed-wing aircraft on mobile platforms

E n esta tesis se propone un nuevo sistema que permite la operación de aeronaves autónomas sin tren de aterrizaje. El trabajo está motivado por el interés industrial en aeronaves con la capacidad de volar a gran altitud, con más capacidad de carga útil y capaces de aterrizar con viento cruzado. El enfoque seguido en este trabajo consiste en eliminar el sistema de aterrizaje de una aeronave de ala fija empleando una plataforma móvil de aterrizaje en tierra. La aeronave y la plataforma deben sincronizar su movimiento antes del aterrizaje, lo que se logra mediante la estimación del estado relativo entre ambas y el control cooperativo del movimiento. El objetivo principal de esta Tesis es el desarrollo de una solución práctica para el aterrizaje autónomo de una aeronave de ala fija en una plataforma móvil. En la tesis se combinan nuevos métodos con experimentos prácticos para los cuales se ha desarrollado un sistema de pruebas específico. Se desarrollan dos variantes diferentes del sistema de aterrizaje. El primero presta atención especial a la seguridad, es robusto ante retrasos en la comunicación entre vehículos y cumple procedimientos habituales de aterrizaje, al tiempo que reduce la complejidad del sistema. En el segundo se utilizan trayectorias optimizadas del vehículo y sincronización bilateral de posición para maximizar el rendimiento del aterrizaje en términos de requerimientos de longitud necesaria de pista, pero la estabilidad es dependiente del retraso de tiempo, con lo cual es necesario desarrollar un controlador estabilizador ampliado, basado en pasividad, que permite resolver este problema. Ambas estrategias imponen requisitos funcionales a los controladores de cada uno de los vehículos, lo que implica la capacidad de controlar el movimiento longitudinal sin afectar el control lateral o vertical, y viceversa. El control de vuelo basado en energía se utiliza para proporcionar dicha funcionalidad a la aeronave. Los sistemas de aterrizaje desarrollados se han analizado en simulación estableciéndose los límites de rendimiento mediante múltiples repeticiones aleatorias. Se llegó a la conclusión de que el controlador basado en seguridad proporciona un rendimiento de aterrizaje satisfactorio al tiempo que suministra una mayor seguridad operativa y un menor esfuerzo de implementación y certificación. El controlador basado en el rendimiento es prometedor para aplicaciones con una longitud de pista limitada. Se descubrió que los beneficios del controlador basado en el rendimiento son menos pronunciados para una dinámica de vehículos terrestres más lenta. Teniendo en cuenta la dinámica lenta de la configuración del demostrador, se eligió el enfoque basado en la seguridad para los primeros experimentos de aterrizaje. El sistema de aterrizaje se validó en diversas pruebas de aterrizaje exitosas, que, a juicio del autor, son las primeras en el mundo realizadas con aeronaves reales. En última instancia, el concepto propuesto ofrece importantes beneficios y constituye una estrategia prometedora para futuras soluciones de aterrizaje de aeronaves.In this thesis a new landing system is proposed, which allows for the operation of autonomous aircraft without landing gear. The work was motivated by the industrial need for more capable high altitude aircraft systems, which typically suffer from low payload capacity and high crosswind landing sensitivity. The approach followed in this work consists in removing the landing gear system from the aircraft and introducing a mobile ground-based landing platform. The vehicles must synchronize their motion prior to landing, which is achieved through relative state estimation and cooperative motion control. The development of a practical solution for the autonomous landing of an aircraft on a moving platform thus constitutes the main goal of this thesis. Therefore, theoretical investigations are combined with real experiments for which a special setup is developed and implemented. Two different landing system variants are developed — the safety-based landing system is robust to inter-vehicle communication delays and adheres to established landing procedures, while reducing system complexity. The performance-based landing system uses optimized vehicle trajectories and bilateral position synchronization to maximize landing performance in terms of used runway, but suffers from time delay-dependent stability. An extended passivity-based stabilizing controller was implemented to cope with this issue. Both strategies impose functional requirements on the individual vehicle controllers, which imply independent controllability of the translational degrees of freedom. Energy-based flight control is utilized to provide such functionality for the aircraft. The developed landing systems are analyzed in simulation and performance bounds are determined by means of repeated random sampling. The safety-based controller was found to provide satisfactory landing performance while providing higher operational safety, and lower implementation and certification effort. The performance-based controller is promising for applications with limited runway length. The performance benefits were found to be less pronounced for slower ground vehicle dynamics. Given the slow dynamics of the demonstrator setup, the safety-based approach was chosen for first landing experiments. The landing system was validated in a number of successful landing trials, which to the author’s best knowledge was the first time such technology was demonstrated on the given scale, worldwide. Ultimately, the proposed concept offers decisive benefits and constitutes a promising strategy for future aircraft landing solutions

Multiterminal HVDC transmissions systems for offshore wind

Offshore wind is emerging as one of the future energy vectors. Offshore wind power plants locations provide more strong and constant wind speed that allows to extract more power compared to onshore locations. In addition, as wind turbine components transportation is less restricted to terrestrial infrastructure, bigger and more powerful wind turbines can be installed offshore. In Europe, 1,567 MW of offshore wind power was installed in 2013. It represents the 14\% of the total wind power installed in Europe. Offshore wind power plants near the shore can be connected to the main grid by means of conventional AC technology. However, if these wind farms are installed further than 80-100 km, the use of AC equipment is economically infeasible due to reactive power issues. In these applications, HVDC system based on static converters can be used. The projects build and commissioned nowadays are based on point-to-point connections, where, each wind farm or wind farm clusters are connected to the terrestrial grid individually. Consequently, these lines might be understood as an extension of the AC system. If different offshore wind farms are interconnected between them and connected at the same time to different AC systems, for example, different countries, the DC grid is created. This scenario creates one of the most important challenges in the electrical power system since its creation, more than 100 years ago. The most relevant challenges to be addressed are the stability and operation of the DC grid and the integration and interaction with the AC grid. This thesis addresses various aspects related to the future Multiterminal-HVDC systems for transmission of offshore wind power. First, the voltage control and the system operations are discussed and verified by means of emulations using an HVDC scaled experimental platform built for this purpose. Voltage stability might be endangered during contingencies due to the different inertia time constant of the AC and the DC system. DC systems only have the inertia of the capacitors compared to synchronous machines rotating masses of the AC systems. Therefore, in faulty conditions the power transmitted through the DC system must be reduced quickly and efficiently. For this reason, in this thesis a coordinated power reduction algorithm taking advantage of Dynamic Braking Resistors (DBR) connected to onshore converter stations and the ability of the power plants to reduce the generated power is presented. From the AC and DC grids integration point of view, the connection point between the offshore grid and the AC grid might be located remotely leading to a connection with a reduced Short Circuit Ratio (SCR). In the literature, several issues regarding the connection of transistor-based power converters to weak AC grid have been reported. In this thesis am advanced control for Voltage Source Converters connected to weak grids is presented and tested by means of simulations. From the AC and DC grids interactions, the voltage stability is not enough to operate a DC grid. Transport System Operators (TSO) operates the power flow through the cables and the power exchanged between by the power converters. In this thesis, a novel hierarchical power flow control method is presented. The aim of the proposed power flow control is to obtain the desired power flows changing the voltage control set-points while the system stability is ensured. Finally, a control procedure for offshore wind farms based on Squirrel Cage Induction Generators connected to a single power converter is introduced.L'energia eòlica marina emergeix com un dels vectors energètics del futur. Les localitzacions eòliques marines proporcionen vens més forts i constants que les terrestres, cosa que permet extreure més potència. A més a més, els aerogeneradors marins poden ser més grans i més potents ja que es redueixen les limitacions de gàlib existent en les infraestructures terrestres. A tall d'exemple, l'any 2013 a Europa es van instal.lar 1.567 MW de potència eòlica marina, cosa que representa un 14\% de la potència eòlica instal.lada a Europa. Els parcs eòlics marins poden ser connectats a la xarxa elèctrica terrestre utilitzant emparamenta convencional de corrent alterna, però quan la distancia amb la costa excedeix els 80-100 km l'ús d'aquesta tecnologia es torna econòmicament inviable degut a l'energia reactiva generada en els conductors. Per solucionar aquest problema, s'emparen els sistemes en corrent continua basats en convertidors estàtics. Els projectes construïts o projectats a dia d'avui es basen en esquemes de connexió punt-a-punt, on, cada parc eòlic o agrupació de parcs eòlics es troba connectat a la xara terrestre individualment. En conseqüència, l'operació d'aquestes línies es pot considerar com una extensió de la xarxa d'alterna. Però, si s'interconnecten diferents parc eòlics amb diferents xarxes terrestres d'alterna (per exemple, diferents països) en corrent continua, s'obtenen xarxes en corrent continua. Aquest nou escenari crea un dels majors reptes des de la creació dels sistema elèctric de potencia, ara fa més de 100 anys. Entre aquests reptes hi ha l'estabilitat i l'operació dels sistemes en corrent contínua i la seva integració i coexistència amb les xarxes en corrent alterna. En la present tesis s'han estudiat diferents aspectes dels futurs sistemes multi terminal en alta tensió en corrent contínua (HVDC, en anglès) per la transmissió de potencia generada mitjançant parcs eòlics marins. Primerament, es descriu el control de tensió i els modes d'operació dels sistemes multi terminal i es verifiquen en una plataforma experimental construïda per aquest propòsit. L'estabilitat de tensió dels sistemes en corrent continua, es pot veure afectada durant una falta a la xarxa d'alterna degut a la reduïda inèrcia dels sistemes multi terminal, només formada pels condensadors dels convertidors i els cables. Així la potència que no pot injectar a la xarxa ha de ser reduïda de forma ràpida i eficient. Per això, en aquesta tesis es presenta un sistema coordinat de reducció de potència que utilitza la resistència de frenat dels convertidors de connexió a la xarxa i els mètodes de reducció de potència dels parcs eòlics. Des del punt de vista de la integració de les xarxes en continua i en alterna, el punt d'interconnexió pot estar localitzat llunys dels grans centres de generació, la qual cosa implica tenir una potència de curtcircuit molt reduïda. En la bibliografia científica s'han descrit diverses problemàtiques a l'hora de connectar un convertidor de commutació forçada a les xarxes dèbils. Per tal de pal.liar aquests inconvenients, en aquesta tesis es presenta un algorisme avançat de connexió de convertidors a xarxes dèbils basat en control vectorial. Des del punt de vista de les interaccions i interoperabilitat dels sistemes en corrent alterna i continua, no n'hi ha suficient en garantir l'estabilitat, ja que el propòsit finals dels operadors de xarxa és fer fluir una potencia a traves de la xarxa per tal de satisfer la demanda. Per aquest propòsit en aquesta tesis es presenta un control jeràrquic de control del flux de potència que fixa el flux de potència a traves d'una xarxa multi terminal canviant les consignes del control primari, tot assegurant l'estabilitat del sistema. Per tancar la tesis, es presenta un nou controlador per parcs eòlics basats en aerogeneradors de gàbia d'esquirol controlats per un sol convertidor

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines

Analysis, design and test of high efficiency electrical machines with a rotor winding

This thesis deals with the analysis, design and test of three-phase high efficiency electrical motors, with particular reference to motors with a rotor winding. At first, the background and the motivations of this work are described. The bibliography on the subjects is deeply examined and a selection of the most relevant papers can be found in the reference. In this scenario, the main objective of this thesis are illustrated. The Line-Start (LS) Synchronous Machine (SyM) design is a subject under investigation since the beginning of the last century, when solid state power converters was not available to drive SyMs. The LS SyM diffusion was limited by the intrinsic difficulties in its design and by the availability of the cheaper and more robust Induction Machine (IM). The working principle of IM and LS SyM are briefly described, as well as the state of the art of the techniques of analysis. Recently, there is a renewed interest on LS SyMs due to the new efficiency requirements and fast analysis techniques are required for the LS SyM design. A Finite-Element (FE) aided analytical model is developed to simulate the LS SyM dynamic. The aim is to develop a model that gives reliable solutions with limited computational efforts compared with other analysis techniques. With this procedure, the LS SyM rotor parameters can be quickly calibrated to fulfill the dynamic load requirements. An innovative analysis technique of LS SyM steady state condition is described. Such an analysis is carried out in the same reference frame used for classical SyMs. It is shown that the analysis can be used to optimize some machine parameters. The issues in LS SyM manufacturing are introduced, with particular reference to the die casting process. The possibility to apply the recent improvements in the SRM design to LS SyM is discussed from the manufacturing point of view. Stochastic optimization has been adopted for the design of electrical motors to reduce the torque ripple, increase the average torque and reduce the losses. The LS SyM torque ripple reduction, achieving at the same time a high average torque, is an important issue even though this topic is not treated extensively in the literature for LS SyM. For this reason, a stochastic optimization is considered in this thesis for the design of a new LS SyM lamination. The analysis is applied on a small size, 2-pole, three-phase LS SyM as this category is still not found in the motor market. The optimization is carried out considering the necessity to achieve a robust design, suitable for the industrial production, as such a LS SyM must be competitive with the workhorse of electrical motors, the IM. One of the most promising design is prototyped. Its performance are compared with the corresponding IM. To demonstrate the feasibility in adopting LS SyM in the large-scale production, an innovative LS SyM design is proposed. The main aim is to use the same lamination for motors of different number of poles so as to reduce the manufacturing cost. A tradeoff between contrasting aspects is necessary in the design step. The performance achievable by these rotor structures are quantified. An analytical model that describes the mutual interaction between coupled electrical circuits in machines with complex rotor structure is developed. Such a model is useful to analyze the parasitic torques in the torque characteristic of motors with rotor cage such as IM and LS SyM. The literature reveals that this topic has been discussed extensively for IM. As regards LS SyM, there is a lack of theoretical studies regarding harmonic phenomena due to the complex machine structure. This part of the thesis aims to fill this gap. The high and unstable cost of rare-earth PMs, together with the advances in solid-state control technology, leads designers to reconsider IM for variable speed drive (VSD) applications. To the aim of making the IM suitable for the full-speed sensorless control, a particular cage design is considered. An intentionally created saliency is introduced in the rotor so as to allow the rotor position to be estimated by means of a high frequency (HF) injected signal in the stator winding also at zero-speed. Different experimental tests are carried out on IMs with asymmetrical rotor cage to validate the analysis techniques and quantify the achievable performance. As far as the HF signal injection sensorless technique is concerned, the cross-saturation differential inductance of SyMs represents an issue. It causes a rotor position estimation error, reducing the region in which such technique is effective. The proper-ties of the cross-saturation inductance are deeply discussed. It is originally shown that the cross-saturation inductance depends from certain machine parameters. With such an analysis, a designer can consider the effect of the cross-saturation inductance in any model-based control algorithm. A rotor winding is added in Surface-mounted permanent-magnet machine (SPM) to create a HF anisotropy that is useful to detect the rotor position by means of a HF signal injection. Such a configuration is called ”ringed-pole”. In literature, this technique has been used on small-size machines. In certain configuration, the presence of the additional rotor winding causes significant rotor losses. This part of the thesis studies the rotor losses in ringed pole machines by means of FE analysis and analytical models. The aim is to investigate if the ringed-pole technique can be adopted also for large machines from the point of view of additional losses. With few exceptions, the work described in this thesis is always supported by means of experimental measurements. Dedicated experiments has been designed. Their results are compared with those achieved with analytical models or FE analysis