Application of Sliding Mode Controller and Linear Active Disturbance Rejection Controller to a PMSM Speed System

Permanent magnet synchronous motor (PMSM) is a popular electric machine in industry for its small volume, high electromagnetic torque, high reliability and low cost. It is broadly used in automobiles and aircrafts. However, PMSM has its inherent problems of nonlinearity and coupling, which are challenges for control systems design. In addition, the external disturbances such as load variation and noises could degrade the systems performance. Both sliding mode control (SMC) and active disturbance rejection control (ADRC) are robust against disturbances. They can also compensate the nonlinearity and couplings of the PMSM. Therefore, in this thesis, we apply both SMC and ADRC to a PMSM speed system. Our control goal is to drive the speed outputs of the PMSM speed system to reference signals in the presences of nonlinearity, disturbance, and parameter variations. Simulation results verify the effectiveness of SMC and ADRC on the speed control for PMSM systems in spite of the presences of external disturbance and internal system uncertaintie

Next-generation equipment and procedures for combined resonant column and torsional shear testing

In this dissertation, work aimed at developing next-generation equipment and procedures for combined resonant column and torsional shear (RCTS) testing are detailed. The work in this dissertation covers three key areas of RCTS testing that need improvement to reach the next level of RCTS testing. The first area involved improvement in measurement resolution with modern control and monitoring equipment. Concurrently, original software was written to enhance the efficiency, accuracy, and repeatability of the test. The second area involved advancing concepts for evaluating and modeling nonlinear behavior of soil, which was done in part by using raw RCTS test data collected and stored from 2013-2017. The third area involved evaluating and modifying the design of the existing RCTS device to accommodate higher levels of shearing strain and provide higher loading capacity. First, when testing at small shear strains (< 0.001%) within the linear-elastic range of soils, very small excitation voltages must be used and very small voltages are recorded from the RCTS sensors. Obtaining accurate measurements in the linear-elastic range is critically important when testing at low confining pressures (in the range of 0.1 to 1 atm). In traditional RCTS data acquisition systems, very small recorded voltages are lost due to limited resolution of the control and monitoring subsystems. Concurrently, the very small recorded voltages are generally heavily contaminated by environmental background noise that invalidates the automated process for reducing raw data into engineering results. Control and monitoring equipment and software were developed that can enhance the measurement and data reduction process when making low-strain measurements. Second, testing of soil in the nonlinear shear strain range (typically greater than 0.001%) is a complex process that departs from traditional dynamic models for single-degree-of-freedom (SDOF) systems. Traditionally, RCTS results from testing in the nonlinear shear strain range involve slight adaptation of traditional SDOF models to obtain nonlinear relationships. Nonlinear dynamics model concepts were taken from literature and adapted to better understand and model nonlinear behavior of soils in RCTS testing. Furthermore, development of nonlinear models at moderate strains help to bridge the spectrum of soil testing which tends to divide into evaluating soils at small to moderate strains (< 0.2%) or at large strains (≥ 0.2%). Third, when testing soils at large shearing strains (> 0.2%), traditional RCTS systems are physically or electronically limited. At higher confining pressures (> 2 atm) where soils become quite stiff, the traditional RCTS control equipment is electronically incapable of driving enough torque output to strain soils in shear above desired levels (> 0.1%). At low confining pressures ( 0.5%). An RCTS testing device was designed that has a torque-output capacity at least three times greater than a traditional RCTS device and an allowable degree of twist that can generate shearing strains above 1%.Civil, Architectural, and Environmental Engineerin

Improved micro-contact resistance model that considers material deformation, electron transport and thin film characteristics

This paper reports on an improved analytic model forpredicting micro-contact resistance needed for designing microelectro-mechanical systems (MEMS) switches. The originalmodel had two primary considerations: 1) contact materialdeformation (i.e. elastic, plastic, or elastic-plastic) and 2) effectivecontact area radius. The model also assumed that individual aspotswere close together and that their interactions weredependent on each other which led to using the single effective aspotcontact area model. This single effective area model wasused to determine specific electron transport regions (i.e. ballistic,quasi-ballistic, or diffusive) by comparing the effective radius andthe mean free path of an electron. Using this model required thatmicro-switch contact materials be deposited, during devicefabrication, with processes ensuring low surface roughness values(i.e. sputtered films). Sputtered thin film electric contacts,however, do not behave like bulk materials and the effects of thinfilm contacts and spreading resistance must be considered. Theimproved micro-contact resistance model accounts for the twoprimary considerations above, as well as, using thin film,sputtered, electric contact

Computational Intelligence Application in Electrical Engineering

The Special Issue "Computational Intelligence Application in Electrical Engineering" deals with the application of computational intelligence techniques in various areas of electrical engineering. The topics of computational intelligence applications in smart power grid optimization, power distribution system protection, and electrical machine design and control optimization are presented in the Special Issue. The co-simulation approach to metaheuristic optimization methods and simulation tools for a power system analysis are also presented. The main computational intelligence techniques, evolutionary optimization, fuzzy inference system, and an artificial neural network are used in the research presented in the Special Issue. The articles published in this issue present the recent trends in computational intelligence applications in the areas of electrical engineering

Switched Flux Permanent Magnet Brushless Machines for Electric Vehicles

This thesis investigates different topologies of switched flux permanent magnet (SFPM) machines and variable flux (VF) methods for high speed applications. Although several novel topologies of SFPM machines have been proposed and investigated recently, their torque-speed capability has not been studied systematically. Therefore, the torque-speed capability as well as the open circuit and electromagnetic performance of conventional SFPM machines with three different stator/rotor pole combinations, i.e. 12/10, 12/13 and 12/14, and three novel SFPM machine topologies, i.e. multi-tooth, E-core and C-core are analysed and investigated by the finite element (FE) method and experiments. Moreover, in order to improve the flux-weakening capability of these machines a variable flux method using flux adjusters (FAs) is employed and the corresponding electromagnetic performance of the machines are investigated, analysed and compared. Both FE and measured results show when the FAs are used the torque-speed capability of the three conventional machines can be improved significantly, while no improvement is shown in the three novel topologies primarily due to the large winding inductances. The technique of using flux adjusters has been improved by reducing the number of FAs. Thus, a new mechanical variable-flux machine topology, which uses only half of FAs outside the stator at alternative stator poles, is proposed, developed and analysed. Open circuit results, electromagnetic performance and torque- and power-speed curves of the 12/10, 12/13 and 12/14 stator/rotor pole SFPM machines with alternative FAs are predicted and compared by 2D and 3D-FE, and experimentally validated. Furthermore, a novel SFPM machine topology with radial and circumferential PMs is proposed, investigated and optimized. This topology reduces the stator flux leakage and offers high magnetic utilization. Moreover, this topology can also be developed as a mechanical variable flux machine. Finally, three SFPM machines with variable flux techniques, i.e. mechanically movable flux adjusters (MMFA), mechanically rotatable permanent magnet set (MRMS) and hybrid excitation with backside DC coils (HEBC) are analysed. Their open circuit results and electromagnetic performance with emphasis on torque-speed characteristic are investigated and compared. Additionally, the required power to switch between flux weakening and strengthening states, flux weakening capability and permanent magnet demagnetization withstand capability are predicted, analysed and compared. The influence of end-effect on the torque-speed capability in the conventional, multi-tooth, E-core and C-core SFPM machines is investigated. Measurements and 3D-FE are performed to obtain the torque-speed curve in order to validate the findings of the research. The 3D-FE predicted results match well with the measured results, while the 2D-FE predicted results are lower due to the high end-effect in the SFPM machines

Modeling and Control of Reluctance Actuators

Los actuadores de reluctancia son dispositivos que se caracterizan por una elevada densidad de fuerza, buena eficiencia, gran tolerancia frente a fallos y un coste reducido. Estas características hacen que estén siendo considerados como una alternativa muy prometedora frente a otro tipo de actuadores electromagnéticos en ciertas aplicaciones que requieren gran velocidad y precisión. Por otro lado, los actuadores de reluctancia también son la solución ideal para algunos dispositivos electromecánicos que requieren unas prestaciones modestas, lo cual es debido principalmente a que son compactos, tienen un bajo coste y consumen relativamente poco. En concreto, los relés electromecánicos y las válvulas de solenoide son dispositivos cuya operación está basada en la fuerza creada por un pequeño actuador de reluctancia.A pesar de sus ventajas, los actuadores de reluctancia son sistemas complejos cuya dinámica es no lineal. Una de sus características más distintivas es que la fuerza magnética que provoca el movimiento es siempre de atracción y, además, depende fuertemente de la posición de la armadura. Básicamente, el comportamiento de esta fuerza es lo que explica que dispositivos como los relés y las electroválvulas sufran fuertes impactos y desgaste cada vez que son activados. Adicionalmente, algunos fenómenos electromagnéticos como la histéresis magnética o las corrientes inducidas hacen que el modelado dinámico de los actuadores de reluctancia sea bastante complejo. El trabajo realizado en esta tesis doctoral está enfocado en estudiar las posibilidades que ofrecen estos actuadores y, en concreto, en analizar el comportamiento dinámico y proponer algoritmos de estimación y control para relés electromecánicos y válvulas de solenoide.El primer objetivo de la investigación es el desarrollo de modelos dinámicos para actuadores de reluctancia, es decir, modelos de orden reducido que puedan ser utilizados para realizar simulaciones transitorias lo más precisas posibles con un bajo coste computacional. Para ello, lo primero que se ha estudiado es el comportamiento electromagnético de estos sistemas. El método de modelado más usado en la tesis es el de los circuitos magnéticos equivalentes (MEC, por sus siglas en inglés). No obstante, también se han realizado algunas simulaciones con modelos de elementos _nitos, en concreto para validar las aproximaciones del método MEC o para calcular la reluctancia del entrehierro. Se han estudiado los principales fenómenos electromagnéticos que aparecen en los actuadores de reluctancia, lo que ha llevado a la obtención de expresiones analíticas para modelar la dispersión de flujo, las corrientes inducidas y la saturación e histéresis magnéticas. Por otra parte, la expresión de la fuerza magnética que produce el movimiento se ha obtenido mediante un balance energético del sistema.El movimiento de la armadura también se ha estudiado en la tesis. Dado que los actuadores de reluctancia tienen generalmente un recorrido físicamente acotado, se han propuesto dos técnicas diferentes que permiten modelar los límites del movimiento y los rebotes de la armadura. Una vez estudiado el movimiento, el modelo mecánico se ha combinado con las ecuaciones electromagnéticas para poder analizar el comportamiento dinámico del actuador en su conjunto. Se han desarrollado cinco modelos dinámicos distintos, desde el más sencillo posible hasta uno que incluye todos los fenómenos electromagnéticos citados con anterioridad, y posteriormente se han comparado teniendo en cuenta su precisión y coste computacional.Las medidas experimentales son fundamentales a la hora de analizar y caracterizar cualquier sistema dinámico. Por ello, otro de los objetivos de la tesis ha sido la evaluación de distintas técnicas de medida que pudieran ayudar a mejorar la comprensión sobre el comportamiento dinámico de los actuadores de reluctancia y, en caso de que fuera posible, formar parte de un bucle de control realimentado. En este sentido, se ha intentado grabar el movimiento de uno de los dispositivos estudiados mediante tres instrumentos ópticos distintos. Los resultados indican que, a pesar de que en ciertas situaciones sí sería posible medir la trayectoria del dispositivo durante su movimiento, ninguno de los instrumentos podría aplicarse en la práctica por su baja flexibilidad y alto coste. Por este motivo, también se ha explorado el uso de otras variables que puedan ser medidas mucho más fácilmente.Otra parte importante de la investigación ha estado centrada en técnicas de estimación. Se han desarrollado dos algoritmos que son capaces de estimar, en tiempo real, el flujo magnético, la resistencia y la inductancia de un actuador dado. Los algoritmos utilizan únicamente medidas de tensión y corriente, lo cual representa una clara ventaja ya que no se necesita utilizar sensores o equipamiento añadido. Las prestaciones de ambos estimadores han sido analizadas mediante simulación y experimentos reales. El problema de estimar la posición de la armadura también se ha abordado en la tesis. En concreto, se ha prestado especial atención en resaltar los efectos que la histéresis magnética produce en la estimación, algo que no había sido estudiado con anterioridad.Finalmente, se han propuesto distintas técnicas de control para actuadores de reluctancia. En concreto, el objetivo principal es lograr que estos sigan un movimiento con aterrizaje suave, es decir, un movimiento que no dé lugar a impactos o rebotes. Como un primer paso, se han estudiado las propiedades básicas de los sistemas de control, es decir, la estabilidad, controlabilidad y observabilidad. Después se ha explorado la técnica de linealización por realimentación como un posible método para diseñar un bucle de control realimentado para la trayectoria de la armadura. Los resultados obtenidos demuestran que el control por realimentación es capaz de controlar el movimiento con gran precisión, siempre y cuando haya disponibles medidas o estimaciones precisas de la posición en tiempo real. Como esta situación es difícil que se dé en la práctica, se ha estudiado el uso de técnicas de control óptimo en bucle abierto para aquellos casos en los que la posición de la armadura no se pueda obtener. En particular, se han obtenido distintas soluciones tiempo óptimo y de energía óptima para un actuador nominal y, posteriormente, se ha analizado su robustez utilizando un método de Montecarlo.Como alternativa a los métodos clásicos, se ha estudiado la aplicabilidad de los métodos Run-to-Run (R2R) en actuadores de relutancia. Estas técnicas están diseñadas específicamente para sistemas que realizan un proceso repetitivo y, por lo tanto, son idóneas para dispositivos como los relés y las válvulas. En concreto, los métodos R2R implícitos se basan en la idea de construir una función que evalúe el desempeño del sistema al final de cada repetición. De esta forma, es posible mejorar el comportamiento dinámico del actuador a lo largo de las repeticiones utilizando un algoritmo de búsqueda.Las posibilidades para diseñar un controlador R2R son prácticamente infinitas, así que en la tesis se dan consejos prácticos sobre cómo elegir y parametrizar la señal de entrada, cómo usar las medidas disponibles para evaluar el comportamiento del sistema o cómo comparar distintos algoritmos de búsqueda. Los experimentos realizados demuestran que el algoritmo R2R diseñado es capaz de mejorar enormemente el comportamiento de un relé electromecánico y que, después de unos pocos ciclos, ,los resultados son incluso mejores que con cualquier estrategia presente en la literatura.Reluctance actuators are characterized by having a high force density, good efficiency, high fault tolerance and reduced cost. These features make them a promising alternative to other electromagnetic actuators for high-speed and high-precision applications. In addition, reluctance actuators are also ideal for small switch-type devices that require a modest performance because of their compactness, low cost, reduced mass and low energy dissipation. In particular, electromechanical switches and solenoid valves are devices whose operation is based on the force created by a small reluctance actuator. Despite their advantages, reluctance actuators are systems with highly nonlinear dynamics. One of their most distinctive features is that the magnetic force that produces the motion is always attractive and varies greatly with the position of the armature. In essence, the nature of this force explains why switch-type devices like relays and valves are subject to strong impacts and wear each time they are operated. In addition to that, electromagnetic phenomena such as magnetic hysteresis and eddy currents make the dynamic modeling of reluctance actuators even more difficult. The work of this thesis aims to investigate the capabilities of reluctance actuators and, in particular, to analyze the dynamic behavior and propose estimation and control algorithms for electromechanical switches and solenoid valves. The first objective of the investigation is the development of control-oriented dynamical models for reluctance actuators, i.e., low-order models that can be used to perform accurate transient simulations with low computational requirements. For that, the electromagnetic behavior of these systems is firstly studied. The magnetic equivalent circuit (MEC) methodology is selected as the primary modeling technique. Simulations from finite element models are also used for some specific purposes, e.g., to verify the assumptions of the MEC approach or to calculate the reluctance of the air gap. Then, the main electromagnetic phenomena that occur in reluctance actuators are studied. Analytic expressions are derived to model magnetic saturation, hysteresis, flux fringing and eddy currents, and an energy balance is used to obtain the expression for the magnetic force that produces the motion. After that, the motion of the armature is incorporated to the analysis. Given that reluctance actuators usually have a limited range of motion, two different techniques are proposed to model the limits of the armature stroke and the bouncing phenomenon. Then, the electromagnetic equations and the mechanical models are combined to describe the overall dynamic behavior of the actuator. Five different dynamical models are presented, ranging from a computationally inexpensive structure to a comprehensive model that includes saturation, hysteresis, eddy currents and flux fringing. The models are compared in terms of accuracy and computational requirements. Measurements play an important role in the analysis and characterization of dynamical systems. Thus, another objective of this thesis is the evaluation of different measurement methodologies that may improve the understanding of the dynamic behavior of reluctance actuators and, if possible, be used as part of a feedback controller. In this regard, three optical instruments are explored in order to record the motion of switch-type actuators. The results show that, even though in some cases it is possible to measure the position of several components of the device, none of the instruments could be applied in a practical situation due to their low flexibility and high cost. For that reason, other variables that are much more easily obtainable are also explored. Another significant part of the research is devoted to estimation in reluctance actuators. Two different algorithms are proposed to estimate the magnetic flux, the resistance and the inductance of the device, both of which can be implemented in real time. The algorithms rely only on measurements of the coil voltage and current, which represents a clear advantage because no additional hardware is required. Simulation and experiments are presented to show the performance of the estimators. Furthermore, the estimation of the armature position is also investigated in this work. In particular, special focus is put on highlighting the effects of magnetic hysteresis on the performance of different estimation approaches. Control strategies are then proposed to achieve soft landing in reluctance actuators, i.e., a controlled motion without impacts or bounces. As a first step, the basic properties of control systems theory---stability, controllability and stability---are investigated for a nominal actuator. Then, feedback linearization is explored as a method to design a trajectory tracking controller for the armature position. The obtained results show that soft landing can be accomplished by means of feedback control provided that accurate measurements or estimates of the position are available. Since this situation is rare in practice, open-loop optimal control is proposed as an alternative technique when the position is not accessible. Different time-optimal and energy-optimal solutions are derived for a nominal actuator and then compared in terms of robustness using a Monte Carlo analysis. Finally, Run-to-Run (R2R) control is explored as another method that may be used to improve the performance of reluctance actuators. These techniques are specifically designed for systems that perform a repetitive operation and, hence, they are very well suited to being applied to switch-type devices. In particular, implicit R2R methods are based on the idea of building a function that evaluates the performance of the system at the end of each repetition. In this way, the dynamic behavior of the actuator can be gradually improved along the repetitions by conducting a black-box search. Considering that the possibilities to design a R2R controller are almost endless, practical advice is given on how to select and parameterize the input profile, how to use measurements to evaluate the system performance and how to compare different search algorithms. The performed experiments show that the designed R2R controller is able to improve greatly the behavior of a switch-type device and that, after a few cycles, it outperforms other methodologies in the literature.<br /

Simulation analysis of ultrasonic testing in steel-based butt weld joint

Within this study, a simulation analysis based on Ultrasonic Testing (UT) is made using Comsol Multiphysics. Comsol Multiphysics is a software that can simplify many aspects of building UT method and also can be used to obtain a fast understanding of the results of altering the fundamental parameters. The software program has useful features which can help in technique development especially for UT inspectors in Non- destructive Testing (NDT) field. The focus of this study is to conduct a simulation analysis of internal weld defects by developing the model of defects in a weld structure sample configured using the software. The model is developed based on actual parameters and characterization of weld structure sample and internal weld defects. The results of analysis show that each type of defects which are incomplete penetration, slag inclusion and lack of fusion have different signal pattern and signal amplitude which are depended on the characterizations of those defects themselves

Pembangunan portal pendidikan teknik dan vokasional: satu kajian awal di kalangan Pelajar Sarjana PTV Jabatan Pendidikan Teknik dan Vokasional Fakulti Teknologi Kejuruteraan

Tujuan kajian ini adalah untuk mengkaji sejauh manakah keperJuan pelajar terhadap portal Pendidikan Teknik dan Vokasional (PTV). Sebuah portal PTV dibangunkan dalam kajian berasaskan produk ini. Sampel bagi kajian ini terdiri daripada pelajar sarjana pendidikan teknik dan vokasional, semester 3. Dapatan kajian ini dianalisis dengan menggunakan perisian SPSS versi 10. Pada peringkat awal projek ini, keperluan pelajar terhadap portal PTV dikenal pasti. Selepas itu, ciri-ciri yang perlu dibangunkan dalam portal PTV dikenal pasti dengan menggunakan kaedah borang soal selidik. Satu portal PTV dibangunkan berdasarkan dapatan kajian tersebut. Pada peringkat akhir projek ini, penilaian dilakukan ke atas portal PTV yang telah dibangunkan. Tujuan penilaian ini adalah untuk mengenal pasti sejauh manakah portal PTV ini memenuhi keperluan pelajar. Daripada dapatan kajian didapati portal PTV amat diperlukan oleh pelajar. Selain daripada itu, daripada dapatan kajian, portal PTV yang telah dibangunkan ini beryaya memenuhi keperluan pelajar. Cadangan untuk memperbaiki portal PTV yang telah dibangunkan ini diberi oleh responden. Kajian lanjutan patut dilakukan ke atas portal PTV yang telah dibangunkan bagi memperbaiki serta memumikan konsep reka bentuk dan pengurusan maklumat

De-Centralized and Centralized Control for Realistic EMS Maglev Systems

A comparative study of de-centralized and centralized controllers when used with real EMS Maglev Systems is introduced. This comparison is divided into two parts. Part I is concerned with numerical simulation and experimental testing on a two ton six-magnet EMS Maglev vehicle. Levitation and lateral control with these controllers individually and when including flux feedback control in combination with these controllers to enhance stability are introduced. The centralized controller is better than the de-centralized one when the system is exposed to a lateral disturbing force such as wind gusts. The flux feedback control when combined with de-centralized or centralized controllers does improve the stability and is more resistant and robust with respect to the air gap variations. Part II is concerned with the study of Maglev vehicle-girder dynamic interaction system and the comparison between these two controllers on this typical system based on performance and ride quality achieved. Numerical simulations of the ODU EMS Maglev vehicle interacting with girder are conducted with these two different controllers. The de-centralized and centralized control for EMS Maglev systems that interact with a flexible girder provides similar ride quality

FLATNESS BASED CONTROL OF MICRO-HYDROKINETIC RIVER ELECTRIFICATION SYSTEM

Published ThesisIn areas where adequate water resource is available, hydrokinetic energy conversion systems are currently gaining recognition, as opposed to other renewable energy sources such as solar or wind energy. The operational principle of hydrokinetic energy is not similar to traditional hydropower generation that explores use of the potential energy of falling water, which has drawbacks such as the expensive construction of dams and the disturbance of aquatic ecosystems. Hence, hydrokinetic energy generates electricity by making use of underwater turbines to extract the kinetic energy of flowing water, with no construction of dams or diversions. A hydrokinetic turbine uses flowing water, which varies with climatic conditions throughout the year, to power the shaft of a generator, hence, generating an unstable energy output. The aim of this dissertation is to develop a controller that will be used to stabilize the output voltage and frequency generated in a hydrokinetic energy system. An overview of various methods used to minimize the fluctuating impacts of power generated from renewable energy sources is included in the current conducted research. Several renewable energy sources such as biomass, wind, solar, hydro and geothermal have been discussed in the literature review. Different control methods and topologies have been cited. Hence, the study elaborates on the adoptive control principles, which include the load ballast control, dummy load control, proportional integral and derivative (PID) controller system, proportional integral (PI) controller system, pulse-width modulation (PWM) control, pitch angle control, valve control, the rate of river flow at the turbine, bidirectional diffuser-augmented control and differential flatness based controller. These control operations in renewable energy power generation are mainly based on a linear control approach. In the case whereby a PI power controller system has been developed for a variable speed hydrokinetic turbine system, a DC-DC boost converter is used to keep constant DC link voltage. The input DC current is regulated to follow the optimized current reference for maximum power point operation of the turbine system. The DC link voltage is controlled to feed the current in the grid through the line side PWM inverter. The active power is regulated by q-axis current while the reactive power is regulated by d-axis current. The phase angle of utility voltage is detected using PLL (phased locked loop) in a d-q synchronous reference frame. The proposed scheme is modelled and simulated using MATLAB/ Simulink, and the results give a high quality power conversion solution for a variable speed hydrokinetic system. In the second case, whereby the differential flatness concept is applied to a controller, the idea of this concept is to generate an imaginary trajectory that will take the system from an initial condition to a desired output generating power. This control concept has the ability to resolve complex control problems such as output voltage and frequency fluctuations of renewable energy systems, while exploiting their linear properties. The results show that the generated outputs are dynamically adjusted during the voltage regulation process. The advantage of the proposed differential flatness based controller over the traditional PI control resides in the fact that decoupling is not necessary and the system is much more robust as demonstrated by the modelling and simulation studies under different operating conditions, such as changes in water flow rate