Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2014. / The application of digital control techniques has become dominant in power electronics owing to several advantages they present, when compared to analogue solutions. Their development is based on the use of microprocessors and microcontrollers, such as Application Specific Integrated Circuit (ASIC), Digital signal processors (DSP), Field Programmable Gate Arrays (FPGA), or a combination of these devices. This thesis presents an investigation of a soft-core based FPGA control system as a solution for power electronic applications. The aim was the development and implementation of a conversion controller, which purpose is to supply control inputs in the form of digital Pulse Width Modulation (PWM) signals, to a number of power electronic applications, such as single half and full bridge DC-DC converters, three phase and multicell inverters. The PWM control technique is achieved via their power semiconductor switching devices. These PWM control signals are necessary for the high frequency conversion of an analog input voltage (AC, DC or unregulated) to an analog output voltage of another level (AC or DC). This was intended to be achieved by exploiting and combining the advantages that FPGA and embedded processors provide such as high reconfigurability and multipurpose ability. This controller’s digital outputs, namely PWM switching signals, can be directly delivered to an analog signal amplification circuit to create an adequate voltage level before being processed by the converters’ switches.

[Truncated abstract] This thesis studies current sensing techniques that are designed to meet the requirements for the next generation of power converters. Power converters are often standardised, so that they can be replaced with a model from another manufacturer without an expensive system redesign. For this reason, the power converter market is highly competitive and relies on cutting-edge technology, which increases power conversion efficiency and power density. High power density and conversion efficiency reduce the system cost, and thus make the power converter more attractive to the customer. Current sensing is a vital task in power converters, where the current information is required for monitoring and control purposes. In order to achieve the above-mentioned goals, existing current sensing techniques have to be improved in terms of cost, power loss and size. Simultaneously, current information needs to be increasingly available in digital form to enable digital control, and to allow the digital transmission of the current information to a centralised monitoring and control unit. All this requires the output signal of a particular current sensing technique to be acquired by an analogue-to-digital converter, and thus the output voltage of the current sensor has to be sufficiently large. This thesis thoroughly reviews contemporary current sensing techniques and identifies suitable techniques that have the potential to meet the performance requirements of the next-generation of power converters. After the review chapter, three novel current sensing techniques are proposed and investigated: 1) The usefulness of the resistive voltage drop across a copper trace, which carries the current to be measured, to detect electrical current is evaluated. Simulations and experiments confirm that this inherently lossless technique can measure high currents at reasonable measurement bandwidth, good accuracy and low cost if the sense wires are connected properly. 2) Based on the mutual inductance theory found during the investigation of the copper trace current sense method, a modification of the well-known lossless inductor current sense method is proposed and analysed. This modification involves the use of a coupled sense winding that significantly improves the frequency response. Hence, it becomes possible to accurately monitor the output current of a power converter with the benefits of being lossless, exhibiting good sensitivity and having small size. 3) A transformer based DC current sense method is developed especially for digitally controlled power converters. This method provides high accuracy, large bandwidth, electrical isolation and very low thermal drift. Overall, it achieves better performance than many contemporary available Hall Effect sensors. At the same time, the cost of this current sensor is significantly lower than that of Hall Effect current sensors. A patent application has been submitted. .... The current sensing techniques have been studied by theory, hardware experiments and simulations. In addition, the suitability of the detection techniques for mass production has been considered in order to access the ability to provide systems at low-cost.

The paper presents design solution and physical implementation of a system for examination of electro hydraulic steering based on OSPE 200 components. The implementation is based on synthesis of required hydraulic and structure parameters, presented in a previous paper. Now we present the interconnection of the digital control system and the closed-loop flow diagram. A formal description of embedded software is presented too, which supports operation of PI control algorithm in real-time. Identification is performed based on experimentally reported the transitional process by developing mathematical models. Presents the structure and capabilities of the models for identification, as well as procedures for their validation.

Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: In the field of power electronic engineering, there is a need for a reconfigurable power electronic controller. Such a controller will enable engineers to stay focussed on their main field of study, not being side-tracked by the process of designing a high-speed digital controller to implement their ideas with. The design, construction and implementation of such a controller is presented in this paper. The design process involved defining the specifications of the controller and finding electronic components to satisfy them. After suitable components had been identified, a schematic design of the system was done. The netlist of the schematic was exported to a printed circuit board (PCB) design program, where the final layout was done and the connections between the devices routed. Before the PCB was manufactured, the firmware for the programmable logic devices (PLDs) was written to ensure that it fits in the selected PLDs of the system. After the PCB was manufactured and all its components fitted, it was tested and eventually used to implement the control of a shunt active power filter. / AFRIKAANSE OPSOMMING: Wanneer navorsing gedoen word in die drywings-elektronika gebied, word ’n behoefte vir ’n heropstelbare drywings-elektroniese beheerder ondervind. So ’n beheerder sal ingenieurs in staat stel om gefokus te bly op hulle hoof studieveld, sonder dat hulle aandag hoef te skenk daaraan om ’n ho¨e spoed digitale beheerder te ontwerp om hulle idees mee te implementeer. Die ontwerp, konstruksie en implementering van so ’n beheerder word in hierdie tesis voorgelˆe. Die ontwerp behels die bepaling van die spesifikasies van die beheerder en die opsporing van elektroniese komponente wat hierdie spesifikasies sal bevredig. Nadat geskikte komponente gevind is, is ’n skematiese ontwerp van die hele beheerder gedoen. Die lys van die verbindings tussen die komponente (Eng. netlist) is na die stroombaanbord ontwerp program gestuur, waar die finale uitleg van die bord gedoen is. Voordat die bord gemaak kon word, is die programmatuur vir die programmeerbare logikatoestelle geskryf om te verseker dat dit in die toestelle wat in die sisteem gebruik word, sal pas. Nadat die stroombaanborde vervaardig is en al die komponente daarop gemonteer is, is die bord getoets en uiteindelik gebruik om die beheer van ’n aktiewe drywingsfilter te implementeer.

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

No description available.

This thesis is about digital control theory and presents an account of methods for enabling and analysing intentional non-uniform sampling in discrete compensators. Most conventional control algorithms cause numerical problems where data is collected at sampling rates that are substantially higher than the dynamics of the equivalent continuous-time operation that is being implemented. This is of relevant interest in applications of digital control, in which high sample rates are routinely dictated by the system stability requirements rather than the signal processing needs. Considerable recent progress in reducing the sample frequency requirements has been made through the use of non-uniform sampling schemes, so called alias-free signal processing. The approach prompts the simplification of complex systems and consequently enhances the numerical conditioning of the implementation algorithms that otherwise, would require very high uniform sample rates. Such means of signal representation and analysis presents a variety of options and thus is being researched and practiced in a number of areas in communications. However, the control communities have not yet investigated the use of intentional non-uniform sampling, and hence the ethos of this research project is to investigate the effectiveness of such sampling regimes, in the context of exploiting the benefits. Digital control systems exhibit bandwidth limitations enforced by their closed-loop frequency requirements, the calculation delays in the control algorithm and the interfacing conversion times. These limitations pave the way for additional phase lags within the control loop that demand very high sample rates. Since non-uniform sampling is propitious in reducing the sample frequency requirements of digital processing, it proffers the prospects of being utilised in achieving a higher control bandwidth without opting for very high uniform sample rates. The concept, to the author s knowledge, has not formally been studied and very few definite answers exist in control literature regarding the associated analysis techniques. The key contributions adduced in this thesis include the development and analysis of the control algorithm designed to accommodate intentional non-uniform sample frequencies. In addition, the implementation aspects are presented on an 8-bit microcontroller and an FPGA board. This work begins by establishing a brief historical perspective on the use of non-uniform sampling and its role for digital processing. The study is then applied to the problem of digital control design, and applications are further discoursed. This is followed by consideration of its implementation aspects on standard hardware.

Within the nuclear industry, there have been numerous instances of radio transmissions interfering with sensitive plant equipment. Instances documented vary from minor instrument fluctuations to major plant transients including reactor trips. With the nuclear power industry moving toward digital technologies for control and reactor protection systems, concern exists regarding their potential susceptibility to contemporary wireless telecommunications technologies. This study evaluates the susceptibility of Comanche Peak's planned turbine controls upgrade to IEEE 802.11 compliant wireless radio emissions. The study includes a review of previous research, industry emissions standards, and technical overview of the various IEEE 802.11 protocols and details the testing methodology utilized to evaluate the digital control system. The results of this study concluded that the subject digital control system was unaffected by IEEE 802.11 compliant emissions even when the transmitter was in direct contact with sensitive components.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979. / Includes bibliographical references. / by John Edward Pieszcynski. / Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1979.

De maneira geral, a necessidade de aumentar o desempenho e diminuir o tamanho dos sistemas mecatrônicos tem levado a indústria moderna a idealizar e desenvolver sistemas de posicionamento com boas características de aceleração e precisão de posicionamento. Por outro lado, a crescente demanda de componentes com melhores características metrológicas e de acabamento, tais corno lentes para raio X e infra vermelho, tem exigido o desenvolvimento de variados tipos de sistemas de microposicionamento capazes de movimentar elementos de máquinas em distâncias muito pequenas com alto grau de exatidão, dentre os quais podem-se destacar os acionados por meio de atuadores piezoelétricos. Este trabalho propõe a utilização de um novo tipo de atuador baseado na propriedade de estricção eletromagnética de certas ligas metálicas (atuadores magnetoestritivos) associado a um sistema de controle digital que utiliza um algoritmo de controle baseado em lógica difusa e redes neurais artificiais para o controle de microposicionamento. Metodologias e princípios de projeto para engenharia de precisão são abordados de forma a auxiliar no desenvolvimento de dois protótipos de posicionadores para uso em usinagem de ultraprecisão. Resultados obtidos em testes experimentais apontam para urna melhoria no comportamento dinâmico dos microposicionadores acionados por atuadores magnetoestritivos. Isto permite sua utilização como alternativa válida no posicionamento submicrométrico. / In general, actual requirements such as high performance and small sizes of mechatronic systems, has led modern industry to design positioning systems with good characteristics of acceleration and positioning accuracy. The increasing demand of components with better metrological and finish characteristics, as X-ray and infra-red lens, has allowed the development of a number of types of micropositioning systems that are able to move machine elements to very small distances with high levels of accuracy. In this work it is proposed the use of a new type of actuator that applies the properties of electromagnetic strain of certain metallic alloys (magnetostrictive actuators). lt is also proposed the application of a digital control system that uses a control algorithm which is based on fuzzy logic and artificial neural networks for the micropositioning control. Design principles and methodologies related to precision engineering are discussed with the purpose of aiding the development of two prototypes of positioners for ultraprecision rnachining, experimental results show that micropositioner driven by magnetostrictive actuators have better dynamics behaviours. This allows the use of such actuators as an valid alternative for positioning in submicrometer range.