370 resultados para Retificador PWM trifásico


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永磁同步伺服电动机(PMSM)以其优越的性能广泛应用于各个机械传动领域。对PMSM的研究具有非常大的实际意义和价值,尤其对于我们单位目前在建大科学工程CSR。本文采用美国TI公司专用于电动机控制的数字信号处理器(DSP)芯片TMs320LF2406A作为核心,设计和开发全数字化的PMSM矢量调速控制系统。深入研究永磁同步电动机的矢量控制理论,建立起相应数学模型,然后提出矢量控制调速方案,并通过Mat lab仿真论证其可行性。介绍了硬件,软件结构及其实现。硬件方面主要介绍了控制电路各部分的设计和调试。在硬件基础上,用T工公司DSP汇编语言编程,实现电流环和速度环的双环控制,给出了系统程序和PWM信号产生的思路,并给出了主要模块的源程序。为了提高程序的运行效率,节省存储空间和提高系统的可靠性,程序中尽可能多的采用了数据表结构。

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本文分析了国内外开关电源的发展和现状,研究了高压开关电源的基本原理以及开关电源在电力直流操作电源系统中的应用。根据兰州重离子加速器的要求,设计了一种高稳定度高压开关电源。该系统在借鉴国外和已有的类似电源的基础上,通过采用新的元器件和新的电力电子技术设计而成。该系统以工GBT作为功率开关器件,构成BUCK开关变换器,采用脉宽调制(PWM)技术来控制输出电压的变化。系统中采用TL494、UC3637、ML57962等一系列集成电路,以实现实时采样电压反馈信号、PWM信号以及工GBT所需要的功率驱动信号。电路中采用斩波调压和逆变分开,各司其职的结构,保证了电路可靠、线性的调节;采用前馈电路进行补偿,确保系统能很好的抑制电网的中频扰动。通过MATLAB的计算仿真证明,这些措施都对对系统的性能起到了很好的作用。为了系统的安全可靠,还设计了软启动和过流保护电路。通过实验证明该系统能安全、可靠运行,达到了设计要求。

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提出一种基于FPGA的可重构嵌入式微处理器控制系统.在FPGA中嵌入两个NiosⅡ软核,用VHDL语言编写用户自定义组件.在一个由NiosⅡ软核组成的处理器上实现PWM信号生成、编码器信号处理以及多电机同步伺服运算等,在另一个处理器实现机器人任务管理.该控制系统针对微小型爬壁机器人的控制系统设计,不仅具有良好的实时多任务处理能力,而且具有可重构的特点,因而可应用于一类微小型机器人控制系统以提高其设计的灵活性.

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为了实现水下机器人(UUV,Unmanned Underwater Vehicle)的高精度控制,深入研究了螺旋桨驱动UUV推进系统各个环节运行机理,并建立了它们各自的数学模型,包括PWM模块、直流永磁电机、螺旋桨、舵的数学模型。多功能仿真试验和湖试试验的系统响应曲线基本吻合,一方面表明本文建立的推进系统模型的正确性,另一方面体现了在多功能仿真平台上调试的控制策略和控制器参数具有很大的可信度。

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本文以863-512型号项目为背景,从运动特性、运动描述、运动控制以及运动规划等几个方面研究履带式移动机器人的行动规划技术;首先从理论上分析了履带式移动机器人的内在运动传递机理,指出了其区别于轮式移动载体的独特的运动特性,尤其是在其转向特性方面,得出了履带式移动机器人运动角速度几乎不可控原理、原地转弯转不准问题、以及履带式车辆行动规划时所要遵循的规则等重要结论,针对履带式移动机器人的纵向运动控制问题,讨论了其速度控制模型,提出了一种速度测量与控制的简单、准确、可靠的方法。在磺向运动方面,提出了一种基于FM-LIKE和AM-LIKE相结合的复合控制技术,解决了难度较大的方向控制问题。最后提供了实验结果,证明了上述方法与结论的正确性。上述方法与结论,作为863-512某型号任务的一部分,业已通过验收。

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To explore the neural mechanisms underlying conditioned immunomodulation, this study employed the classical taste aversion (CTA) behavioral paradigm to establish the conditioned humoral and cellular immunosuppression (CIS) in Wistar rats, by paring saccharin (CS) with intraperitoneal (i.p.) injection of an immunosuppressive drug cyclophophamide (UCS). C-fos immunohistochemistry method was used to observe the changes of the neuronal activities in the rat brain during the acquisition, expression and extinction of the conditioned immunosuppression (CIS). The followings are the main results: 1. Five days after one trial of CS-UCS paring, reexposure to CS alone significantly decreased the level of the anti-ovalbumin (OVA) IgG in the peripheral serum. Two trials of CS-UCS paring and three reexposures to CS not only resulted in further suppression of the primary immune response, but also reduced the numbers of peripheral lymphocytes and white blood cells. This finding indicates that CS can induce suppression of the immune function, and the magnitude of the effects is dependent on the intensity of training. 2. On day 5 following two trials of CS-UCS pairing, CS suppressed the spleen lymphocytes responsiveness to mitogens ConA, PHA and PWM, and decreased the numbers of peripheral lymphocytes and white blood cells. On day 15, only PHA induced lymphocyte proliferation was suppressed by CS. On day 30, presentation of CS did not have any effect on these immune parameters. These results suggest that the conditioned suppression of the cellular immune function can retain 5-15 days, and extinct after 30 days. 3. CTA was easily induced by one or two CS-UCS parings, and remained robust even after 30 days. These data demonstrate that CIS can be dissociated from CTA, and they may be mediated by different neural mechanisms. 4. Immunohistochemistry assays revealed a broad pattern of c-fos expression throughout the rat brain following the CS-UCS pairing and reexposure to CS, suggesting that many brain regions are involved in CIS. Some brain areas including the solitary tract nucleus (Sol), lateral parabrachial nucleus (LPB) and insular cortex (IC), showed high level c-fos expressions in response to both CS and UCS, suggesting that they may be involved in the transmission and integration of the CS and UCS signals in the brain. There were dense c-FOS positive neurons in the paraverntricular nucleus (PVN) and supraoptic nucleus (SO) of hypothalamus, subfornical organ (SFO) and area postrema (AP) etc. after two trials of CS-UCS paring and after the reexposure to CS 5 days later, but not in the first training and after the extinction of CIS (30 days later). The results reflect that these nuclei may have an important role in CIS expression, and may also response to the immunosuppression of UCS. The conditioned training and reexposure to CS 5 days later induced high level c-fos expression in the cingulate cortex (Cg), central amygdaloid nucleus (Ce), intermediate part of lateral septal nucleus (LSI) and ventrolateral parabrachial nucleus (VLPB) etc. But c-fos induction was not apparent when presenting CS 30 days later. These brain regions are mainly involved in CIS, and may be critical structures in the acquisition and expression of CIS. Some brain regions, including the frontal cortex (Fr), ventral orbital cortex (VO), IC, perirhinal cortex (PRh), LPB and the medial part of solitary nucleus (SolM), showed robust c-FOS expression following the conditioning training and reexposure to CS both on day 5 and day 30, suggesting that they are critically involved in CTA.

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Monoclonal antibodies of the OKT series were used to identify T lymphocytes (OKT3+) and their inducer (OKT4+) and suppressor-cytotoxic (OKT8+) subsets in the peripheral blood mononuclear cells (PBMC) of 32 healthy old-aged people more than 70 years old (16 men and 16 women) compared to 47 adults (29 men, 18 women) less than 40 years old. The absolute lymphocyte count in the peripheral blood was not significantly influenced by age or sex. Both the proportions and the absolute numbers of T3+ and T4+ cells were significantly lower in aged than in young participants. The proportions but not the absolute counts of OKT8+ cells were higher in the elderly. Most interesting is the influence of sex and these parameters. Old women have normal numbers and proportions of T3+, T4+ and T8+ cells when compared to young women. The latter have a significantly higher proportion of T8+ cells than young adult males. Old men have a striking reduction of both the numbers and proportions of OKT3+ and OKT4+ cells when compared with young men and with women. In addition, old men have an elevated proportion, but a normal absolute number, of OKT8+ cells. The responses of PBMC to phytohaemagglutinin extent (PHA), concanavalin A (Con A) and pokeweed mitogen (PWM) are reduced to the same extent in ageing male and female subjects when compared to young adults. In the older group, the magnitude of the lymphocyte response to PHA and Con A but not to PWM is negatively correlated with the proportions of OKT8+ cells. Surprisingly, these correlations are observed only in old women but not in old men. The latter finding excludes the possibility that the age-associated decline of the lymphocyte response to T cell mitogens is secondary to an imbalance between T4+ and T8+ lymphocytes.

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Este trabajo revisa la evolución y estado actual de la automoción eléctrica; analiza las ventajas ambientales, de eficiencia energética y de costes del motor eléctrico frente al de combustión interna; y presenta como limitaciones para el uso del vehículo eléctrico, el desarrollo actual de las baterías recargables y la lenta implantación de electrolineras. Con el objetivo de contribuir al desarrollo de una actividad económica respetuosa con el medio ambiente y basada en nuevas tecnologías, se proyecta, a partir de experiencias previas, una instalación de puntos de recarga para una ciudad de 50.000 habitantes con un parque de 100 vehículos eléctricos que dispone de dos plazas de recarga rápida (poste trifásico 400V CA), siete plazas de recarga lenta (postes monofásicos 230V CA) y de 50 módulos fotovoltaicos que producen diariamente la energía equivalente a la recarga lenta de un vehículo en los meses fríos y de dos en los meses cálidos.

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A new universal power quality manager is proposed. The proposal treats a number of power quality problems simultaneously. The universal manager comprises a combined series and shunt three-phase PWM controlled converters sharing a common DC link. A control scheme based on fuzzy logic is introduced and the general features of the design and operation processes are outlined. The performance of two configurations of the proposed power quality manager are compared in terms of a recently formulated unified power quality index. The validity and integrity of the proposed system is proved through computer simulated experiments

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System efficiency and cost effectiveness are of critical importance for photovoltaic (PV) systems. This paper addresses the two issues by developing a novel three-port DC-DC converter for stand-alone PV systems, based on an improved Flyback-Forward topology. It provides a compact single-unit solution with a combined feature of optimized maximum power point tracking (MPPT), high step-up ratio, galvanic isolation and multiple operating modes for domestic and aerospace applications. A theoretical analysis is conducted to analyze the operating modes followed by simulation and experimental work. The paper is focused on a comprehensive modulation strategy utilizing both PWM and phase-shifted control that satisfies the requirement of PV power systems to achieve MPPT and output voltage regulation. A 250 W converter was designed and prototyped to provide experimental verification in term of system integration and high conversion efficiency.

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Power electronics plays an important role in the control and conversion of modern electric power systems. In particular, to integrate various renewable energies using DC transmissions and to provide more flexible power control in AC systems, significant efforts have been made in the modulation and control of power electronics devices. Pulse width modulation (PWM) is a well developed technology in the conversion between AC and DC power sources, especially for the purpose of harmonics reduction and energy optimization. As a fundamental decoupled control method, vector control with PI controllers has been widely used in power systems. However, significant power loss occurs during the operation of these devices, and the loss is often dissipated in the form of heat, leading to significant maintenance effort. Though much work has been done to improve the power electronics design, little has focused so far on the investigation of the controller design to reduce the controller energy consumption (leading to power loss in power electronics) while maintaining acceptable system performance. This paper aims to bridge the gap and investigates their correlations. It is shown a more thoughtful controller design can achieve better balance between energy consumption in power electronics control and system performance, which potentially leads to significant energy saving for integration of renewable power sources.

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Dissertação para obtenção do grau de Mestre em Engenharia Electrotécnica Ramo de Automação e Electrónica Industrial

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Dissertação para obtenção do grau de Mestre em Engenharia Electrotécnica Ramo Energia

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O objetivo deste trabalho consistiu em projetar, construir e testar um protótipo em laboratório de uma fonte de alimentação de alta tensão que permita descargas elétricas {estáveis e de dimensões reduzidas}, de modo a que possa ser utilizada, dada a sua essencialidade, na fabricação de redes de período longo (LPG) em fibra ótica nos chamados turning points. Estes são pontos de elevada sensibilidade, fundamentais no desenvolvimento tecnológico de sensores em fibra ótica, em particular, de sensores refractométricos. O protótipo da fonte de alimentação é composto por um regulador do tipo BUCK, um inversor para alimentação do transformador de alta tensão, o circuito de realimentação e controlo PWM e um microcontrolador para o comando da fonte. Posteriormente procedeu-se à otimização dos parâmetros de descarga, o que conduziu a fabricação de redes de período longo com períodos inferiores a 150 micrómetros. Este é um resultado sem paralelo a nível internacional no que concerne ao uso da técnica do arco elétrico.

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O acionamento eletrónico de motores desempenha um papel cada vez mais importante nos transportes e mobilidade, devido às inúmeras aplicações, entre as quais o controlo de velocidade e direção dos motores das cadeiras de rodas elétricas. No entanto, as soluções disponíveis no mercado apresentam um custo elevado, e consequentemente são inacessíveis para muitas pessoas. O objetivo desta dissertação é projetar o sistema de acionamento eletrónico para um veículo unipessoal de mobilidade urbana, de acordo com os requisitos estabelecidos, e realizar um protótipo funcional com o mínimo custo possível. O sistema estará subdividido em quatro módulos: interface com o utilizador, controlador central, sistema de potência e atuadores. A sua implementação será feita através da programação num Arduino, o sistema de potência utiliza drivers, e o controlo de velocidade dos motores CC será efetuado por PWM. O sistema de controlo foi implementado de uma forma modular e parametrizada para que numa próxima fase se possa afinar os parâmetros de controlo do movimento adequando o veículo para diferentes condições de operação. Numa perspetiva futura, pretende-se que este veículo unipessoal de mobilidade urbana seja comercializado de forma económica e possibilite a mobilidade total em meio urbano a pessoas com limitações de ordem motora.