Simulation model for the study of overhead rail current collector systems dynamics, focused on the design of a new conductor rail

Overhead rigid conductor arrangements for current collection for railway traction have some advantages compared to other, more conventional, energy supply systems. They are simple, robust and easily maintained, not to mention their flexibility as to the required height for installation, which makes them particularly suitable for use in subway infrastructures. Nevertheless, due to the increasing speeds of new vehicles running on modern subway lines, a more efficient design is required for this kind of system. In this paper, the authors present a dynamic analysis of overhead conductor rail systems focused on the design of a new conductor profile with a dynamic behaviour superior to that of the system currently in use. This means that either an increase in running speed can be attained, which at present does not exceed 110 km/h, or an increase in the distance between the rigid catenary supports with the ensuing saving in installation costs. This study has been carried out using simulation techniques. The ANSYS programme has been used for the finite element modelling and the SIMPACK programme for the elastic multibody systems analysis.

Improved design of an overhead rail current conductor for application in underground lines

Overhead rail current collector systems for railway traction offer certain features, such as low installation height and reduced maintenance, which make them predominantly suitable for use in underground train infrastructures. Due to the increased demands of modern catenary systems and higher running speeds of new vehicles, a more capable design of the conductor rail is needed. A new overhead conductor rail has been developed and its design has been patented [13]. Modern simulation and modelling techniques were used in the development approach. The new conductor rail profile has a dynamic behaviour superior to that of the system currently in use. Its innovative design permits either an increase of catenary support spacing or a higher vehicle running speed. Both options ensure savings in installation or operating costs. The simulation model used to optimise the existing conductor rail profile included both a finite element model of the catenary and a three-dimensional multi-body system model of the pantograph. The contact force that appears between pantograph and catenary was obtained in simulation. A sensitivity analysis of the key parameters that influence in catenary dynamics was carried out, finally leading to the improved design.

Simulation techniques for design of overhead conductor rail lines for speeds over 140 km/h

In overhead conductor rail lines, aluminium beams are usually mounted with support spacing between 8 and 12 meters, to limit the maximum vertical deflection in the center of the span. This small support spacing limits the use of overhead conductor rail to tunnels, therefore it has been used almost exclusively in metropolitan networks, with operation speeds below 110 km/h. Nevertheless, due to the lower cost of maintenance required for this electrification system, some railway administrations are beginning to install it in some tunnels on long-distance lines, requesting higher operation speeds [1]. Some examples are the Barcelona and Madrid suburban networks (Spain), and recent lines in Turkey and Malaysia. In order to adapt the design of the overhead conductor for higher speeds (V > 160 km/h), particular attention must be paid to the geometry of the conductor rail in critical zones as overlaps, crossings and, especially, transitions between conductor rail and conventional catenary, since the use of overhead conductor rail is limited to tunnels, as already mentioned. This paper describes simulation techniques developed in order to take into account these critical zones. Furthermore, some specific simulations results are presented that have been used to analyze and optimizes the geometry of this special zones to get a better current collection quality, in a real suburban network. This paper presents the work undertaken by the Railways Technology Research Centre (CITEF), having over 10 years of experience in railways research [1-4].

Design of a compact objective for SWIR applications

Lately the short-wave infrared (SWIR) has become very important due to the recent appearance on the market of the small detectors with a large focal plane array. Military applications for SWIR cameras include handheld and airborne systems with long range detection requirements, but where volume and weight restrictions must be considered. In this paper we present three different designs of telephoto objectives that have been designed according to three different methods. Firstly the conventional method where the starting point of the design is an existing design. Secondly we will face design starting from the design of an aplanatic system. And finally the simultaneous multiple surfaces (SMS) method, where the starting point is the input wavefronts that we choose. The designs are compared in terms of optical performance, volume, weight and manufacturability. Because the objectives have been designed for the SWIR waveband, the color correction has important implications in the choice of glass that will be discussed in detail

X-parameters based analytical design of non-linear microwave circuits Application to oscillator design

Resumen El dise��o cl��sico de circuitos de microondas se basa fundamentalmente en el uso de los par��metros s, debido a su capacidad para caracterizar de forma exitosa el comportamiento de cualquier circuito lineal. La relaci��n existente entre los par��metros s con los sistemas de medida actuales y con las herramientas de simulaci��n lineal han facilitado su ��xito y su uso extensivo tanto en el dise��o como en la caracterizaci��n de circuitos y subsistemas de microondas. Sin embargo, a pesar de la gran aceptaci��n de los par��metros s en la comunidad de microondas, el principal inconveniente de esta formulaci��n reside en su limitaci��n para predecir el comportamiento de sistemas no lineales reales. En la actualidad, uno de los principales retos de los dise��adores de microondas es el desarrollo de un contexto an��logo que permita integrar tanto el modelado no lineal, como los sistemas de medidas de gran se��al y los entornos de simulaci��n no lineal, con el objetivo de extender las capacidades de los par��metros s a reg��menes de operaci��n en gran se��al y por tanto, obtener una infraestructura que permita tanto la caracterizaci��n como el dise��o de circuitos no lineales de forma fiable y eficiente. De acuerdo a esta filosof��a, en los ��ltimos a��os se han desarrollado diferentes propuestas como los par��metros X, de Agilent Technologies, o el modelo de Cardiff que tratan de proporcionar esta plataforma com��n en el ��mbito de gran se��al. Dentro de este contexto, uno de los objetivos de la presente Tesis es el an��lisis de la viabilidad del uso de los par��metros X en el dise��o y simulaci��n de osciladores para transceptores de microondas. Otro aspecto relevante en el an��lisis y dise��o de circuitos lineales de microondas es la disposici��n de m��todos anal��ticos sencillos, basados en los par��metros s del transistor, que permitan la obtenci��n directa y r��pida de las impedancias de carga y fuente necesarias para cumplir las especificaciones de dise��o requeridas en cuanto a ganancia, potencia de salida, eficiencia o adaptaci��n de entrada y salida, as�� como la determinaci��n anal��tica de par��metros de dise��o clave como el factor de estabilidad o los contornos de ganancia de potencia. Por lo tanto, el desarrollo de una formulaci��n de dise��o anal��tico, basada en los par��metros X y similar a la existente en peque��a se��al, permitir��a su uso en aplicaciones no lineales y supone un nuevo reto que se va a afrontar en este trabajo. Por tanto, el principal objetivo de la presente Tesis consistir��a en la elaboraci��n de una metodolog��a anal��tica basada en el uso de los par��metros X para el dise��o de circuitos no lineales que jugar��a un papel similar al que juegan los par��metros s en el dise��o de circuitos lineales de microondas. Dichos m��todos de dise��o anal��ticos permitir��an una mejora significativa en los actuales procedimientos de dise��o disponibles en gran se��al, as�� como una reducci��n considerable en el tiempo de dise��o, lo que permitir��a la obtenci��n de t��cnicas mucho m��s eficientes. Abstract In linear world, classical microwave circuit design relies on the s-parameters due to its capability to successfully characterize the behavior of any linear circuit. Thus the direct use of s-parameters in measurement systems and in linear simulation analysis tools, has facilitated its extensive use and success in the design and characterization of microwave circuits and subsystems. Nevertheless, despite the great success of s-parameters in the microwave community, the main drawback of this formulation is its limitation in the behavior prediction of real non-linear systems. Nowadays, the challenge of microwave designers is the development of an analogue framework that allows to integrate non-linear modeling, large-signal measurement hardware and non-linear simulation environment in order to extend s-parameters capabilities to non-linear regimen and thus, provide the infrastructure for non-linear design and test in a reliable and efficient way. Recently, different attempts with the aim to provide this common platform have been introduced, as the Cardiff approach and the Agilent X-parameters. Hence, this Thesis aims to demonstrate the X-parameter capability to provide this non-linear design and test framework in CAD-based oscillator context. Furthermore, the classical analysis and design of linear microwave transistorbased circuits is based on the development of simple analytical approaches, involving the transistor s-parameters, that are able to quickly provide an analytical solution for the input/output transistor loading conditions as well as analytically determine fundamental parameters as the stability factor, the power gain contours or the input/ output match. Hence, the development of similar analytical design tools that are able to extend s-parameters capabilities in small-signal design to non-linear ap- v plications means a new challenge that is going to be faced in the present work. Therefore, the development of an analytical design framework, based on loadindependent X-parameters, constitutes the core of this Thesis. These analytical nonlinear design approaches would enable to significantly improve current large-signal design processes as well as dramatically decrease the required design time and thus, obtain more efficient approaches.

Analysis and design of a thrombectomy device by using simulation techniques

Purpose: In this work, we present the analysis, design and optimization of one experimental device recently developed in the UK, called the 'GP' Thrombus Aspiration Device (GPTAD). This device has been designed to remove blood clots without the need to make contact with the clot itself thereby potentially reducing the risk of problems such as downstream embolisation. Method: To obtain the minimum pressure necessary to extract the clot and to optimize the device, we have simulated the performance of the GPTAD analysing the resistances, compliances and inertances effects. We model a range of diameters for the GPTAD considering different forces of adhesion of the blood clot to the artery wall, and different lengths of blood clot. In each case we determine the optimum pressure required to extract the blood clot from the artery using the GPTAD, which is attached at its proximal end to a suction pump. Result: We then compare the results of our mathematical modelling to measurements made in laboratory using plastic tube models of arteries of comparable diameter. We use abattoir porcine blood clots that are extracted using the GPTAD. The suction pressures required for such clot extraction in the plastic tube models compare favourably with those predicted by the mathematical modelling. Discussion & Conclusion: We conclude therefore that the mathematical modelling is a useful technique in predicting the performance of the GPTAD and may potentially be used in optimising the design of the device.

Design of envelope amplifier based on interleaved multiphase buck converter with minimum time control for RF application

In this paper, an interleaved multiphase buck converter with minimum time control strategy for envelope amplifiers in high efficiency RF power amplifiers is proposed. The solution for the envelope amplifier is to combine the proposed converter with a linear regulator in series. High efficiency of envelope amplifier can be obtained through modulating the supply voltage of the linear regulator. Instead of tracking the envelope, the buck converter has discrete output voltage that corresponding to particular duty cycles which achieve total ripple cancellation. The transient model for minimum time control is explained, and the calculation of transient times that are pre-calculated and inserted into a lookup table is presented. The filter design trade-off that limits capability of envelope modulation is also discussed. The experimental results verify the fast voltage transient obtained with a 4-phase buck prototype.

EMI filter design of a three-phase buck-type rectifier for aircraft applications

An EMI ���lter for a three-phase buck-type medium power pulse-width modulation recti���er is designed. This ���lter considers differential mode noise and complies with MIL-STD- 461E for the frequency range of 10kHz to 10MHz. In industrial applications, the frequency range of the standard starts at 150kHz and the designer typically uses a switching frequency of 28kHz because the ���fth harmonic is out of the range. This approach is not valid for aircraft applications. In order to design the switching frequency in aircraft applications, the power losses in the semiconductors and the weight of the reactive components should be considered. The proposed design is based on a harmonic analysis of the recti���er input current and an analytical study of the input ���lter. The classical industrial design does not consider the inductive effect in the ���lter design because the grid frequency is 50/60Hz. However, in the aircraft applications, the grid frequency is 400Hz and the inductance cannot be neglected. The proposed design considers the inductance and the capacitance effect of the ���lter in order to obtain unitary power factor at full power. In the optimization process, several ���lters are designed for different switching frequencies of the converter. In addition, designs from single to ���ve stages are considered. The power losses of the converter plus the EMI ���lter are estimated at these switching frequencies. Considering overall losses and minimal ���lter volume, the optimal switching frequency is selected

New Considerations in the Input Filter Design of a Three-Phase Buck-Type PWM Rectifier for Aircraft Applications

An EMI filter for a three-phase buck-type medium power pulse-width modulation rectifier is designed. This filter considers differential mode noise and complies with MIL-STD-461E for the frequency range of 10kHz to 10MHz. In industrial applications, the frequency range of the standard starts at 150kHz and the designer typically uses a switching frequency of 28kHz because the fifth harmonic is out of the range. This approach is not valid for aircraft applications. In order to design the switching frequency in aircraft applications, the power losses in the semiconductors and the weight of the reactive components should be considered. The proposed design is based on a harmonic analysis of the rectifier input current and an analytical study of the input filter. The classical industrial design does not consider the inductive effect in the filter design because the grid frequency is 50/60Hz. However, in the aircraft applications, the grid frequency is 400Hz and the inductance cannot be neglected. The proposed design considers the inductance and the capacitance effect of the filter in order to obtain unitary power factor at full power. In the optimization process, several filters are designed for different switching frequencies of the converter. In addition, designs from single to five stages are considered. The power losses of the converter plus the EMI filter are estimated at these switching frequencies. Considering overall losses and minimal filter volume, the optimal switching frequency is selected.

Optimum Design of an Envelope Tracking Buck Converter for RF PA using GaN HEMTs

In this paper, filter design methodology and application of GaN HEMTs for high efficiency Envelope Amplifier in RF transmitters are proposed. The main objectives of the filter design are generation of the envelope reference with the minimum possible distortion and high efficiency of the amplifier obtained by the optimum trade-off between conduction and switching losses. This optimum point was determined using power losses model for synchronous buck with sinusoidal output voltage and experimental results showed good correspondence with the model and verified the proposed methodology. On the other hand, comparing to Si MOSFETs, GaN HEMTs can provide higher efficiency of the envelope amplifier, due to superior conductivity and switching characteristics. Experimental results verified benefits of GaN devices comparing to the appliance of Si switching devices with very good Figure Of Merit, for this particular application

On the biomimetic design of agile-robot legs

The development of functional legged robots has encountered its limits in human-made actuation technology. This paper describes research on the biomimetic design of legs for agile quadrupeds. A biomimetic leg concept that extracts key principles from horse legs which are responsible for the agile and powerful locomotion of these animals is presented. The proposed biomimetic leg model defines the effective leg length, leg kinematics, limb mass distribution, actuator power, and elastic energy recovery as determinants of agile locomotion, and values for these five key elements are given. The transfer of the extracted principles to technological instantiations is analyzed in detail, considering the availability of current materials, structures and actuators. A real leg prototype has been developed following the biomimetic leg concept proposed. The actuation system is based on the hybrid use of series elasticity and magneto-rheological dampers which provides variable compliance for natural motion. From the experimental evaluation of this prototype, conclusions on the current technological barriers to achieve real functional legged robots to walk dynamically in agile locomotion are presented.

Some methodological issues in the design of CIAO - A generic, parallel concurrent constraint system

We informally discuss several issues related to the parallel execution of logic programming systems and concurrent logic programming systems, and their generalization to constraint programming. We propose a new view of these systems, based on a particular definition of parallelism. We arg��e that, under this view, a large number of the actual systems and models can be explained through the application, at different lev��is of granularity, of only a few basic principies: determinism, non-failure, independence (also referred to as stability), granularity, etc. Also, and based on the convergence of concepts that this view brings, we sketch a model for the implementation of several parallel constraint logic programming source languages and models based on a common, generic abstract machine and an intermed��ate kernel language.

Some methodological issues in the design of CIAO, a generic, parallel concurrent constraint system

We informally discuss several issues related to the parallel execution of logic programming systems and concurrent logic programming systems, and their generalization to constraint programming. We propose a new view of these systems, based on a particular definition of parallelism. We arg��e that, under this view, a large number of the actual systems and models can be explained through the application, at different lev��is of granularity, of only a few basic principies: determinism, non-failure, independence (also referred to as stability), granularity, etc. Also, and based on the convergence of concepts that this view brings, we sketch a model for the implementation of several parallel constraint logic programming source languages and models based on a common, generic abstract machine and an intermed��ate kernel language.

Pounding force assessment in performance-based design of bridges

Bridges with deck supported on either sliding or elastomeric bearings are very common in mid-seismicity regions. Their main seismic vulnerabilities are related to the pounding of the deck against abutments or between the different deck elements. A simplified model of the longitudinal behavior of those bridges will allow to characterize the reaction forces developed during pounding using the Pacific Earthquake Engineering Research Center framework formula. In order to ensure the general applicability of the results obtained, a large number of system parameter combinations will be considered. The heart of the formula is the identification of suitable intermediate variables. First, the pseudo acceleration spectral value for the fundamental period of the system (Sa(Ts)) will be used as an intensity measure (IM). This IM will result in a very large non-explained variability of the engineering demand parameter. A portion of this variability will be proved to be related to the relative content of high-frequency energy in the input motion. Two vector-valued IMs including a second parameter taking this energy content into account will then be considered. For both of them, a suitable form for the conditional intensity dependence of the response will be obtained. The question of which one to choose will also be analyzed. Finally, additional issues related to the IM will be studied: its applicability to pulse-type records, the validity of scaling records and the sufficiency of the IM.

Programmed design of ship forms

This paper describes a new category of CAD applications devoted to the definition and parameterization of hull forms, called programmed design. Programmed design relies on two prerequisites. The first one is a product model with a variety of types large enough to face the modeling of any type of ship. The second one is a design language dedicated to create the product model. The main purpose of the language is to publish the modeling algorithms of the application in the designer knowledge domain to let the designer create parametric model scripts. The programmed design is an evolution of the parametric design but it is not just parametric design. It is a tool to create parametric design tools. It provides a methodology to extract the design knowledge by abstracting a design experience in order to store and reuse it. Programmed design is related with the organizational and architectural aspects of the CAD applications but not with the development of modeling algorithms. It is built on top and relies on existing algorithms provided by a comprehensive product model. Programmed design can be useful to develop new applications, to support the evolution of existing applications or even to integrate different types of application in a single one. A three-level software architecture is proposed to make the implementation of the programmed design easier. These levels are the conceptual level based on the design language, the mathematical level based on the geometric formulation of the product model and the visual level based on the polyhedral representation of the model as required by the graphic card. Finally, some scenarios of the use of programmed design are discussed. For instance, the development of specialized parametric hull form generators for a ship type or a family of ships or the creation of palettes of hull form components to be used as parametric design patterns. Also two new processes of reverse engineering which can considerably improve the application have been detected: the creation of the mathematical level from the visual level and the creation of the conceptual level from the mathematical level. �� 2012 Elsevier Ltd. All rights reserved. 1. Introduction