Datos geográficos de tipo raster en R

El paquete raster proporciona un gran número de funciones para procesar datos geográficos de tipo raster. El diseño de este paquete, basado en clases S4, hace el análisis de estos datos más amigable al usuario. También ha ocasionado el desarrollo de paquetes más específicos para trabajar con datos raster en R. rasterVis proporciona un conjunto de métodos de visualización e interacción gráfica, desde gráficos de nivel y contorno, histogramas o matrices de dispersión, hasta gráficos apropiados para datos espacio-temporales. gdistance proporciona nuevas clases para cálculos basados en rutas y movimientos a través de espacios discretizados. Implementa métodos como la distancia de coste e introduce métodos recientemente desarrollados basados en caminos aleatorios. En la charla se explicará el diseño del paquete raster y se demostrará las posibilidades que ofrecen estos paquetes con ejemplos concretos

Simulation of Freight Trains Equipped with Partially Filled Tank Containers and Related Resonance Phenomenon

To study the fluid motion-vehicle dynamics interaction, a model of four, liquid filled two-axle container freight wagons was set up. The railway vehicle has been modelled as a multi-body system (MBS). To include fluid sloshing, an equivalent mechanical model has been developed and incorporated. The influence of several factors has been studied in computer simulations, such as track defects, curve negotiation, train velocity, wheel wear, liquid and solid wagonload, and container baffles. SIMPACK has been used for MBS analysis, and ANSYS for liquid sloshing modelling and equivalent mechanical systems validation. Acceleration and braking manoeuvres of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. The coupling gear consists of UIC standard traction hooks and coupling screws that are located between buffers. One of the coupling screws is placed in the traction hook of the opposite wagon thus joining the two wagons, whereas the unused coupling screw rests on a hanger. Simulation results showed that, for certain combinations of type of liquid, filling level and container dimensions, the liquid cargo could provoke an undesirable, although not hazardous, release of the unused coupling screw from its hanger. The coupling screw's release was especially obtained when a period of acceleration was followed by an abrupt braking manoeuvre at 1 m/s2. It was shown that a resonance effect between the liquid's oscillation and the coupling screw's rotary motion could be the reason for the coupling screw's undesired release. Possible solutions to avoid the phenomenon are given.Acceleration and braking manoeuvres of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. The coupling gear consists of UIC standard traction hooks and coupling screws that are located between buffers. One of the coupling screws is placed in the traction hook of the opposite wagon thus joining the two wagons, whereas the unused coupling screw rests on a hanger. This paper reports on a study of the fluid motion-train vehicle dynamics interaction. In the study, a model of four, liquid-filled two-axle container freight wagons was developed. The railway vehicle has been modeled as a multi-body system (MBS). To include fluid sloshing, an equivalent mechanical model has been developed and incorporated. The influence of several factors has been studied in computer simulations, such as track defects, curve negotiation, train velocity, wheel wear, liquid and solid wagonload, and container baffles. A simulation program was used for MBS analysis, and a finite element analysis program was used for liquid sloshing modeling and equivalent mechanical systems validation. Acceleration and braking maneuvers of the freight train set the liquid cargo into motion. This longitudinal sloshing motion of the fluid cargo inside the tanks initiated a swinging motion of some components of the coupling gear. Simulation results showed that, for certain combinations of type of liquid, filling level and container dimensions, the liquid cargo could provoke an undesirable, although not hazardous, release of an unused coupling screw from its hanger. It was shown that a resonance effect between the liquid's oscillation and the coupling screw's rotary motion could be the reason for the coupling screw's undesired release. Solutions are suggested to avoid the resonance problem, and directions for future research are given.

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.

Dynamic analysis using finite elements to calculate the critical wear section of the contact wire in suburban railway overhead conductor rails

The purpose of this study is to determine the critical wear levels of the contact wire of the catenary on metropolitan lines. The study has focussed on the zones of contact wire where localised wear is produced, normally associated with the appearance of electric arcs. To this end, a finite element model has been developed to study the dynamics of pantograph-catenary interaction. The model includes a zone of localised wear and a singularity in the contact wire in order to simulate the worst case scenario from the point of view of stresses. In order to consider the different stages in the wire wear process, different depths and widths of the localised wear zone were defined. The results of the dynamic simulations performed for each stage of wear let the area of the minimum resistant section of the contact wire be determined for which stresses are greater than the allowable stress. The maximum tensile stress reached in the contact wire shows a clear sensitivity to the size of the local wear zone, defined by its width and depth. In this way, if the wear measurements taken with an overhead line recording vehicle are analysed, it will be possible to calculate the potential breakage risk of the wire. A strong dependence of the tensile forces of the contact wire has also been observed. These results will allow priorities to be set for replacing the most critical sections of wire, thereby making maintenance much more efficient. The results obtained show that the wire replacement criteria currently borne in mind have turned out to be appropriate, although in some wear scenarios these criteria could be adjusted even more, and so prolong the life cycle of the contact wire.

Safety assessment of underground vehicles passing over highly resilient straight tracks in the presence of a broken rail

In this paper, vehicle-track interaction for a new slab track design, conceived to reduce noise and vibration levels has been analyzed, assessing the derailment risk for trains running on curved track when encountering a broken rail. Two different types of rail fastening systems with different elasticities have been analysed and compared. Numerical methods were used in order to simulate the dynamic behaviour of the train-track interaction. Multibody system (MBS) modelling techniques were combined with techniques based on the finite element method (FEM). MBS modelling was used for modelling the vehicle and FEM for simulating the elastic track. The simulation model was validated by comparing simulated results to experimental data obtained in field testing. During the simulations various safety indices, characteristic of derailment risk, were analysed. The simulations realised at the maximum running velocity of 110 km/h showed a similar behaviour for several track types. When reducing the running speed, the safety indices worsened for both cases. Although the worst behaviour was observed for the track with a greater elasticity, in none of the simulations did a derailment occur when running over the broken rail.

Effectiveness of resilient wheels in reducing noise and vibrations

This study focuses on the effectiveness of resilient wheels in reducing railway noise and vibrations, and compares the effectiveness of three types of wheels. The finite elements method has been used to characterise the vibratory behaviour of these wheels. The model has been excited with a realistic spectrum of vertical track irregularities, and a spectral analysis has been carried out. Results have been post-processed in order to estimate the sound power emitted. These calculations have been used to assess the effectiveness of the resilient wheel designs in reducing noise emitted to the environment and in propagating structural vibrations.

Safety assessment of underground vehicles passing over highly resilient curved tracks in the presence of a broken rail

Vehicle–track interaction for a new resilient slab track designed to reduce noise and vibration levels was analysed, in order to assess the derailment risk on a curved track when encountering a broken rail. Sensitivity of the rail support spacing of the relative position of the rail breakage between two adjacent rail supports and of running speed were analysed for two different elasticities of the rail fastening system. In none of the cases analysed was observed an appreciable difference between either of the elastic systems. As was expected, the most unfavourable situations were those with greater rail support spacing and those with greater distance from the breakage to the nearest rail support, although in none of the simulations performed did a derailment occur when running over the broken rail. When varying the running speed, the most favourable condition was obtained for an intermediate speed, due to the superposition of two antagonistic effects.

Metro de Madrid rolling stock models and comparative studies relating to comfort

This paper presents the work carried out by Metro de Madrid and the Railway Technology Research Centre (Polytechnic University of Madrid), aimed at setting up rolling stock simulation models with a high level of detail. To do this, the features of the SIMPACK simulation tool used to create models have been briefly outlined, explaining the main features of models in two of the series modelled: 7000 and 8000. Finally, the results obtained from comparing comfort in the 7000 and 8000 series are presented.

Optimización de la captación de corriente con catenaria rígida

La catenaria rígida presenta algunas características que la hacen especialmente apropiada para su montaje en líneas de metro, si bien el aumento del límite de velocidad de los vehículos destinados a las líneas modernas exige un diseño más eficiente para estos sistemas. En este trabajo se ha analizado el comportamiento dinámico de este tipo de sistemas de captación, a fin de diseñar un nuevo carril conductor con un comportamiento dinámico superior al de los ya existentes. Esto implica la posibilidad de aumentar la velocidad de circulación o la distancia entre soportes, con el consiguiente ahorro del coste de instalación. A tal fin, se ha modelizado un sistema pantógrafo-catenaria real, empleando técnicas avanzadas de modelado y simulación. Se ha realizado un estudio de sensibilidad, para analizar la influencia de cada variable de diseño sobre el comportamiento dinámico del conjunto, y se ha diseñado un carril conductor con mejores prestaciones que el actual.

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.

Comparison of vibration and rolling noise emission of resilient and solid monobloc railway wheels in underground lines

Flat or worn wheels rolling on rough or corrugated tracks can provoke airborne noise and ground-borne vibration, which can be a serious concern for nearby neighbours of urban rail transit lines. Among the various treatments used to reduce vibration and noise, resilient wheels play an important role. In conventional resilient wheels, a slightly prestressed V­shaped rubber ring is mounted between the steel wheel centre and tyre. The elastic layer enhances rolling noise and vibration suppression, as well as impact reduction on the track. In this paper the effectiveness of resilient wheels in underground lines, in comparison to monobloc ones, is assessed. The analysed resilient wheel is able to carry greater loads than standard resilient wheels used for light vehicles. It also presents a greater radial resiliency and a higher axial stiffness than conventional V­wheels. The finite element method was used in this study. A quarter car model was defined, in which the wheelset was modelled as an elastic body. Several simulations were performed in order to assess the vibrational behaviour of elastic wheels, including modal, harmonic and random vibration analysis, the latter allowing the introduction of realistic vertical track irregularities, as well as the influence of the running speed. Due to numerical problems some simplifications were needed. Parametric variations were also performed, in which the sensitivity of the whole system to variations of rubber prestress and Poisson’s ratio of the elastic material was assessed.Results are presented in the frequency domain, showing a better performance of the resilient wheels for frequencies over 200 Hz. This result reveals the ability of the analyzed design to mitigate rolling noise, but not structural vibrations, which are primarily found in the lower frequency range.

Fenómenos de resonancia asociados al transporte de mercancías líquidas por ferrocarril

Los vagones de mercancías se unen entre sí mediante acoplamientos UIC estándar. Aunque cada plataforma está equipada con un tensor de enganche en ambos extremos, sólo uno de ellos se utiliza, mientras que el otro descansa apoyado en un gancho. Debido a los efectos de oleaje del líquido contenido en las cisternas, este tensor en reposo puede entrar en resonancia con la frecuencia natural de algunos fluidos, llegando a oscilar de forma apreciable. En ocasiones llega a saltar fuera de su alojamiento, provocando ciertas molestias durante la circulación, aunque sin entrañar ningún riesgo para la seguridad de la marcha. Con el propósito de simular la influencia de diversos factores sobre el comportamiento dinámico asociado a estos fenómenos de oleaje, se ha desarrollado un modelo de la interacción fluido-vehículo, empleado técnicas de modelado de sistemas multicuerpo y de elementos finitos.

Comparación de la emisión de vibraciones y ruido de ruedas ferroviarias elásticas y monobloque en líneas de metro

Las ruedas de ferrocarril con avanzado estado de desgaste o poligonalización pueden ser una fuente transmisora de ruidos y vibraciones, lo que supone un serio inconveniente para los vecinos próximos a la línea ferroviaria. Se han adoptado distintas soluciones para mitigar este efecto, entre las que las ruedas elásticas desempeñan un papel importante.Las ruedas elásticas convencionales presentan un anillo de goma, en forma de V, que se encuentra ligeramente comprimido entre el cubo y la banda de rodadura, construidos en acero. Esta capa elástica favorece la supresión del ruido y vibraciones transmitidos, al tiempo que reduce los impactos sobre la vía. En este estudio se ha valorado la eficacia de las ruedas elásticas en líneas metropolitanas, comparándolas con las ruedas monobloque. Se ha utilizado para ello el método de los elementos finitos. Se han llevado a cabo diversas simulaciones para estudiar el comportamiento vibratorio de las ruedas elásticas y monobloque, incluyendo análisis modal, respuesta en frecuencia y análisis de vibraciones estocásticas.

RVDynDB: Repositorio abierto para el intercambio de datos dinámicos de vehículos ferroviarios

En este artículo se describe el proceso de diseño e implementación de la base de datos RVDynDB (Rail Vehicle Dynamic parameters DataBase), que pretende ser un extenso repositorio de los modelos de dominio público empleados en la simulación dinámica de vehículos ferroviarios en todo el mundo. Atendiendo a sus características de flexibilidad, extensibilidad e independencia de la plataforma, se ha escogido un modelo de datos XML, que facilita el almacenamiento de datos de procedencia muy heterogénea, al tiempo que permite compartir el contenido de la base de datos con otros usuarios a través de internet. Se ha presentado también el lenguaje RVDynML (Rail Vehicle Dynamic parameters Markup Language), que define la estructura de la información almacenada en la base de datos. Al ser un lenguaje basado en XML, con el tiempo podría llegar a convertirse en un estándar para el intercambio de datos sobre los principales parámetros constructivos que definen el comportamiento dinámico de los vehículos.Se han seleccionado 173 referencias bibliográficas, cuyos datos se han utilizado para construir la base de datos, constituida por un total de 957 registros. Finalmente, se ha desarrollado una aplicación específica con MATLAB para gestionar las búsquedas en la base de datos. Para ello se ha empleando una API de Java que proporciona una interfaz para el DOM, que permite permiten acceder, modificar, insertar o eliminar los elementos y atributos que componen un documento XML.

Estudios de confort de vehículos ferroviarios mediante técnicas combinadas de simulación FEM y MBS

La elasticidad de la caja de viajeros de los vehículos ferroviarios tiene una gran influencia sobre el confort. Por esta razón, cuando se desea simular el comportamiento dinámico del vehículo para estudios de confort, resulta conveniente construir un modelo elástico de caja, a fin de obtener resultados más precisos. La construcción de este tipo de modelos pasa por el desarrollo de dos etapas fundamentales, que comprenden la generación de un modelo de caja mediante la técnica de los elementos finitos (FEM) para su caracterización dinámica como cuerpo elástico y la definición de un modelo de sistema multicuerpo (MBS) que englobe los restantes componentes del vehículo. En este artículo se presentan los resultados obtenidos en un estudio comparativo llevado a cabo con modelos de caja rígida y elástica, en los que se ha valorado el nivel de confort obtenido con ambas configuraciones. Para ello, se ha simulado el comportamiento del vehículo a dos velocidades distintas, de 70 y 110km/h, y con dos niveles de irregularidades. Se han analizado las aceleraciones de la caja, que se han procesado de acuerdo a las especificaciones de la norma EN12299, a fin de obtener el índice de comodidad. Este parámetro se ha utilizado para comparar el nivel de confort obtenido con ambos modelos, habiéndose encontrado una gran diferencia en los índices calculados con caja rígida y con caja elástica, lo que confirma la gran influencia de la elasticidad de la caja en los estudios de confort llevados a cabo mediante técnicas de simulación dinámica.