Influence of the track quality and of the properties of the wheel rail rolling contact on vehicle dynamics

This work describes an analytical approach to determine what degree of accuracy is required in the definition of the rail vehicle models used for dynamic simulations. This way it would be possible to know in advance how the results of simulations may be altered due to the existence of errors in the creation of rolling stock models, whilst also identifying their critical parameters. This would make it possible to maximize the time available to enhance dynamic analysis and focus efforts on factors that are strictly necessary.In particular, the parameters related both to the track quality and to the rolling contact were considered in this study. With this aim, a sensitivity analysis was performed to assess their influence on the vehicle dynamic behaviour. To do this, 72 dynamic simulations were performed modifying, one at a time, the track quality, the wheel-rail friction coefficient and the equivalent conicity of both new and worn wheels. Three values were assigned to each parameter, and two wear states were considered for each type of wheel, one for new wheels and another one for reprofiled wheels.After processing the results of these simulations, it was concluded that all the parameters considered show very high influence, though the friction coefficient shows the highest influence. Therefore, it is recommended to undertake any future simulation job with measured track geometry and track irregularities, measured wheel profiles and normative values of wheel-rail friction coefficient

Fast Correction of Tiled Display Systems on Planar Surfaces

A method for fast colour and geometric correction of a tiled display system is presented in this paper. Such kind of displays are a common choice for virtual reality applications and simulators, where a high resolution image is required. They are the cheapest and more flexible alternative for large image generation but they require a precise geometric and colour correction. The purpose of the proposed method is to correct the projection system as fast as possible so in case the system needs to be recalibrated it doesn’t interfere with the normal operation of the simulator or virtual reality application. This technique makes use of a single conventional webcam for both geometric and photometric correction. Some previous assumptions are made, like planar projection surface and negligibleintra-projector colour variation and black-offset levels. If these assumptions hold true, geometric and photometric seamlessness can be achievedfor this kind of display systems. The method described in this paper is scalable for an undefined number of projectors and completely automatic

Analysis and 2D Simulation of a Hexapod Robot Leg for Remote Exploration

A walking machine is a wheeled rover alternative, well suited for work in an unstructured environment and specially in abrupt terrain. They have some drawback like speed and power consumption, but they can achieve complex movements and protrude very little the environment they are working on. The locomotion system is determined by the terrain conditions and, in our case, this legged design has been chosen based in a working area like Rio Tinto in the South of Spain, which is a river area with abrupt terrain. A walking robot with so many degrees of freedom can be a challenge when dealing with the analysis and simulations of the legs. This paper shows how to deal with the kinematical analysis of the equations of a hexapod robot based on a design developed by the Center of Astrobiology INTA-CSIC following the classical formulation of equation

Modelling and simulation of a hydraulic power assisted steering system through Bond Graphs

The hydraulic power assisted steering (HPAS) system is one of the most sensitive vehicle interfaces to the driver perception. Comfort and performance parameters such as ride, handling, tactile transfer functions and overall noise levels are directly affected by its performance. The modeling of a HPAS system using the bond graph technique makes possible the combination of hydraulic and mechanical components. This allows physical and design variables such as fluid compressibility and hoses diameters to be evaluated simultaneously. HPAS should be used as a design and tuning tool to develop different system configurations before prototype test build, representing an improvement in terms of product development time and cost for both component and vehicle level

Sensitivity analysis to assess the influence of the inertial properties of railway vehicle bodies on the vehicle’s dynamic behaviour

A sensitivity analysis has been performed to assess the influence of the inertial properties of railway vehicles on their dynamic behaviour. To do this, 216 dynamic simulations were performed modifying, one at a time, the masses, moments of inertia and heights of the centre of gravity of the carbody, the bogie and the wheelset. Three values were assigned to each parameter, corresponding to the percentiles 10, 50 and 90 of a data set stored in a database of railway vehicles. After processing the results of these simulations, the analyzed parameters were sorted by increasing influence. It was also found which of these parameters could be estimated with a lesser degree of accuracy for future simulations without appreciably affecting the simulation results. In general terms, it was concluded that the most sensitive inertial properties are the mass and the vertical moment of inertia, and the least sensitive ones the longitudinal and lateral moments of inertia

Simulation of the `GP´ MTD Device intended for the extraction of blood clots by using the Bond Graph technique

This article covers the analysis and research into a device recently developed by the University of Wolverhampton (UK), called a 'GP' MTD Mechanical Thrombectomy Device, under the direction of Dr G. Pearce. This device will improve the process of extracting thrombosis clots in the cerebral arteries. On the one hand, the development of the simulation model of this device is shown by using Bond-Graph formalism and, on the other hand, the optimization of its performance in the very near future, from the interpretation of the results

Caracterización de vehículos ferroviarios para analizar la sensibilidad de sus parámetros dinámicos

Este trabajo forma parte de un proyecto más amplio, cuya finalidad es realizar un estudio de sensibilidad que permita determinar qué grado de exactitud se requiere en la definición de los principales parámetros que influyen en la dinámica de los vehículos ferroviarios. Como paso previo a este análisis de sensibilidad, es preciso seleccionar un vehículo de referencia en el que basar dicho estudio. Dicho vehículo se empleará como punto de partida, para después variar el valor de los parámetros que lo caracterizan, a fin de determinar su influencia sobre la dinámica de marcha. Para alcanzar este objetivo se ha construido una base de datos de vehículos ferroviarios, que almacena las características de los parámetros que afectan al comportamiento dinámico de los vehículos. El valor de referencia correspondiente a cada parámetro puede asociarse al promedio de los valores almacenados en la base de datos, y sus rangos de variación pueden obtenerse a partir de las medidas de dispersión de estos datos. Se ha realizado un test de normalidad sobre los datos almacenados en la base de datos, encontrándose que la hipótesis de normalidad resulta, en general, inapropiada, lo que requiere el uso de estimadores más robustos de los habituales. Aunque el estudio de sensibilidad podría basarse en el vehículo ficticio definido por los valores promedio de cada parámetro, cabe la posibilidad de que este vehículo promedio presente un comportamiento dinámico distinto al que tendría un vehículo real. Para evitar este posible contratiempo, se han utilizado técnicas de escalado multidimensional para seleccionar los registros de la base de datos más próximos al vehículo promedio. Para determinar cuál de estos vehículos resulta más apropiado, se ha comparado su comportamiento dinámico empleando técnicas de simulación de sistemas multicuerpo. A partir de los resultados obtenidos en estas simulaciones, se ha valorado el comportamiento de cada modelo desde el punto de vista de la seguridad, de la agresión a la vía y del confort, siguiendo las indicaciones de la norma EN-14363. Finalmente, se ha seleccionado como vehículo de referencia aquél que, presentando un comportamiento adecuado, requiere el menor esfuerzo computacional para llevar a cabo las simulaciones

Simuladores de conducción urbanos: una técnica de optimización de bases de datos visuales utilizando aspectos perceptivos

El objetivo del presente artículo es exponer una técnica de optimización de entornos virtuales urbanos, los cuales constituyen bases de datos visuales orientadas a su utilización en simuladores de conducción. La base de la técnica se fundamenta en la identificación de aquellos factores que intervienen en el diseño constructivo del escenario virtual, determinando si son estadísticamente significativos en localidad y en el grado de realismo percibidos por el usuario del simulador gráfico. Este planteamiento supone una nueva vía de simplificación de este tipo de escenarios complejos ya que permite decidir la combinación óptima de modificaciones en las geometrías de los modelos, de tal forma que la base de datos visual resultante se comporte adecuadamente en tiempo real sin comprometerla latencia de la simulación y mostrando al mismo tiempo al usuario final un escenario totalmente reconocible e inmersivo. Se establece un modelo estadístico basado en el diseño de experimentos donde se estudia el efecto que, sobre cada una de las variables respuestas elegidas, tienen el conjunto de factores de diseño del escenario virtual. El modelo ha sido validado experimentalmente en un escenario virtual implementado en un simulador de conducción de bajo coste. La ventaja fundamental de esta contribución es la asignación selectiva de los recursos necesarios a la hora de modelar las geometrías del escenario, permitiendo la reducción de costes y tiempos de desarrollo durante el proceso de generación 3D

Simulation Model of the Scanner Servocontrols for the Orientation of a Fighter Aircraft by Using the Bond Graph Technique

Nowadays the use of complex models has increased the requirements of the simulation tools and techniques for working and analyzing with different domains at the same time. This work focuses on the study of the Scanner servocontrols of a fighter aircraft. The model has the feature of integrating various physical domains into the same system (electrical, mechanical and system control environments) with different dimensions in each domain. The technique used is the Bond Graph (BG), which is typically used in fields where different physical domains coexist, just as in the case we are dealing with, where such domains are fundamental. At the beginning of the study, the different coordinate references are introduced and the physical subsystems are also described. After this the different subsystems are presented in the form of BG submodels one by one and the global Multibond Graph (MBG) model is displayed. Lastly, an example of simulation is shown and some important conclusions are reached

Modelling the Interoperability and the Use of Control Equipment in Electrical Substations

Simulators can be defined as information systems which reliably reproduce specific phenomena and they are mainly used in training, although their field of application has grown to include manufacturing and medicine among others. In electrical engineering, simulation is an indispensable tool when working with complex systems due to the fact that it enables engineers to understand how systems work without actually needing to see them. They can learn how they work in different circumstances and optimize their design with considerably less cost in terms of time and money than if they had to carry out tests on a physical system. By using computer simulation, not only can an electrical system be designed, but it can also be optimized and its behavior examined in-depth more quickly and cheaply than by using prototypes, tests or analytical studies. Therefore, by being able to see the responses produced as the different parameters are varied, a much deeper understanding of the system under study is reached. In order to properly simulate a virtual world, technologies such as realistic graphics and dynamic simulation with real-time calculations must be used. Peripherals must be used for the system to interact with the user and the immersion comes as a result of stimuli to sight, hearing and touch. A critical factor is the possibility to solve the equations in real-time; that is, there should be no delay compared to the normal environment’s response. There is an important amount of effort being directed towards these objectives. This paragraphs deals with the development of an operation simulator for training and the fundamental objective is to develop a simulator for electrical substations. It will present the methodology to model, simulate and optimize the interoperability and the use of control equipment in electrical an substation to train operators by means of a virtual reality environment