Jose Manuel Mera

Assessment of the influence of the elastic properties of rail vehicle suspensions on safety, ride quality and track fatigue

A sensitivity analysis has been performed to assess the influence of the elastic properties of railway vehicle suspensions on the vehicle dynamic behaviour. To do this, 144 dynamic simulations were performed modifying, one at a time, the stiffness and damping coefficients, of the primary and secondary suspensions. 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 analysed parameters were sorted by increasing influence. It was also found which of these parameters could be estimated with a lesser degree of accuracy in future simulations without appreciably affecting the simulation results. In general terms, it was concluded that the highest influences were found for the longitudinal stiffness and the lateral stiffness of the primary suspension, and the lowest influences for the vertical stiffness and the vertical damping of the primary suspension, with the parameters of the secondary suspension showing intermediate influences between them.

Efficient simulation of mechanism kinematics using bond graphs

Abstract This paper presents a methodology for obtaining the equations corresponding to a mechanism that are necessary for carrying out a kinematic simulation. A simulation of this kind means obtaining the coordinates dependent on the system according to the movements imposed by the degrees of freedom. Unlike a dynamic simulation, where the set of elements moves according to the different external forces existing, in kinematic simulation the movement of the whole set depends exclusively on imposing movement on one or more of the bodies according to the degrees of freedom initially possessed by the mechanism. After presenting an analysis of how to obtain the necessary equations for several simple systems, this methodology is applied to the particular case of a front-loader, where in order to move and tilt the bucket, various closed mechanisms are integrated.

A full-scale simulation model to reproduce urban traffic in real conditions in driving simulators

This paper describes a model capable of simulating large-scale traffic in an urban environment. The goal is of this work is the realistic and detailed simulation of the traffic, reproducing the behavior of each vehicle involved in the environment individually. This model has been developed in order to be integrated in an immersive driving simulator, where the driving position is the center of the simulation and the traffic model reproduces what happens around them. The general behavior of the traffic model is based on the following theory. Depending on the size of the urban environment to be simulated, the number of vehicles involved, and the traffic density, the environment can be studied as a whole or segmented in adjacent areas. Each vehicle model has two components. First, the behavior of the vehicle is simulated individually, modeling acceleration and braking, depending on the type and characteristics of each vehicle (mass, power, size, etc.). Second, the behavior of the drivers is also modeled, by type (passive, moderate, aggressive), playing various maneuvers also common in urban traffic circulation, such as lane changes, behavior at crossings and intersections, etc. A traffic light regulation model and the complete signposting of the urban environment are also included. As a result, the developed traffic model is applicable to large-scale traffic simulation integrated in an immersive driving simulator and is very useful when investigating complex behaviors of these environments. The model has been validated comparing it with results obtained from various references and very satisfactory results have been obtained.

Expert system using multi-objective optimization of the direct current railway power supply system

AbstractThere are many different aspects to be analyzed when designing a railway infrastructure. The energy system, which withstands the demand for energy from operating trains, must consider many factors to create a functional infrastructure, in terms of demanded energy and cost sustainable. The methodology proposed gives a set of possible solutions to the designer or engineer. On the one hand, this method works with a multi-objective genetic algorithm (NSGA-II), with high time efficiency. The main target of this work is to obtain the best electrical configuration in terms of number and location of substations and characteristics of the overhead line system. On the other hand, best configurations must take into account things such as real railway operation, signalling system, infrastructure, costs linked with environment, maintenance, construction and connection with general electric network, losses of energy dissipated along the catenary. Hence, this methodology must combine all of these skills and inte...

Comparative study of railway drive systems using bond-graph

Since the first railways were built, they have not ceased to increase their capacity for transport, speed and energy consumption. This paper presents a comparative study of how present-day railway drive systems perform. Special emphasis is placed on consumption and energy efficiency. By using theoretical computer simulation models, simulations are conducted of the performance of present-day railway drive systems under certain specific boundary conditions. Bond-Graph Technique has been used to design the models. This technique is widely known and accepted for its suitability and capability for modeling dynamic systems in any field of science or technology, and particularly for modeling vehicular systems. Modeling is done systematically taking account of all the mechanical, dynamic, electrical, electromagnetic and regulation phenomena involved in the operation of railway drive systems. A detailed study of the simulation results has enabled a comparative analysis to be conducted of the most significant variables. Important conclusions have been drawn from this analysis about the drive systems that have been shown to be comparatively more efficient.

Using Bond-Graph Technique for Modelling and Simulating Railway Drive Systems

This work presents the application of Bond-Graph Technique to modelling and simulating the behaviour of railway transport as a tool for studying its dynamic behaviour, consumption and energy efficiency, and environmental impact. The basic aim of this study is to make a contribution to the research and innovation into new technologies that will lead to the discovery of ever more efficient environmentally-friendly transport. We begin with an introduction to the study of longitudinal train dynamics as well as a description of the most currently used railway drive systems. Bond-Graph technique enables this modelling to be done systematically taking into account all the fields of science and technology involved while bringing together all the mechanical, electrical, electromagnetic, thermal, dynamic and regulatory aspects. Once the models have been developed, the behaviour of the drive systems is simulated by reproducing actual railway operating conditions along a standard section of track. Through a detailed study of the simulation results and choosing the most significant parameters, a comparison can be made of how the different systems perform. We end with the most important conclusions from which it can be deduced which drive systems are comparatively more efficient and environmentally-friendly.

Simulation of an Electrical Substation Using the Bond Graph Technique

Simulation and especially computer simulation, is a basic tool since 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. There is a wide range of commercial brands on the market offering products for electrical simulation. These are powerful tools, but require the engineer to have a perfect knowledge of the electrical field. This work will firstly develop the simulation models of different elements that characterise an electrical substation in isolation; they will then be put together to model the full system, all of this using the Bond Graph technique. Finally, the system thus developed will be compared with the one developed in a specific electrical simulation program.

An agent-based support system for railway station dispatching

A D-Agent support system is modular designed for railway station dispatching.The D-Agent can behave as a dispatcher by embedding expert dispatching knowledge.MIPL formulations are integrated to optimize the railway traffic control.The D-Agent can keep improving by extending skills and learning.Its ability of communication prepares it to work in a dynamic environment. For those railway stations without being automated, railway traffic dispatching still depends on dispatchers, especially under disturbed circumstances. In this study, an agent-based support system, named D-Agent, is developed to assist human dispatchers to make decisions in station operation. To this end, the common knowledge and possible difficulties concerning a station dispatcher in his/her routine work are firstly studied, and the D-Agent is proposed with the purpose of working out practicable solutions to these challenging tasks as a dispatcher does. Then the general model of the D-Agent is established, containing five basic modules: local database, knowledge base, skill base, reasoning mechanism and communication interfaces. The internal skills of the D-Agent are designed to execute various tasks in different scenarios. Besides, a skill extension of the D-Agent with mathematical formulations is particularly discussed in this paper, to find feasible and optimal traffic control solutions in disturbance situations such as train delays and route conflicts. The D-Agent is designed to learn from its own experimental history in applying different skills, and evaluate the skills by preference weights of alternative solutions in a particular task. This procedure allows the agent to have potential for continuous improvement. To verify the applicability of the proposed support system, a D-Agent for a terminal station of subway is simulated. The numerical example of train delays and route conflicts shows that the D-Agent can generally perform as a station dispatcher in fulfilling the specific tasks, estimate the traffic state in different operation strategies and support the decision-making of favored solutions. Significantly, it indicates that the mathematical methods can also been employed by an intelligent agent.

INFLUENCE OF THE "ATD" POSITIONING BY USING FINITE ELEMENTS AND BOND GRAPH TECHNIQUE

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. To obtain the minimum pressure necessary to extract the clot and to optimize the device, we simulate the performance of the GPTAD analyzing the resistances, compliances and inertances effects. Previous full models have been undertaken using the Bond Graph technique. However in this paper we also include an analysis of the interaction between device and artery, by the

Mathematical modelling of purely ODE systems by using the Bond Graph technique and taking the inherent causalities

Abstract Simulation and especially computer simulation, is a basic tool since 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. In the presented work, an automatic procedure for reducing a system of algebraic-differential equations to a purely differential one, i.e. the minimum number of equations, within a simulation model carried out with a bond graph, and based only on causal assignation, is presented. Depending on the different types of causal paths and algebraic loops coexisting, through a succession of algebraic operations carried out on matrices, the method is capable of obtaining a system of reduced equations. One advantage of this approach is the ease with which the matrix simplification can be programmed by means of a series of operations and derivations, which is especially interesting when it comes to generating symbolic equations for a bond graph model, once they have been reduced and simplified. In each ZCP case will firstly develop the different algorithms and it will then applied to a model, all of this using the Bond Graph technique.