1,721,034 research outputs found
Feasibility of Degraded Adhesion Tests in a Locomotive Roller Rig
No full textIn railway applications, the testing of on-board components is necessary to optimize the efficiency of the systems and to allow high safety levels. In order to reduce the time and the cost of the testing phase, the use of dedicated test rigs is being increased. The current paper summarizes some studies for the realization of a full-scale locomotive roller rig. The main mechanical and control problems that arise in the design of this type of test rig have been highlighted, and in particular, the feasibility of tests with degraded adhesion conditions between the wheel and the rail is simulated
Ricostruzione della velocità e della posizione del rotabile a partire dalle misure tachimetriche relative a due assi.
No full textVSC of a servo-actuated ATR90-type pantograph
No full textOne of the problems in high-speed-train transportation systems is related to the current collection quality, that can dramatically decrease because of oscillations of the pantograph-catenary system. In the recent literature this problem has been addressed by means of active pantographs. In order to reduce the costs, a common requirement of the train companies is that the control system could be applied to the actually used pantographs. In this paper we present the preliminary results about the possible implementation of VSC techniques on a servo-actuated symmetric pantograph that can be obtained by modifying a passive high-speed pantograph Ansaldo ATR90, currently used by Italian Railways. We consider the equivalent mechanical characteristics of the catenary as uncertainties to compensate for, and the use of a robust, nonlinear, control scheme is proposed. Recent results about the influence of fast actuators in second-order sliding mode control schemes are exploited to avoid the destroying effect of a resonant actuator and the system performance are verified by simulation, under the hypothesis of knowing the actual contact force. The contact force results to be very close to the desired value in various operating conditions
Probabilistic Analysis of Braking Performance in Railways
No full textTo increase safety and efficiency in the management of railway traffic, a new speed control system, named SCMT, is currently being developed by RFI and Trenitalia for the Italian Railways. Other innovative speed supervision systems are being developed in Europe, such as the ETCS/ERTMS, which will also be installed on the new high-speed line Roma-Napoli.
All traffic management systems are generally based on a set of supervision curves relating the allowed velocity of the train to the running distance, in order to ensure the respect of speed restrictions on the line by 'soft' or 'hard' intervention such as an acoustic and visual warning to the driver (soft) and/or service or emergency braking (hard) in the case of train velocity exceeding the permitted one. To elaborate this set of supervision curves, the on-board unit requires train deceleration depending on time and speed as basic information about the braking behaviour of the train.
The implementation of a speed supervision system requires a preliminary definition of braking models that allow the conversion of the general parameters affecting the braking performances of trains (such as a braked weight percentage, goods/passenger brake position, brake equipment, train length, etc.) into a basic deceleration profile as a function of time, during the deceleration rise phase, and of speed, during fully developed braking. The deceleration used to evaluate braking curves is obtained by applying a proper safety margin to the nominal deceleration value (which depends on train characteristics).
In this paper a probabilistic analysis of train deceleration is carried out, starting from probability distributions of parameters affecting the braking. For the major parameters, the probability distribution was determined on the basis of technical knowledge and experimental results. The aim of this work is to determine the probability that the real deceleration is lower than the nominal value multiplied by a given safety margin
Odometric estimation for automatic train protection and controlsystems
No full textThe paper summarises the main features concerning the definition of an efficient odometry algorithm to be used in modern automatic train protection and control (ATP/ATC) systems. The availability of a reliable speed and travelled distance estimation is essential for the efficiency and the safety of the whole system. The first essential step in odometric subsystem design is the choice of the sensors, whose output signals will be used for velocity estimation. Then a suitable procedure fusing sensor signals has to be defined as a function of number and type of sensors and accuracy and safety targets. In the paper, the main features of an innovative solution will be summarised and its performance will be presented, in terms of precision in speed and travelled distance estimation. © 2011 Taylor & Francis
Search & Inspection archaeological underwater campaigns in the framework of the European ARROWS project
Full text linkAutonomous Underwater Vehicles (AUVs), benefiting from significant investments in the past years, are commonly used for military security and offshore Oil&Gas applications. The ARROWS project, aimed at exporting the AUV technology to the field of underwater archaeology, a low-budget research field compared to the previous ones. The paper focuses on the strategy for vehicle coordination adopted within the project, a Search and Inspection (S&I) approach borrowed from the defense field (e.g., mine countermeasure – MCM) that proved to be an efficient solution also for the main phases of an underwater archaeological mission. The other main novelty aspect is represented by MARTA (MArine Robotic Tool for Archaeology) AUV: it is a modular vehicle easily and quickly reconfigurable developed in the framework of ARROWS according to the project Archaeological Advisory Group (AAG) guidelines. Results from the final demonstration of the project, held in Estonia during Summer 2015, are proposed in the paper as an experimental proof of the validity of the proposed S&I strategy, and MARTA functioning and its adaptability to the mission requirements. Even in its first prototype version, MARTA successfully played the Inspection role within the AUV team, collaborating with a commercial Search AUV. Acoustic and optical data collected during the mission and processed to increase their intelligibility for the human operator are proposed and discussed
A parametric library for the simulation of UIC pneumatic braking system
Full text linkEuropean trains are equipped with a pneumatic braking system that has to respect severe specifications concerning both performances and safety. The pneumatic braking system is composed of hundreds of different pneumatic components that reproduce the prescribed response by a complex logic of pneumatic and mechanical elements. In this paper a tool for a complete simulation of the pneumatic braking system is described, it was developed using the Matlab-Simulink numerical environment.
The tool is composed of three different libraries of pneumatic components. The first includes the elementary components such as pipes, orifices, valves and the reservoir. By assembling elementary components, an advanced user can build a customized version of general pneumatic components or plants. Complex components of general use for railway pneumatic brake such as brake cylinders, distributors, pressure transformers and brake valves are available in a second library that can be used to assemble a customized braking plant for a vehicle. The last library is composed of macro-pneumatic subsystems that reproduce the braking system of a typical railway vehicle. Many common plant layouts are reproduced in this library (freight car, passenger coaches, locomotives, etc.). The pneumatic brake system of a train can be simulated by assembling in a single Matlab-Simulink model the elements of the library. In this paper the main features of this numerical tool and the test procedures developed to validate the software are described. Experimental data have been kindly supplied by Trenitalia SPA and they are referred to several test campaigns managed by Italian railway in order to verify and release existing components of the pneumatic brake
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