1,721,073 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
State-of-charge estimation based on model-adaptive Kalman filters
No full textThis article presents a set of algorithms for the estimation of state of charge, specifically deployed for lithium-ion batteries. These algorithms are based on appropriate battery models. These models can be developed having different levels of accuracy, also including the possibility to correctly represent the hysteresis voltage behaviour of the selected lithium cells. In addition, different identification methods of the battery model parameters may also be considered, considering tabulated parameters, calibrated in previous tests, or online parametrization tools. State of charge is then evaluated using non-linear Kalman filter techniques. Effectiveness of identification methods, also with the performance offered by Kalman filter itself, has been accurately evaluated through experimental tests. To verify the robustness of the proposed algorithms, some disturbances were introduced and evaluation was also conducted at different state of charge initial conditions and sampling times
Reversible Traction Substations in DC Railway Systems: A Comparative Study of Approaches
No full textIn line with the overall goals of EU climate commitment and railway operators, reducing CO2 emission and eco-friendly transport systems together with increased energy efficiency have received more attention during the last years. In this context, a significant contribution of studies is dedicated to the capabilities and potentials of utilizing regenerative braking energy (RBE). Among different methods of recuperating RBE, adopting reversible/bidirectional substations to feed back the RBE into the upstream grid is a promising solution. In this paper, different methods and configurations regarding the implementation of reversible substations (RSS) with bidirectional power flow capability are discussed and compared. Meanwhile, the challenges of transforming the existing traditional traction substations (TSS) into reversible substations together with their impacts on the energy efficiency of the electric railway system (ERS) are outline
High performance Vector Ultrasound Anemometer based on Capacitive Micromachined Ultrasonic Transducers
No full textWind speed sensors provide fundamental measurements for applications ranging from environmental monitoring to autonomous systems. A Planar Vector Anemometer (PVA) can measure the speed and direction of wind on a plane. Standard PVAs are based on a mechanical setup composed of a directional air-foil and a tangential turbine. Their miniaturization is difficult, and reliability is penalized by the presence of mechanical moving parts, subject to friction and wear. Ultrasound PVAs address these limitations by measuring the time of flight of an ultrasound wave from two opposite sensors placed on two orthogonal axes. In these devices, the large size of typical sensors, i.e. 1 cm, 40 kHz piezoelectric ultrasonic transducers (PT), prevents further miniaturization due to the perturbation of the air flow by the sensors themselves (shading effect). In this study, we investigate the possibility to miniaturize PVAs by using a novel polymer-based capacitive micromachined ultrasonic transducer (CMUT) technology to reduce the sensors size and the total encumbrance of the PVA
Simplified Approach for Developing Efficiency Maps of High-Speed PMSM Machines for Use in EAT Systems Starting from Single-Point Data
No full textElectrically Assisted Turbochargers (EATs) have shown the potential of solving turbo-lag issues and improving exhaust energy recovery in turbocharged engines. Ultra-High-Speed (UHS) Permanent Magnet Synchronous Machines (PMSMs) were found to be well suited for EAT use. However, data required for preliminary system modelling are hard to come by and literature typically presents electrical quantities and power losses of a single operating point. This paper presents an easy-to-use approach for developing in the Simulink ambient a simplified model capable of providing Motor-Generator Unit (MGU) efficiency maps starting from single-point data and to easily perform machine scaling taking account of rotordynamics constraints
VSC 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
Design of a hydraulic servo-actuation fed by a regenerative braking system
Full text linkMany conventional truck and working machines are equipped with additional hydraulic tooling or manipulation systems which are usually fed through a mechanical connection with the internal combustion engine, involving a poor efficiency. In particular, this is a common situation for industrial vehicles whose mission profiles involves a relevant consumption of energy by the on board hydraulic systems, respect to the one really needed for only traction purpose. In this work it is proposed an innovative solution based on the adoption of a system aimed to recover braking energy in order to feed an efficient on board hydraulic actuation system. The proposed system is then adopted to a real application, an Isuzu truck equipped with a hydraulic tooling for garbage collection. A prototype of the system has been designed, assembled and tested showing a relevant improvement of system efficiency and the feasibility of the proposed approach. In the paper the proposed solution is presented, showing the simulation models and preliminary validation results including experimental devices assembled to perform the tests
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
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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