1,720,983 research outputs found
A centimetre-scale bi-directional wind turbine for energy harvesting applications: Design and experimental tests
No full textIn this work, new cm-scale wind turbines for powering sensor nodes devoted to monitoring/diagnostic of railway vehicles are designed, built and tested in a wind tunnel. Two rotors, having four airfoil blades with a diameter of 3 and 4 cm, are designed following the blade element momentum-based approach. The two rotors, tested in a wind tunnel, reach a power coefficient (without considering the losses in the conditioning circuit) ranging between 20% and 30%, in line with the maximum values of the Schmitz theory; the correspondence between the numerical estimates and the experimental data is discrete. The 4 cm diameter rotor, once connected to a conditioning circuit, reaches a maximum net efficiency of about 15%, equal to the maximum value found in the literature, but with a 13,5 cm diameter rotor. Considering the practical application on trains and the fact that the rotor has to work for two opposite velocity directions (it must be bi-directional), a 4 cm diameter symmetrical rotor with a constant blade pitch and flat plate blade section is also built. With the symmetric rotor, we can observe that the generated power is about 50% lower than that produced by the same rotor with airfoil blades. Finally, the turbine is set inside a duct to protect it and increase performance. The tests performed on this ducted turbine (4 cm diameter, symmetric) allow us to understand that the duct significantly increases the performance of the rotor in downwind conditions, from 1% to 6%, while it is almost irrelevant in upwind conditions. Moreover, the diffuser increases the efficiency by about 20%, while the contraction cone does not significantly modify the performance of the turbine
Wireless sensor nodes for freight trains condition monitoring
No full textObjective of the present work is to present the design and the laboratory tests of Wireless Sensor Nodes (WSNs) equipped with three different on-board energy production systems, to be installed on freight trains for condition monitoring and structural diagnosis of the railway vehicle. The three sensor nodes are designed to be completely energetically autonomous, exploiting three different energy sources easily available on a moving train: Solar, Wind and Mechanical vibration power. a PCB board hosts different ICs, able to convert the uncontrolled and unregulated power sources in order to properly feed all the on-board components and possibly to charge the battery. The electronics for the acquisition, elaboration and wireless transmission of data, is presented and analyzed in terms of performances and consumptions. The three WSNs, based on the different energy sources, are designed and compared in terms of fatigue behavior and performances by means of laboratory tests
Thermomechanical Model Predictive Cascade Control for Blended Braking of an IWM Vehicle
No full textThe paper proposes an online control algorithm that optimizes the distributions of the electric and hydraulic torques to each wheel of an In WheelMotor (IWM) vehicle. The torque allocation strategy considers the driver's requests and the vehi-cle's longitudinal and lateral dynamics in relation to the available driving and braking torques of the IWMs and the hydraulic brakes. The blended braking action considers the dynamics of the actuators, the adherence limits, and the thermal limits of the electric motors. The objective of minimizing the energy consumption of the system has been achieved by implementing a linear MPC cascade controller aimed at computing the minimum effort of the actuators based on a linearized model of the vehicle system, on the thermal model of the electric motors, and on the dynamics of the hydraulic braking system. The effectiveness of the control action has been verified through different simulation scenarios, evaluating the full potential of the algorithm even in hard driving and braking maneuvers
Preliminary design of an alternative energy storage system for a city car based on flywheel
Full text linkVehicle energy storage systems have a crucial impact on the spreading of hybrid and electric vehicles.Nowadays the most adopted solution is represented by batteries which suffer of ageing that reduces the battery capacity; moreover, the battery recycling at the end of its life is still a challenge and generate pollution. This paper presents a preliminary design of a kinetic energy storage system for city micro-car. The energy is stored by means of flywheel. First, an energetic model of the car powertrain including flywheel and bearings is proposed and used to evaluate the car energy requirement to accomplish its typical journey. Then, material, geometry and motor have been selected to fit all the vehicle space requirements. Then, analysis on the gyroscopic effects induced by the flywheel is shown when it is subjected to car chassis acceleration. Finally, preliminary considerations on bearing layout are drawn by comparing different bearings types
Optimal powertrain design and control of an electric race car
No full textPowertrain design undoubtedly plays an important role to improve the overall performance of the unprecedented rapidly developing Electric Vehicles (EVs) in recent years. Generally, parameters of the motor and transmission are the primary considerations to meet the performance requirements in electric vehicle design. However, the conventional powertrain design approach in most of the existing work limits the further improvements of the desired performances. In this work, the powertrain design and control problem of a 4-Independent-Wheel-Driving (4-IWD) electric race car with minimum lap time on a given circuit as evaluation criteria is investigated, based on a 7-DOF vehicle model. In particular, the investigated problem is formulated as an optimal control problem and solved with a software package GDYNOPT, taking into account the nonlinear load transfer and the powertrain mass variation that depends on the design parameters. At last, both the optimal design and control parameters are obtained at the same time
Crack Detection in Railway Axles Using Axle-Box Vibration Measurements: Experimental Investigation Using a Full-Scale Roller Rig
No full textIn this paper, an experimental investigation is carried out to assess the possible use of axle-box acceleration measurements to identify the presence of a transverse crack in railway axles, detecting components of axle vibration occurring at frequencies that are integer multiples of the axle’s frequency of revolution (N × Rev components). The experimentation was performed propagating the cracks of different dimensions induced into a pair of railway axles mounted on a freight wagon by means of full-scale roller rig tests. The results show that the 3 × Rev components of the horizontal axle-box acceleration is well correlated to the size of the crack and less sensitive to the effect of disturbances induced at the roller-wheel contact with respect to the vertical acceleration. Hence, they represent a promising possibility for the continuous monitoring of axle integrity. Specifically, the obtained experimental results suggest the possibility of detecting cracks with sizes larger than 11–12%..
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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