1,720,973 research outputs found
Model-based simulation of dynamic behaviour of electric powertrains and their limitation induced by battery current saturation
No full textThe wide-spread e-mobility revolution is asking for new software solutions capable of providing meaningful information not only for the mechanical part of the vehicle architecture, as in the past, but also for novel electric and hybrid driveline components. The objective of the paper is to provide a lightweight model for a fully electric vehicle powertrain, trying to assess the current constraints imposed by the battery to the whole driveline, and able to reflect this limitation throughout the transmission line, down to the electric motor and thus to the performance of the full vehicle. The model is suitable for real-time performances thanks to the effective computation of the powertrain via analytical solutions. Moreover, the whole system has been modelled following a model-based approach in Modelica language and is made part of the Altair activate car real-time library, in which both the electrical and mechanical parts integrate smoothly
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
A soft soil contact model with adaptive level of detail for predicting off-road vehicle mobility
No full textThis work presents a model for soft soil that can interact with wheeled or tracked vehicles in a multibody simulation framework. In sake of high performance, the soil is represented by arbitrary triangular meshes, where the level of detail of the mesh is automatically increased as tire lugs or track shoes come into contact
Lightweight dynamic vehicle models oriented to vehicle electrification
No full textThe paper deals with the development of fast and lightweight vehicle dynamics models oriented to the vehicle electrification. Two models are created, as they are concerned with different accuracy levels. The first one is very essential: it consists of three dynamics, that is full vehicle, front wheels and rear wheels; regularised Coulomb friction model is adopted. The second model is more advanced since it comprehends the vertical dynamics due to the suspension system and tyre friction model comes from Pacejka’s theory. The dynamics models are subsequently compared with a very sophisticated and accurate model developed thanks to Chrono::Engine (C::E): because C::E is a powerful and reliable software, this process can be considered as a first validation of the more essential vehicle descriptions. Afterwards, models are connected to an electric powertrain to evaluate the effects of the different mechanical models with respect to the same electric system; this also aims to estimate the characteristic quantities of the electric domain
A Unified Analytical Expression of the Tangent Stiffness Matrix of Holonomic Constraints
Full text linkSolving variational inequalities and cone complementarity problems in nonsmooth dynamics using the alternating direction method of multipliers
Full text linkThis work presents a numerical method for the solution of variational inequalities arising in nonsmooth flexible multibody problems that involve set-valued forces. For the special case of hard frictional contacts, the method solves a second order cone complementarity problem. We ground our algorithm on the Alternating Direction Method of Multipliers (ADMM), an efficient and robust optimization method that draws on few computational primitives. In order to improve computational performance, we reformulated the original ADMM scheme in order to exploit the sparsity of constraint jacobians and we added optimizations such as warm starting and adaptive step scaling. The proposed method can be used in scenarios that pose major difficulties to other methods available in literature for complementarity in contact dynamics, namely when using very stiff finite elements and when simulating articulated mechanisms with odd mass ratios. The method can have applications in the fields of robotics, vehicle dynamics, virtual reality, and multiphysics simulation in general
Deformable soil with adaptive level of detail for tracked and wheeled vehicles
No full textThis paper describes a model for deformable soil based on triangular meshes with vertical deformation. Such soil model can be used in a multi-body simulation environment to study the performance of wheeled or tracked vehicles. The formulation is inspired by the soil contact model (SCM), but unlike the original idea, our implementation uses triangular meshes with arbitrary topology. We leverage on this representation of the soil in order to provide a system that automatically refines the level of detail (LOD) of the mesh when tyres or track shoes sink into the soil; this allows the use of coarse meshes as initial approximations of large areas, for the sake of faster performance and low overhead on computer memory. A general-purpose collision detection algorithm is used to detect the shape of contacting objects, hence allowing the use of generic geometries to represent lugs, tyre threads, or even track shoes or robotic legs. The method has also been tested with deformable tyres
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