Abstract

Due to development of novel and more efficient energy storage systems we bear witness to the dawn of a new era of mobile systems. They have become sophisticated in terms of hardware components and software applications which have made it possible to develop integrated solutions for a large number of imaginable applications ranging from electric vehicles all the way to fully autonomous systems operating in a wide variety of ecosystems, e.g., service, surveillance or bio-inspired robots. Generally it is expected that a mobile system exhibits a sufficient degree of autonomy in the sense of energy availability such that it at least accomplishes the mission objectives for which it is intended. Nevertheless, such autonomy, is influenced to a large extent by the remaining energy that can be retrieved from its energy storage system and by the environment conditions in which the system operates. Assessing the reliability of a mission requires using systems internal and external situational awareness to determine if the available energy at least meets the energy needs demanded by the future operation of the mobile system in order to determine its remaining useful life (RUL). Having this information as soon as possible may allow the decision maker to apply a contingency plan to intervene and reconfigure the mission execution strategy in order to improve the probability of success, in those situations in which the system becomes incapable of achieving the original mission objectives. Numerous studies have been published for assessing mission reliability and estimating the RUL of mobile systems. However, they deal with structured environment conditions and thus with relatively deterministic loads. Moreover, these approaches neglect the inherent uncertainty which stems from multiple sources such as the lack of knowledge about the true energy available in the mobile system, the noise introduced by sensors or the randomness of the operation environment, just to mention a few. The approach presented in this work is built around the belief that the RUL estimation is formulated as an uncertainty propagation problem. Accordingly, to estimate the RUL multiple sources of uncertainty involved in its estimation are first characterized and then propagated with the aim of computing their combined effect, expressed in terms of a probability density function. The approach developed here achieves this estimation in a Monte-Carlo fashion in which several RUL realizations are simulated in order to accurately estimate its entire probability distribution. The aim of this work is therefore devoted to develop a solution capable of estimating the RUL with application to energy-constrained mobile systems operating in stochastic environments.

Abstract

This paper presents results of an experimental study on 3-dimensional scour at submarine pipelines with uniform sediments under a unidirectional steady current. A dimensional analysis is first conducted to identify all the important non-dimensional parameters. Laboratory experiments are then conducted to study the development of a 3-dimensional pipeline scour hole under different sets of environmental conditions. The results are recorded and the corresponding propagation velocities of the free span calculated. The effects of four parameters on the propagation velocity are studied through the conduct of several groups of experiments; each of which exclusively focuses on one particular parameter. Moreover, the scour pattern under different combinations of environmental conditions is discussed to obtain an improved understanding on the mechanism of scour hole propagation at the span shoulder of pipelines.

Abstract

Pipeline right-of-way maintenance activities face great challenges that have come from different climates, slopes, soils and other environmental conditions. Control of surface drainage and erosion is an important element in the restoration and maintenance of pipeline right-of-ways, since erosion can result in risk of pipe exposure and its consequences. Evaluation of this risk can be a powerful tool to ensure reliability of buried pipelines. The universal soil loss equation is used as a model to estimate the rates of erosion at sections of rights-of-way of a gas pipeline right-of-way near Vitoria city in southeast of Brazil. The confrontation of these rates to the actual pipe cover depths is used as a basis to derive a probabilistic procedure for determining the time period over which exposure may occur for a given level of uncertainty. Then, risk can be estimate as a product of the probability (or frequency) of product leakage due to pipeline exposure and the associated consequences of this event. Such risk definition is used to estimate results in an effective guideline to engineers, since it leads to the achievement of optimum and safe erosion control and superficial drainage system projects and results in efficient mitigation planning programs. The results obtained are very promising and show relevant correspondence with the erosion process and cover depth reduction identified on the right-of-way.

Abstract

Due to shorter product life-cycles, increasing product customization and the co-existence of electric and combustion engine vehicles, variant flexibility is gaining importance in the automobile production. The automobile body shop is characterized by inflexible, rigid fixture systems dedicated to meet the geometrical requirements of specific body parts. Changes in part geometry or dimension require the development of new fixture systems, thus increasing product variety results in higher fixture costs. This paper presents an approach for a fixtureless body shop based on component-integrated fixture-functions, increasing variant flexibility and reducing fixture costs. The approach is implemented using a body part assembly of an electric vehicle. Document type: Article

Abstract

Due to the conceptual degrees of freedom in their product structure, electric vehicles offer high potential for remanufacturing-oriented product design. This potential is, however, not realized yet. Remanufacturing as one fundamental element of a circular economy is characterized by specific challenges caused by uncertain information about the condition and the timing of the returning product. By means of a case study within the remanufacturing industry, the effects of uncertainties on remanufacturing operations are examined and different approaches within the field of production management to meet these specific challenges are pointed out. Based on the result of the case study a production management framework outlining fields of action to deal with remanufacturing specific uncertainties is developed. In this context, the requirements for remanufacturing of electric vehicles are derived by analyzing similarities from other industry sectors. In conclusion, a solution approach for the implementation for electric vehicles is presented for strategic, tactical and operational procurement logistics and remanufacturing operations. Document type: Article

Abstract

Cities are a hotspot for resource consumption and related impacts. This is induced, among others, by transportation, production and the use of products and services. Industrial production is commonly associated with negative impacts, e.g. on the environment or traffic. Through positive integration of production sites into urban surroundings, negative impacts can be eliminated, and even positive impacts achieved. To reach a higher degree of integration of different utilizations in cities, resource-efficiency, new conceptual approaches are required for urban factories, city authorities and further stakeholders. For this purpose, a methodology has been developed that describes the planning processes of the involved disciplines and their interdependencies concerning content and timing. Subsequently, an analysis of Urban Factories within a reference framework called the factory-city-system and its key resources is carried out in an exemplary case study. Measures to enhance resource-efficiency are thus dentified, exemplarily described and examined regarding their potential to raise resource-efficiency.

Abstract

This paper focuses on the hardware aspects of battery management systems (BMS) for electric vehicle and stationary applications. The purpose is giving an overview on existing concepts in state-of-the-art systems and enabling the reader to estimate what has to be considered when designing a BMS for a given application. After a short analysis of general requirements, several possible topologies for battery packs and their consequences for the BMS’ complexity are examined. Four battery packs that were taken from commercially available electric vehicles are shown as examples. Later, implementation aspects regarding measurement of needed physical variables (voltage, current, temperature, etc.) are discussed, as well as balancing issues and strategies. Finally, safety considerations and reliability aspects are investigated. Document type: Article

Abstract

Copyright © 2014 Vilnius Gediminas Technical University (VGTU) Press. In academia as in practice, seaports are increasingly viewed as elements in supply chains. It is argued that seaports should add value to shippers by aligning their own business activities with shippers Supply Chain Management (SCM) strategies and requirements. The implications of this port-SCM philosophy are not fully explored, however. In this context, it is especially important to create mutual understanding between shippers, in terms of their SCM strategies, and port actors, in terms of services provided. In this paper a framework is developed, which aims to improve mutual understanding between shippers and port actors from a SCM point of view. It thereby aims to contribute to the dialogue on how the port logistics system can be better integrated into shippers SCM strategies. Three SCM reference models are analysed and twelve SCM subsystems identified that represent broad design areas of shippers SCM strategies. Further, the seaport system is discussed in terms of system boundaries and the actors involved. Port actors and SCM subsystems are then combined into one explanatory framework, the SCM-port actor matrix. Finally, applying the matrix, three cases retrieved from academic and trade literature in which port actors are actively involved in conducting shippers supply chain strategies are discussed. The paper concludes with a brief outlook on future research needs. 2014 Document type: Article

Abstract

Public transport is an especially promising sector for full electric vehicles due to the high amount of cycles and predictable workload. This leads to a high amount of different vehicle concepts ranging from large batteries, designed for a full day of operation without charging, to fast-charging systems with charging power up to a few hundred kilowatts. Hence, many different issues have to be addressed in the whole design and production process regarding high-voltage (HV) batteries for buses. In this work, the design process for electric public buses is analyzed in detail, based on two systems developed by the research projects Smart Wheels/econnect and SEB eOPNV. The complete development process starting, with the demand analysis and the operating scenario, including the charging routine, is discussed. This paper also features details on cell selection and cost estimations as well as technical details on the system layout, such as the management system and passive components as well as thermal management. Document type: Article