International Journal of System of Systems Engineering (11 papers in press)
A study of an adaptive approach for systems-of-systems integration
by Ilyas Ed-daoui, Mhamed Itmi, Abdelkhalak El Hami, Nabil Hmina, Tomader Mazri
Abstract: Systems-of-systems are a growing composition of complex, autonomous and heterogeneous systems that collaborate in order to achieve complex and evolving targets that exceed the sum of the parts. In fact, the biggest challenge in such environment lays in the preservation of the viability of the system-of-systems and its evolvement while handling component systems dynamic integrations. This also represents a pressing issue in systems-of-systems engineering. In this paper, we present a collection of definitions dedicated to sire the system-of-systems concept, their characteristics and typology. Next, we detail the challenges facing the integration process in systems-of-systems. Then, we present our proposition to manage this issue. It is based on an adaptive integration approach to systems-of-systems typology. Two case studies are provided in order to experiment our theory. We evaluate the performance of the approach in both cases. Results are cross-compared.
Keywords: interoperability; performance evaluation; simulation; systems-of-systems architecture; systems-of-systems integration.
SCORING THE RISK MATRIX
by Paul R. Garvey
Abstract: In systems engineering, the risk matrix is a popular protocol for binning risks into a collection of probability and consequence cells. It can be used to produce an ordinal ranking of cells according to their position in an ordered list. Although the risk matrix provides a way to rank cells that contain risks, its ordinal aspects limit measuring differences between them. Understanding these differences can be important in management decisions. To address this limitation, this paper presents a way to transform a rank ordered list of risk matrix cells into a cardinal measurement scale. The transformation produces a risk scored risk matrix. This allows relative differences among cells to be meaningfully compared, which broadens its use in management decisions. A risk scored risk matrix provides greater insights into the urgency of risks grouped within cells than is possible in a traditional risk matrix, while remaining within its ease and popularity of use.
Keywords: systems engineering; engineering management; risk management; risk; risk matrix.
Spark! : An Integrated Resource Planning and Dispatch Tool for Power Grid Modelling
by Ange-Lionel Toba, Mamadou Seck
Abstract: The power grid infrastructure faces multiple challenges due to, not only the growing demands, but also the widespread deployment of renewable generation. The increasing level of renewable penetration in the energy mix requires to re-think the way the grid works, operates, and also how it is structured. This makes energy planning more critical as it will necessarily have to account for the effects of intermittence and variability of these sources, and the dynamic behavior of the overall system. Power grid models can play an important role in performing that task. What is needed, is a new, faster computational model that can simulate large-scale grid operations, while capturing generating units constraints, system flexibility and architecture. We present Spark!, a grid simulation model, for large scale future power grids over long term horizons. The model developed in Python, and built on a DEVS (Discrete Event System Specification) platform, captures the intermittent and stochastic nature of renewable energy resources and their associated forecast error, the thermal constraints of conventional generation resources, geographical and climate information, the transmission network, with a flexible time resolution.
Keywords: Renewable Energy; Grid modelling; discrete-event; simulation.
Minimum variance control strategy for closed loop linear time invariant system
by Wang Jianhong
Abstract: To design one feedback controller in a closed loop linear time invariant system, the idea of minimum variance control is used to realize this goal. Two explicit forms corresponding to the closed loop system are considered, i.e. its general form and rational transfer function form respectively. Firstly one closed form solution of the minimum variance controller is derived in the general form of the closed loop linear time invariant system, and an optimization algorithm is proposed to obtain controller in practice. Secondly in the rational transfer function form of the closed loop linear time invariant system, the minimum variance controller is determined, while guaranteeing the modified variances of output and input as small as possible.
Keywords: Minimum variance control; modified cost; Closed form solution; Alternating direction method of multipliers.
Special Issue on: Critical Success Factors for Public Transportation
Wheel Maintenance in Rolling Stock: Safety Challenges in the Defect Detection Process
by Maria Mikela Chatzimichailidou, Alberto Martinetti, Arnab Majumdar, Leo A.M. Van Dongen, WASHINGTON Y. OCHIENG
Abstract: The proper and timely maintenance of railway rolling stock is essential for the safety of railway operations. Inaccurate inspection can lead to inadequate repair of defects and to great safety challenges in respect to the entire railway system. The detection and repair of any defect, such as cracks, in the wheels prior to a failure can significantly reduce train derailments and improved operational performance. This paper examines the wheel maintenance process in maintenance depots in the Netherlands on the basis of literature review, observations and interviews. First, it highlights various detection methods, including the risks of the incorrect detection of a flawed wheel profile. This paper introduces a flowchart as a concise illustration of the maintenance process; that is, both the detection and treatment of defects. With this in hand, the authors, as well as anyone involved in maintenance, are able to identify the points where the process is vulnerable and may be prone to incidents/accidents. Based on this procedure, improvements to the current wheel maintenance process can be proposed. The method that the flowchart is based on is also presented herein, along with the findings obtained throughout its steps.
Keywords: Maintenance; Safety; Wheel Defect; Rolling Stock.
The Redesign Process of the Timetable for the Dutch Railway Sector: a Theoretical Approach
by Femke Bekius, Sebastiaan Meijer
Abstract: The design of a new timetable for a railway system is a complex process, especially when the design starts from scratch. In this case the process is fundamentally different and much more complex than the yearly design process. Focussing only on the product, i.e., the timetable, and the exchange of information from one design phase to the next, does not cover the complexity and dynamics of the design process. Strategic actor behaviour and contextual factors are underexposed by other papers on theory of designing civil infrastructures, such as timetable design for railway systems. Therefore, we investigate the redesign process of the timetable for the Dutch railway sector from two perspectives: (i) an engineering perspective, and (ii) an actor and context perspective. To indicate the successes and failures of the redesign process of the timetable the design process is characterised using a framework that includes these two perspectives: the PSI framework. Several design phases are distinguished and at the transitions between the design phases misalignments are identified. The theoretically found misalignments are compared with empirical data to conclude on a set of improvements for design processes in the Dutch railway sector. Areas perceived as particularly problematic are knowledge transfer between the first design phases, decomposition of one design phase into several separate products, and composition of multiple products into one final design with corresponding actors and institutions.
Keywords: design theory; design process; Dutch railway sector; railways; PSI framework; case study; complexity; Complex Adaptive Systems; Systems of Systems.
Validity of Railway Microscopic Simulations Under the Microscope: Two Case Studies
by Bill Roungas, Sebastiaan Meijer, Alexander Verbraeck
Abstract: Simulations are the core of every railway system. Changes in the timetable and the infrastructure, or even in the internal processes of a railway company should be, and usually are, first tested through simulations. Given their significance and potential impact, simulations should be primarily validated; validation ensures - at least to some extent - that the returned results are credible and can be used for the intended purpose. This study is a detailed report on two case studies from the railway sector. The aim of this paper is to identify critical factors that can advance or hinder the validity and the effective usage of simulation models.
Keywords: simulations; validation; railways; case study.
There is no spoon: applying virtual reality for maintenance training of rolling stock technicians
by Alberto Martinetti, Koen 't Hart, Roy Damgrave, Leo Van Dongen, Robin Turkenburg, Andre Nouwens
Abstract: Introducing into operations new rolling stocks requires re-educating technicians and operators for being able to properly work on new and different assets. The training sessions are often performed under substantial time constraints and with a lack of resources. Re-training the technicians is a cost intensive process as it is for training new employees. The aim of the paper is to test and evaluate a Virtual Reality (VR) training solutions to decrease costs and to increase technicians availability, safety during maintenance operations and education performance with the support of Netherlands Railways (Nederlandse Spoorwegen NS). Firstly, the study explores the possible maintenance tasks analysing the benefits for VR implementations; secondly, it evaluates the attitude of technicians trained with the proposed VR approach. Finally, it discusses the results and provides general applicable suggestions for the use of VR in other training activities.
Keywords: Maintenance; Virtual Reality; Rolling Stocks; Training.
DEMATEL-AHP technique to minimize departure delays due to airspace congestion: A case in Mactan-Cebu International Airport
by Rosein Jr. Ancheta, Miriam Bongo, Lanndon Ocampo, Dennis Anthony Kilongkilong, Miraflor Amit, Odiza Cuizon, Nikki Joy Arda
Abstract: Airspace congestion has a direct effect on departure schedules of aircraft. In events when there is a constrained airspace due to various factors such as adverse weather, departure delays may be potentially serious. Due to the complexity of the problem of choosing the best possible option in addressing airspace congestion, a combined multiple criteria decision making (MCDM) approach is used for the decision-making process. Furthermore, this paper incorporates the views of experts representing air traffic service and airlines management which is significant in choosing a viable solution to both stakeholders operating air transport. It has been found that both air traffic service and airlines management give most priority to safety, thus, prefer to apply for ground delay program during airspace congestion.
Keywords: departure delays; airspace congestion; analytic hierarchy process (AHP); decision making trial and evaluation laboratory (DEMATEL); multiple criteria decision making (MCDM).
Framing success: the Netherlands railways experience
by Mohammad Rajabalinejad, Leo A.M. Van Dongen
Abstract: Here we introduce the success framework, an integral view on the critical success factors to accommodate flexibilities required for tacking with the dynamism of rail industry both technically and organisationally. The success framework adapts two basic strategies that contribute to success. First, a clear set of objectives across the stakeholders. Second, cooperation and co-creation of values for achieving the objectives. We propose an integral approach for identification and accomplishment of the critical success factors. The application of the framework is further explained through a case study.
Keywords: critical success factor; CSF; success framework; railway; Netherlands.
Special Issue on: Soft Operations Research Methods for Complex Systems
Using rich pictures outside of soft systems methodology: a case study analysis
by Tessa Berg, Simon Bell, Steve Morse
Abstract: The aim of this paper is twofold. Firstly we will highlight how a problem structuring tool, namely the Rich Picture, is being used across many disciplines outside of the soft system methodology which has historically been its home. Secondly, we highlight the controversial presence of non-conforming Rich Picture research and an apparent reluctance to publish from the systems community. In this paper we provide examples of rich picture research used independent from methodology and focus on one case study that uses a novel method of content analysis to appreciate the significance of the stories within their pictures. We demonstrate the theoretical justification and efficacy of an innovation in the assessment of the Rich Picture and its use as a tool to discern issues of importance across mixed groups. We discuss the responses to this work and the implications for innovation within soft OR research. We propose that the Rich Picture should not be seen as sacrosanct just because it derives from a well-established and much respected methodology. We argue that the Rich Picture can be a flexible space where any practitioner can negotiate shared understanding without methodological constraint.
Keywords: rich picture; soft systems methodology; SSM; innovation; problem structuring.