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  • 1.
    Aronsson, Martin
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Kjellqvist, Tommy
    Östlund, Stefan
    An Integrated Adaptive Maintenance Concept2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a novel maintenance concept based on condition monitoring and dynamic maintenance packaging, by showing how to connect the information flow from low-level sensors to high-level operations and planning under uncertainty. Today, condition-based maintenance systems are focused on data collection and custom-made rule based systems for data analysis. In many cases, the focus is on measuring "everything" without considering how to use the measurements. In addition, the measurements are often noisy and the future is unpredictable which adds a lot of uncertainty. As a consequence, maintenance is often planned in advance and not replanned when new condition data is available. This often reduces the benefits of condition monitoring. The concept is based on the combination of robust, dynamically adapted maintenance optimization and statistical data analysis where the uncertainty is considered. This approach ties together low-level data acquisition and high-level planning and optimization. The concept has been illustrated in a context of rail vehicle maintenance, where measurements of brake pad and pantograph contact strip wear is used to predict the near future condition, and plan the maintenance activities.

  • 2.
    Aronsson, Martin
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    MILP formulations of cumulative constraints for railway scheduling - A comparative study2009Inngår i: The Proceedings of the 9th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS), Internationales Begegnungs- und Forschungszentrum für Informatik (IBFI), Schloss Dagstuhl, Germany , 2009, 13Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper introduces two Mixed Integer Linear Programming (MILP) models for railway traffic planning using a cumulative scheduling constraint and associated pre-processing filters. We compare standard solver performance for these models on three sets of problems from the railway domain and for two of them, where tasks have unitary resource consumption, we also compare them with two more conventional models. In the experiments, the solver performance of one of the cumulative models is clearly the best and is also shown to scale very well for a large scale practical railway scheduling problem.

  • 3.
    Aronsson, Martin
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Mixed integer-linear formulations of cumulative scheduling constraints - A comparative study2007Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper introduces two MILP models for the cumulative scheduling constraint and associated pre-processing filters. We compare standard solver performance for these models on three sets of problems and for two of them, where tasks have unitary resource consumption, we also compare them with two models based on a geometric placement constraint. In the experiments, the solver performance of one of the cumulative models, is clearly the best and is also shown to scale very well for a large scale industrial transportation scheduling problem.

  • 4.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    A Local Search System for Solving Constraint Problems of Declarative Graph-Based Global Constraints2004Inngår i: Proceedings of the 15th International Conference on Applications of Declarative Programming and Knowledge Management, 2004, 1Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a local search constraint solver in which constraints are expressed using cost functions on graph structures of filter constraints of equal type. A similar theoretical approach has previously been used to model a large number of complex global constraints, which motivates the use of such a model in practice. In a local search context, we view global constraints as complex cost functions, encapsulating the structure of the constraints using a graph of variables, values and filter constraints. This representation gives us a declarative model, which can also be used to efficiently compute a cost as well as conflict levels of the variables in the constraints. We have implemented these ideas in a compositional C++ framework called Composer, which can be used to solve systems of graph-based constraints. We demonstrate the usability of this approach on several well-known global constraints, and show by experimental results on two problems that an approach using a graph basis for global constraint modeling is not only possible in practice, but also competitive with existing constraint-based local search systems.

  • 5.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    A Local Search System for Solving Constraint Problems of Declarative Graph-Based Global Constraints2005Inngår i: Applications of Declarative Programming and Knowledge Management: 15th International Conference on Applications of Declarative Programming and Knowledge Management, INAP 2004, and 18th Workshop on Logic Programming: Revised Selected Papers, Springer , 2005, 1, , s. 308s. 166-184Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a local search constraint solver in which constraints are expressed using cost functions on graph structures of filter constraints of equal type. A similar theoretical approach has previously been used to model a large number of complex global constraints, which motivates the use of such a model in practice. In a local search context, we view global constraints as complex cost functions, encapsulating the structure of the constraints using a graph of variables, values and filter constraints. This representation gives us a declarative model, which can also be used to efficiently compute a cost as well as conflict levels of the variables in the constraints. We have implemented these ideas in a compositional C++ framework called Composer, which can be used to solve systems of graph-based constraints. We demonstrate the usability of this approach on several well-known global constraints, and show by experimental results on two problems that an approach using a graph basis for global constraint modeling is not only possible in practice, but also competitive with existing constraint-based local search systems.

  • 6.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    A Study of Combinatorial Optimization Problems in Industrial Computer Systems2009Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A combinatorial optimization problem is an optimization problem where the number of possible solutions are finite and grow combinatorially with the problem size. Combinatorial problems exist everywhere in industrial systems. This thesis focuses on solving three such problems which arise within two different areas where industrial computer systems are often used. Within embedded systems and real-time systems, we investigate the problems of allocating stack memory for an system where a shared stacks may be used, and of estimating the highest response time of a task in a system of industrial complexity. We propose a number of different algorithms to compute safe upper bounds on run-time stack usage whenever the system supports stack sharing. The algorithms have in common that they can exploit commonly-available information regarding timing behaviour of the tasks in the system. Given upper bounds on the individual stack usage of the tasks, it is possible to estimate the worst-case stack behaviour by analysing the possible and impossible preemption patterns. Using relations on offset and precedences, we form a preemption graph, which is further analysed to find safe upper-bounds on the maximal preemptions chain in the system. For the special case where all tasks exist in a single static schedule and share a single stack, we propose a polynomial algorithm to solve the problem. For generalizations of this problem, we propose an exact branch-and-bound algorithm for smaller problems and a polynomial heuristic algorithm for cases where the branch-and-bound algorithm fails to find a solution in reasonable time. All algorithms are evaluated in comprehensive experimental studies. The polynomial algorithm is implemented and shipped in the developer tool set for a commercial real-time operating system, Rubus OS. The second problem we study in the thesis is how to estimate the highest response time of a specified task in a complex industrial real-time system. The response-time analysis is done using a best-effort approach, where a detailed model of the system is simulated on input constructed using a local search procedure. In an evaluation on three different systems we can see that the new algorithm were able to produce higher response times much faster than what has previously been possible. Since the analysis is based on simulation and measurement, the results are not safe in the sense that they are always higher or equal to the true response time of the system. The value of the method lies instead in that it makes it possible to analyse complex industrial systems which cannot be analysed accurately using existing safe approaches. The third problem is in the area of maintenance planning, and focus on how to dynamically plan maintenance for industrial systems. Within this area we have focused on industrial gas turbines and rail vehicles. We have developed algorithms and a planning tool which can be used to plan maintenance for gas turbines and other stationary machinery. In such problems, it is often the case that performing several maintenance actions at the same time is beneficial, since many of these jobs can be done in parallel, which reduces the total downtime of the unit. The core of the problem is therefore how to (or how not to) group maintenance activities so that a composite cost due to spare parts, labor and loss of production due to downtime is minimized. We allow each machine to have individual schedules for each component in the system. For rail vehicles, we have evaluated the effect of replanning maintenance in the case where the component maintenance deadline is set to reflect a maximum risk of breakdown in a Gaussian failure distribution. In such a model, we show by simulation that replanning of maintenance can reduce the number of maintenance stops when the variance and expected value of the distribution are increased. For the gas turbine maintenance planning problem, we have evaluated the planning software on a real-world scenario from the oil and gas industry and compared it to the solutions obtained from a commercial integer programming solver. It is estimated that the availability increase from using our planning software is between 0.5 to 1.0 %, which is substantial considering that availability is currently already at 97-98 %.

  • 7.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Constraint satisfaction by local search2002Rapport (Annet vitenskapelig)
    Abstract [en]

    The constraint satisfaction problem and its derivate, the propositional satisfiability problem (SAT), are fundamental problems in computing theory and mathematical logic. SAT was the first proved NP-complete problem, and although complete algorithms have been dominating the constraint satisfaction field, incomplete approaches based on local search has been successful the last ten years. In this report we give a general framework for constraint satisfaction using local search as well as an different techniques to improve this basic local search framework. We also give an overview of algorithms for problems of constraint satisfaction and optimization using heuristics, and discuss hybrid methods that combine complete methods for constraint satisfaction with local search techniques.

  • 8.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Bruce, Lars
    Redesign of the Oz Compiler2002Rapport (Annet vitenskapelig)
    Abstract [en]

    This master of science thesis describes a new design and its implementation for an Oz compiler. The project is based on the existing Oz compiler. The new compiler is designed more modular, with separate software components that can be replaced and modified locally. A prototype has been implemented, but further development is necessary. We give an overview of the language Oz, its features and the underlying calculus. The features of Oz regarding object orientation, functional programming, logic and constraint programming are also discussed. The liveness analysis and register allocation problems in general and regarding Oz specific compilers are analyzed, together with current and future optimizations suitable for the Mozart platform. The design of the new compiler and information about the old one is presented, and future work regarding the compiler, optimizations, and analysis phases is discussed. Appendices describing the interfaces between the phases of the compiler is included, together with documentation regarding the internal code formats used.

  • 9.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Dahms, Florian
    Flier, Holger
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Optimal Freight Train Classification using Column Generation2012Konferansepaper (Fagfellevurdert)
  • 10.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Scheduling Gas Turbine Maintenance Based on Condition Data2009Inngår i: Proceedings of the 21st Innovative Applications of Artificial Intelligence Conference, 2009, 6Konferansepaper (Fagfellevurdert)
  • 11.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Steinert, Rebecca
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Wärja, Mathias
    A Tool for Gas Turbine Maintenance Scheduling2009Inngår i: Proceedings of the Twenty-First Conference on Innovative Applications of Artificial Intelligence (IAAI'09), IEEE Computer Society , 2009, 20Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We describe the implementation and deployment of a software decision support tool for the maintenance planning of gas turbines. The tool is used to plan the maintenance for turbines manufactured and maintained by Siemens Industrial Turbomachinery AB (SIT AB) with the goal to reduce the direct maintenance costs and the often very costly production losses during maintenance downtime. The optimization problem is formally defined, and we argue that feasibility in it is NP-complete. We outline a heuristic algorithm that can quickly solve the problem for practical purposes, and validate the approach on a real-world scenario based on an oil production facility. We also compare the performance of our algorithm with results from using mixed integer linear programming, and discuss the deployment of the application. The experimental results indicate that downtime reductions up to 65% can be achieved, compared to traditional preventive maintenance. In addition, using our tool is expected to improve availability with up to 1% and reduce the number of planned maintenance days with 12%. Compared to a mixed integer programming approach, our algorithm not optimal, but is orders of magnitude faster and produces results which are useful in practice. Our test results and SIT AB’s estimates based on operational use both indicate that significant savings can be achieved by using our software tool, compared to maintenance plans with fixed intervals.

  • 12.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Steinert, Rebecca
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Wärja, Mathias
    Searching for Gas Turbine Maintenance Schedules2010Inngår i: AI Magazine, Vol. 31, nr 1, s. 21-36Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Preventive maintenance schedules occurring in industry are often suboptimal with regard to maintenance coal-location, loss-of-production costs and availability. We describe the implementation and deployment of a software decision support tool for the maintenance planning of gas turbines, with the goal of reducing the direct maintenance costs and the often costly production losses during maintenance downtime. The optimization problem is formally defined, and we argue that the feasibility version is NP-complete. We outline a heuristic algorithm that can quickly solve the problem for practical purposes and validate the approach on a real-world scenario based on an oil production facility. We also compare the performance of our algorithm with results from using integer programming, and discuss the deployment of the application. The experimental results indicate that downtime reductions up to 65% can be achieved, compared to traditional preventive maintenance. In addition, the use of our tool is expected to improve availability with up to 1% and reduce the number of planned maintenance days by 12%. Compared to a integer programming approach, our algorithm is not optimal, but is much faster and produces results which are useful in practice. Our test results and SIT AB’s estimates based< on operational use both indicate that significant savings can be achieved by using our software tool, compared to maintenance plans with fixed intervals.

  • 13.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ekman, Jan
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    The opportunistic replacement and inspection problem for components with a stochastic life time2011Rapport (Annet vitenskapelig)
    Abstract [en]

    The problem of finding efficient maintenance and inspection schemes in the case of components with a stochastic life time is studied and a mixed integer programming solution is proposed. The problem is compared with the two simpler problems of which the studied problem is a generalisation: The opportunistic replacement problem, assuming components with a deterministic life time and The opportunistic replacement problem for components with a stochastic life time, for maintenance schemes without inspections.

  • 14.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Flier, Holger
    Maue, Jens
    Matúš, Mihalák
    Track Allocation in Freight-Train Classification with Mixed Tracks2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We consider the process of forming outbound trains from cars of inbound trains at rail-freight hump yards. Given the arrival and departure times as well as the composition of the trains, we study the problem of allocating classification tracks to outbound trains such that every outbound train can be built on a separate classification track. We observe that the core problem can be formulated as a special list coloring problem in interval graphs, which is known to be NP-complete. We focus on an extension where individual cars of different trains can temporarily be stored on a special subset of the tracks. This problem induces several new variants of the list-coloring problem, in which the given intervals can be shortened by cutting off a prefix of the interval. We show that in case of uniform and sufficient track lengths, the corresponding coloring problem can be solved in polynomial time, if the goal is to minimize the total cost associated with cutting off prefixes of the intervals. Based on these results, we devise two heuristics as well as an integer program to tackle the problem. As a case study, we consider a real-world problem instance from the Hallsberg Rangerbangård hump yard in Sweden. Planning over horizons of seven days, we obtain feasible solutions from the integer program in all scenarios, and from the heuristics in most scenarios.

  • 15.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Flier, Holger
    Maue, Jens
    Mihalák, Matúš
    Hump Yard Track Allocation with Temporary Car Storage2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In rail freight operation, freight cars need to be separated and reformed into new trains at hump yards. The classification procedure is complex and hump yards constitute bottlenecks in the rail freight network, often causing outbound trains to be delayed. One of the problems is that planning for the allocation of tracks at hump yards is difficult, given that the planner has limited resources (tracks, shunting engines, etc.) and needs to foresee the future capacity requirements when planning for the current inbound trains. In this paper, we consider the problem of allocating classification tracks in a rail freight hump yard for arriving and departing trains with predetermined arrival and departure times. The core problem can be formulated as a special list coloring problem. We focus on an extension where individual cars can temporarily be stored on a special subset of the tracks. An extension where individual cars can temporarily be stored on a special subset of the tracks is also considered. We model the problem using mixed integer programming, and also propose several heuristics that can quickly give feasible track allocations. As a case study, we consider a real-world problem instance from the Hallsberg Rangerbangård hump yard in Sweden. Planning over horizons over two to four days, we obtain feasible solutions from both the exact and heuristic approaches that allow all outgoing trains to leave on time.

  • 16.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Flier, Holger
    Maue, Jens
    Mihalák, Matúš
    Hump Yard Track Allocation with Temporary Car Storage2010Rapport (Annet vitenskapelig)
    Abstract [en]

    In rail freight operation, freight cars need to be separated and reformed into new trains at hump yards. The classification procedure is complex and time consuming, and hump yards often constitute bottlenecks in the rail freight network. One of the problems is that planning for the allocation of tracks at hump yards is difficult, given that the planner has limited resources (tracks, shunting engines, etc.) and needs to foresee the future capacity requirements when planning for the current inbound trains. In this paper, we consider the problem of allocating classification tracks in a rail freight hump yard for arriving and departing trains. Arrival and departure times are predetermined and may originate in timetables or estimated arrival and departure times (in case of disturbances in the rail system). The core problem can be formulated as a special list coloring problem. We focus on an extension where individual cars can temporarily be stored on a special subset of the tracks. We model the problem using mixed integer programming, and also propose several heuristics that can quickly give feasible track allocations. As a case study, we consider a real-world problem instance from the Hallsberg Rangerbangård hump yard in Sweden. Planning over horizons over two to four days, we obtain feasible solutions from both the exact and heuristic approaches that allow all outgoing trains to leave on time.

  • 17.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Forsgren, Malin
    Utvärdering av simulerat dynamiskt underhåll för spårbundna fordon2008Rapport (Annet vitenskapelig)
    Abstract [sv]

    Rapporten beskriver ett antal provkörningar av TIMM-demonstratorn utförda för att undersöka hur antalet besök i verkstaden varierar givet en förväntad underhållsvinst från CBM. TIMM-demonstratorn är en programvara framtagen för att under drift planera in underhållsbesök för ett antal simulerade fordon i spårtrafik, där underhållsbehovet styrs av dynamiskt varierande mätvärden på fordonen.

  • 18.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Forsgren, Malin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Levin, Björn
    RISE - Research Institutes of Sweden, ICT, SICS.
    Aronsson, Martin
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Steinert, Rebecca
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Reducing vehicle maintenance using condition monitoring and dynamic planning2008Inngår i: Proceedings of the 4th IET International Conference on Railway Condition Monitoring (RCM'08), 2008, 1Konferansepaper (Fagfellevurdert)
  • 19.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Optimerad rangering: slutsatser och resultat från projektet RANPLAN2013Rapport (Annet vitenskapelig)
    Abstract [sv]

    Sammanfattning Rapporten innehåller kortfattade slutsatser och resultat från en studie genomförd i projektet RANPLAN, som har utförts av SICS Swedish ICT AB på uppdrag av Trafikverket under åren 2010-2013. Fokus är på Hallsbergs rangerbangård, men resultaten är tillämpbara även på andra rangerbangårdar med vall. Datorkörningar visar att blanddragen kan öka kapaciteten på rangerbangårdar väsentligt, mätt i antalet samtidiga tåg som kan hanteras, till en kostnad av en ökad mängd vagnsrörelser. I en jämförande datorstudie av simulering och optimering framgick också att de optimala planerna var betydligt effektivare, mätt i antalet vagnsrörelser, än de simulerade planerna. Resultaten pekar tydligt på att datorstödd optimering av planeringsprocessen för rangerbangårdar både är praktiskt möjligt och kan ge stora effektivitetsvinster.

  • 20.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Dahms, Florian
    RWTH Aachen University, Germany.
    Mihalák, Matúš
    ETH Zurich, Switzerland.
    Flier, Holger
    ETH Zurich, Switzerland.
    Optimization Methods for Multistage Freight Train Formation2015Inngår i: Transportation Science, ISSN 0041-1655, E-ISSN 1526-5447, Vol. 50, nr 3, s. 823-840Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers mathematical optimization for the multistage train formation problem, which at the core is the allocation of classification yard formation tracks to outbound freight trains, subject to realistic constraints on train scheduling, arrival and departure timeliness, and track capacity. The problem formulation allows the temporary storage of freight cars on a dedicated mixed-usage track. This real-world practice increases the capacity of the yard, measured in the number of simultaneous trains that can be successfully handled. Two optimization models are proposed and evaluated for the multistage train formation problem. The first one is a column-based integer programming model, which is solved using branch and price. The second model is a simplified reformulation of the first model as an arc-indexed integer linear program, which has the same linear programming relaxation as the first model. Both models are adapted for rolling horizon planning and evaluated on a five-month historical data set from the largest freight yard in Scandinavia. From this data set, 784 instances of different types and lengths, spanning from two to five days, were created. In contrast to earlier approaches, all instances could be solved to optimality using the two models. In the experiments, the arc-indexed model proved optimality on average twice as fast as the column-based model for the independent instances, and three times faster for the rolling horizon instances. For the arc-indexed model, the average solution time for a reasonably sized planning horizon of three days was 16 seconds. Regardless of size, no instance took longer than eight minutes to be solved. The results indicate that optimization approaches are suitable alternatives for scheduling and track allocation at classification yards.

  • 21.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Dahms, Florian
    Mihalák, Matúš
    Flier, Holger
    Optimized shunting with mixed-usage tracks2013Rapport (Annet vitenskapelig)
    Abstract [en]

    We consider the planning of railway freight classification at hump yards, where the problem involves the formation of departing freight train blocks from arriving trains subject to scheduling and capacity constraints. The hump yard layout considered consists of arrival tracks of sufficient length at an arrival yard, a hump, classification tracks of non-uniform and possibly non-sufficient length at a classification yard, and departure tracks of sufficient length. To increase yard capacity, freight cars arriving early can be stored temporarily on specific mixed-usage tracks. The entire hump yard planning process is covered in this paper, and heuristics for arrival and departure track assignment, as well as hump scheduling, have been included to provide the neccessary input data. However, the central problem considered is the classification track allocation problem. This problem has previously been modeled using direct mixed integer programming models, but this approach did not yield lower bounds of sufficient quality to prove optimality. Later attempts focused on a column generation approach based on branch-and-price that could solve problem instances of industrial size. Building upon the column generation approach we introduce a direct arc-based integer programming model, where the arcs are precedence relations between blocks on the same classification track. Further, the most promising models are adapted for rolling-horizon planning. We evaluate the methods on historical data from the Hallsberg shunting yard in Sweden. The results show that the new arc-based model performs as well as the column generation approach. It returns an optimal schedule within the execution time limit for all instances but from one, and executes as fast as the column generation approach. Further, the short execution times of the column generation approach and the arc-indexed model make them suitable for rolling-horizon planning, while the direct mixed integer program proved to be too slow for this. Extended analysis of the results shows that mixing was only required if the maximum number of concurrent trains on the classification yard exceeds 29 (there are 32 available tracks), and that after this point the number of extra car roll-ins increases heavily.

  • 22.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Khoshniyat, Fahimeh
    Evaluation of planning policies for marshalling track allocation using simulation2012Rapport (Annet vitenskapelig)
    Abstract [en]

    Planning the operational procedures in a railway marshalling yard is a complex problem. When a train arrives at a marshalling yard, it is uncoupled on an arrival yard and then its cars are rolled to a classification yard. All cars should eventually be rolled to the classification track that has been assigned to the train they’re supposed to depart with. However, there is normally not enough capacity to compound all trains at once. In Sweden, cars arriving before a track has been assigned to their train can be stored on separate tracks called mixing tracks. All cars on mixing tracks will be pulled back to the arrival yard, and then rolled to the classification yard again to allow for reclassification. Today all procedures are planned by experienced dispatchers, but there are no documented strategies or guidelines for efficient manual planning. The aim of this paper is to examine operational planning strategies that could help dispatchers find a feasible marshalling schedule that minimizes unnecessary mixing. In order to achieve this goal, two different online planning strategies have been tested using deterministic and stochastic simulation. The Hallsberg marshalling yard was used as a case study, and was simulated for the time period between December 2010 and May 2011. The first tested strategy simply assigns tracks to trains on a first come-first served basis, while the second strategy uses time limits to determine when tracks should be assigned to departing trains. The online planning algorithms have been compared with an offline optimized track allocation. The results from both the deterministic and the stochastic simulation show that the optimized allocation is better than all online strategies and that the second strategy with a time limit of 32 hours is the best online method.

  • 23.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gestrelius, Sara
    RISE., Swedish ICT, SICS.
    Khoshniyat, Fahimeh
    Simulation of planning strategies for track allocation at marshalling yards2013Konferansepaper (Fagfellevurdert)
  • 24.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ekman, Jan
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Sellin, Ola
    Lindström, Björn
    Larsen, Stefan
    Statistical Anomaly Detection for Train Fleets2012Konferansepaper (Fagfellevurdert)
  • 25.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Hänninen, Kaj
    Mäki-Turja, Jukka
    Shared stack analysis in transaction-based systems2007Konferansepaper (Fagfellevurdert)
  • 26.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Hänninen, Kaj
    Mäki-Turja, Jukka
    Nolin, Mikael
    Bounding shared-stack usage in systems with offsets and precedences2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The paper presents two novel methods to bound the stack memory used in preemptive shared stack.

  • 27.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kocjan, Waldemar
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Designing Global Scheduling Constraints for Local Search: A Generic Approach2002Rapport (Annet vitenskapelig)
    Abstract [en]

    In this work we present a novel method to automate the computation of global constraints cost for local search. The method is based on the representation of a global constraints as graph properties on a binary constraint network. This formulation simplifies the implementation of global constraints in local search, and provides a cost that can be readily compared to one obtained for subproblems using binary constraints exclusively. The cost obtained can be efficiently updated during the search using incremental methods. The representation of a global constraint as outlined above can also be used for generation of suitable neighborhoods for the constraint. This is done using simple repair functions applied on the elementary constraints in the global constraint graph. We show the usability of our approach by presenting formulations of global constraints in non-overlapping and cumulative scheduling.

  • 28.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Aronsson, Martin
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Forsgren, Malin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ansatser för flexibel planering och schemaläggning av tågtidtabeller2006Rapport (Annet vitenskapelig)
    Abstract [sv]

    Rapporten beskriver möjliga ansatser för att lösa det abstraherade tidtabellproblemet som bl.a. diskuteras i rapporten "Leveranstågplan: Specifikation och åtagande" (DDTP Arbetsdokument SICS-DDTP-002). Till grund för de olika ansatserna ligger en modell med avgångstider och hålltider (dvs. väntetider och i viss mån traverseringstider) som tillåts variera inom vissa tidsintervall. Huvudidén är att arbeta med förenklade kapacitetsvillkor på bana och bangård, för att på ett effektivt sätt kunna beräkna tidtabeller på en nivå som tillåter anpassning av tidtabellen till det gällande transportbehovet och den rådande trafiksituationen.

  • 29.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Lu, Yue
    Kraft, Johan
    Kreuger, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Nolte, Thomas
    Best-Effort Simulation-Based Timing Analysis using Hill-Climbing with Random Restarts2009Inngår i: Proceedings of the 15th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, IEEE Computer Society , 2009, 6Konferansepaper (Fagfellevurdert)
  • 30.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Pearson, JustinÅgren, Magnus
    Proceedings of LSCS'04, the 1st International Workshop on Local Search Techniques in Constraint Satisfaction2004Konferanseproceedings (Fagfellevurdert)
  • 31.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Wärja, Mathias
    Maintenance Optimization with Duration-Dependent Costs2012Inngår i: Annals of Operations ResearchArtikkel i tidsskrift (Fagfellevurdert)
  • 32.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Wärja, Mathias
    Optimization Maintenance for Multi-unit Industrial Gas Turbine Installations2010Konferansepaper (Fagfellevurdert)
  • 33.
    Bohlin, Markus
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Wärja, Mathias
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Slottner, Pontus
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Optimization of Condition-Based Maintenance for Industrial Gas Turbines: Requirements and Results2009Konferansepaper (Fagfellevurdert)
  • 34.
    Doganay, Kivanc
    et al.
    RISE., Swedish ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Maintenance plan optimization for a train fleet2010Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Maintenance planning is an important problem for railways, as well as other application domains that employ machinery with expensive replacements and high downtime costs. In a previous paper, we have developed methods for efficiently finding optimized maintenance schedules for a single unit, and proposed that the maintenance plan should be continuously re-optimized based on the condition of components. However, fleet-level resources, such as the availability of expensive spare parts, have largely been ignored. In this paper, we extend our previous approach by proposing a solution for the fleet level maintenance scheduling problem with spare parts optimization. The new solution is based on a mixed integer linear programming formulation of the problem. We demonstrate the merits of our approach by optimizing instances of maintenance schedules based on maintenance data from railway companies operating in Sweden.

  • 35.
    Doganay, Kivanc
    et al.
    RISE., Swedish ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Sellin, Ola
    Search Based Testing of Embedded Systems Implemented in IEC 61131-3: An Industrial Case Study2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a case study of search-based test generation for embedded system software units developed using the Function Block Diagrams (FBDs), a graphical language in the IEC 61131-3 standard aimed at programmable logic controllers (PLCs). We consider 279 different components from the train control software developed by Bombardier Transportation, a major rail vehicle manufacturer. The software is compiled into C code with a particular structure. We use a modified hill climbing algorithm for generating test data to maximize MC/DC coverage for assignments with logical expressions in the C code, while retaining the semantics of the original FBD implementation. An experimental evaluation for comparing the effectiveness (coverage rate) and the efficiency (required number of executions) of hill climbing algorithm with random testing is presented. The results show that random testing performs well for most units under test, while around 30% of the artifacts significantly benefit from the hill climbing algorithm. Structural properties of the units that affect the performance of hill climbing and random testing are also discussed.

  • 36.
    Doganay, Kivanc
    et al.
    RISE., Swedish ICT, SICS.
    Eldh, Sigrid
    Mälardalen University, Sweden; Karlstad University, Sweden.
    Afzal, Wasif
    Mälardalen University, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Search-Based Testing for Embedded Telecom Software with Complex Input Structures2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we discuss the application of search-based software testing techniques for unit level testing of a real-world telecommunication middleware at Ericsson. Our current implementation analyzes the existing test cases to handle non-trivial variables such as uninitialized pointers, and to discover any setup code that needs to run before the actual test case, such as setting global system parameters. Hill climbing (HC) and (1+1) evolutionary algorithm (EA) metaheuristic search algorithms are used to generate input data for branch coverage. We compare HC, (1+1)EA, and random search with respect to effectiveness, measured as branch coverage, and efficiency, measured as number of executions needed. Difficulties arising from the specialized execution environment and the adaptations for handling these problems are also discussed.

  • 37.
    Doganay, Kivanc
    et al.
    RISE., Swedish ICT, SICS.
    Eldh, Sigrid
    Afzal, Wasif
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Search-based Testing for Embedded Telecommunication Software with Complex Input Structures: An Industrial Case Study2014Rapport (Annet vitenskapelig)
    Abstract [en]

    In this paper, we discuss the application of search-based software testing techniques for unit level testing of a real-world telecommunication middleware at Ericsson. Input data for the system under test consists of nested data structures, and includes non-trivial variables such as uninitialized pointers. Our current implementation analyzes the existing test cases to discover how to handle pointers, set global system parameters, and any other setup code that needs to run before the actual test case. Hill climbing (HC) and (1+1) evolutionary algorithm (EA) metaheuristic search algorithms are used to generate input data for branch coverage. We compare HC, (1+1)EA, and random search as a baseline of performance with respect to effectiveness, measured as branch coverage, and efficiency, measured as number of executions needed. Difficulties arising from the specialized execution environment and the adaptations for handling these problems are also discussed.

  • 38.
    Ekman, Jan
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Holst, Anders
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Aronsson, Martin
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Forsgren, Malin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Larsen, Stefan
    TIME - en gemensam informationsutbytesplattform för järnvägstransportbranschen2006Rapport (Annet vitenskapelig)
    Abstract [sv]

    TIME står för Train Information Management Environment. TIME är ett tänkt övergripande informationssystem för Järnväg. Viktiga aspekter hos TIME är utformningen av en plattform för kommunikation mellan aktörerna i järnvägstransportbranschen och information mellan fordon och system med en fast plats. TIME gäller alla delar i ett informationssystem, hur data produceras och processas, infrastruktur för information och principer för datalagring och informationsutbyte samt funktioner och tjänster baserade på denna information. TIME avser t.ex. att medverka till att samverkan mellan järnvägstransportbranschens aktörer fungerar bra, dessa aktörers egen verksamhet blir effektiv och att kunder till järnvägen och andra som beror av järnvägen erhåller rätt information.

  • 39. Enoiu, Eduard Paul
    et al.
    Doganay, Kivanc
    RISE., Swedish ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Sundmark, Daniel
    RISE., Swedish ICT, SICS.
    Pettersson, Paul
    MOS: An Integrated Model-based and Search-based Testing Tool for Function Block Diagrams2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a new testing tool for safety critical applications described in Function Block Diagram (FBD) language aimed to support both a model and a search-based approach. Many benefits emerge from this tool, including the ability to automatically generate test suites from an FBD program in order to comply to quality requirements such as component testing and specific coverage measurements. Search-based testing methods are used to generate test data based on executable code rather than the FBD program, alleviating any problems that may arise from the ambiguities that occur while creating FBD programs. Test cases generated by both approaches are executed and used as a way of cross validation. In the current work, we describe the architecture of the tool, its workflow process, and a case study in which the tool has been applied in a real industrial setting to test a train control management system.

  • 40.
    Flemström, Daniel
    et al.
    Mälardalen University, Sweden.
    Potena, Pasqualina
    RISE - Research Institutes of Sweden, ICT, SICS.
    Sundmark, Daniel
    Mälardalen University, Sweden.
    Afzal, Wasif
    Mälardalen University, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Similarity-based prioritization of test case automation2018Inngår i: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 26, nr 4, s. 1421-1449Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The importance of efficient software testing procedures is driven by an ever increasing system complexity as well as global competition. In the particular case of manual test cases at the system integration level, where thousands of test cases may be executed before release, time must be well spent in order to test the system as completely and as efficiently as possible. Automating a subset of the manual test cases, i.e, translating the manual instructions to automatically executable code, is one way of decreasing the test effort. It is further common that test cases exhibit similarities, which can be exploited through reuse when automating a test suite. In this paper, we investigate the potential for reducing test effort by ordering the test cases before such automation, given that we can reuse already automated parts of test cases. In our analysis, we investigate several approaches for prioritization in a case study at a large Swedish vehicular manufacturer. The study analyzes the effects with respect to test effort, on four projects with a total of 3919 integration test cases constituting 35,180 test steps, written in natural language. The results show that for the four projects considered, the difference in expected manual effort between the best and the worst order found is on average 12 percentage points. The results also show that our proposed prioritization method is nearly as good as more resource demanding meta-heuristic approaches at a fraction of the computational time. Based on our results, we conclude that the order of automation is important when the set of test cases contain similar steps (instructions) that cannot be removed, but are possible to reuse. More precisely, the order is important with respect to how quickly the manual test execution effort decreases for a set of test cases that are being automated. 

  • 41.
    Gestrelius, Sara
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Aronsson, Martin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Joborn, Martin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Towards a comprehensive model for track allocation and roll-time scheduling at marshalling yards2017Inngår i: Journal of Rail Transport Planning & Management, ISSN 2210-9706, E-ISSN 2210-9714, Vol. 7, nr 3, s. 157-170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper considers multi-stage train formation with mixed usage tracks at a marshalling yard without departure yard. A novel integer programming model for scheduling shunting tasks as well as allocating arrival yard tracks and classification bowl tracks is presented. By taking a comprehensive view of the marshalling yard operations, more effective schedules can be found, and a variety of characteristics can be optimised, including shunting work effort, number or cost of tracks, and shunting task start times. Two different objective functions are evaluated: minimising work effort in terms of wagon pull-backs and minimising track costs. A procedure for finding a hot-start solution with few wagon pull-backs is also presented. The proposed model is tested on real data from Sävenäs marshalling yard in Sweden. The results show that the method is able to return an optimal schedule for a planning period of 4 days if the hot-start solution is optimal or the remaining problem is tractable for the heuristics in CPLEX.

  • 42.
    Gestrelius, Sara
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Aronsson, Martin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Joborn, Martin
    RISE - Research Institutes of Sweden, ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Towards a comprehensive model for track allocation and roll-time scheduling at marshalling yards2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper considers multi-stage train formation with mixed usage tracks at a marshalling yard without departure yard. A novel integer programming model for scheduling shunting tasks as well as allocating arrival yard tracks and classification bowl tracks is presented. By taking a comprehensive view of the marshalling yard operations, more effective schedules can be found, and a variety of characteristics can be optimised, including shunting work effort, number or cost of tracks, and shunting task start times. Two different objective functions are evaluated: minimising work effort in terms of wagon pull-backs and minimising track costs. A procedure for finding a hot-start solution with few wagon pull-backs is also presented. The proposed model is tested on real data from Sävenäs marshalling yard in Sweden. The results show that the method is able to return an optimal schedule for a planning period of 4 days if the hot-start solution is optimal or the remaining problem is tractable for the heuristics in CPLEX.

  • 43.
    Gestrelius, Sara
    et al.
    RISE., Swedish ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Aronsson, Martin
    RISE - Research Institutes of Sweden, ICT, SICS.
    On the uniqueness of operation days and delivery commitment generation for train timetables2015Inngår i: Proceedings of the 6th International Conference on Railway Operations Modelling and Analysis (RailTokyo2015), 2015, 7Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the 2014 finalised timetable for Sweden 314 operation days had a unique set of trains i.e. a unique traffic pattern. Despite this, the finalised timetable generally provides only one conflict resolved train path for each train, and this train path is to be used for all of the train’s operation days. Further, once the yearly timetable has been finalised train paths may not be changed, causing great inflexibility in later planning stages. Rather than finalizing entire train paths only certain characteristics of a train path, called delivery commitments, could be finalised. This allows for more flexibility in later planning stages. Delivery commitments could e.g. be arrival and departure times at important locations or the total running time, depending on the needs of the operator. In this paper we present a method for generating delivery commitments based on analyzing a yearlong timetable, called the control timetable. The control timetable is constructed using rolling horizon planning and a MIP-model that optimises the train paths for each day individually. Further, different train path characteristics are optimized for different operators. The proposed method was tested in a case study from Sweden. The results show that by constructing one train path for each individual day rather than one for the entire year the resulting delivery commitments allow for a more efficient use of infrastructure. The results also show that the proposed method allows for different train path characteristics to be optimised for different operators.

  • 44.
    Gestrelius, Sara
    et al.
    RISE., Swedish ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Danielsson, Per
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Aronsson, Martin
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Teknisk slutrapport för RANPLAN - Beräkningstöd för planering och resursallokering på rangerbangården2011Rapport (Annet vitenskapelig)
    Abstract [sv]

    I denna rapport presenteras de modeller och resultat som projektet/RANPLAN-beräkningsstöd för planering och resursallokering/ producerat. RANPLAN finansierades av Trafikverkets FUD-program (F 09-11546/AL50) och pågick från januari 2010 till december 2011. Under projektets gång har ett flertal heuristiska algoritmer och optimeringmodeller tagits fram som skulle kunna förbättra och förenkla planeringen vid rangerbangårdar. En demonstrator baserad på historiska data visar att metoderna är så pass skalbara och effektiva att de är attraktiva för kommersiell implementering. Vidare presenteras förslag på lämpliga effektivitets- och kvalitetsmått för rangering.

  • 45.
    Gestrelius, Sara
    et al.
    RISE., Swedish ICT, SICS.
    Dahms, Florian
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Optimisation of simultaneous train formation and car sorting at marshalling yards2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Efficient and correct freight train marshalling is vital for high quality carload freight transportations. During marshalling, it is desirable that cars are sorted according to their individual drop-off locations in the outbound freight trains. Furthermore, practical limitations such as non-uniform and limited track lengths and the arrival and departure times of trains need to be considered. This paper presents a novel optimisation method for freight marshalling scheduling under these circumstances. The method is based on an integer programming formulation that is solved using column generation and branch and price. The approach minimises the number of extra shunting operations that have to be performed, and is evaluated on real-world data from the Hallsberg marshalling yard in Sweden.

  • 46.
    Ghaviha, Nima
    et al.
    Mälardalen University, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Holmberg, Christer
    Bombardier Transportation, Sweden.
    Dahlquist, Erik
    Mälardalen University, Sweden.
    Speed profile optimization of catenary-free electric trains with lithium-ion batteries2019Inngår i: Journal of Modern Transportation, ISSN 2095-087X, E-ISSN 2196-0577, Vol. 27, nr 3, s. 153-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Catenary-free operated electric trains, as one of the recent technologies in railway transportation, has opened a new field of research: speed profile optimization and energy optimal operation of catenary-free operated electric trains. A well-formulated solution for this problem should consider the characteristics of the energy storage device using validated models and methods. This paper discusses the consideration of the lithium-ion battery behavior in the problem of speed profile optimization of catenary-free operated electric trains. We combine the single mass point train model with an electrical battery model and apply a dynamic programming approach to minimize the charge taken from the battery during the catenary-free operation. The models and the method are validated and evaluated against experimental data gathered from the test runs of an actual battery-driven train tested in Essex, UK. The results show a significant potential in energy saving. Moreover, we show that the optimum speed profiles generated using our approach consume less charge from the battery compared to the previous approaches.

  • 47.
    Ghaviha, Nima
    et al.
    Mälardalen University, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Holmberg, Christer
    Bombardier Transportation, Sweden.
    Dahlquist, Erik
    Mälardalen University, Sweden.
    Skoglund, Robert
    Mälardalen University, Sweden.
    Jonasson, Daniel
    Mälardalen University, Sweden.
    A driver advisory system with dynamic losses for passenger electric multiple units2017Inngår i: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 85, s. 111-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Driver advisory systems, instructing the driver how to control the train in an energy efficient manner, is one the main tools for minimizing energy consumption in the railway sector. There are many driver advisory systems already available in the market, together with significant literature on the mathematical formulation of the problem. However, much less is published on the development of such mathematical formulations, their implementation in real systems, and on the empirical data from their deployment. Moreover, nearly all the designed driver advisory systems are designed as an additional hardware to be added in drivers’ cabin. This paper discusses the design of a mathematical formulation and optimization approach for such a system, together with its implementation into an Android-based prototype, the results from on-board practical experiments, and experiences from the implementation. The system is based on a more realistic train model where energy calculations take into account dynamic losses in different components of the propulsion system, contrary to previous approaches. The experimental evaluation shows a significant increase in accuracy, as compared to a previous approach. Tests on a double-track section of the Mälaren line in Sweden demonstrates a significant potential for energy saving.

  • 48.
    Ghaviha, Nima
    et al.
    Mälardalen University, Sweden.
    Campillo, Javier
    Mälardalen University, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Dahlquist, Erik
    Mälardalen University, Sweden.
    Review of Application of Energy Storage Devices in Railway Transportation2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Regenerative braking is one of the main reasons behind the high levels of energy efficiency achieved in railway electric traction systems. During regenerative braking, the traction motor acts as a generator and restores part of the kinetic energy into electrical energy. To use this energy, it should be either fed back to the power grid or stored on an energy storage system for later use. This paper reviews the application of energy storage devices used in railway systems for increasing the effectiveness of regenerative brakes. Three main storage devices are reviewed in this paper: batteries, supercapacitors and flywheels. Furthermore, two main challenges in application of energy storage systems are briefly discussed. © 2017 The Authors.

  • 49.
    Ghaviha, Nima
    et al.
    Mälardalen University, Sweden.
    Holmberg, Christer
    Bombardier Transportation, Sweden.
    Bohlin, Markus
    RISE - Research Institutes of Sweden, ICT, SICS.
    Dahlquist, Erik
    Mälardalen University, Sweden.
    Modeling of Losses in the Motor Converter Module of Electric Multiple Units for Dynamic Simulation Purposes2017Inngår i: Energy Procedia, Elsevier Ltd , 2017, Vol. 142, s. 2303-2309Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Simulation of power consumption in electric trains is categorized in two categories: electrical power simulation and mechanical power simulation. The mechanical power is calculated as speed times tractive effort and it gives an overall view on the total energy consumption of the train during different driving cycles. Detailed calculation of losses in different components in the propulsion system is however done using complex electrical models. In this paper, we introduce a nonlinear regression model generated from validated electrical equations for the calculation of the power loss in the motor converter module of electric trains. The function can be used instead of efficiency maps to evaluate the trains' performance during the operation or dynamic simulations.

  • 50.
    Gonzalez-Hernandez, Loreto
    et al.
    University of Skövde, Sweden.
    Lindström, Birgitta
    University of Skövde, Sweden.
    Offutt, Jeff
    George Mason University, USA.
    Andler, Sten F.
    University of Skövde, Sweden.
    Potena, Pasqualina
    RISE - Research Institutes of Sweden, ICT, SICS.
    Bohlin, Markus
    RISE - Research Institutes of Sweden.
    Using Mutant Stubbornness to Create Minimal and Prioritized Test Sets2018Inngår i: 2018 IEEE International Conference on Software Quality, Reliability and Security,  QRS 2018, 2018, s. 446-457Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In testing, engineers want to run the most useful tests early (prioritization). When tests are run hundreds or thousands of times, minimizing a test set can result in significant savings (minimization). This paper proposes a new analysis technique to address both the minimal test set and the test case prioritization problems. This paper precisely defines the concept of mutant stubbornness, which is the basis for our analysis technique. We empirically compare our technique with other test case minimization and prioritization techniques in terms of the size of the minimized test sets and how quickly mutants are killed. We used seven C language subjects from the Siemens Repository, specifically the test sets and the killing matrices from a previous study. We used 30 different orders for each set and ran every technique 100 times over each set. Results show that our analysis technique performed significantly better than prior techniques for creating minimal test sets and was able to establish new bounds for all cases. Also, our analysis technique killed mutants as fast or faster than prior techniques. These results indicate that our mutant stubbornness technique constructs test sets that are both minimal in size, and prioritized effectively, as well or better than other techniques.

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