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- Ahmadi, Alireza
(författare)
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Aircraft scheduled maintenance programme development : decision support methodologies and tools
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The air transport business is large in its operations, integrated, automated and complex. Air carriers are constantly striving to achieve high standards of safety and simultaneously to attain an increased level of availability performance at minimal cost. This needs to be supported through an effective maintenance programme which has a major impact on the availability performance and which ultimately can enhance the aircraft’s capability to meet market demands at the lowest possible cost. The development of a maintenance programme is challenging, but can be enhanced by supporting methodologies and tools. The purpose of this study is to develop decision support methodologies and tools for aircraft scheduled maintenance programme development within the framework of Maintenance Review Board (MRB) process. To achieve the purpose of the research, literature studies, case studies, and simulations have been conducted. Empirical data have been collected through document studies, interviews, questionnaires, and observations from the aviation industry. For data analysis, theories and methodologies within risk, dependability and decision making have been combined with the best practices from the aviation industry. One result of the research is the identification of potential areas for improving the use of MSG-3 methodology in aircraft scheduled maintenance development. Another result is the development of a systematic methodology guided by the application of an Event Tree Analysis (ETA) for the identification and quantification of different operational risks caused by aircraft system failures, to support decision making for maintenance task development. A third result is a proposed methodology, based on a combination of different Multi-Criteria Decision Making (MCDM) methodologies, for selecting the most effective maintenance strategy for aircraft scheduled maintenance development. Finally, the fourth result is a proposed Cost Rate Function (CRF) model supported by a graphical approach. The approach can be used to identify the optimum maintenance interval and frequencies of Failure Finding Inspection (FFI) and to develop a combination of FFI and restoration tasks for the aircraft’s repairable items which are experiencing aging. These results are related to some of the specific industrial challenges, and are expected to enhance the capability of making effective and efficient decisions during the development of maintenance tasks. The results have been verified through interaction with experienced practitioners within major aviation manufacturers and air operators.
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| 2. |
- Candell, Olov
(författare)
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Development of information support solutions for complex technical systems using eMaintenance
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Deployment and use of complex technical systems are common in society and in industry. Many of the complex technical systems have stringent requirements on safety, dependability and cost, which necessitate frequent updates and modification in response to new developments in technology and changing functional requirements. Hence, correct, role-adapted, situation-adapted, context-adapted and timely information and information support, is crucial to access, manage, maintain and improve the required services to be provided by these systems. Given the technological development and the changing business environment, system and support providers need to improve the design and provision of information support solutions. This can be facilitated by the utilisation of new and innovative Information & Communication Technology (ICT), manifested in emerging approaches such as eMaintenance. However, there is still a need of methodologies and tools that enable the development and provision of support information services by an integration of business and maintenance processes at both customers and providers to achieve novel business solutions such as Performance-Based Logistics (PBL) in the context described above.Hence, the purpose of this research is to describe how providers of support solutions can develop and provide effective information support solutions related to complex technical systems by enhanced utilisation of ICT. To fulfil this purpose, a single case study within military aviation was performed. Empirical data was collected through interviews, observations, archival records, workshops and action research. The analysis was based on existing, adapted and developed theories, model-based simulations and available international standards, considering an eMaintenance framework.The results of the research are: I) a definition of system-oriented, service-oriented, process-oriented and lifecycle oriented eMaintenance solutions; II) an identification of critical information and information support requirements of customers and providers while implementing e-maintenance; III) an identification of ICT-related methodologies and technologies suitable to fulfil the information support requirements of customers and providers; and IV) an approach for development and provision of ICT-based information support solutions that satisfy the requirements of customers and providers. Even though these results are achieved within the context of a modern military aircraft, the results throughout the research process indicate that they to a large extent are generic in nature and can be applicable to other complex technical systems within the process, power generation and transportation industries as well.
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| 3. |
- Nissen, Arne
(författare)
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Development of life cycle cost model and analyses for railway switches and crossings
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infrastructure managers need to have a safe and available infrastructure, so that train operators can deliver a transport product at an affordable price. In the future, as traffic volume increases, higher utilisation of the existing capacity, less time for maintenance and fewer unplanned interruptions will be critical for meeting the ever increasing need of transport capacity. Improved performance and added capacity on the existing track can be achieved by optimising the operation and maintenance of infrastructure systems. In general, RAMS (Reliability, Availability and Maintainability and Safety) and LCC (Life cycle cost)-analyses are used as tools to optimize the performance of infrastructure and make it economically viable. RAMS analysis is used to establish the need of maintenance by analysing corrective and preventive maintenance data. LCC is a method of highlighting the cost for investment, operation, maintenance and unplanned interruptions throughout an asset's life cycle. Switches and crossings (S&Cs) are one of the major subsystems in the superstructure of the railway. The major function of an S&C is to allow trains to shift from one track to another track in a safe way. To enable this, an S&C consists of movable and fixed mechanical parts, as well as signalling and electrical systems. Each of these systems has a need for maintenance and is susceptible to failures which ultimately lead to train disturbances. The investment costs for new S&Cs are high and the technical lifespan is often very long (over 40 years). Therefore, the maintenance cost is considerable. If the S&C is causing many train interruptions, the cost for train delays is also an important factor for consideration. During the course of this research study, reliability and maintainability characteristics of switches and crossings are analysed using real data from Banverket. In addition, an LCC model is developed using information from Banverket. By applying this model, correct maintenance and investment decisions can be made. Some parts of the Research work have been performed within the European Framework of FP 6 IP Project INNOTRACK with a goal of reducing the LCC of infrastructure by 30 %.This research study confirms that the infrastructure managers have enough data to apply the LCC models for the S&Cs. The model developed can be used to evaluate new S&C designs and to take decisions regarding alternatives for S&C specification to be used under different traffic situations. Also the issue of decisions regarding renewal versus extended life through maintenance is highlighted by use of the LCC model.
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| 4. |
- Patra, Ambika Prasad
(författare)
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Maintenance decision support models for railway infrastructure using RAMS & LCC analyses
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today's railway sector is imposing high demands for service quality on railway infrastructure managers. Since railway infrastructure has a long asset life, it requires efficient maintenance planning to perform effectively throughout its life cycle to meet these high demands. Traditionally maintenance decisions for the railway infrastructure have been based on past experience and expert estimations. The application of RAMS (Reliability, Availability, Maintainability and Safety) analysis for railway infrastructure is limited. The focus of this thesis is to demonstrate the applicability of RAMS analysis in effective maintenance planning. Within the scope of this research, various case studies associated with Banverket (the Swedish National Rail Administration and ALSTOM Transport have been carried out. The research presents approaches and models for estimating RAMS targets based on the service quality requirements of the railway infrastructure. The availability target of the infrastructure has been estimated by considering the capacity and punctuality requirements of the infrastructure, whereas the safety goal of the track has been estimated by calculating the probability of derailment by means of undetected rail breaks and poor track quality. Effective estimation of the RAMS targets will help infrastructure managers to predict the maintenance investment in the railway infrastructure needed over a period of time in order to achieve the targets. Nevertheless, the availability target of the infrastructure can lead to train delay. A model has been developed to achieve the availability target in both the scheduled and the condition based maintenance regimes by choosing an effective maintenance interval and detection probability respectively. This has been illustrated by a case study on track circuits. Different maintenance strategies can help in achieving the RAMS targets. In order to determine the cost-effective solution, LCC (life cycle cost) should be used. The maintenance strategy with lowest LCC will be the cost effective maintenance strategy. This has been demonstrated by a case study on a signalling system. Sensitivity analyses have been performed to calculate the maximum cost effectiveness of the system for different maintenance parameters. LCC estimation for a maintenance strategy should always consider the risks associated with the strategy. A fair degree of uncertainty is also associated with LCC estimation due to the statistical characteristics of RAMS parameters. An approach has been developed in this thesis to calculate the uncertainties associated with LCC estimation. Petri-Net analyses, Monte Carlo simulations, Design of Experiment have been used to develop models to achieve the objectives of this thesis. This thesis discusses the applicability of RAMS and LCC analyses for railway infrastructure and demonstrates models for effective infrastructure maintenance planning.
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| 5. |
- Rodriguez, Emilio
(författare)
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Track circuits’ robustness : Modeling, measurement and simulation
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In countries with rough weather conditions, frequent delays cause railway companies to waste time and money. Many of these delays are related to the train detection systems, as the old DC track circuits are still used in some countries, including Sweden, our case study. Since the most important factor in the railway system is safety, in some cases, the train detection system gets incorrect information and detects a non-existent train. The train slows down to avoid a problem in the track (with other trains or other faults), causing prolonged delays with cascading effects. The analysis in this licentiate contributes to the detection and reduction of TC failures; this, in turn, will save money for the railway community.A classification of the most probable causes of failures related to the train detection system was derived from the Swedish failures report database 0FELIA. After classifying failures, we focussed on the three most common worst case scenarios: low resistance between the rails, external interference such as a lightning strike, and iron-powder-bridges in the insulated joint.Electromagnetic interferences (EMI) are a problem for the railway system in general. One source of electromagnetic (EM) transients is the return current harmonic produced by the engine of the rolling stock itself. In the first stage of this licentiate, we implemented a Matlab model of the power supply system of the Swedish railway infrastructure, using the characteristics and previous measures of a real source. A model of a train as an active load validated by the manufacturer was integrated as a subsystem in different positions of the infrastructure. This method was used to study the behaviour of the low frequency system from an electrical point of view but it could also be used as input for an electromagnetic model using high frequencies. The model was validated through measurements taken in northern Sweden.In addition, a 3D model of the whole railway system was proposed. The simulation software was CST STUDIO SUITE® (Computer Simulation Technology Studio Suite), supported by real measurements on site and the lab to tune and validate the model. The results of the simulation show that the model fits with reality and is reliable for the study of track circuit sections.Some measurements followed the current standards, but we also analysed points not covered by them, allowing us to update the current standards
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