Reliability, Availability, Maintainability, Safety Research Articles

The path towards increasing RAMS for novel complex missions based on CubeSat technology

The paper presents the initial outcomes of a project, currently ongoing under the supervision of the European Space Agency, having the main objective to specify and design a Fault Detection Isolation and Recovery (FDIR) system by making use of relevant RAMS (Reliability, Availability, Maintainability, Safety) analyses for missions in non-deterministic environment with limited resources. The initial project tasks have been to select a study case represented by a CubeSat complex mission, analyse in detail both its mission and system requirements and, based on them, define a set of relevant RAMS analyses to be carried out in the second phase of the project, as inputs for the development of a FDIR concept aimed at a careful balance of the limited spacecraft resources in case of critical failures. Two possible study cases have been identified: LUMIO, a 12U CubeSat mission for the observation of micro-meteoroid impacts on the Lunar farside, and M-ARGO, a 12U deep-space CubeSat which will rendezvous with a near-Earth asteroid and characterize its physical properties for the presence of in-situ resources. Although both missions are characterized by a high level of autonomy and complexity in a harsh environment, LUMIO has been eventually selected as study case for the project. In the paper, the challenges and features of this mission are shortly presented. The specificities of the RAMS analysis and FDIR concept for this specific class of small satellite missions (including the selected study case) are highlighted in the paper, looking in particular at aspects such as the improvement of reliability while maintaining the CubeSat philosophy, the tuning of mission and system requirements in view of facilitating the design and implementation of the FDIR concept, and the current gaps within the RAMS/FDIR body of knowledge. The conclusions drawn during this first project phase provide a real view of how systems engineering must work in tandem with RAMS analyses and FDIR to achieve a more robust and functional mission architecture, thus improving the mission reliability.

실시간 수요대응 자율주행 모빌리티 평가 항목 정의

정해진 경로를 규칙적으로 운행하는 대중교통수단은 이용자 감소의 영향으로 효율성이 떨어져 정부의 지속적인 보조금 투입이 필요하거나 노선 감축으로 인해 이용자 불편이 예상된다. 최근 자율주행기술의 발전으로 대중교통수단에 자율주행기술을 접목하고, 이를 활용하여 이용자의 요청에 따라 운행하는 수요대응형 교통수단으로 발전 시키고자 노력하고 있다. 이러한 새로운 시스템이 제공하는 대중교통 서비스는 시스템 측면에서 충분한 기계적 신뢰성이 확보되고, 운영 알고리즘과 서비스 측면에서 대중교통 이용자의 요구사항이 만족되어야 한다. 본 연구는 수요대응 자율주행 대중교통 서비스의 공공성 확보를 위해 고려해야 할 요인들을 검토하고 평가 항목 구성 방안을 제시하고자 하였다. 이에 수요대응 자율주행 대중교통 서비스의 공공성을 정의하고, 기존의 국내외 대중교통 평가체계 검토 결과와 철도시스템의 RAMS(Reliability, Availability, Maintainability, Safety) 개념을 바탕으로 시스템 관점과 이용자 관점에서 평가항목을 새로이 정의하였다. 본 연구에서 정의한 항목들은 수요대응 자율주행 대중교통이 갖추어야 할 최소한의 요구사항으로, 수요대응 자율주행 대중교통이 공공성이 확보된 수단으로 자리매김하는데 기여할 수 있을 것으로 기대한다.

Comparison of Battery Architecture Dependability

This paper presents various solutions for organizing an accumulator battery. It examines three different architectures: series-parallel, parallel-series and C3C architecture, which spread the cell output current flux to three other cells. Alternatively, to improve a several cell system reliability, it is possible to insert more cells than necessary and soliciting them less. Classical RAMS (Reliability, Availability, Maintainability, Safety) solutions can be deployed by adding redundant cells or by tolerating some cell failures. With more cells than necessary, it is also possible to choose active cells by a selection algorithm and place the others at rest. Each variant is simulated for the three architectures in order to determine the impact on battery-operative dependability, that is to say the duration of how long the battery complies specifications. To justify that the conventional RAMS solutions are not deployed to date, this article examines the influence on operative dependability. If the conventional variants allow to extend the moment before the battery stops to be operational, using an algorithm with a suitable optimization criterion further extend the battery mission time.

Application of IoT for the Maintaining Rolling Stocks

<p><strong>Purpose:</strong> This paper presents a framework for simulation on IoT based CBM (condition based monitoring) for rolling stocks. This enables to allocate maintenance resources effectively while satisfying preventive maintenance requirements.</p><p><strong>Methodology/Approach:</strong> We exploits Reliability centered maintenance (RCM) based on KTX (Korea Tran eXpress, Korea’s high-speed rail system) motor reduction unit failure data for three years by utilising the internet of things (IoT) and RAMS (Reliability, Availability, Maintainability, Safety) methods.</p><p><strong>Findings:</strong> We come up with the predictive maintenance indicator; reliability functions as to the desired service level; and the failure and defect prediction indicator takes the form of cumulative failure function in the form of probability distribution function, which aim to realise the real-time condition monitoring and maintaining technical support services. Internet of Things (IoT) has been an important apparatus to improve the maintenance efficiency.</p><p><strong>Research Limitation/implication:</strong> This paper has limitations that the data are collected from references, not actual data; the detailed descriptions of IoT application to the railway rolling stocks are omitted, and it is not dealt in depth how maintenance efforts and performance are improved through the suggested reliability centered maintenance.</p><strong>Originality/Value of paper:</strong> This study has the academic importance in a sense that it integrates RAMS based maintenance methods and IoT. RAMS centered maintenance provides powerful rules for deciding a failure management policy; when it is technically appropriate; and for providing precise criteria for deciding how often routine tasks should be carried out. It will lead to the improved cost efficiency, sustainability and maintainability of railway maintenance system since the staff do not have to visit installation sites frequently. Lately, there is general agreement that prevention was better than inspection and that an increase in preventive cost was the means of reducing total quality costs. In connection with this issue, we will address the way of reducing failure costs and prevention costs with IoT: new appraisal method.

Features measurement and reliability considerations on a proposed main converter for LHC experiments

Equipment working in hostile environment are the aim of this paper. Devices operating in the hostile environment such as found in future experiments at LHC will be called to work with a level of background radiation able to cause accumulation of a Total Ionizing Dose (TID) up to 10kGy in Silicon, and fluences up to 2×1013protons/cm2 and 8×1013neutrons/cm2 but also a high level of magnetic field. This new scenario will be taken into account and it will be very important in future when the High Luminosity (HL) LHC will be operative. It is so important, at this aim, to consider the fact that also the electronic converters devoted to generate the supply for the electronic circuits can be often called to operate in hostile environment. Thus, the power supply is a key aspects in this scenario and new converters need to be ad-hoc re-designed in order to meet the future requirements that will be very stringent. In this paper a main DC–DC power converter, developed by authors in the framework of the APOLLO R&D project, has been proposed. The experimental activity devoted to its electrical and thermal characterization, which can be defined as mandatory in order to obtain an evaluation of the features, is presented and deeply discussed. It is also important to characterize the system in order to evaluate the dependability features such as the RAMS (Reliability, Availability, Maintainability Safety) requirements. In particular, reliability is a very important aspect in experiments as ATLAS at CERN where maintenance should be scheduled only during the shutdown time. Also these aspects have been considered and discussed in the paper.

경량전철사업의 RAMS 활동을 지원하기 위한 SE전산도구 적용에 관한 연구

There have been growing demand of Light Rail Transit(LRT) which have a lot of advantages such as construction costs lower than the recent subway, reduction of operational costs, availability of line planning, operation of railway non-beneficiary region, flexible operations of trains, unmanned operation and also have eco-friendly advantages, it is now becoming urban railway systems when environmental issues have been highlighted all over the world. Therefore, RAMS(Reliability, Availability, Maintainability, Safety) Process and activities for effective implementation of light rail transit projects have become a very important element, and also the utilization of computerized tools to perform these more systematically and productively is sought after these days. In this paper, we have presented a plan that can support the RAMS activities by utilizing the function of the computerized SE(Systems Engineering) tool(CORE). Through support of the computerized SE tool, it would be possible more clear and efficient railway project execution.

철도차량 신뢰성기반유지보수 방안 연구

철도차량을 유지보수 하는 목적은 열차가 운행하는 동안 고장이 발생하지 않도록 하는 것이다. 최근의 철도차량은 전기전자 부품은 물론 IT기술이 접목되어 주기적인 예방정비 방식으로는 차량고장을 근본적으로 예방할 수 없게 되었다. 따라서 KTX에 RAMS가 적용되어 도입된 이후 코레일에서 도입하는 철도차량은 RAMS를 적용하고 있다. 새로 제작되는 차량은 운행초기 하자보증기간 동안 신뢰성 검증을 하게 되며, 유지보수 과정에서는 RCM 기법을 적용한다. 본 논문에서는 철도차량의 특성 및 운영 환경에 적합한 철도차량 신뢰성유지보수체계인 RCRM(Reliability Centered Rolling stocks Maintenance) 방안을 제시하고자 한다. The purpose of maintaining rolling stock is to perform train service without failure during operation. It is not possible to prevent failure, however, by using periodic preventive maintenance methods, because new rolling stock is made from many electric components and requires the application of IT skills. RAMS (Reliability, Availability, Maintainability, Safety) methods have consequently been applied to new manufactured rolling stock in KORAIL since implementation of the KTX. With this approach it is possible to verify the reliability at the operating stage, and RCM (Reliability Centered Maintenance) methods for maintenance have been applied to manufactured rolling stock since the beginning of KTX service. A RCRM (Reliability Centered Rolling-stocks Maintenance) system suitable for the characteristics of rolling stock and operational factors is introduced in this paper.

Investigation of the structure of a networked system

The information coming from the network topology, which does not depend on the failure and repair probabilities of its elements, is useful in the preliminary RAMS (Reliability, Availability, Maintainability, Safety) analysis and in the Security assessment of critical infrastructures. We propose an approach to investigate the network structure by ranking its elements through Importance and Sensitivity measures.The System performances are referred to User nodes (Partial risks) and to the whole network (Global risk). The First order Differential Importance Measure and a so-called Hybrid measure allow the ranking of elements according to their Importance and to the Sensitivity of the model outputs. The ranking of Edges through the above measures super-imposes the ranking of the (unfaultable) User nodes.The original proposals of the paper concern the use of the Total order Differential Importance Measures in order to consider the “interactions” among the independent input variables of the model (Edges unavailability) and the investigation of the system structure through the estimation of measures in the whole range of values [0;1]. The proposed approach is applied to a simple case study; the simplicity emphasizes the obtained results, allows judging them quantitatively and qualitatively and is not a limitation for real case applications.

Training in RAMS in Collaboration with Industrial Companies and Institutions

This paper presents two activities carried out by Engineering students from the Telecommunication Engineering School of the University of Vigo. The activities described have been organized within the subject "Reliability of Electronic Systems", which covers the four aspects of RAMS (Reliability, Availability, Maintainability, Safety).The activities focus on collaboration with local companies and institutions, so that the students can undertake real tasks related to the content of the subject as part of the subject assessment system. The first activity gets the students to work with real problems inside a local company. The second one is carried out by Engineering students in collaboration with Translation students from the Faculty of Philology and Translation of the University of Vigo and the Spanish Association for Standardization and Certification. This collaboration implies joint efforts of students from different degrees and active involvement in their own training.The methodology of both activities stimulates active and collaborative learning and introduces the students to professional activity and interdisciplinary group work. The results achieved clearly demonstrate the interest of encouraging interdisciplinary teamwork competences and involving local companies and institutions in the training of university students.

Evaluation of reliability, availability, maintainability and safety requirements for manned space vehicles with extended on-orbit stay time

The recent manned space transportation vehicles studies performed by ESA and European Industry, investigate the possibility of extended on-orbit stay time. From the RAMS (Reliability, Availability, Maintainability, Safety) point of view, these vehicles will have to meet, in addition to the multi-phase mission safety and reliability constraints, stringent on-orbit availability levels which will be among the most important design and operations drivers. The objective of the paper is to derive the lessons learnt from the Assured Crew Return Vehicle (ACRV) feasibility phase study, in terms of RAMS requirements specification. The paper briefly assesses the deterministic RAMS requirements derived from ESA and NASA applicable standards and focuses on the probabilistic requirements which were the subject of numerous interpretations. Different approaches are presented together with their impacts on the design (maintainability, testability, on-orbit replaceable units concept,…) and on the operations (check-out frequency, logistics,…). The main uncertainties are also assessed. In conclusion, recommendations are made for the specification of RAMS requirements for manned space vehicles with extended on-orbit stay time.