System Operational Availability Research Articles

Multi-component system maintenance optimization of a rail transit train based on opportunistic correlations

Abstract In order to deal with the problems of insufficient or excessive maintenance in the current maintenance activities of China transit trains, this paper develops a novel multi-component system maintenance optimization approach based on an opportunistic correlation model. Based on the minimal reliability and failure rate change rule of each train component, the novel proposed maintenance optimization benefits from an improved opportunistic maintenance model with system structure correlation, fault correlation and reliability correlation under imperfect maintenance. Then, different maintenance modes can be determined by a proposed maintenance factor under the different conditions of components. Specifically, the reliability threshold of each component is also considered to optimize the maintenance cost by the system reliability and operational availability of the train. Furthermore, as the mentioned problem belongs to the NP-Hard optimization problems, a modified particle swarm optimization (PSO) with the improvement of inertia weight is proposed to cope with the optimization problem. Based on a specific case under the practical recorded failure data, the analysis shows that the proposed model and approach can effectively cut the maintenance cost.

A Method to Account for Personnel Risk Attitudes in System Design and Maintenance Activity Development

Systems engineering practices in the maritime industry and the Navy consider operational availability as a system attribute determined by system components and a maintenance concept. A better understanding of the risk attitudes of system operators and maintainers may be useful in understanding potential impacts the system operators and maintainers have on operational availability. This article contributes to the literature a method that synthesizes the concepts of system reliability, and operator and maintainer risk attitudes to provide insight into the effect that risk attitudes of systems operators and maintainers have on system operational availability. The method consists of four steps providing the engineer with a risk-attitude-adjusted insight into the system’s potential operational availability. Systems engineers may use the method to iterate a system’s design or maintenance concept to improve expected operational availability. If it is deemed necessary to redesign a system, systems engineers will likely choose new system components and/or alter their configuration; however, redesign is not limited to physical alteration of the system. Several other options may be more practical depending the system’s stage in the life cycle to address low risk-adjusted operational availability such as changes to maintenance programs and system supportability rather than on component and system reliability. A simple representative example implementation is provided to demonstrate the method and discussion of the potential implications for Navy ship availability are discussed. Potential future work is also discussed.

A Theoretical Framework on Reliability Optimization for Improving System Operational Availability

Purpose: We seek to identify an optimization model from among reliability optimization models to overcome the trade-off between a high level of availability and high cost.BRMethods: Using sensitivity analysis, we identify the main factors affecting operational availability and investigated the cost of each factor for achieving the target operational availability. We then minimized the total cost incurred for achieving the target operational availability by using an optimization model. Here, we also present an alternative optimization model in which the operational availability is maximized subject to a budget limitation.BRResults: We show that an optimal investment can be achieved by using special cost functions such as linear and convex functions. It is challenging to attain optimality with more general nonlinear cost functions.BRConclusion: We not only present an efficient approach to assessing the cost-efficiency for a high level of readiness of a system, but also provide insights into the manner of setting an appropriate target availability and identifying the factors to invest in for achieving the target availability.

Identification of Critical Factors to System Performance Using Availability Modeling and Simulation Analysis

Availability analysis presents a means to understand the impact of existing maintenance system and maintenance resources to the overall system operational availability. The practical method for conducting availability analysis of a plant system at operation phase is illustrated and discussed via a case study of an acid gas removal system of gas processing plant. This study demonstrates that the availability modeling and simulation is effective in assessing the existing and future system configurations and determining possible impacts and critical factors to systems availability. These findings can significantly assist management to make right actions in improving plant system performances.

Planning performance based contracts considering reliability and uncertain system usage

This paper investigates a novel quantitative approach for planning and contracting performance-based logistics in the presence of uncertain system usage. Our efforts focus on an integrated service delivery environment where the manufacturer develops capital-intensive systems and also provides after-sales support. We propose an analytical model to characterize system operational availability by comprehending five performance drivers: inherent failure rate, usage rate, spare parts inventory, repair time, and the fleet size. This analytical insight into the system performance allows the service supplier to minimize the total cost across system design, production, maintenance, and repair. Two contracting schemes are investigated under cost minimization and profit maximization schemes. For the first time in literature, reliability design and service parts logistics are seamlessly integrated into one decision support model for improving operational availability while lowering the lifecycle cost. Numerical examples are provided to demonstrate the applicability and the effectiveness of the proposed decision support tool.

Optimizing reliability and service parts logistics for a time-varying installed base

Performance based contracting (PBC) emerges as a new after-sales service practice to support the operation and maintenance of capital equipment or systems. Under the PBC framework, the goal of the study is to increase the system operational availability while minimizing the logistics footprint through the design for reliability. We consider the situation where the number of installed systems randomly increases over the planning horizon, resulting in a non-stationary maintenance and repair demand. Renewal equation and Poisson process are used to estimate the aggregate fleet failures. We propose a dynamic stocking policy that adaptively replenishes the inventory to meet the time-varying parts demand. An optimization model is formulated and solved under a multi-phase adaptive inventory control policy. The study provides theoretical insights into the performance-driven service operation in the context of changing system fleet size due to new installations. Trade-offs between reliability design and inventory level are examined and compared in various shipment scenarios. Numerical examples drawn from semiconductor equipment industry are used to demonstrate the applicability and the performance of the proposed method.

Application of Extended Coloured Stochastic Petri Nets for Modelling and Analysis of RAMS+C of Production Systems

Modern production systems are characterized by numerous conjoint and interacting production machines each with sophisticated maintenance and logistic processes. To remain competitive, it is necessary to reduce the system downtimes by applying the optimal maintenance strategy and therefore reducing life cycle costs. Condition monitoring often is a very effective way to minimize downtimes of crucial system components such as ball screws, ball bearings and drives. But sometimes condition monitoring is not cost-effective or even reduces the system's operational availability. The decision whether it's reasonable to implement condition based maintenance or not requires a detailed analysis of the system's behavior. Since many analytical models of technical systems have significant limitations and simplifications, simulation techniques are applied very often In our paper we will present an improved comprehensive methodology for the modeling and analysis of production systems which has been basically introduced at the RAMS-Symposium in 2008. The model incorporates an extended colored stochastic Petri net (ECSPN) and a reliability block diagram (RBD) in a conjoint modeling procedure which allows a close-to-reality representation of a complex production system's behavior.

A GOAL PROGRAMMING MODEL FOR OPTIMIZING RELIABILITY, MAINTAINABILITY AND SUPPORTABILITY UNDER PERFORMANCE BASED LOGISTICS

Reliability, Maintainability and Supportability (R, M and S) are the main drivers of the system operational effectiveness (SOE). New procurement strategies have been developed by both public and private sectors to focus on the R, M and S characteristics inherent to the design of a system. One such strategy known as Performance Based Logistics (PBL) has gained popularity due to its success in improving the operational effectiveness of the system. In a PBL contract the customer buys performance, typically measured using R, M and S metrics, instead of contracting for a specified collection of resources defining the underlying support infrastructure. In this paper we have developed a mathematical model, using Goal Programming to optimize multiple performance measures of a design. We show how the best design is chosen from competing design alternatives when systems engineering principles are considered in defining the evaluation measures. The proposed mathematical model simultaneously considers multiple system engineering metrics during the design stage of the product development. The engineering metrics considered are a representation of the system's operational availability, reliability, maintainability, supportability and total cost of ownership. The Goal Programming model developed in the paper can be easily solved using software such as LINDO, LINGO and Excel Solver.

Hierarchical control of multiple resources in distributed real-time and embedded systems

Real-time and embedded systems have traditionally been designed for closed environments where operating conditions, input workloads, and resource availability are known a priori, and are subject to little or no change at runtime. There is increasing demand, however, for adaptive capabilities in distributed real-time and embedded (DRE) systems that execute in open environments where system operational conditions, input workload, and resource availability cannot be characterized accurately a priori. A challenging problem faced by researchers and developers of such systems is devising effective adaptive resource management strategies that can meet end-to-end quality of service (QoS) requirements of applications. To address key resource management challenges of open DRE systems, this paper presents the Hierarchical Distributed Resource-management Architecture (HiDRA), which provides adaptive resource management using control techniques that adapt to workload fluctuations and resource availability for both bandwidth and processor utilization simultaneously. This paper presents three contributions to research in adaptive resource management for DRE systems. First, we describe the structure and functionality of HiDRA. Second, we present an analytical model of HiDRA that formalizes its control-theoretic behavior and presents analytical assurance of system performance. Third, we evaluate the performance of HiDRA via experiments on a representative DRE system that performs real-time distributed target tracking. Our analytical and empirical results indicate that HiDRA yields predictable, stable, and efficient system performance, even in the face of changing workload and resource availability.

Military digital avionics fiber-optic network design for maintainability and supportability

The use of avionics fiber optics technology is becoming more prevalent. Optical fiber is immune electromagnetic interference, gives increased bandwidth, saves space, and reduces weight. If used smartly, fiber optics technology can effectively future-proof avionics networks. The Boeing 777 PlaneNet program provided a textbook example of to build and deploy fiber optic networks on commercial aircraft (Anderson and Beranek, 1998). Tactical aircraft, however, do not yet have history draw upon for operational readiness, particularly in the area of aircraft squadron fiber optic network maintainability and supportability. Military aircraft fiber optic network designs must not only consider the harsh operational and maintenance environment, but also need be deployed in a maintainable and supportable manner. The term maintainability defines how quickly, easily, and cost effectively an avionics fiber optic network design can return operational status (whether by preventive or corrective maintenance). Mean time repair (MTTR) is used quantify and measure maintainability. Supportability, on the other hand, is the degree which the avionics fiber optic network design characteristics minimize the logistics resources (people, skill levels, parts, publications, tools, test equipment, space) required sustain the system's operational availability (AO) at an affordable cost throughout the life of the system

A simulation model for evaluating aircraft system operational availability

The cost effective utilisation and acquisition of equipment is vitally important to the air force of any national defence force. This paper describes a simulation model which was developed to aid the decision makers of such an air force in determining aircraft system requirements for carrying out specific missions within different conflict scenarios. Comprehensive validation of the model has not been completed.

Personal Rapid Transit Déjà Vu

Although the basic concept of personal rapid transit (PRT) was originally explored at an earlier time, the decade from about 1965 to 1975 saw a flurry of interest and activity in the PRT field. During that period, the highly successful Morgantown PRT system was developed and built on the campus of the University of West Virginia in Morgantown. That system is still operating effectively and is currently upgrading its automatic control system technology, now about 30 years old. Little more had been accomplished in the PRT field until recent years when Chicago and Raytheon joined forces in a project aimed at developing and installing a PRT system in Rosemont, adjacent to O’Hare Airport. The Raytheon PRT 2000 system, currently operating on a factory test track in Marlborough, Massachusetts, is the first serious PRT activity since the Morgantown system was implemented 25 years ago. Much has been written in the intervening years about the benefits of PRT as applied to densely developed urban centers. There are, however, some substantial technical obstacles to attaining the full potential of those systems. Three types of obstacles are discussed. These obstacles involve limitations on station interval, size, and complexity requirements for high-capacity PRT stations, and how they affect system operational availability. These factors are examined in the context of a comprehensive system serving a densely developed central business district instead of the limited application as exemplified by the Morgantown system.

Standard Hardware Acquisition and Reliability Program: Concepts, Benefits, and Potential

ABSTRACTThe Standard Hardware Acquisition and Reliability Program (SHARP) includes three major categories of hardware standards. They are Standard Electronic Modules (SEM), Standard Power Supplies (SPS), and Standard Electronic Enclosures (SES). SHARP responsibilities include development and testing of these standards and their integration into electronic systems. The purpose of SHARP is to reduce development, production, and logistics support costs of electronic systems; to improve system operational availability; and to shorten the system acquisition cycle. The basic concepts applied towards this purpose are: functional standardization; functional specification; a disciplined quality program; design flexibility; and emphasis on design for maintenance and repair. The paper describes the application of these concepts in the SHARP program and how they result in:— improved performance and supportability;— multisystem application of functional standards:— standard interfaces between system elements;— competitive procurement of hardware;— improved system readiness;— interchangeability of spares;— introduction of new technology into deployed systems;— improved testability; and— reduced cost to the Department of Defense (DoD).SHARP experience and benefits to the user are described, including specific applications of SHARP hardware in DoD systems and examples of multimillion dollar cost savings to these systems. The status of current SHARP initiatives and potential savings through broader application of SHARP in system developments are then discussed.

An optimum multiechelon repair policy and stockage model

AbstractCurrently, sophisticated multiechelon models compute stockage quantities for spares and repair parts that will minimize total inventory investment while achieving a target level of weapon system operational availability. The maintenance policies to be followed are input to the stockage models. The Optimum Allocation of Test Equipment/Manpower Evaluated Against Logistics (OATMEAL) model will determine optimum maintenance as well as stockage policies for a weapon system. Specifically, it will determine at which echelon each maintenance function should be performed, including an option for component or module throwaway. Test equipment requirements to handle work load at each echelon are simultaneously optimized. Mixed‐integer programming (MIP) combined with a Lagrangian approach are used to do the constrained cost minimization, that is, to minimize all costs dependent on maintenance and stockage policies while achieving a target weapons system operational availability. Real‐life test cases are included.

Availability analysis of a repairable system with non-repairable stand-by units

This paper presents a Markov model containing n identical units of which one is functioning and ( n −1) are stand-bys. The availability rate of the repairmen is considered. The state probability equations are developed to obtain system operational availability.