Remaining useful life prediction for engineering systems under dynamic operational conditions: A semi-Markov decision process-based approach

For critical engineering systems such as aircraft and aerospace vehicles, accurate Remaining Useful Life(RUL) prediction not only means cost saving, but more importantly, is of great significance in ensuring system reliability and preventing disaster. RUL is affected not only by a system's intrinsic deterioration, but also by the operational conditions under which the system is operating. This paper proposes an RUL prediction approach to estimate the mean RUL of a continuously degrading system under dynamic operational conditions and subjected to condition monitoring at short equi-distant intervals. The dynamic nature of the operational conditions is described by a discrete-time Markov chain, and their influences on the degradation signal are quantified by degradation rates and signal jumps in the degradation model. The uniqueness of our proposed approach is formulating the RUL prediction problem in a semi-Markov decision process framework, by which the system mean RUL can be obtained through the solution to a limited number of equations. To extend the use of our proposed approach in real applications, different failure standards according to different operational conditions are also considered. The application and effectiveness of this approach are illustrated by a turbofan engine dataset and a comparison with existing results for the same dataset.     

Integrated automatic vehicle location systems

The state-of-the-art transportation management system integrates automatic vehicle location, in-vehicle systems, customer information networks, and management information systems. As advanced technologies are integrated into transportation systems, the transit system becomes more efficient and reliable, which, in turn, makes it more attractive to users. The greatest benefit will not be realized until all of these technologies are integrated. Transit agencies and system integrators who take a total systems approach to the integration of advanced technologies will have a competitive advantage. They will provide services which provide the greatest utility to prospective users, riders, and the transit agency at the lowest cost     

Recent developments of electric vehicles and their propulsionsystems

Major recent electric vehicle (EV) programs in North America, Europe, and Japan are reviewed. The developments discussed include electric vehicles for fleet operation and electric passenger cars for urban transit. All major auto makers have had their own concept electric vehicle programs, targeted at commercial production in the late 1990s. It Is noted that, with different objectives for various electric vehicles, considerations such as cost, reliability, efficiency, maintenance, durability, weight, size, and noise level should be compromised for the propulsion system design. Consequently, DC motor drives, induction motor drives, and permanent magnet brushless DC motor drives will continually be used for EV propulsion systems in the future, with DC drives being gradually replaced by AC drives. The rapid advances in power semiconductor devices and microprocessors have made it possible to build reliable and cost-effective AC drive systems     

发动机控制系统限时派遣运行的成本优化方法

限时派遣TLD可以提高飞机的签派可靠度,降低由于航班延误或取消导致的运行损失。面向TLD分析建立了典型发动机控制系统马尔可夫模型,利用连续时间马尔可夫链CTMC推导了状态稳态频率公式,构建了系统单位时间运行成本模型。以平均完整性要求及签派可靠度要求为约束条件,以带故障派遣时间为决策变量,以系统单位时间运行成本以及签派可靠度为优化目标,分别构建了TLD分析的单目标和多目标优化模型。结合简化的发动机控制系统和实际全权限数字式发动机电子控制FADEC系统给出了工程应用实例,验证了模型的有效性。实例表明本文方法能够保证飞机在满足安全性要求和签派可靠度要求的条件下降低运行成本。     

复杂城市环境下GNSS/INS轻轨轨道中线精密测量方法CSCD

在城市轻轨线路的中线精密测量中,传统的基于GNSS的测量方式往往受高楼、站台、上跨桥及声屏障等复杂环境信号遮挡影响,甚至无法接收到GNSS信号,难以得到满足精度要求的轨道中线坐标;而基于全站仪的测量方式需建立轨道控制网,作业效率低下。为了满足城市轻轨中线精密测量高精度和高效率的需求,采用GNSS/INS轨道中线精密测量方法,基于Kalman滤波将惯导、GNSS数据进行融合,并根据轨道检测仪在轨道上不发生垂向和侧向运动的特点,采用运动约束算法,以提升组合导航系统测量精度。同时设计了基于新息滤波的抗差检测,以剔除定位质量差的GNSS数据。通过将里程计比例因子误差增广到状态向量的方式进行参数估计,以减小里程计测量误差。通过集成惯导、GNSS、里程计等传感器的轨检小车,采集城市轻轨轨道测量数据。经数据处理和对比分析,在GNSS信号较差的复杂场景下能够得到厘米级的轻轨轨道中线坐标,且测量效率大大提升。     

Reliability Predictions and System Support Costs

A case study demonstrates that spares requirements based on operational reliability predictions result in the system being undersupported during its burn-in and useful-life phases by average factors of 42.2 and 4.22, respectively. However, systems spares requirements based on logistics estimates result in the system being oversupported during its burn-in phase by an average factor of 4.26 with this factor probably increasing as the system enters the useful-life phase of its life cycle. Adequate system support within predetermined cost estimates will be achieved only when reliability predictions are accurate and when systems spares requirements are computed separately for the equipment burn-in phase and useful-lfe phase.     

重型火箭下面级发动机基本参数分析

分析了已有重型火箭动力系统的结构和基本参数,以满足载人登月的任务要求为前提,提出了任务要求以及一套重型火箭箭体结构方案.从性能、经济性、技术难度、工作可靠性等方面综合考虑,提出重型火箭下面级的基本方案,包括推力量级、推进剂以及发动机循环方式的选择.采用面向对象的通用顺序化计算方法,建立发动机系统仿真模型,计算得到9个发动机方案的最高室压及功率平衡参数,分析了燃烧室压强和混合比对发动机性能的影响.经综合分析,建议重型火箭下面级发动机可选择推力4 500～5 000 kN富氧预燃室补燃循环液氧煤油发动机.      

Instrumenting embedded test software in support system integration, factory production, and depot repair

Embedded built-in test (BIT) software typically provides a system-level go/no-go indication and, in the presence of a failure, may provide some level of sub-system isolation. This level of reporting, while meeting the customer's operational requirements, does little to support system integration, production, and repair. To support these other needs, "instrumentation code" is added to the BIT software to provide detailed test data through an external interface. Since the BIT software already accesses the hardware parameters for testing, it becomes the most logical component for the instrumentation. This paper describes the techniques of embedding instrumentation during BIT design and development to support a broad range of program test needs. It explains the costs and benefits associated with the use of instrumentation. It gives specific examples of instrumented software and describes how instrumentation data can be used during environmental tests, factory test, and depot test. The impact instrumentation has on software development time, code size, execution time, and reliability is discussed as well as the cost of retrofitting BIT software to add instrumentation. Some of the benefits as well as the challenges to developing effective embedded instrumentation is also examined.     

Modular Stores Management System

Advanced Military aircraft operational requirements demand an ever increasing variety and quantity of Stores, coupled with continuous improvement in mission success, safety of operation, aircrew and groundcrew workload, interoperability and ground support facilities. Until now these ever more demanding requirements have been met by costly customized stores management system designs. GEC Avionics has surveyed the potential SMS requirements of a comprehensive range of aircraft and weapon types, in order to define a universal SMS design concept based on system availability, integrity and reliability, operational functions, peripheral interfaces and maintenance/human factors. This advanced concept not only includes provision for all existing weapon types but also has growth potential for the evolving MIL-STD-1760 weapon interfaces. System interface requirements have been rationalized in order to achieve a Modular Stores Management System (MSMS) design based on major factors such as cost, mission requirements and customer specifications. The key work for a successful MSMS design is flexibility and GEC Avionics has evolved a set of standard modules which can be packaged to satisfy specific customer needs. Typically, the standard modules provide over 80% of the hardware in every Stores Management application. The MSM concept features much reduced development costs and timescales, commonality between aircraft types minimizing parts inventory, VLSI technology providing high reliability and a common product support and maintenance philosophy. The MSM design offers a highly cost effective low risk concept for meeting the needs of modernization and new aircraft programs.     

Unmanned scientific exploration throughout the solar system

Velocity requirements for scientific probe vehicles operating throughout the entire solar system are presented. Both direct flights and those using planetary swingby modes are considered. Launch-vehicle and payload sizes necessary to perform useful scientific missions are examined. Scientific investigation of the solar system is shown to be much less difficult than is commonly believed.     

现代企业财务管理模式初探

企业是社会经济的细胞，资金是企业的血液，而财务则是企业的灵魂，是现代企业制度下企业管理的核心。传统财务管理目标缺乏一定的科学性，观念落后的财务管理制度难以适应新经济的要求。本文探讨了现代企业制度下的财务管理模式。     

商用飞机项目中的技术经济方法

商用飞机的自主研发需要科学系统的技术经济分析方法解决技术先进性、研制成本以及使用经济性三者之间的矛盾。因此需要综合考虑市场竞争、技术性能、经济环境等多方面的因素,建立全寿命周期成本模型、基于直接运营成本的竞争定价模型和面向使用经济性的优化模型。通过项目盈亏平衡、基于EBOM的成本控制和发动机选型三个案例,分析说明了技术经济方法在商用飞机项目技术决策过程中的作用。     

先进空间运输系统气动设计综述

天地往返运输系统是能够自由进出空间轨道、安全返回地球表面、执行天地往返运输任务的航天运输体系。近年来,随着先进动力、新材料、新工艺的带动效应逐渐显现,各航天集团开始了新一轮先进天地往返系统的研究,其中大量研究项目针对具备完全可重复使用、可大幅降低运送有效载荷进入太空成本的先进天地往返运输系统展开。本文针对这一热点领域进行综述性研究,对不同类型进出大气层飞行器的气动设计特点进行了分析,结果表明跨大气层飞行器是天地往返运输系统的主要载体,认为未来主要以火箭助推入轨滑翔再入和水平起飞水平返回为主要发展方向,两类飞行在气动设计方面有高超飞行器宽域飞行适应性的共性难题,同时在气动-动力一体化化设计方面又有较大的差异。     

Intelligent UUVs: Some issues on ROV dynamic positioning

Intelligent unmanned underwater vehicles (UUVs) fall under two main group categories: the remotely operated vehicles (ROVs), which are characterized by remote operation and presence of a tether cable; and the autonomous underwater vehicles (AUVs), which are characterized by their autonomous behavior and absence of a tether cable. One fundamental issue of the UUV design is the dynamic position control system. This system plays a crucial role together with the sensor architecture in the degree of system autonomy that can be achieved. This paper is concerned with a few issues when dynamically positioning remotely operated underwater vehicles (ROVs). By restricting the operating regime of ROVs to slow velocity requirements the paper investigates the implementation of a few decentralized control strategies and compare their performance measures, which are assessed by simulating a nonlinear ROV system model for each control strategy. Issues concerning input tracking, disturbance rejection, and plant variations are discussed. The evaluations consider the use of linear PID feedback and feedforward variants, and a robust nonlinear control strategies applied to a full order, fully coupled, and nonlinear vehicle model. These evaluations consider a vehicle undertaking standard mission activities where the tether cable dynamics, with load estimates obtained from a lumped mass cable model, and the vehicle actuator system are present. The paper shows that much of the performance deterioration may be attributed mainly due to cable inertia. The authors also verify that the nonlinear robust control strategy does not necessarily allow for better performance over the linear feedback control strategies implemented when vehicle motions are confined to slow velocity profiles. These and other partial results will aid the design of the control system for an underwater vehicle currently under construction     

飞机机载维护系统的设计考虑

飞机机载维护系统的主要目标是支持客户要求的飞机检修,以达到最小的维修成本和操作成本,达到最大的操作可靠性,因此在飞机设计中需要考虑如何设计机载维护系统。从机载维护系统的设计理念、系统安全与维护、飞机机载维护系统(OMS)故障处理、系统接口、维护处理、人机接口进行了探讨,希望能让读者更好地了解飞机机载维护系统,扩展设计思路,设计更好的机载维护系统。     

重型运载火箭动力系统分析

讨论了两种载人登月的动力系统方案,分析了已有重型火箭动力系统的结构和基本参数,以满足载人登月的任务要求为前提,提出了重型火箭箭体结构和任务要求.从性能、经济性、技术难度、工作可靠性等方面综合考虑,提出重型火箭下面级的基本方案.提出了一套重型火箭动力系统,建立了一个运载火箭系列,并对其运载能力进行了计算.经综合分析,提出登月火箭可采用8 m直径的三级半结构,助推级、第一级和第二级均为推力5 000 kN量级富氧预燃室补燃循环液氧煤油发动机,第三级为2台50 t氢氧发动机.      

空间飞行器综合定轨与参数分析软件COMPASS的研发——需求分析

对空间飞行器精密定轨软件COMPASS的开发作了详细的需求分析,包括软件功能、定轨模式、可分析的数据类型、参数解算、运行环境等,以便为COMPASS软件系统的设计提供依据。     

Benefits and challenges of Integrated Sensor Systems

Projection of avionics system costs shows unacceptable escalation as a percentage of flyaway cost. Time sharing of RF modules between Radar, EW and CNI offers savings. The Air Forces' PAVE PACE program defined the benefits and initial architecture approaches. From this, an optimum Integrated Sensor System (ISS) design was defined that reduces the life cycle cost of the fleet of vehicles using the common modules. The ISS program will design, build and test modules to prove the approach. Challenges to overcome include system complexity, real time control, test and calibration, and diagnostics. The most stressing requirements were determined by analyzing requirements for Radar, EW and CNI. Open interface specifications and module partitioning were developed that can meet all the requirements     

Enhanced space integrated GPS/INS (SIGI)

Safe, reliable, and low cost space-based navigation is being provided with embedded INS/GPS systems such as the space integrated GPS/INS (SIGI). The SIGI is being used for various space vehicle applications such as launch vehicles, orbital vehicles, and re-entry vehicles. This paper describes current space vehicle navigation capabilities. The SIGI is being enhanced to provide additions to these existing capabilities with such items as higher processing and a commercial-off-the-shelf operating system. This will allow hosting of various software applications such as advanced navigation functions, flight control, guidance and vehicle management algorithms. The SIGI can host redundancy management functions by incorporating a cross channel data link card (CCDL) using a high speed firewire bus. The SIGI can then be used as a redundancy management platform which has application to current space vehicle avionics topologies incorporating distributed processing architectures     

PAVE PACE: system avionics for the 21st century

The PAVE PACE Initiative has been established to validate system avionics concepts for advanced military aircraft. The author presents the rationale of why the advanced architecture established by the PAVE PILLAR program should be continued under PAVE PACE to achieve: practical and affordable airborne versions of modular parallel processing network architectures for many applications currently beyond real-time implementation, readily available avionics for use in all avionics and, greatly improved techniques to reduce the cost of software development and support. An approach to the overall design structure for future avionics is also presented that entails: the use of CAD (computer-aided design) tools to assist in the development of system, hardware and software requirements, the use of replicated hardware modules (some at the wafer level), the use of reuseable software modules and the use of CAD tools to tailor hardware/software modules for specific application requirements. Continued use of the PAVE PILLAR high-speed data bus and operating system is recommended as the means to integrate and control the data input and output of physically and functionally separate parallel networks