Leaky Coaxial Cable Resource Protection Sensor Performance Analysis

The performance of an RF intrusion detection system which uses a leaky coaxial cable sensor is analyzed. A simple cable sensor field model is assumed which gives good agreement between the computed response and observation. Expressions that describe the performance of several deployment configurations and receiver types are developed. The probability of detection and the zone of containment are computed and their uniformity is examined as a function of cable propagation constants.     

An annunciator architecture for the year 2000

Exciting new safeguards and security technologies are on the horizon, and some are even on the shelves today. Self-testing sensors, smart sensors, and intelligent alarm analyzers are all designed to provide useful information to the operator. However, today's current annunciator systems were not designed to accommodate these new technologies. New display technologies are also changing the look and feel of the annunciator of the future. Annunciator technology needs to “catch up” to these other security technologies. This paper presents the concept for a new, object-oriented approach to annunciator architecture design. The new architecture could accommodate simple, switch-closure devices as well as information-rich sensors and intelligent analyzers. In addition the architecture could allow other leading-edge interfaces to be easily integrated into the annunciator system. These technologies will reduce operator workload and aid the operator in making informed security decisions     

“Dakota Sun”-the next generation solar powered racingvehicle

Based on the experience gained from Sunrayce '95, the Solar Motion Team has made many changes to the design of the next generation solar car. These changes have resulted in a vehicle that is very different from the “Solar Rolar”, The Dakota Sun is a three wheeled vehicle with separate cab and solar array. This design allows for improved aerodynamics, decreased weight, lower rolling resistance, and ease of manufacture compared to the four wheeled catamaran used in the last race. However, this design sacrifices total enclosed wheel base area, additional room for components, and added power from side solar panels, The major objectives for the team's redesigned Sunrayce '97 entry are: systems integration; decrease the weight of the car; decrease aerodynamic drag; more efficient use of available energy; and increased driver safety. The team has set a standard to use the latest available technology. Although this increases the complexity of the components, by using a systems engineering approach the “Dakota Sun” has evolved into a more integrated vehicle. This philosophy of integrated design has resulted in great improvements in mechanical design and manufacturing techniques, as well as electrical innovations. The major design changes evident from the original Sunraycen '95 vehicle are the result of an evolutionary design process that has produced the highly competitive Sunraycel '97 design outlined in this article     

Detection and diagnosis of sensor and actuator failures using IMMestimator

An approach to detection and diagnosis of multiple failures in a dynamic system is proposed. It is based on the interacting multiple-model (IMM) estimation algorithm, which is one of the most cost-effective adaptive estimation techniques for systems involving structural as well as parametric changes. The proposed approach provides an integrated framework for fault detection, diagnosis, and state estimation. It is able to detect and isolate multiple faults substantially more quickly and more reliably than many existing approaches. Its superiority is illustrated in two aircraft examples for single and double faults of both sensors and actuators, in the forms of “total”, “partial”, and simultaneous failures. Both deterministic and random fault scenarios are designed and used for testing and comparing the performance fairly. Some new performance indices are presented. The robustness of the proposed approach to the design of model transition probabilities, fault modeling errors, and the uncertainties of noise statistics are also evaluated     

新一代航空电子总线系统结构研究

航空电子总线系统结构是航空电子系统的神经中枢,直接决定着航空电子综合化程度的高低和性能的优劣。本文通过对航空电子数据总线结构现状和发展要求的分析,提出了新一代航空电子总线系统的设计原则和体系结构,并论述了其核心技术综合模块化航空电子系统的通用模块和综合核心处理机的组成。     

Investment Costs of Terrestrial Long-Haul Telecommunication Facilities

The investment costs of long-haul, modern, radio relay and coaxialcable systems, as determined from data submitted to the Federal Communications Commission, are presented. Formulas to determine costs per voice-circuit-mile, and per television-channel-mile, are developed. The specific facilities investigated are the TD-2, TD-3, and TH radio relay systems, and the L-3 12-tube and L-4 20-tube coaxial cable systems. The radio relay systems are significantly, with one exception, less expensive than coaxial cable systems over their design capacity ranges. The L-4 20-tube coaxial cable system (32 400 voice circuits) and the TD-3 radio relaysystem (12 000 voice circuits) have approximately equal investment costs per voice-circuit-mile ($3.40) at full capacity.     

Censoring sensors: a low-communication-rate scheme for distributeddetection

We consider a new scheme for distributed detection based on a “censoring” or “send/no-send” idea. The sensors are assumed to “censor” their observations so that each sensor sends to the fusion center only “informative” observations, and leaves those deemed “uninformative” untransmitted. The main result of this work is that with conditionally independent sensor data and under a communication rate constraint, in order to minimize the probability of error, transmission should occur if and only if the local likelihood ratio value observed by the sensor does not fall in a certain single interval. Similar results are derived from Neymarr-Pearson and distance-measure viewpoints. We also discuss simplifications for the most interesting case that the fusion center threshold is high and the communication constraint is severe. We compare censoring with the more common binary-transmission framework and observe its considerable decrease in communication needs. Finally, we explore the use of feedback to achieve optimal performance with very little communication     

Simulation and control of a 20-kHz spacecraft power system

A detailed computer representation of four Mapham inverters connected in a series-parallel arrangement has been implemented. System performance is illustrated by computer traces for the four Mapham inverters connected to a Litz cable with parallel resistance and DC receiver loads at the receiving end of the transmission cable. Methods of voltage control and load sharing between the inverters are demonstrated. The computer representation is used to design and demonstrate the advantages of a feedforward voltage-control strategy. It is shown that with a computer simulation of this type, the performance and control of spacecraft power systems can be investigated with relative ease and facility     

TCAS 系统故障隔离及容错架构设计方法研究

针对TCAS 系统运行过程典型功能危险场景和架构设计过程，本文采用系统工程过程的正向设计流 程方法，针对潜在的功能失效风险，开展TCAS 系统域的故障检测和容错设计技术研究，形成覆盖系统、软件 和硬件层级的故障检测及隔离架构设计方案，以提高装机运行过程中防撞告警的置信度，减少由于误警和虚警 对飞行安全产生的不利影响。     

Replacement strategy for aging avionics computers

With decreasing defense dollars available to purchase new military aircraft, the inventory of existing aircraft will have to last many more years than originally anticipated. As the avionics computers on these aging aircraft get older, they become more expensive to maintain due to parts obsolescence. In addition, expanding missions and changing requirements lead to growth in the embedded software which, in turn, requires additional processing and memory capacity. Both factors, parts obsolescence and new processing capacity, result in the need to replace the old computer hardware with newer, more capable microprocessor technology. New microprocessors, however, are not compatible with the older computer instruction set architectures. This generally requires the embedded software in these computers to be rewritten. A significant savings-estimated in the billions of dollars-could be achieved in these upgrades if the new computers could execute the old embedded code along with any new code to be added. This paper describes a commercial-off-the-shelf (COTS)-based form, fit, function, and interface (F³I) replacement strategy for legacy avionics computers that can reuse existing avionics code “as is” while providing a flexible framework for incremental upgrades and managed change. It is based on a real-time embedded software technology that executes legacy binary code on the latest generation COTS microprocessors. This technology promises performance improvements of 5-10 times that of the legacy avionics computer that it replaces. It also promises a 4× decrease in cost and schedule over rewriting the code and provides a “known good” starting point for incremental upgrades of the embedded flight software. Code revalidation cost and risk are minimized since the structure of the embedded code is not changed, allowing the replacement computer to be retested at the “blackbox” level using existing qualification tests     

Attitude control system design and on-orbit performance analysis of nano-satellite––‘‘Tian Tuo 1’’

‘‘Tian Tuo 1'(TT-1) nano-satellite is the first single-board nano-satellite that was successfully launched in China. The main objective of TT-1 is technology demonstration and scientific measurements. The satellite carries out the significant exploration of single-board architecture feasibility validation, and it is tailored to the low-cost philosophy by adopting numerous commercialoff-the-shelf(COTS) components. The satellite is featured with three-axis stabilization control capability. A pitch bias momentum wheel and three magnetic coils are adopted as control actuators.The sun sensors, magnetometers and a three-axis gyro are employed as the measurement sensors.The quaternion estimator(QUEST) and unscented Kalman filter(UKF) method are adopted for the nano-satellite attitude determination. On-orbit data received by ground station is conducted to analysis the performance of attitude determination and control system(ADCS). The results show that the design of ADCS for TT-1 is suitable, robust and feasible.     

机载嵌入式可重构信号处理系统设计

为使机载嵌入式信号处理系统性能更加均衡,更好地适应机载嵌入式环境,在比较三种传统的机栽信号处理系统架构的基础上,提出了一种系统可伸缩、功能可重构的信号处理系统架构,并分析了其系统特性和关键技术。从可编程能力、处理性能、通用性以及可扩展性等方面比较了三种信号处理系统架构,结果表明:可重构信号处理系统架构具有较强的综合性能,能更好地满足机载嵌入式应用的需求。     

航空电子系统功能综合的收益分析研究

综合化航空电子系统是根据应用的需求,基于已有的能力,采用综合技术,实现面向应用的任务合成,提升应用效能;面向能力的功能综合,提升能力品质;面向物理的操作模式综合,提升资源效率。功能综合的过程本质上是一个系统设计的过程,是依据物理架构,在不同功能组合中进行收益分析比较,选择收益较大的一种功能架构,本文基于分布式模块化航空电子物理架构(DIMA),提出基于系统工程的功能综合设计方法,并提出了相应的功能综合收益评价指标,以综合探测为例对提出的方法进行了验证。     

Application of nonlinear filtering to navigation system designusing passive sensors

The problem of navigation system design for autonomous aircraft landing is addressed. New nonlinear filter structures are introduced to estimate the position and velocity of an aircraft with respect to a possibly moving landing site, such as a naval vessel, based on measurements provided by airborne vision and inertial sensors. By exploring the geometry of the navigation problem, the navigation filter dynamics are cast in the framework of linear parametrically varying systems (LPVs). Using this set-up, filter performance and stability are studied in an H_∞ setting by resorting to the theory of linear matrix inequalities (LMIs). The design of nonlinear, regionally stable filters to meet adequate H_∞ performance measures is thus converted into that of determining the feasibility of a related set of LMIs and finding a solution to them, if it exists. This is done by using-widely available numerical tools that borrow from convex optimization techniques. The mathematical framework that is required for integrated vision/inertial navigation system design is developed and a design example for an air vehicle landing on an aircraft carrier is detailed     

The case for like-sensor predetection fusion

There has been a great deal of theoretical study into decentralized detection networks composed of similar (often identical), independent sensors, and this has produced a number of satisfying theoretical results. At this point it is perhaps worth asking whether or not there is a great deal of point to such study-certainly two sensors can provide twice the illumination of one, but what does this really translate to in terms of performance? We take as our metric the ground area covered with a specified Neyman-Pearson detection performance. To be fair, the comparison will be of a multisensor network to a single-sensor system where both have the same aggregate transmitter power. The situations examined are by no means exhaustive but are, we believe, representative. Is there a case? The answer, as might be expected, is “sometimes.” When the statistical situation is well behaved there is very little benefit to a fused system; however, when the environment is hostile the gains can be significant. We see, depending on the situation, gains from colocation, gains from separation, optimal gains from operation at a “fusion range,” and sometimes no gains at all     

先进战斗机强度设计技术发展与实践

新一代先进战斗机对机体平台的要求可以总结为轻重量、长寿命、多功能以及高承载。实现这个目标，除了材料与制造（新材料、新工艺、新结构/装配）的贡献，主机所强度设计/分析/验证技术也必须提升以适应先进战斗机的研制要求。本文阐述了强度设计团队围绕结构完整性要求，近年来在结构强度设计/分析/验证方面的研究成果、技术发展与设计实践，主要包括：面向新一代战斗机强度设计与验证的规范架构，基于多维包线的结构载荷筛选技术，基于统一模型的全机内力分析技术，复合材料整体化结构分析技术，高精度快速细节应力分析技术，内埋武器舱预紧舱门原理与强度设计，双曲面加筋壁板快速建模及声疲劳分析方法，结构故障预测与健康管理系统设计等。上述研究成果已成功应用于新一代战斗机机体平台研制。     

数字孪生技术在飞机设计验证中的应用

随着工业4.0技术的发展,数字孪生技术正在不断渗透到工业生产和新产品研发的各个领域,并为新产品研发带来综合性能整体优化、研发成本降低、研制周期缩短等优势,是提升新产品市场竞争力的重要手段。在现代民用飞机研发过程中,从型号需求、初步定义、详细设计、生产试制、试飞取证和运营维护等产品全生命周期内,都可以利用数字孪生技术,实现虚拟和物理的无缝对接,尤其在飞机设计验证方面,更可以做到更优、更广、更快、更省。然而,在我国民用飞机研制项目中,还未形成数字孪生应用体系。本文通过对飞机架构模型设计、多模型构架集成以及模型参数辨识和验证几个方面,对数字孪生技术在飞机设计验证过程中的应用技术进行了探讨。经研究发现,数字孪生技术对飞机型号研制各阶段的设计验证,尤其是集成试验验证提供了重要的指导作用和技术支持,为民用飞机适航验证和运维服务提供了更快、更经济、更强有力的支持与保障。     

Channelization: the two-fault tolerant attitude control functionfor the Space Station Freedom

The Space Station Freedom was, from the mid-1980's through 1993, the design for an international orbiting laboratory facility. The Space Station Freedom was comprised of “utility” systems, such as power generation and distribution, thermal management, and data processing, and “user” systems such as communication and tracking, propulsion, payload support, and guidance, navigation, and control. These systems are required to work together to provide various station functions. To protect the lives onboard and the investment in the station, the systems and their connectivity had to be designed to continue to support critical functions after any single fault for early assembly stages, and after any two faults for later stages. Of these critical functions, attitude control was the most global, incorporating equipment from nearly all major systems. The challenge was to develop an architecture, or integration, of these systems that would achieve the specified level of fault tolerant attitude control and operate, autonomously, for the three-month unmanned periods during the assembly process. Additionally, this architecture had to maintain the desired utility of the station for each stage of the assembly process. This paper discusses the approach developed for integrating the systems such that the fault tolerance requirements were met for all stages of assembly. Some of the key integration issues are examined and the role of analysis tools are described. The resultant design was a highly channelized one, and the reasons and the benefits of this design will be explored. The final design was accepted by the Space Station Control Board as the design baseline in July 1992     

Multifunctional structures technology experiment on Deep Space 1Mission

Lockheed Martin Astronautics has developed the Multifunctional Structure (MFS) concept as a new system for spacecraft design that eliminates chassis, cables, connectors and folds the electronics into the walls of the spacecraft. Concurrent engineering will be essential to integrate the electronic, structure, and thermal design. Design methodologies are in work to manage all power, grounding and shielding concerns. The MFS approach offers significant savings in mass and volume and supports the “faster-better-cheaper” philosophy in new spacecraft programs. The technology will be demonstrated as an experiment on the New Millenium Program Deep Space 1 (DS 1) mission     

MEMs for Aerospace Navigation

The MEMS aerospace market has its own specificities in terms of market size, standards, and performance characteristics (very long term stability, reliability, and safety levels). Improvements are needed for future applications. THALES Avionics has a twenty-year experience in quartz and silicon MEMS design and manufacturing and is recognized as a leader by the French MOD in this field. MEMS pressure sensors and accelerometers are manufactured in large volume and used for safety-critical applications. THALES technology policy focused on planar architecture, die vacuum packaging, and deep reactive ion etching (DRIE) allowing good characteristics for sensors in development. A Silicon Vibrating Beam Accelerometer single chip is now under development. Its operating principle is described with two resonators in push-pull configuration. A tuning fork planar rate gyro is also developed with exactly the same technology for industrial efficiency. Performance results will be addressed. The development and industrialization road-map of theses inertial products is described for the following five years. Gyro-compassing grade inertial sensors would be available during the next decade allowing low-cost, high-grade navigators using simultaneously GNSS receivers and inertial MEMS navigators.