基于Nash均衡与进化计算的协调航迹规划

在对策论框架下研究多无人飞行器的协调航迹规划问题,提出了一种基于Nash平衡和进化计算的航迹规划算法.协调航迹规划是一个多目标合作优化问题,也是一个非合作对策问题.飞行器编队的分布结构提供了一种隐性偏好信息,有助于找到飞行器编队的最优协调航迹和最优飞行代价分配.本文算法使用特定的航迹个体表示方法和进化算子,按照层次方法处理各种航迹约束.不同飞行器间的协同和竞争关系定义在航迹评价函数里.仿真结果验证了基于博弈论航迹规划算法的可行性和优越性.     

Trajectory reshaping based guidance with impact time and angle constraints

This study presents a novel impact time and angle constrained guidance law for homing missiles. The guidance law is first developed with the prior-assumption of a stationary target, which is followed by the practical extension to a maneuvering target scenario. To derive the closed-form guidance law, the trajectory reshaping technique is utilized and it results in defining a specific poly-nomial function with two unknown coefficients. These coefficients are determined to satisfy the impact time and angle constraints as well as the zero miss distance. Furthermore, the proposed guidance law has three additional guidance gains as design parameters which make it possible to adjust the guided trajectory according to the operational conditions and missile’s capability. Numerical simulations are presented to validate the effectiveness of the proposed guidance law. ? 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).     

The observational data base on the motion and evolution of comets and asteroids

Current observational data base on the motion of comets and asteroids is reviewed. Particular attention is paid to the absolute and relative abundances of different dynamical types of objects, and to the time intervals between their first and last observations. The latter quantity, ranging from two days to two milliennia for individual objects, is the dominant measure of the accuracy of the orbit determination. Distribution of the tracking times of comets (distinguished by dynamical age: new, long-period, Halley type, Jupiter family) and asteroids (distinguished by stability: Apollos, Amors, main-belt asteroids, outer librators, outer unstable objects) are reconstructed. The peculiar shapes of individual distributions can be explained by the complex mechanisms of discoveries, rediscoveries, orbit computations, follow-up observations and backward identifications. A comparison is also made with the dynamical data base on meteoroids, as regards the accuracy of their orbits.The cumulative tracking times (170000 yr for all 7600 objects with known orbits taken together) are compared with the lifetimes and occurrence rates of different events of evolutionary significance. Only in the case of short-period comets the evolution is rapid enough to render observable a variety of important changes, ranging from drastic transformations of orbits to disruption or total outgassing. For asteroids, only minor cratering collisions which do not result in detectable changes of their orbits are covered by the whole observational history.Expected future improvements of observing and data-handling techniques are outlined. With these in view, the size and character of the data to become available by the end of this century are predicted. Dynamical types of objects, which are currently known in only one or a few examples, are pointed out. Apparently, other types of rare occurrence and short survival time still escape detection. A list of easiest targets of short-duration spacecraft missions is presented.The deficiencies of current statistics due to observational selection; the broad variety of regimes of motion occupied by widely differing proportional representations of the known objects; and demands for suitable targets of future spacecraft missions make it highly desirable to maintain the present rapid rate of augmentation of the data base for the years to come.Recent passages of two comets — 1983d IRAS-Araki-Alcock and 1983e Sugano-Saigusa-Fujikawa — near the Earth indicate that both the collision rate given in Table VIII and the contribution of long-period comets to it may have been slightly underestimated. The appropriate adjustment of the log-t values by less than — 0.10 has no effect of the general conclusions, however.The success of the orbiting observatory IRAS in detecting faint interplanetary objects lends better promises for the increase of the number of known objects (in particular comets) than anticipated in Section 6 and estimated in Table IX. Obviously, the outcome will largely depend on the implementation, time coverage and degree of exploitation of similar projects in the near future.     

Short-range radio navigation systems: current status and prospects

The problems of the development of short-range navigation aids as integrated multifunctional systems for the near future while implementing them in poorly equipped regions, ice-breaker fleets, and on remote oil platforms are discussed. Conclusions are drawn about the reasonability of utilization for those purposes of various modifications of the existing integrated short-range navigation systems. These systems provide highly accurate operation, have a convenient ρ-&thetas; coordinate system, and are capable in some cases of providing the additional functions     

Information systems requirements analysis and design: a balancedapproach

Over the last decade information engineering has become the methodology of choice for developing information systems. There are as many definitions of information engineering as there are practitioners of the techniques. This paper addresses information engineering from a practical perspective; it discusses how information engineering techniques can be applied to the real-life problem of identifying system requirements and satisfying those requirements with a computer-based information system. The paper also shows that information engineering, rather than being a new methodology, is made up of components of existing methodologies     

Three-body cooperative active defense guidance law with overload constraints: A small speed ratioperspective

In air combat, one effective way to counter an incoming missile attacking an aircraft is tolaunch a defense missile compared with traditional passive defense strategies such as decoy and elec-tronic countermeasures. To address this issue, this paper proposes a three-body cooperative activedefense guidance law with overload constraints from the perspective of a small speed ratio. First, acooperative guidance-oriented model for active defense is established and linearized to provide afoundation for the design of the guidance law. Then, the essential quantity known as Zero-Effort-Miss(ZEM) is analyzed during the engagement process. In order to minimize the influenceof inaccurate estimates of remaining flight time in the ZEM, the concept of Zero-Effort-Velocity(ZEV) is introduced. Subsequently, utilizing the sliding mode control method, the guidance lawis designed by selecting the ZEM and ZEV as sliding mode surfaces, combined with the fast powerreaching law, and its finite-time stability is analyzed using the Lyapunov method. Furthermore, toquantitatively evaluate the performance of the proposed active defense guidance law, the intercep-tion rendezvous angle index is introduced. The proposed active defense guidance law considers inte-grating information from the incoming missile, aircraft, and defense missile with fewersimplifications and assumptions, and ensures that the aircraft is effectively protected with less over-load required for the defense missile. Finally, simulation experiments demonstrate the effectivenessand adaptability of the proposed active defense guidance law.     

Satellite passive intermodulation: systems considerations

Passive intermodulation (PIM) occurring in multicarrier transmission systems can have deleterious effects on system performance by significantly increasing the noise level. An argument is presented for system-level testing for PIM, particularly for high-power communications satellites. In the past, two-carrier, component-level tests were employed to ensure that PIM would not degrade system S/N performance     

Space power systems requirements and issues: the next decade

Some of the more important space power technology issues, requirements, and challenges of the 1990s are described, and the impact of new component technology on the overall performance of space power systems is assessed. Advanced component, subsystem and system technologies that will significantly affect the performance, reliability, and survivability of next-generation baseload and burst mode space power systems are emphasized. Technology disciplines related to power sources (solar/nuclear and chemical), power conversion, energy storage, power conditioning/distribution and control, and waste-heat acquisition, transport, and rejection are primarily addressed. For some of them, performance trends that can be used as the basis for projecting future advanced power-system performance are developed. Performance capabilities for several different types of space power system for both baseload and burst mode applications are postulated on the basis of evolving technology and point designs that incorporate projections of advanced component capabilities     

Physical protection systems cost and performance analysis: a casestudy

Design and analysis of physical protection systems requires: (1) identification of mission critical assets; (2) identification of potential threats that might undermine mission capability; (3) identification of the consequences of loss of mission-critical assets (e.g., time and cost to recover required capability and impact on operational readiness); and (4) analysis of the effectiveness of physical protection elements. CPA-Cost and Performance Analysis-addresses the fourth of these four issues. CPA is a methodology that joins activity based cost estimation with performance-based analysis of physical protection systems. CPA offers system managers an approach that supports both tactical decision making and strategic planning. Current exploratory applications of the CPA methodology address analysis of alternative conceptual designs. Hypothetical data is used to illustrate this process     

基于实数编码量子进化算法和模态区间数学的航空发动机设计

本文将实数编码量子进化算法和模态区间数学相结合用于解决模态区间数学中的某些难以求解的问题。应用量子进化算法进行了模态区间数学方程组的求解和模态区间矩阵的求逆,将量子进化算法和模态区间数学用于航空发动机的设计,给出了基于模态区间数学的航空发动机总体性能设计方法。这种设计方法能够考虑设计的不确定性。并以某型涡喷发动机为例进行计算,设计结果更符合实际情况。     

分级型进化算法及其在翼型跨声速气动优化中的应用

提出了变精度模型的分级型进化算法并对初始翼型为NACA0012的二维翼型进行了跨声速流动下的形状增升优化。借鉴自然进化中不同进化阶段个体适应度评估环境不同的机理,构造了分级精度模型以加速优化过程。对翼型进行了给定气动条件下的形状增升优化,给出了优化结果,并与传统基因算法及单精度模型算法结果进行了对比。     

Implementing high integrity systems: the VIPER microprocessor

The author describes the development of VIPER and points out some of the practical problems encountered over the four years of the project. Informal proofs of correctness, carried out in the early stages of the project, are outlined. A peer review group criticized the lack of multiplication and division instructions in VIPER 1. This deficiency is corrected in VIPER 2, and the performance is increased to 3 MIPs     

Magnetic suspension and balance systems

Conditions necessary for controlled magnetic suspension are reviewed, and various types and configurations of systems are described. The principal components of these systems are discussed. The use of magnetic suspension and balance systems in wind tunnels is then considered, and some aerodynamic results are examined     

ISE: intelligent synthesis environment for future aerospace systems

The Intelligent Synthesis Environment (ISE) being developed by NASA, UVA, and JPL for significantly enhancing the rapid creation of innovative affordable products and missions is described. ISE uses a synergistic combination of leading-edge technologies, including high-performance computing, high-capacity communications and networking, virtual product development, knowledge-based engineering, computational intelligence, human-computer interaction, and product information management. The environment will link scientists, design teams, manufacturers, suppliers, and consultants who participate in the mission synthesis, as well as in the creation and operation of the aerospace system. It will radically advance the process by which complex science missions are synthesized, and high-tech engineering systems are designed, manufactured, and operated. The evolution of engineering design is described along with the shortcomings of current product development techniques. The need for ISE to create high-science payoff missions and aerospace systems at affordable costs is discussed. The five major components critical to ISE and some of their sub-elements are described: namely, human-ISE interaction; infrastructure for distributed collaboration; rapid synthesis and simulation tools; intelligent life-cycle system integration; and cultural change in the creative process. Related government and industry programs are outlined and future impact of ISE on complex missions and aerospace systems is discussed.     

Designing security systems: changing the way we think

Today's world demands new ways of thinking about security solutions. The problem space is complex and ambiguous. Solutions must be multi-dimensional, incorporating not only technology, but the social, economic, political, and religious dynamics of a security intervention. A facilitator-led experiential training program was designed for our technical staff that leads them out of the box. The course design is based upon the theories of cognitive flexibility and situated cognition, and uses a socio-constructivist approach. Participants are led by a senior systems engineer/facilitator through a series of exercises in which they observe contextually relevant right way/wrong way videos, engage in critical thinking assessments about what they observed, and solve logic puzzles. Group interaction and problem-solving is emphasized. As in the real world, there is no one right solution. Outcomes can include a broader understanding of the threat space, creative solutions that enable survival in spite of an evolving enemy, and a deeper sense of the complex dynamics involved in any security decision. Training impact is being evaluated using a mixed qualitative/quantitative approach. Survey data combined with ethnographic interviewing techniques will determine whether participants have transferred their new understandings to the work environment.     

FlexRay in aerospace and safety-sensitive systems

The FlexRay field bus has potential for integrating existing networks and as a shared local sub-system network in the next generation of airplanes - leveraging a low-cost, dependable bus designed for the automotive domain. Herein, we present an overview of FlexRay and investigate FlexRay's dependability for use as a field bus in the aerospace domain. FlexRay supports all major requirements for integrating systems on a single network, if controllers are deployed with a guardian to achieve good hardware fault coverage. Despite including a guardian, some vulnerability may remain, such as software-induced failures and physical layer properties.