基于静态存储方式的通用链表设计

本文将链表与数组存储的概念相结合,提出一种基于静态存储方式的通用链表,应用于机载防撞系统软件设计中。结果表明,这种通用链表结构设计能有效提高代码的可重用性以及避免内存泄露等可能的安全隐患。     

基于预测控制的无人机编队内部避碰

针对无人机编队内部避碰问题,首先采用基于预测控制的方法,解决了在即将发生碰撞情况下无人机的航向调整问题;然后,建立了航路回归模型,解决了无人机避碰后,迅速回归预定航路的问题。仿真结果表明,文章给出的避碰方法能够有效解决无人机编队内部碰撞问题。     

Long term and safe relative orbit design for heterogeneous spacecraft clusters

The problem of obtaining long term relative orbit configurations for spacecraft clusters with realistic operational considerations such as safety, station keeping and inter-spacecraft distances is addressed. Two different approaches are developed for station keeping and safety objectives. In the first approach, relative orbit configurations, or relative TLEs, are found minimizing deviations from reference mean orbit which would maximize the station-keeping objective. In second one, relative configurations are found from a reference initial condition by minimizing probability of collision, hence maximizing the safety objective, between the spacecraft in the cluster which are propagated numerically through a high precision orbit propagator. For the design optimization, a derivative free algorithm is proposed. Effectiveness of the approaches is demonstrated through simulations. Using this design framework, several configurations can be found by exploring the limits of the clusters in terms of spacecraft number, distance bounds and probabilities of collision for long time intervals.     

Group force mobility model and its obstacle avoidance capability

Many mobility models attempt to provide realistic simulation to many real world scenarios. However, existing mobility models, such as RPGM [X. Hong, M. Gerla, G. Pei, C. Chiang, A group mobility model for ad hoc wireless networks, in: Proceedings of ACM/IEEE MSWiM’99, Seattle, WA, August 1999, pp. 53–60] and others, fail to address many aspects. These limitations range from mobile node (MN) collision avoidance, obstacle avoidance, and the interaction of MNs within a group. Our research, the group force mobility model (GFMM) [S.A. Williams, D. Huang, A group force mobility model, Appeared at 9th Communications and Networking Simulation Symposium, April 2006], proposes a novel idea which introduces the concept of attraction and repulsion forces to address many of these limitations. Williams and Huang [A group force mobility model, Appeared at 9th Communications and Networking Simulation Symposium, April 2006] described some of the limitations and drawbacks that many models neglect. This model effectively simulates the interaction of MNs within a group, the interaction of groups to one another, the coherency of a group, and the avoidance of collision with groups, nodes, and obstacles. This paper provides an overview of GFMM and particularly illustrates the GFMM's ability to avoid collision with obstacles, which is a vital property to posses in order to provide a realistic simulaition. We compare our model with the commonly used RPGM model and provide statistical assessments based on connectivity metrics such as link changed, link duration, and relative speed. All will be detailed and explained in this paper.     

地球静止轨道卫星撞击解体的数值模拟

分析了地球静止轨道（GE0）环内的物体现状,引入美国家航空航天局（NASA）的标准解体模型,给出了卫星撞击解体算法,编写了数值仿真软件,仿真研究了GEO卫星撞击解体形成碎片的特征及其轨道分布。结果表明：撞击会产生大量碎片,对空间环境造成长期的严重危害。研究结果对分析卫星撞击解体特性、保护空间环境有一定的参考价值。     

Three-dimensional path planning for unmanned aerial vehicle based on interfered fluid dynamical system

This paper proposes a method for planning the three-dimensional path for low-flying unmanned aerial vehicle(UAV) in complex terrain based on interfered fluid dynamical system(IFDS) and the theory of obstacle avoidance by the flowing stream. With no requirement of solutions to fluid equations under complex boundary conditions, the proposed method is suitable for situations with complex terrain and different shapes of obstacles. Firstly, by transforming the mountains, radar and anti-aircraft fire in complex terrain into cylindrical, conical, spherical, parallelepiped obstacles and their combinations, the 3D low-flying path planning problem is turned into solving streamlines for obstacle avoidance by fluid flow. Secondly, on the basis of a unified mathematical expression of typical obstacle shapes including sphere, cylinder, cone and parallelepiped, the modulation matrix for interfered fluid dynamical system is constructed and 3D streamlines around a single obstacle are obtained. Solutions to streamlines with multiple obstacles are then derived using weighted average of the velocity field. Thirdly, extra control force method and virtual obstacle method are proposed to deal with the stagnation point and the case of obstacles’ overlapping respectively. Finally, taking path length and flight height as sub-goals, genetic algorithm(GA) is used to obtain optimal 3D path under the maneuverability constraints of the UAV. Simulation results show that the environmental modeling is simple and the path is smooth and suitable for UAV. Theoretical proof is also presented to show that the proposed method has no effect on the characteristics of fluid avoiding obstacles.     

无人机自主防撞关键技术与应用分析

无人机与有人机在多机种和不同合作程度下共享空域飞行是未来的发展趋势,防撞问题成为制约无人机飞出隔离空域的关键挑战。结合现有飞机防撞体系,从无人机防撞特殊性出发分析无人机自主防撞需求,提出无人机自主防撞系统的框架,归纳分析两大主要关键技术——感知探测技术和防撞算法,以及二者的不同应用范围和主要问题,在此基础上提出无人机自主防撞管理体系架构,总结探讨无人机自主防撞关键技术的发展趋势。     

考虑避免碰撞的编队卫星自适应协同控制

基于势函数法研究具有模型不确定性的编队飞行卫星避免碰撞的自适应协同控制.势函数法的思想为设计碰撞区域势函数值较大,所设计的控制律使得系统势函数具有减小的趋势,从而实现避免碰撞的编队飞行任务.首先,在无外部参考轨迹的情况下,通过引入避免碰撞势函数,提出一种自适应协同控制器,编队卫星最终实现速度一致和避免碰撞.进一步,考虑已知外部参考轨迹的情形,基于新的势函数方法,设计新的自适应协同控制器,能够同时实现避免碰撞、速度一致、卫星跟踪参考轨迹的目的.对于所提出的两种控制方法,均通过合理地应用Lyapunov稳定性理论分析了闭环系统的稳定性.仿真结果表明了所设计控制方法的有效性.     

复杂环境下多无人机轨迹姿态协同控制

考虑多无人机在实际飞行过程中的避障需求，在建立面向控制的四旋翼无人机轨迹姿态模型基础上，为克服传统多无人机为每架无人机规划轨迹的不足，研究了基于多无人机中心点的轨迹设计策略。进一步，考虑避障约束，基于半定规划进行迭代区域扩张完成了多无人机的安全飞行区域及队形设计。在此基础上，基于干扰补偿策略为每架无人机设计了协同控制器，最终确保了多无人机在多障碍环境下的安全飞行。     

空间目标态势行为与事件本体设计与构建

针对空间目标态势威胁响应和预警研究不完善的问题，为实现空间目标行为和事件的智能推理、实时响应和主动预警，保障航天活动和空间利益，提出面向行为与事件的空间目标态势本体模型(BEO-SO2)。基于基本形式本体(BFO)，构建空间目标态势行为与事件本体模型。在统一时空框架下建立空间目标关系模型，实现空间目标行为执行和事件发生过程的动态推演。以空间目标碰撞威胁为背景，设计对象实体等级体系和碰撞威胁行为与事件要素，建立碰撞威胁推理规则，基于空间目标态势行为与事件本体进行实现、验证与展示。结果表明,空间目标态势行为与事件本体能够实现空间目标碰撞威胁的等级推理与预警，并指导进一步的空间活动，为航天任务与空间活动提供有效保障。