不确定环境下多无人机协同搜索算法研究

不确定环境下多无人机协同搜索是多无人机协同控制的一个重要研究内容。多架无人机同时对一个不确定区域进行搜索,目的在于获取搜索区域的信息,降低环境的不确定度,并尽可能发现隐藏在环境中的目标。针对这一问题,提出一种基于协同进化算法的多无人机协同区域搜索算法。首先,建立搜索概率图来描述搜索环境的不确定性,并使用贝叶斯准则更新搜索概率图,然后,使用协同进化算法,在线生成多UAV协同搜索的路径。仿真结果验证了算法的有效性。     

具有时间约束的多无人机协同航迹控制研究

以多架无人机为研究对象,控制多无人机对目标实施协同攻击,并保证多无人机以指定时间到达目标或同时到达目标,最大限度地提高作战效能,是一个极具理论价值和军事应用的问题。确定了多无人机多级分布式协调策略,明确了协同变量与协同函数的概念和相应的数学表达式,以及领机与僚机间的通讯关系,最后利用基于协同变量和协同函数的多级分布式控制策略,有效解决了具有时间约束的多无人机协同航迹控制问题,设计仿真算法,并通过具体的仿真分析,验证了算法的有效性。     

快速一致性控制算法下的多UAV分布式协同控制

多无人机系统中,系统状态的一致性是实现多无人机分布式协同控制的基础, 一致性控制算法是多无人机系统实现状态一致的有效方法。通信约束条件下, 无人机平台基于局部交互信息, 通过一致性控制算法, 控制系统状态演化一致。为解决改变通信拓扑结构和多跳路由通信的不可操作性问题, 引入状态差值和预测状态,设计新的快速一致性控制算法。给出新算法收敛性和快速性的相关定理,并进行了严格的数学证明, 在分布式协同控制结构下实现多无人机快速任务协同。理论分析和仿真实验验证了算法的可行性和有效性。     

基于模糊动态博弈的多无人机空战策略研究

不确定环境下多无人机空战决策问题已成为无人机作战系统的一个重要研究课题。首先通过分析无人机空战态势信息的不确定性, 建立模糊信息下的多无人机动态博弈的作战优势函数; 将动态扩展式博弈转化成静态策略式博弈, 构建基于模糊信息的双方博弈的支付矩阵。将模糊结构元方法和粒子群算法相结合, 给出模糊信息下动态博弈的混合战略的纳什均衡求解方法。最后通过仿真实验验证了该方法的可行性和有效性。     

通信约束下的多无人机协同航路规划

针对存在通信约束的多无人机协同航路规划问题,在考虑多无人机同时到达目标点和避免相互碰撞的条件下,使用改进的A*算法规划出多无人机飞行的原始航路;通过不断计算和比较无人机间的距离来限制无人机的飞行,使无人机之间的距离始终保持在允许通信距离范围内;通过减小最大允许通信距离和增大最小安全距离来消除通信时间延迟对协同航路规划的影响,从而建立了存在通信距离限制和通信时间延迟条件下的多无人机协同航路规划算法。仿真结果验证了该算法的有效性。     

多无人机任务集结合作博弈优化自组织协同控制

基于一致性理论的多无人机系统自组织协同作战是未来无人机应对突发任务的重要方式,任务集结是协同作战的首要行动和自组织协同控制的重要内容。为优化集结行动中系统任务状态协调过程能量最优性、协同控制动态响应性和集结行动时效性3个性能指标,采用基于快速一致性控制算法的协同控制结构,在合作博弈框架下给出多无人机系统自组织协同与优化控制问题描述,建立了优化控制输入的Pareto解集,采用Nash讨价还价方法给出基本合作博弈优化一致性控制算法。在基本算法中引入过去状态差值,并以优化目标构建适应度函数,采用遗传算法优化代价函数的加权矩阵,得到改进合作博弈优化一致性控制算法。理论分析和仿真实验验证了方法的可行性和有效性。     

多无人机时序到达协同控制方法

时序到达控制是无人机协同控制方向新近产生的典型问题, 对异构无人机协同执行搜索、跟踪、打击、评估等任务具有重要潜在价值。引入计算几何学中的Laguerre图用于航路规划, 当两个威胁区域不相交时, Laguerre图生成的初始航路必然从它们之间的空隙内穿过。针对时序控制精度不高的问题, 采用周期性的速度修正方法, 有效提高了到达时间精度。仿真结果表明, 所提出的时序到达控制方法能够有效实现多无人机时序到达, 并且具有较高的鲁棒性和控制精度。     

基于改进一致性算法的无人机集群饱和攻击

针对无人机一般难以单独打击空防严密的高价值目标问题,采用低成本无人机集群饱和攻击技术,提出协同控制下的三阶段一致性饱和攻击策略,根据不同阶段的任务特点,设计对应的改进一致性算法,并在满足饱和攻击任务多条件协同的基础上,加入Dubins曲线增加飞行轨迹约束,平滑无人机飞行航迹,缩短航程.此外,在高精度队形保持的任务环境下,设计改进的二阶一致性控制器,确保飞行精度,加快收敛速度.最后,将各阶段改进算法的实际效果与传统算法进行对比,在验证改进算法有效性的同时,检验算法延展性.仿真结果表明,该算法可应用于大规模无人机集群并具有良好的效果,为饱和攻击战略决策部署与战术实现提供了依据和参考.     

无人机空对地多目标攻击的满意分配决策技术

任务分配是多无人机协同控制的重要内容。建立了多机协同多目标攻击排序的数学模型、并提出基于满意决策的攻击分配算法, 根据参与目标分配的每架无人机完成任务的预估效益和预估代价提出满意集, 建立拒绝函数和选择函数从而获得满意分配结果, 最后在Matlab环境下进行了数值仿真。仿真结果表明, 所研究的基于满意决策的多无人机协同攻击的目标分配方法是有效的。     

面向不确定性环境的多无人机协同防碰撞

随着无人机碰撞事故的增加, 防碰撞已成为多无人机共空域飞行亟待解决的问题。首先, 进行多无人机协同防碰撞体系结构设计, 然后, 提出一种新的模型预测控制方法: 应用扩展卡尔曼滤波预测不确定性环境空间的障碍物和目标轨迹, 无人机通过机间通信实现环境信息共享, 基于模型预测控制方法进行多无人机协同防碰撞制导决策。仿真结果表明所提方法的有效性, 同时协同机制的效果明显。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Call for Papers

正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its