基于覆盖圆的太阳同步回归轨道卫星目标轨迹调整方法

遥感卫星星座在环境监测、地理测绘等领域运用中,需要考虑目标轨迹分布的优化问题.轨迹分布与星座的重访能力和进出站间隔保持等应用需求密切相关.目前对星下点轨迹分布的优化和调整还缺乏准确实用的方法,存在卫星数目增多带来的计算量增加问题和对多种需求综合考虑不够的问题.为了克服现有技术的不足,解决太阳同步回归轨道遥感卫星星座的目...     

基于BABFA的XNOR/OR电路面积优化

基于XNOR/OR的固定极性Reed-Muller（FPRM）电路面积优化是当前集成电路设计领域的研究热点之一。由于基于XNOR/OR的FPRM电路面积优化属于组合优化问题，提出了一种二进制自适应细菌觅食算法（BFA）。该算法在复制操作中加入概率模式，提高种群多样性，采用模糊规则对复制概率和迁移概率进行修正，提高算法的收敛速度。使细菌在邻域内进行搜索，替代细菌群体感应机制中的斥力操作，细菌无需感应其他个体位置对其的影响。提出一种基于XNOR/OR的FPRM电路面积优化方法，利用提出的二进制自适应细菌觅食算法搜索电路面积最小的FPRM电路。基于MCNC Benchmark电路的实验结果表明:面积最大优化率为18%，时间最大节省率为46%。      

基于FFT的国标数字电视系统帧头模式捕获方法

在分析国标数字电视传输系统帧头信号特征的基础上,提出一种基于FFT(Fast Fourier Transforms)的帧头PN (Pseudorandom Noise)模式捕获方法.该方法基于每种帧头的特点及硬件实现的难易程度,选取3种特定的本地基础序列在各自通道中与接收到的信号帧进行基于FFT的相关运算,并通过比较每通道的相关峰值与相应的判决门限来判定本通道是否捕获成功,从而选择捕获成功的通道所对应的帧头模式作为最终识别出的帧头模式.与应用时域相关运算的捕获识别方法相比,提出的方法能够降低计算复杂度,提高捕获速度.仿真结果显示,该方法能够捕获识别出各种帧头PN模式,验证了方法的可行性.     

基于搜索意图交互的无人机集群协同搜索算法

针对无先验信息条件下无人机集群的协同搜索问题,提出一种以覆盖率为引导,以机间安全距离、通信距离、偏航角调整及搜索边界等为约束的无人机集群协同搜索算法。通过建立环境地图矩阵对任务区域进行描述,进一步定义环境地图更新算子实现搜索过程中环境地图的快速更新。设计了集群协同搜索任务的回报函数,采用粒子群算法进行求解,得到每架无人机在已知环境地图下的最优决策,即决策意图。每架无人机在获取其他成员决策意图的基础上重新进行决策,实现协同决策。针对不同规模集群提出了集中式和分布式2种协同决策方案。仿真结果表明,所提算法能够对存在未知威胁的不规则任务区域进行有效覆盖搜索,覆盖率远高于不进行协同决策的个体决策方法。      

Mitigation of receiver biases in ionospheric observables from PPP with ambiguity resolution

PPP (Precise Point Positioning) is a GNSS (Global Navigation Satellite Systems) positioning method that requires SSR (State Space Representation) corrections in order to provide solutions with an accuracy of centimetric level. The so-called RT-PPP (Real-time PPP) is possible thanks to real-time precise SSR products, for orbits and clocks, provided by IGS (International GNSS Service) and its associate analysis centers such as CNES (Centre National d'Etudes Spatiales). CNES SSR products also enable RT-PPP with integer ambiguity resolution. In GNSS related literature, PPP with ambiguity resolution (PPP-AR) in real-time is often referred as PPP-RTK (PPP – Real Time Kinematic). PPP-WIZARD (PPP - With Integer and Zero-difference Ambiguity Resolution Demonstrator) is a software that is made available by CNES. This software is capable of performing PPP-RTK. It estimates slant ionospheric delays and other GNSS positioning parameters. Since ionospheric effects are spatially correlated by GNSS data from active networks, it is possible to model and provide ionospheric delays for any position in the network coverage area. The prior knowledge ionospheric delays can reduce positioning convergence for PPP-RTK users. Real-time ionospheric models could benefit from highly precise ionospheric delays estimated in PPP-AR. In this study, we demonstrate that ionospheric delays obtained throughout PPP-AR estimation are actu ally ionospheric observables. Ionospheric observables are biased by an order of few meters caused by the receiver hardware biases. These biases prohibit the use of PPP-WIZARD ionospheric delays to produce ionospheric models. Receiver biases correction is essential to provide ionospheric delays while using PPP-AR based ionospheric observables. In this contribution, a method was implemented to estimate and mitigate receiver hardware biases influence on slant ionospheric observables from PPP-AR. In order to assess the proposed approach, PPP-AR data from 12 GNSS stations were processed over a two-month period (March and April 2018). A comparison between IGS ionospheric products and PPP-AR based ionospheric observables corrected for receiver biases, resulted in a mean of differences of −39 cm and 51 cm standard deviation. The results are consistent with the accuracy of the IGS ionospheric products, 2–8 TECU, considering that 1 TECU is ~16 cm in L1. In another analysis, a comparison of ionospheric delays from 5 pairs of short baselines GNSS stations found an agreement of 0.001 m in mean differences with 22 cm standard deviation after receiver biases were corrected. Therefore, the proposed solution is promising and could produce high quality (1–2 TECU) slant ionospheric delays. This product can be used in a large variety of modeling approaches, since ionospheric delays after correction are unbiased. These results indicate that the proposed strategy is promising, and could benefit applications that require accuracy of 1–2 TECU (~16–32 cm in L1).     

不规则区域成像覆盖星座构型优化设计

近年来卫星对地观测需要呈现逐年上升趋势.从单个目标点的对地观测卫星星座构型设计方法入手,推广为设计满足不规则大范围成像区域重访时间需求的卫星星座.以卫星数目最少及满足重访时间要求为优化目标,采用改进的模拟退火算法,结合改进的等面积网格点覆盖法,提出了一种针对不规则区域成像全覆盖的卫星星座构型优化设计方法.分析了光照因素对重访时间、所需卫星数目以及星座构型的影响,并通过仿真分析验证了算法的可行性.      

时间触发CAN总线实时性分析及评估方法

针对目前时间触发控制器局域网(CAN,Controller Area Network)总线缺乏统一评估方法的现状,提出了一套系统建立与评估方案.采用均匀装载算法建立系统调度矩阵,实现了周期信息的实时传输.结合CAN总线的传输机制与时间触发的特点,改进了时间触发系统中非周期信息最坏延迟的计算方法.在此基础上针对不满足系统实时性要求的信息提出了计算其失效概率的方法,建立了时间触发CAN总线系统的设计与评估流程,提出了系统参数调整方案.评估方案能够提高设计效率,利用信息失效概率以及最坏延迟对系统实时性进行分析,使分析结果更加精确、实用.     

基于自适应学习策略的改进鸽群优化算法

鸽群优化（PIO）算法已广泛用于无人机编队和控制参数优化等领域，但标准PIO算法容易陷入局部最优。提出了一种基于自适应学习策略的改进鸽群优化（ALPIO）算法。该算法引入了基于容差的搜索方向调整策略、基于自学习的候选者生成策略以及基于竞争学习的预测策略，通过增强种群的多样性，可提高算法全局最优概率，其已在8个基准函数上进行测试。仿真试验结果表明:所提算法在多峰函数优化问题中的收敛精度和收敛速度有了显著提升，并且能够更有效避免陷入局部最优解。      

数字电视大范围载波频偏快速捕获算法

根据中国数字电视地面传输标准帧结构特点,提出了一种大范围频率偏差捕获方法.该算法利用PN(Pseudo Noise)序列移位相加后仍为PN序列这一特征,通过帧头PN序列与本地PN序列的差分互相关得到待求的频偏值,然后利用BLUE(Best Linear Unbiased Estimator)方法,在不损失频偏精度的前提下扩大频偏估计范围.该算法能在帧同步前快速捕获大范围频偏,为可靠实现帧同步以及频偏跟踪过程提供了必要条件.仿真结果表明,相对于传统的差分互相关算法,该算法能在一个帧头时间内快速锁定频偏,频偏估计范围扩大了H倍且频偏精度不变.