一种改进的GNSS整周模糊度解相关算法

GNSS整周模糊度解相关算法的性能直接影响到整周模糊度的搜索速度和解算成功率。为了在不降低GNSS整周模糊度解相关算法解相关程度的前提下,提高解相关算法的计算效率,在深入分析典型解相关方法优缺点的基础上,提出基于对角线预排算的解相关算法。该方法源于对直接对角线排序解相关算法的预排序思想,采用矩阵分解后对角线元素中最小值并将其转换到对应对角线位置的方式,用更少的迭代次数达到比直接对角线排序更好的解相关效果。将新算法与其他算法进行仿真比较得出,其性能优于直接对角线排序算法,解相关功能与联合解相关算法等效,且计算效率略占优势。     

Ambiguity resolution performance with GPS and BeiDou for LEO formation flying

The evolving BeiDou Navigation Satellite System constellation brings new opportunities for high-precision applications. In this contribution the focus will be on one such application, namely precise and instantaneous relative navigation of a formation of LEO satellites. The aim is to assess the ambiguity resolution performance with the future GPS and BeiDou constellations depending on system choice (GPS, BeiDou, or GPS+BeiDou), single- or dual-frequency observations, receiver noise, and uncertainties in ionosphere modelling. In addition, for the GPS+BeiDou constellation it will be shown how the growing BeiDou constellation in the years to come can already bring an important performance improvement compared to the GPS-only case. The performance will be assessed based on the percentage of time that the required precision can be obtained with a partial ambiguity resolution strategy.     

幅相联合技术下导引装置测向性能仿真分析

在介绍了国外反辐射无人机导引装置幅相联合测向技术的基础上,分别就干涉仪、比幅法测向条件下导引装置测向性能进行了仿真分析。结果表明,导引装置采用干涉仪测向时精度较比幅法测向的精度高,但存在测向模糊;比幅法测向精度不高,但可以解除干涉仪测向产生的模糊。最后,分析给出了测角范围与目标雷达频率、测角误差与测量到达角的关系,得出了导引装置采用幅相联合测向的优势。     

多基线组合求解深空航天器载波相位模糊方法

针对深空航天器高精度定位需求,提出多基线组合求解载波相位模糊方法,获得比群时延更精确的相时延,极大地提高无线电干涉测量精度。首先建立多基线组合求解载波相位模糊的数学模型,推导该方法对长短基线组合的约束条件。然后利用美国甚长基线阵(VLBA)对本文方法进行仿真校验,结果表明航天器定位精度可以达到纳弧度量级。最后结合我国已有干涉测量网,分析在我国未来深空探测任务中采用多基线组合测量载波相时延的可行性,给出满足方法约束的站址选择建议,可为我国深空导航无线电干涉测量技术的发展和深空测控网的完善提供参考。     

Multipath mitigation method based on Gaussian mixture model in RF relative measurement

Radio Frequency (RF) technology represents a high-precision relative navigation solution that has significant potential for application to earth-orbiting satellites. In precision applications, multipath errors dominate the total error because observables, which are used to estimate carrier-phase integer ambiguity, are not always subject to a Gaussian distribution when dual-frequency ambiguity estimation methods are used in the presence of multipath. As it has been shown that ranging observables obey a Gaussian mixture distribution, this study proposes improvements to the accuracy of estimation based on multipath mitigation founded on the Gaussian mixture model. To this end, such a model is created for integer ambiguity resolution in the presence of multipath, using which the theoretical error in dual-frequency ambiguity estimation is derived. Expectation Maximization (EM), which aids dual-frequency ambiguity estimation, is subsequently proposed to reduce the effect of multipath errors. Finally, two experimental scenarios are implemented to test the performance of the proposed method. The results show that EM-aided dual-frequency ambiguity estimation reduces the range error to approximately 20% in comparison with simple dual-frequency ambiguity estimation. Therefore the proposed technique is effective for multipath mitigation in RF relative measurement.     

紧凑式换热器全高度传热特性研究

发展了可工程应用的紧凑式换热器传热模型,从三个层次对换热器进行讨论。针对空气循环制冷系统中的换热器,分析了二轮低压除水和二轮高压除水空气循环制冷系统中换热器的传热特性,计算结果与试验数据符合良好。该方法利用较少的实验数据即可得到全高度特性,不仅满足工程计算的要求,而且为评估换热器性能提供了理论依据。     

基于高低周复合疲劳试验技术的叶片失效故障复现

针对某涵道尾桨风扇叶片在风洞试验中发生的断裂故障,基于叶片破坏模式和载荷形式,初步分析为离心载荷/低循环疲劳(LCF)和气动载荷/高循环疲劳(HCF)耦合作用导致的疲劳破坏。基于此,通过正交载荷解耦和协调加载控制等关键技术开展联合载荷作用下的叶片复合疲劳(CCF)试验技术研究和试验考核验证。试验结果表明,离心载荷控制精度优于±1%,气动载荷控制精度优于±8‰。试验应变响应频率与试验加载频率一致性较好,满足试验加载和控制的同步性要求。最终,通过对叶片故障复现验证失效原因分析的正确性,为叶片结构优化设计、寿命评估和复合疲劳试验奠定技术基础。     

低成本GNSS终端中北斗三号多频观测的分析及应用CSCD

低成本消费级GNSS芯片相较于传统测绘级接收机在体积、功耗等方面具有突出优势,在未来无人驾驶、物联网等新兴应用领域具有极大潜力。然而当前低成本GNSS芯片的观测量存在非常严重的噪声和误差,为了改善观测质量,低成本芯片正逐渐从单频向多频过渡。首先调研了目前低成本GNSS接收机对多频信号的支持情况,然后介绍了北斗三号多频观测在电离层延迟和整周模糊度估计等方面的应用。通过对真实数据的采集和分析,针对当前原始观测量存在的诸多问题,提出了具体的预处理方案,并在此基础上开展了信号强度、电离层和模糊度实验。实验结果表明,基于华为Mate 40手机的低成本GNSS方案的北斗三频电离层延迟估计误差的均值为-2.97m,三频整周模糊度估计的成功率达93.8%,相较于单频整周模糊度估计的3.11%成功率有显著提升。     

空间用太阳能热动力发电装置热力参数优化计算

介绍了空间用太阳能热动力发电装置的结构、特点及其应用前景，并以１０ｋＷ闭式布雷顿循环太阳能热动力发电装置为对象，重点对以系统总质量和总当量阻力面积最小为目标 参数进行优化计算。计算结果为此类发电装置提供了选取涡轮压比，压气机入口温度等参数的方法。