基于功率估计的方位数据关联算法

将功率信息与电波传播相关理论引入到测向交叉定位的数据关联问题中,提出一种基于功率估计的方位数据关联算法。推导了阵列协方差矩阵中信号功率与阵列流型之间的关系,利用空间协方差逆矩阵高阶幂逼近噪声子空间的方法,在已知阵列流型的基础上准确获取各目标的功率参数,避免了幅值特征类关联算法易受噪声与信号波形影响的问题;根据功率和传播路径的衰减关系,构造方位组合与功率信息的关联置信度函数,挑选出正确的关联组合。仿真结果表明了算法的有效性和优越性。     

基于UKF的机载无源定位算法

提出了一种基于UKF(Unscented Kalman Filter)的机载无源定位算法,并结合应用背景,对系统模型以及通常的UKF算法作了相应的改进。该算法对量测模型非线性问题采用UKF予以解决,克服了EKF(Extended Kalman Filter)中引入的较大线性化误差对性能的影响。与基于EKF的定位算法相比,本文提出的算法滤波性能更好,对初始估计误差不敏感,并且算法不用计算雅可比或黑赛矩阵,更容易实现。仿真结果验证了提出算法的优越性。     

浅谈经济责任审计的重要性及着力点

经济责任审计在我国审计机关中普遍运用,是监督和提拔领导干部的一项措施,属我国审计系统的一大特色,由于开展经济责任审计工作时间短,无法借鉴和吸收过去的经验,在工作中需要进行探索。     

桨扇发动机性能仿真建模与初步分析

为了获得更高的推进效率和更低的耗油率及CO2排放,本文采用变定压比热的方法建立了桨扇发动机的性能仿真模型．计算和分析了设计点飞行高度、飞行马赫数、动力涡轮膨胀比和桨扇效率变化对发动机设计性能的影响。     

飞机大部件对接中的位姿计算方法

在飞机的大部件对接中,为了达到较高的对接精度,需要准确地分析大部件的位姿,因此大部件位姿计算方法是首先需要解决的问题.本文简要介绍了奇异值分解法、三点法、最小二乘法计算位姿,并以三点法计算的结果作为最小二乘法的初值.比较了3种方法在点无误差和有误差时的部件拟合误差,分析了测量点的个数对部件拟合误差的影响,讨论了误差对部...     

日地L1点探测任务设计与结果分析

日地L1点是太阳观测任务的理想观测点,对于中国后续太阳观测任务具有重要意义,因此在嫦娥五号的拓展任务阶段设计并实施了中国首次日地L1点探测任务,通过在轨飞行验证了日地L1点转移轨道、环绕轨道设计的正确性,对日地L1点的测控链路环境、太阳辐照环境、三体动力学环境、空间辐射环境等飞行环境进行了探测和验证。轨道飞行和各项环境探测的结果与设计模型的预示结果之间比对一致性较好,通过在轨飞行数据验证了设计模型的正确性。各项试验获得了预期的技术成果,进一步丰富了嫦娥五号任务的成果产出,对中国后续深空探测任务和产品的设计具有重要借鉴意义。     

拦截机动目标的三维协同中末一体化制导律

针对空中来袭目标机动能力较大、单枚导弹无法有效拦截的问题,提出了拦截机动目标的三维协同中-末一体化制导律。根据目标和拦截弹的最大机动能力计算所需的最少拦截弹数量,解算出末制导的初始阵位约束,根据阵位约束,设计基于改进比例导引的协同末制导律。基于中制导开始时目标速度,迭代求解出预测命中点以及中末交班约束,提出基于预测命中点的时间角度协同中制导律。在三维场景下对协同中末制导律进行仿真验证,结果表明：该方法能够有效满足中末交班的阵位要求以及末段拦截精度,实现对机动目标的有效拦截。     

A new stochastic model considering satellite clock interpolation errors in precise point positioning

Precise clock products are typically interpolated based on the sampling interval of the observational data when they are used for in precise point positioning. However, due to the occurrence of white noise in atomic clocks, a residual component of such noise will inevitable reside within the observations when clock errors are interpolated, and such noise will affect the resolution of the positioning results. In this paper, which is based on a twenty-one-week analysis of the atomic clock noise characteristics of numerous satellites, a new stochastic observation model that considers satellite clock interpolation errors is proposed. First, the systematic error of each satellite in the IGR clock product was extracted using a wavelet de-noising method to obtain the empirical characteristics of atomic clock noise within each clock product. Then, based on those empirical characteristics, a stochastic observation model was structured that considered the satellite clock interpolation errors. Subsequently, the IGR and IGS clock products at different time intervals were used for experimental validation. A verification using 179 stations worldwide from the IGS showed that, compared with the conventional model, the convergence times using the stochastic model proposed in this study were respectively shortened by 4.8% and 4.0% when the IGR and IGS 300-s-interval clock products were used and by 19.1% and 19.4% when the 900-s-interval clock products were used. Furthermore, the disturbances during the initial phase of the calculation were also effectively improved.     

Satellite availability and positioning performance of uncombined precise point positioning using BeiDou-2 and BeiDou-3 multi-frequency signals

To realize the smooth transition from regional BeiDou Navigation Satellite System (BDS-2) to the global one (BDS-3), the integration of BDS-2 and BDS-3 is important for providing continuous, stable and reliable positioning, navigation and timing (PNT) services for global users. This work used 154 globally distributed multi-GNSS (Global Navigation Satellite System) experiment stations spanning 30 days to analyze the satellite availability and positioning performance of uncombined precise point positioning (UC-PPP) under current BDS-2 and BDS-3 constellations. We focused on three issues: the influence of BDS-3 receiver tracking abilities, the positioning performance among different areas, and the benefit of multi-frequency observations. The results show that the elliptical zone caused by poor BDS-2 satellite visibility is disappeared when the evenly distributed BDS-3 medium earth orbit satellites are introduced. When BDS-3 are integrated with BDS-2, the area with the Position Dilution of Precision (PDOP) less than 2 can be expanded to 75° S-75° N and 30° E-150° W. The positioning performance of BDS-3 and BDS-2/BDS-3 UC-PPP are seriously affected by the receiver tracking abilities of BDS-3 signals. When the maximum pseudo-random noise sequences (PRNs) of BDS-3 satellites tracked by stations are within 30 or 37, the positioning accuracy of static UC-PPP can be improved by 22.94% or 8.27% due to the integration of BDS-2 and BDS-3. Besides, the most improvement of BDS-2 and BDS-3 integration is achieved in Asia-Pacific regions, especially for the kinematic UC-PPP or the poor receiver tracking abilities of BDS-3. Similar to the multi-frequency BDS-2 UC-PPP, the benefit of multi-frequency signals for BDS-3 or BDS-2/BDS-3 UC-PPP is also non-vital. The three-dimensional positioning accuracy of BDS-2/BDS-3 multi-frequency UC-PPP in static mode and kinematic mode are 2.24 cm and 5.39 cm, while the corresponding convergence time are 49.62 min and 73.80 min, respectively. Compared with BDS-2, both the positioning accuracy and the convergence time of BDS-2/BDS-3 joint UC-PPP are improved by approximately over 50%, which indicates that BDS-3 has a great potential to provide high-quality PNT services as other global navigation satellite systems.     

CE5T拓展试验轨道精度分析

针对嫦娥5T服务舱(CE5T)拓展试验中的绕地大椭圆轨道，分析了轨道动力学演化趋势，通过测轨数据类型组合策略分析了统一S频段测量(USB)和甚长基线干涉测量(VLBI)在定轨中的贡献，得到了百米级的精密定轨精度；针对地月第二平动点(L2)绕飞轨道，分析了地心和月心积分的轨道动力学差异，制定了精密定轨的参数求解策略，得到了百米级的精密定轨精度；针对月球交会对接轨道的特点，选取三种不同的重力场模型定轨，比较了三者在轨道预报和数据拟合的差异，并与嫦娥3号(CE3)环月轨道的定轨精度进行比对，验证了不同重力场的适用范围，从计算精度和效率两方面制定了优化的定轨策略。