基于转子磁场定向矢量控制的感应电机改进磁链观测方法

传统的磁链观测方法通常采用低通滤波器取代电压模型的纯积分环节,由于其易于实现,较多应用于工程实践。但其忽略了直流偏置,并随之引入了相位偏差以及幅值上的误差。针对这一现象,提出改进磁链观测的方法,采用高通与低通滤波环节串联的方式,在此基础上推导出相对应的相位及幅值的偏差补偿策略,解决了直流偏置问题。最后通过仿真和试验对所述方法进行有效性和准确性的验证。     

Tightly combined GPS/Galileo RTK for short and long baselines: Model and performance analysis

To ensure the compatibility and interoperability with modernized GPS, Galileo satellites are capable of broadcasting navigation signals on carrier phase frequencies that overlap with GPS, i.e., GPS/Galileo L1-E1/L5-E5a. Moreover, the GPS/Galileo L2-E5b signals have different frequencies with wavelength differences smaller than 4.2?mm. Such overlapping and narrowly spaced signals between GPS and Galileo bring the opportunity to use the tightly combined double-differenced (DD) model for precise real-time kinematic (RTK) positioning, resulting in improved performance of ambiguity resolution and positioning with respect to the classical standard or loosely combined DD model. In this paper, we focus on the model and performance assessment of tightly combined GPS/Galileo L1-E1/L2-E5b/L5-E5a RTK for short and long baselines. We first investigate the tightly combined GPS/Galileo DD observational model for both short and long baselines with simultaneously considering the GPS/Galileo overlapping and non-overlapping frequencies. Particularly, we introduce a reparameterization approach to solve the rank deficiency that caused by the correlation between the DISB parameters and the DD ionospheric parameters for both overlapping and non-overlapping frequencies. Then we present performance assessment for the tightly combined GPS/Galileo RTK model with real-time estimation of the differential inter-system bias (DISB) parameters for short and long baselines in terms of ratio value, ambiguity dilution of precision (ADOP), ambiguity conditional number, decorrelation number, search count, empirical success rate, time-to-first-fix (TTFF), and positioning accuracy. Results from both static and kinematic experiments demonstrated that compared to the loosely combined model, the tightly combined model can deliver improved performance of ambiguity resolution and precise positioning with different satellite visibility. For the car-driven short baseline experiment with 10° elevation cut-off angle, the tightly combined model can not only significantly increase the ratio value by approximately 27.5% (from 16.0 to 20.4), but also reduce the ambiguity ADOP, the conditional number, and the search count in LAMBDA by approximately 22.2% (from 0.027 to 0.021 cycles), 14.9% (from 199.2 to 169.6), and 25.4% (from 150.1 to 112.0), respectively. Comparable decorrelation number, empirical success rate, and positioning accuracy are also obtained. For the car-driven long baseline experiment, it is also observed that the ambiguity resolution performance in terms of the ratio value, the decorrelation number, the condition number, and the search count are significantly improved by approximately 18.5% (from 2.7 to 3.2), 22.0% (from 0.186 to 0.227), 55.9% (from 937.6 to 413.7), and 10.3% (from 43.8 to 39.3), respectively. Moreover, comparable ADOP, empirical success rate, and positioning accuracy are obtained as well. Additionally, the TTFF can be reduced (from 54.1 to 51.8 epochs with 10° elevation cut-off angle) as well from the results of static experiments.     

激光捷联惯导系统温度误差补偿研究

针对激光陀螺惯性导航系统中惯性器件零偏随温度变化的情况,在-30℃～+50℃温度范围内,通过大量的温度实验,建立了零偏与温度变化的多项式模型,并用该模型对实验数据进行了补偿,扣除地速和重力加速度的分量,惯性器件输出几乎为零。最后在不同温度下进行了初始对准实验,实验结果表明：经过温度补偿后,在-30℃～+50℃ 温度内,俯仰角误差平均在0.0019° 以内,横滚角误差平均在0.0038°以内,航向角误差平均在0.014° 以内,接近了常温下的初始对准精度,满足了系统的指标要求。     

偏视场光学系统视场优化设计方法

文章以同轴三反偏视场光学系统型式为例,利用ZEMAX宏建立优化函数,实现了将光学系统视场中心位置、视场大小作为变量进行优化设计,从而实现了综合考虑光学系统视场、像质及相关尺寸要求的整体优化.     

基于陀螺和星敏感器的卫星姿态确定算法

主要研究了基于陀螺和星敏感器配置的卫星姿态确定算法.为保证卫星姿态确定的高精度,利用星敏感器提供的姿态四元数结合扩展卡尔曼滤波,对陀螺漂移进行实时补偿.并利用在轨数据,通过matlab数学仿真,验证了高精度滤波算法的有效性.所设计的滤波器能准确估计陀螺漂移,估计误差优于5.56×10-5(°)/s;姿态估计误差优于0....     

Multi-GNSS contributions to differential code biases determination and regional ionospheric modeling in China

Due to the limited number and uneven distribution globally of Beidou Satellite System (BDS) stations, the contributions of BDS to global ionosphere modeling is still not significant. In order to give a more realistic evaluation of the ability for BDS in ionosphere monitoring and multi-GNSS contributions to the performance of Differential Code Biases (DCBs) determination and ionosphere modeling, we select 22 stations from Crustal Movement Observation Network of China (CMONOC) to assess the result of regional ionospheric model and DCBs estimates over China where the visible satellites and monitoring stations for BDS are comparable to those of GPS/GLONASS. Note that all the 22 stations can track the dual- and triple-frequency GPS, GLONASS, and BDS observations. In this study, seven solutions, i.e., GPS-only (G), GLONASS-only (R), BDS-only (C), GPS + BDS (GC), GPS + GLONASS (GR), GLONASS + BDS (RC), GPS + GLONASS + BDS (GRC), are used to test the regional ionosphere modeling over the experimental area. Moreover, the performances of them using single-frequency precise point positioning (SF-PPP) method are presented. The experimental results indicate that BDS has the same ionospheric monitoring capability as GPS and GLONASS. Meanwhile, multi-GNSS observations can significantly improve the accuracy of the regional ionospheric models compared with that of GPS-only or GLONASS-only or BDS-only, especially over the edge of the tested region which the accuracy of the model is improved by reducing the RMS of the maximum differences from 5–15 to 2–3 TECu. For satellite DCBs estimates of different systems, the accuracy of them can be improved significantly after combining different system observations, which is improved by reducing the STD of GPS satellite DCB from 0.243 to 0.213, 0.172, and 0.165 ns after adding R, C, and RC observations respectively, with an increment of about 12.3%, 29.4%, and 32.2%. The STD of GLONASS satellite DCB improved from 0.353 to 0.304, 0.271, and 0.243 ns after adding G, C, and GC observations, respectively. The STD of BDS satellite DCB reduced from 0.265 to 0.237, 0.237 and 0.229 ns with the addition of G, R and GR systems respectively, and increased by 10.6%, 10.4%, and 13.6%. From the experimental positioning result, it can be seen that the regional ionospheric models with multi-GNSS observations are better than that with a single satellite system model.     

恒速偏频/机抖激光陀螺惯导系统半实物仿真

提出一种恒速偏频/机抖激光陀螺惯导系统方案。用一个不随偏频机构旋转 的机抖激光陀螺,改善恒速偏频激光陀螺惯导系统在偏频旋转轴方向的载体角速度测量 精度。给出了偏频旋转轴方向等效陀螺采样值的计算方法和关键结构参数标校方法;分 析了纯惯导的系统误差特性,在初始对准卡尔曼滤波模型中,增加了偏频旋转轴方向的 陀螺漂移以及耦合偏差造成的等效北向陀螺漂移作为误差状态。恒速偏频/机抖激光陀 螺惯导系统的半实物仿真实验结果表明：在静基座条件下,初始对准10min 后,方位角收 敛到10″ （1σ） 内; 初始对准20min 后, 纯惯导4h, 北向和东向位置误差最大值均小于 200m。     

基于最大似然估计的TDOA/FDOA无源定位偏差补偿算法

在到达时差/到达频差(TDOA/FDOA)无源定位系统中,定位问题的非线性使得定位的结果存在偏差,特别是在噪声较大或者接收站布站不合理的情况下,定位的偏差尤其显著。针对这一问题,提出了一种基于最大似然估计的偏差补偿算法。该方法分为3步:首先,利用最大似然估计器对目标的位置和速度进行求解;其次,通过利用目标定位的估计值和含噪的测量值,对目标的位置和速度偏差值进行理论分析和推导;最后,将最大似然估计解减去理论偏差值,得到经过偏差补偿的新的目标定位解。理论分析和实验仿真证明,在一定噪声的情况下,所推导的目标位置和速度的理论偏差值与实际偏差值相符,并且经过偏差补偿后的定位算法,在保持目标定位的均方根误差(RMSE)与原最大似然算法一致的情况下,目标的位置和速度偏差值远远小于原最大似然算法的偏差值,目标定位精度得到了有效的提高。     

如何避免态度测量偏差

从心理学的角度，阐述态度测量过程中影响被调查者作出正确反应的各种因素，并对消除这些因素的影响进行研究，改为进测量设计、提高测量结果的准确性提供依据。     

自适应两级UKF算法及其在时变偏差估计中的应用

针对存在时变偏差的非线性系统状态估计问题，提出了一种新型的自适应两级UKF算法（ATUKF，adaptive two—stage unscented Kalman filter）．该算法利用衰减因子补偿模型的不确定性，对状态和偏差实施分离估计，并利用估计偏差对状态进行更新．将该算法用于存在随机时变偏差的近地卫星自主导航系统的状态估计问题中，仿真结果验证了其有效性，并利用可观测性分析方法对导航系统的可观测性进行了分析．