移动卫星通信低成本多传感器融合姿态估计方法

针对低成本移动卫星通信终端的天线姿态估计问题,提出了一种基于自适应滤波的低成本多传感器融合姿态估计方法.该方法通过融合微机械陀螺信息和加速度计重力场测量信息来得到精确的水平姿态角估计;通过融合单基线GPS高精度的航向角测量与陀螺信息保证航向角精度.在单基线GPS失锁的情况下,利用机动加速度观测对融合滤波器进行自适应控制,与标准平方根无迹卡尔曼滤波器相比,有效地克服了机动加速度影响.实验结果表明:所提出的低成本姿态估计方法在单基线GPS锁定或短时间失锁情况下,能够满足宽带移动卫星通信天线波束对准精度要求,三维姿态角误差均小于0.5°.     

宽带移动卫星通信低成本组合姿态确定算法

针对现有低成本微机械惯性器件无法满足宽带移动卫星通信系统在机动状态下天线指向精度的问题,提出了微机械惯性测量单元与闭环跟踪信息相结合的姿态确定算法.该算法在航向上引入闭环跟踪的指向偏差角,经PI控制器反向校正航向陀螺的漂移误差,并利用跟踪指向信息的低频分量和陀螺的高频分量估计航向角.在横滚和俯仰上,首先以改进欧拉角作为状态向量,根据陀螺角速率信息和加速度计的重力场信息分别建立状态方程和测量方程;然后依据航向角速率和俯仰角偏差对载体运动状态进行判别,并在载体机动下调整方差矩阵以依赖陀螺进行姿态估计,克服机动加速度的扰动.实验结果表明,该算法与自适应卡尔曼滤波器相比,在载体机动状态下精度更高,其航向估计精度在±0.8°,倾角在±0.5°内,满足动中通姿态稳定精度要求.     

宽带移动卫星通信系统低成本姿态估计算法

针对低成本微机电惯性测量单元无法满足宽带移动卫星通信系统姿态估计精度的问题,提出了以单基线GPS为辅助传感器的低成本姿态估计(LCAE)算法.该算法通过互补滤波器对陀螺测量值与加速度计姿态角进行传感器融合.为了克服机动加速度干扰,借助单基线GPS的速率信息及航向信息,加入了机动加速度补偿和侧滑角补偿;为了降低算法对GPS信号的依赖,加入了开关结构.实验结果表明,LCAE算法能够有效去除加速度计测量值中的非重力信息,隔离载体运动对加速度计输出的干扰,姿态角估计精度在GPS信号完全锁定的情况下达到±0.5°以内,在GPS信号不完全锁定的情况下,姿态角估计精度优于开关卡尔曼方法,达到±1°以内,满足低成本移动卫星通信系统要求.     

基于惯性测量单元旋转的陀螺漂移估计和补偿方法

陀螺仪的漂移误差是影响惯性导航系统的姿态测量精度的重要因素。常用的陀螺漂移估计及航向角误差修正方法需要用磁强计或GPS等外部传感器的辅助数据来实现,存在室内、磁干扰等环境下应用受限的问题。对此该文提出了惯性测量单元旋转的改进方法。该方法在测量过程中对陀螺仪施加独立于物体运动的特定旋转,通过旋转前后不同姿态下陀螺仪和加速度计输出的倾角数值,得到惯性测量单元漂移估计。实验表明,该估计算法可有效地提高航向角的测量精度。     

基于平方根Unscented卡尔曼滤波的无陀螺卫星的姿态估计

针对无陀螺卫星的姿态和速度估计问题，提出基于平方根UKF滤波（square Root Unscented Kalman Filter）的估计算法。为了避免欧拉角带来的奇异问题，采用四元数描述卫星的姿态参数。考虑卫星的非线性模型，采用Cholesky和QR分解，从而平方根UKF滤波方法不仅能保证协方差矩阵的正定性，并且还可以提高算法的计算精度。利用测量矢量的信息，该算法能估计三轴稳定卫星的姿态，且计算简单，无需计算Jacobian矩阵。数值仿真结果表明，所给出的方法是可行而有效的。     

基于四元数EKF算法的小型无人机姿态估计

针对小型无人机设计的姿态测量系统,提出一种用于小型无人机姿态估计的四元数扩展Kalman滤波算法.该算法通过建立四元数姿态运动模型和航姿传感器测量模型,构建了以四元数和陀螺仪随机漂移为状态向量、以加速度计测量值和磁阻仪解算的航向角为观测向量的扩展Kalman滤波器,并设计了自适应测量噪声协方差矩阵修正法.实验结果表明,该算法不但解决了微机电系统惯性器件用于载体姿态测量时精度低、易发散、易被干扰的问题,而且显著减小了陀螺仪随机漂移对姿态估计的影响,有效提高了姿态估计的精度.     

移动卫星通信系统组合姿态估计算法

针对宽带移动卫星通信系统传感器直接融合姿态估计算法易受外界因素干扰、估算误差难以校正的问题,提出了一种移动卫星通信系统组合姿态估计算法。该算法以移动卫星地球站载体的位置误差、速度误差和姿态误差为系统状态量,建立了9状态的组合导航姿态估计模型;通过使用GPS航向角辅助观测解决了组合姿态估计算法航向角可观性弱、姿态角估计值易发散的问题;通过将转弯判断规则和Sage-Husa自适应控制算法进行融合,降低了GPS航向角测量误差对姿态估计的影响,提高了组合姿态估计算法的精度。实验结果表明:移动卫星通信系统组合姿态估计算法计算简单、实时性好,姿态估计精度优于传感器直接融合算法,其姿态估计误差可控制在±0.5°以内,最小均方误差值小于0.4,满足低成本宽带移动卫星通信波束对准要求。     

一种油运船舶的组合姿态测量模型

实时准确地测量船舶姿态,对船舶运输安全作业、舰船减摇控制等具有重要意义.对坐标系及其转换关系进行了定义,推导构建了基于加表、陀螺和GPS的组合姿态测量系统测量元件模型和全量模型,通过状态方程和测量方程的分析推导对全量模型进行了线性化处理,并对连续系统模型作了离散化处理.依据姿态角、陀螺漂移和速度的误差状态方程,引进GPS测量值,对系统状态进行卡尔曼信息滤波估计,从而得到陀螺的漂移误差,使姿态角的测量达到良好的效果.     

组合导航中磁强计干扰估计与补偿方法

针对磁场干扰较大导致组合导航定位中磁强计解算航向角严重失准的问题,提出一种磁强计的磁场干扰补偿方法。分析了磁强计输出模型,利用陀螺仪求解的航向角差、横滚角和俯仰角,建立磁场干扰模型。将三轴磁场干扰转化为两轴磁场干扰,再采用最小二乘拟合法对其进行估计并补偿,输出补偿后的航向角。在人为设置磁场干扰源的条件下进行转台实验,实验结果表明,该方法补偿后的磁强计磁场干扰得到有效抑制,航向角精度有效提高。     

MIMU在不同情况下的可观测性分析

基于微机电系统(MEMS)技术的微惯性测量单元(MIMU)在体积、重量、功耗都具有显著优势,但是其较大的惯性器件误差限制了其应用范围。通过引入旋转调制技术抑制其影响,使得MIMU能够实现寻北应用,目前这方面已经得到比较多的研究。但是不足之处在于缺乏对MIMU的可观测性分析,而状态是否可观测与Kalman滤波能否准确估计误差状态量是紧密联系的。该文针对MIMU在静止、多位置、连续旋转3种情况下,基于实测数据用Kalman滤波分析其可观测性。结果表明:静止情况下MIMU的航向姿态角误差很大,无法自对准;通过绕航向轴及俯仰轴旋转的多位置方案,可以使得MIMU的误差状态量完全可观测;连续旋转情况下,Kalman滤波可以在较短时间内估计出航向角及天向加速度计零偏,并在一段时间后估计出方位陀螺漂移,但是无法准确估计出水平方向的陀螺漂移及加速度计零偏,不过寻北算法可以估计出水平方向的惯性器件常值误差。该研究结果为提高MIMU自对准精度以及评估其性能提供了途径和理论依据。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.