An iterative calibration method for nonlinear coefficients of marine triaxial accelerometers

Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance. However, two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect. Firstly, the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers. Secondly, the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately. These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation. Based on the digital signal sampling property, the square coefficients and cross-coupling coefficients of accelerometers are considered. Meanwhile, the asymmetry scale factors are considered in the I-F conversion unit. Thus, a nonlinear model of specific force measurement is established compared to the linear model. Based on the three-axis turntable, the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers. Considering the nonlinear combination, the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure. Besides, an efficient specific force calculation model is approximately derived to reduce the real-time computation cost. Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients. The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.     

地球自转与扁率对导弹射程偏差影响研究

针对地球扁率对远程导弹射程的影响,本文以惯性空间为基准,建立弹道导弹主动段在发射惯性坐标系中的运动方程,并假设地球为均质球体,在极坐标系中建立导弹被动飞行段弹道方程,通过简化公式,对地球自转和地球扁率对导弹射程偏差的影响进行了计算,并通过多条弹道进行仿真分析,仿真结果表明,地球扁率对导弹射程偏差的影响比单独考虑地球自转时显著增加,因此,计算大射程导弹射程及预测落点偏差时,必须考虑地球自转及扁率的影响,否则误差较大。该研究对提高导弹的命中精度意义重大。     

路堤下盖板涵的竖向土压力分布

由于盖板在填土压力作用下发生挠曲变形,针对盖板涵对竖向土压力分布的影响,推导了盖板涵竖向土压力分布计算公式.假设盖板发生弹性挠曲变形,填土服从Winkler弹性地基条件,对盖板上修正的Marston填土涵洞竖向土压力分布进行了分析.结果表明,该修正公式考虑了盖板涵内外土柱差异沉降的应力集中效应,可计算由于盖板挠曲变形而引起的土压力重分布.通过对鹤大高速公路某盖板涵进行现场测试以及有限元数值模拟分析,结果显示盖板涵土压力的分布特点与本文理论分析相一致,且理论公式计算结果值与现场实测值吻合较好.     

GPS天线相位中心水平方向偏差的检测与校正

针对常规旋转天线法中旋转角度不准确以及天线相位中心具有随机性的情况,提出了利用均值法进行GPS接收机天线相位中心水平方向上偏差的检测和校正.该方法是将两台接收机安置在超短基线两端,固定其中一台接收机,将另外一台接收机天线均匀旋转,基线解算,计算旋转的接收机天线相位中心水平方向偏差大小.结合实例证明:新的检测方法快捷、简便,适合野外利用超短基线进行天线相位中心水平方向偏差的检测.     

竖直窄矩形流道液泛研究

为了研究窄小流道内气液两相逆向流动问题,以空气-水为工质,对竖直窄矩形流道内液泛过程及液泛特征点进行了实验研究和理论分析,并与传统流道液泛进行了比较.结果表明,竖直窄矩形流道内液泛起始点符合Wallis关系式,与传统流道液泛起始点以压差突变进行判断不同,窄矩形流道内液泛起始点的判断以有水被携带出流道为标志.窄矩形流道内完全携带点与水流量大小、实验段入口条件无关,只与气体流量大小有关;流向反转点与试验段壁面干燥程度有关,与水流量大小及气体入口条件无关.     

基于提升小波变换的冲击性负荷电能表设计

分析了提升小波变换的分解原理,提出了基于提升小波变换的冲击性负荷电能计量新方法,并进行了冲击性负荷电能表的硬件设计。与传统电能表相比,该电能表能适应冲击性负荷情况下电流动态范围大、频带宽的测量特点。通过仿真实验,论证了该方法的可行性,并证明了该方法在实时处理速度上要优于第一代小波变换。     

基于多尺度积视觉特性的多聚焦图像融合算法

针对传统多尺度图像融合算法不能有效抑制噪声的缺陷,提出一种基于提升静态小波变换（LSWT）多尺度积的多聚焦图像融合算法,并在LSWT域中引入了局部可见度以及局部视觉特性对比度的概念.在融合低频子带系数和各高频子带系数时,分别提出了基于局部可见度和基于多尺度积的局部视觉特性对比度的系数选择方案.实验表明,该算法不仅能有效抑制噪声对融合算法的影响,而且能够得到比传统方法视觉效果更好和更优量化指标的融合图像.     

Visual Localization in Urban Area Using Orthogonal Building Boundaries and a GIS Database

A framework is presented for robustly estimating the location of a mobile robot in urban areas based on images extracted from a monocular onboard camera, given a 2D map with building outlines with neither 3D geometric information nor appearance data. The proposed method firstly reconstructs a set of vertical planes by sampling and clustering vertical lines from the image with random sample consensus (RANSAC), using the derived 1D homographies to inform the planar model. Then, an optimal autonomous localization algorithm based on the 2D building boundary map is proposed. The physical experiments are carried out to validate the robustness and accuracy of our localization approach.     

基于提升小波变换的图像融合新算法

给出了一种基于提升小波变换的图像融合方法,并对小波分解的不同频率域,分别采用不同的融合规则。选择低频系数时,是基于边缘的方法,选择高频系数时,把小波系数的方差与绝对值综合起来考虑来决定融合小波系数。实验结果表明,提出的方法融合效果要优于一般融合方法。     

草履蚧在法桐上的空间垂直分布及防治

通过调查发现草履蚧在法桐上空间垂直分布为聚集分布,掌握了草履蚧在三门峡市发生危害的规律,为防治提供了科学依据,并且提出了有效防治措施。