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雨滴谱是云及降水物理学中重要的研究对象,基于北京2015年8月7日的强降水雨滴谱观测数据,计算得到该过程的雨滴谱、质量加权直径、平均直径等雨滴尺寸分布特征,由雨滴谱观测数据计算得到降水强度、液态水含量和雷达反射率,分析这些降水参数在此次降水过程中的变化特征。综合分析雨滴谱参数和S波段天气雷达反射率表明此次降水过程具有飑线特征,可划分为前端的引导对流性降水、过渡降水和尾部层状降水三个阶段。最后讨论不同降水阶段雨滴谱参数及降水参量的变化及其对雷达定量降水估测Z-R关系的影响。结果表明对流性降水阶段的雨滴数浓度(大于4600个/m3)、质量加权直径(2.69 mm)、最大直径(6.3 mm)均远高于过渡和层状降水阶段,对流降水阶段和过渡阶段雨滴直径分布范围类似(标准差均大于0.3 mm),层状降水分布较窄(标准差0.24)。不同降水阶段拟合得到的Z-R关系明显不同,拟合得到此次降水整个过程的Z-R指数经验关系系数a=674.91,指数b=1.39。 相似文献
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激光雨滴谱仪降水量反演及误差修正 总被引:1,自引:0,他引:1
对激光雨滴谱仪监测的降水粒子粒径、末速度、粒子数等信息进行分析,得到降水粒子的粒径-末速度函数和雨滴谱等关系函数。通过计算得到的降水强度与气象数据对比,得到误差函数;根据误差函数建立降水量反演算法,对降水强度进行修正得到修正后降水强度和降水量,修正后降水量误差减少了10%以上,最后给出降水类型的判断方法。 相似文献
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针对单相全桥工频逆变器设计过程欠缺规范的问题,该文提出了一种以动态设计指标为条件解耦设计主电路滤波参数和控制器参数的公式化分步设计法.以阻性负载跃变量为条件,分析了单相全桥工频逆变器在两种极端情况下的最优负载瞬态响应过程,推导了最优负载瞬态特性关于滤波参数的数学表达式,并给出了表达式适用范围-输出电压跌落量低于10%,且结合逆变器的动态设计指标提出了一种滤波器参数设计方法,再以滑模控制为例,结合动态设计指标给出了一种滑模控制器设计方法.仿真实验结果验证了最优负载瞬态响应过程的存在性,最优负载瞬态特性表达式的正确性和有效性,也验证了解耦设计法的正确性和有效性.该解耦设计法具有良好的理论价值和工程价值. 相似文献
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提出了一种精确测试电吸收调制激光器(EML)集成芯片高频特性的方法。待测芯片制作在带有微带线的热沉上,同时采用光探测器作为光电转换器,二者构成待测双口网络。被测双口网络的一端是共面线,使用微波探针作为测试夹具加载信号,另一端是同轴线,两个测试端口不同,不能采用简单的同轴校准方法校准待测系统。测试过程中采用扩展的开路-短路-负载(OSL)误差校准技术对集成器件的测试夹具微波探针进行校准,扣除了测试中使用的微波探针对集成光源高频特性的影响,同时采用光外差的方法扣除了高速光探测器的频率响应对结果的影响,得到集成光源散射参数的精确测试结果。 相似文献
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在光学辅助惯性导航系统中,观测信息的最优融合依赖于相机与惯性测量单元六自由度转换的精确校准。针对火星软着陆自主导航中的测量信息最优融合问题,提出了基于扩展卡尔曼滤波的导航敏感器相对位姿校准算法。该算法仅利用火星表面可获取的路标特征点信息,不借助额外的测量设备,对相机与惯性测量单元相对位姿进行精确的校准,同时,能够估计着陆器的位置、速度和姿态。考虑到着陆器机动和火星自旋的影响,建立了宽视场相机及惯性测量单元的高精度测量模型。最后通过数学仿真对所提出的校准算法的可行性和有效性进行了验证。 相似文献
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Bor-Sen Chen You-Li Chen 《Signal Processing, IEEE Transactions on》1995,43(10):2302-2312
The use of the Kalman filter is investigated in this work for interpolating and estimating values of an AR or MA stochastic signal when only a noisy, down-sampled version of the signal can be measured. A multirate modeling theory of the AR/MA stochastic signals is first derived from a block state-space viewpoint. The missing samples are embedded in the state vector so that missing signal reconstruction problem becomes a state estimation scheme. Next, Kalman state estimation theory is introduced to treat the combined estimation-interpolation problem. Some extensions are also discussed for variations of the original basic problem. The proposed Kalman reconstruction filter can be also applied toward recovering missing speech packets in a packet switching network with packet interleaving configuration. By analysis of state estimation theory, the proposed Kalman reconstruction filters produce minimum-variance estimates of the original signals. Simulation results indicate that the multirate Kalman reconstruction filters possess better estimation/interpolation performances than a Wiener reconstruction filter under adequate numerical complexity 相似文献
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In OFDM systems, time‐varying channels destroy orthogonality between subcarriers causing Inter‐Carrier Interference. To reduce this effect, a Kalman filter, as a benchmark, is used for channel estimation, based on comb‐type pilot arrangements of the OFDM system. An advantage of comb‐type pilot arrangements in channel estimation is the ability to track the variation of the channel caused by Doppler frequency. Kalman method has been proposed to estimate the channel frequency response (CFR) at the pilot locations, then CFR, at data subchannels, is obtained by means of interpolation between estimates at pilot locations. The low‐complexity Kalman method is introduced to reduce the complexity of the system while achieving the same BER/SNR. Different types of interpolations have been also compared such as Low‐pass, Spline‐cubic and Linear interpolation methods. The BER/SNR performance of BPSK modulation schemes are considered for time varying Rayleigh fading channels. Our results has shown that the low‐complexity Kalman estimation, used with the pilot arrangement and a suitable interpolation method, gives almost the same performance as that of the Kalman method specially for low SNR values and hence the effect of Doppler shift effect is controlled. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A new fast recursive least squares (RLS) algorithm, the Kalman gain estimator (KaGE), is introduced. By making use of RLS interpolation as well as prediction, the algorithm generates the transversal filter weights without suffering the poor numerical attributes of the fast transversal filter (FTF) algorithm. The Kalman gain vector is generated at each time step in terms of interpolation residuals. The interpolation residuals are calculated in an order recursive manner. For an N/sup th/-order problem, the procedure requires O(Nlog/sub 2/N) operations per iteration. This is achieved via a divide-and-conquer approach. Computer simulations suggest that the new algorithm is numerically robust, running successfully for many millions of iterations. 相似文献
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针对多模多频接收机面临同时处理大量数据的压力,提出了一种基于插值和卡尔曼滤波的接收机钟差预测方法。插值方法分别用拉格朗日和三次样条,三次样条端点的一阶导数采用“差分法代替求导法”来确定。首先由插值方法得出每隔1s的卫星坐标、速度、钟差、频漂和伪距测量值,然后基于单星授时方法计算出静止接收机钟差,接着用卡尔曼滤波算法对接收机钟差和频漂进行预测,最后将预测的接收机钟差与加拿大空间参考系统( CSRS )提供的精密接收机钟差数据进行比较。结果表明,拉格朗日插值由于存在龙格效应,其接收机钟差的抖动幅度比三次样条略大,它们与CSRS钟差数据相比,均方根误差在3 ns之内。 相似文献
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Significant errors of train axle generators (tachometers) are due to wheel slip and slide. An algorithm is designed to compensate for these errors. The algorithm identifies the wheel slip and slide by examining the variation of the processed vehicle longitudinal acceleration. Whenever wheel slip/slide is identified, then the vehicle speed is adjusted if a certain condition is met. The adjustment is a simple linear interpolation between the two speed values recorded before and after wheel slip/slide detection. In addition, a speed and acceleration observer using a Kalman filter is implemented. Experimental results using three different axle encoders aboard a freight train are provided to illustrate the performance of the proposed algorithm 相似文献
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针对激光器产生的相位噪声会严重影响相干光正交频分复用(CO-OFDM)系统的性能问题,提出了一种新颖容积卡尔曼滤波(CKF)相位噪声补偿算法。该算法利用导频信息,先通过扩展卡尔曼滤波(EKF)和线性插值算法补偿公共相位误差(CPE)噪声,然后对相位噪声粗补偿后的信号进行预判决,在时域对预判决后的信号进行次符号处理的CKF实现对载波间干扰(ICI)相位噪声的精细补偿。对补偿后的信号进行二次迭代,从而提高补偿效果。分析和仿真表明:提出的新颖CKF算法能有效补偿相位噪声对信号的影响,在相位噪声线宽较大时能有效增强对ICI相位噪声的补偿效果,改善CO-OFDM系统对激光器线宽的容忍度,有效提高系统的性能。 相似文献
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CDKF在GPS/SINS组合导航系统非线性模型中的应用 总被引:3,自引:0,他引:3
GPS/SINS组合导航系统模型的非线性会导致扩展卡尔曼滤波(EKF)的估计精度降低。而中心差分卡尔曼滤波(CDKF)的新型非线性滤波方法,则利用插值公式对非线性系统的状态估计进行逼近,从而减小线性化误差对系统精度的影响。针对GPS/SINS导航系统的特点,建立了一种非线性误差模型,并将EKF与CDKF分别应用于组合导航系统模型中进行仿真比较。仿真结果表明,该算法简单易实现,且能满足系统在非线性模型下的导航要求,并具有较高的精度和收敛性。 相似文献
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提出了一种基于并行卡尔曼滤波的递推最小二乘算法.利用最小二乘算法对卡尔曼滤波的并行多路收敛输出值进行二次优化估计.将本算法应用于正弦波测频,与只采用卡尔曼滤波的算法相比,可使频率估计精度得到明显提高.仿真证明在信噪比0~100 dB区间内采用本算法为卡尔曼滤波算法的测频误差的1/10左右. 相似文献