共查询到19条相似文献,搜索用时 218 毫秒
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基于渐消记忆自适应滤波的船舶动力定位算法仿真 总被引:1,自引:0,他引:1
由于船舶在海上运动的复杂性和非线性,精确的船舶动力定位系统数学模型难以建立.为了实现有效的动力定位控制,需要应用一定的状态估计滤波算法得到所需的船舶运动低频信号.采用常规的Kalman滤波,状态变量的新测量值对预测值的修正作用下降,旧测量值的影响随着计算步数的累积而相对提高,这是引起滤波发散的主要原因之一.文章针对船舶动力定位系统中使用常规的Kalman滤波而存在的模型不精确、 不能准确表达系统噪声和测量噪声等问题,采用渐消记忆自适应滤波估算低频运动信息,在状态估计算法中引入渐消记忆因子,减小旧测量值对状态估计值的影响权重,从而增大新测量值的作用;并根据滤波发散判断准则,选择适当的渐消记忆因子值来抑制滤波器的发散,使控制器输出较为平稳,从而降低推力系统不必要的能耗.仿真实验表明,所设计的自适应滤波器的收敛性、跟踪性优于常规的Kalman滤波,有效地提高了系统的定位精度和稳定性. 相似文献
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采用小波图像降噪方法容易去除图像的边缘细节特征,导致关键信息丢失,提出一种有效保留图像细节的自适应图像消噪方法。采用局部二值拟合方法对图像进行二值化处理,提取图像的边缘轮廓特征并进行多尺度分割,采用局部区域梯度模特征匹配方法调整邻域的大小,对图像进行全局分割,从而有效保留了图像的细节特征,在此基础上利用变尺度的小波降噪方法实现图像自适应降噪。仿真结果表明,采用该方法进行图像消噪能有效保留图像细节特征,图像消噪输出的峰值信噪比较高,说明图像质量较好,性能优越。 相似文献
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小波消噪已经成为目前信号消噪的主要方法之一,小波变换由于在时频两域都具有良好的局部性能,尤其在信号处理过程中,采样信号都不可避免地受到各种噪声和干扰的影响,利用小波分析可以对实验数据进行消噪处理。本文详细介绍了目前小波消噪的各种方法,揭示了小波消噪的数学背景和滤波特性;并阐述了针对不同信号的自身局部特性以及使用不同的小波变换函数和构造出适合的闻值之间的联系。对一个含有噪声的多普勒测试信号和一个含噪声图像分别进行了多尺度一维离散平稳小波分解和二维离散平稳小波消噪分析,仿真的结果表明:小波分析可以对信号更有效地消噪。 相似文献
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低水头枢纽通常采用消力池底流消能的方式来消减泄水闸下泄水流的能量,而消力墩的位置对水跃的形式、强弱影响较大,从而影响整个消力池的消能率。采用计算流体力学软件Fluent的VOF模型,探讨消力墩位置对消力池内水跃特征、湍动能耗散率分布及消能率的影响。结果表明:消力墩位置会影响消力池消能率——消力墩布置在消力池长度的0.65及以上时,其消能效果与不布置消力墩时相差不大;消力墩布置在消力池长度的0.35处时,消力池的消能率最大,比布置在0.65时消能率提高约10.5%。 相似文献
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针对前馈网络BP算法所存在的收敛速度慢且常遇局部极小值等缺陷,提出一种基于U-D分解的渐消记忆推广Kalman滤波学习新方法。与EKF相比,该方法不仅大大加快了学习收敛速度,数值稳定性好,而且比BP算法需较少学习次数和隐节点数,学习效果也更好,将这种学习算法应用在船舶操纵的神经网络控制器中,仿真结果表明该方法是提高网络学习速度改善学习效果的一种有效方法,可有效解决非线性系统的控制问题。 相似文献
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KYD水库底孔泄洪洞平底渐扩式消力池优化试验 总被引:1,自引:1,他引:0
通过新疆青河县KYD水库底孔泄洪洞平底渐扩式消力池设计方案的试验,发现消力池池深、池长、边墙高远不能满足安全泄流要求。优化方案试验结果表明,对于渐扩角1.37°的渐扩式消力池按等宽度矩形消力池估算时池长基本满足要求,但是池深估算误差较大。联立溢洪道设计规范中的渐扩式消力池共轭水深计算公式和渐扩式消力池池深经验公式可较准确地计算池深。为了减小跃后水流剧烈脉动,降低跃后水深,采用了悬栅式消能工。试验结果表明,水跃淹没度增大,悬栅起到了破碎栅条上部水跃剧烈回旋运动引起的表面漩滚,消力池内水深降低,最大水深减小1.0 m,陡坡段和消力内水流脉动明显减弱,浪花溅起高度明显小于加悬栅前。 相似文献
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In underwater target detection, the bottom reverberation has some of the same properties as the target echo, which has a great impact on the performance. It is essential to study the difference between target echo and reverberation. In this paper, based on the unique advantage of human listening ability on objects distinction, the Gammatone filter is taken as the auditory model. In addition, time-frequency perception features and auditory spectral features are extracted for active sonar target echo and bottom reverberation separation. The features of the experimental data have good concentration characteristics in the same class and have a large amount of differences between different classes, which shows that this method can effectively distinguish between the target echo and reverberation. 相似文献
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In underwater target detection, the bottom reverberation has some of the same properties as the target echo, which has a great impact on the performance. It is essential to study the difference between target echo and reverberation. In this paper based on the unique advantage of human listening ability on objects distinction, the Gammatone filter is taken as the auditory model. In addition, time-frequency perception features and auditory spectra features are extracted for active sonar target echo and bottom reverberation separation. The features of the experimental data have good concentration characteristics in the same class and have a large amount of differences between different classes, which shows that this method can effectively distinguish between the target echo and reverberation. 相似文献
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在浅海环境中混响是造成主动声呐性能下降的主要原因之一。混响是由发射信号引起的,其频域上覆盖区域与发射信号基本重合,时域上与发射信号及目标回波强相关,这给混响和目标的分离造成了很大的困难。本文借鉴PD雷达中的动目标检测方法,提出一种适用于声呐动目标检测的滤波器设计算法。该算法利用运动目标回波和混响在时频域上的不同特性,设计了级联自适应滤波器实现混响抑制和目标增强。在此基础上进行匹配滤波等处理可以获得理想的效果。该算法可大幅提高信混比,有效改善运动目标的检测能力。 相似文献
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《船舶与海洋工程学报》2019,(3)
Elastic acoustic scattering is important for buried target detection and identification. For elastic spherical objects, studies have shown that a series of narrowband energetic arrivals follow the first specular one. However, in practice, the elastic echo is rather weak because of the acoustic absorption, propagation loss, and reverberation, which makes it difficult to extract elastic scattering features, especially for buried targets. To remove the interference and enhance the elastic scattering, the de-chirping method was adopted here to address the target scattering echo when a linear frequency modulation(LFM) signal is transmitted. The parameters of the incident signal were known. With the de-chirping operation, a target echo was transformed into a cluster of narrowband signals, and the elastic components could be extracted with a band-pass filter and then recovered by remodulation.The simulation results indicate the feasibility of the elastic scattering extraction and recovery. The experimental result demonstrates that the interference was removed and the elastic scattering was visibly enhanced after de-chirping, which facilitates the subsequent resonance feature extraction for target classification and recognition. 相似文献
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红外序列图像帧间匹配算法研究 总被引:1,自引:0,他引:1
文章在现有单帧图像检测算法的基础上,提出了一种可同步跟踪运动目标的帧间匹配算法。算法采取对相邻两帧间像素点匹配,匹配过程与当前两帧外的其余帧无关,把匹配结果兴趣区域像素点对应的另一个全零矩阵位置值赋为1,顺利输入检测后的单帧图像,执行匹配操作,实时形成目标运动轨迹。该算法结构简单、存储量少、计算速度快,硬件平台要就低,可有效地完成对多个目标、交叉目标、迎头目标的检测与跟踪。根据仿真和实拍照片的试验,证实了算法理论上的优点,有较高的应用价值。 相似文献
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介绍一种基于MATLAB方法的无线衰落信道的建模。对于不相关Rician信道和具有多普勒频移Rayleigh衰落信道的典型小尺度衰落信道进行了研究,分析了相移键控信号通过Rician衰落信道的性能估计,同时给出仿真波形。 相似文献
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The analysis and characteristic extraction of target echo characteristics are important in underwater target detection and recognition. Rigid acoustic scattering components are generally used as major echo contributors with relatively stable characteristic information. Previous studies focus on echo characteristics from a single angle, thereby limiting the amount of extracted characteristic information. This paper aims to establish a full-angle rigid echo components model and overcome the difficulty of the extraction of time delay characteristics of narrow-band acoustic scattering echoes. On the basis of the analysis of the target echo highlight model, the echo characteristics of rigid acoustic scattering components are extracted in the cepstrum domain, and a wavelet process is proposed to enhance the effect of time delay estimation. Experimental data indicate that the extracted time delay characteristics accord with the rigid echo characteristics of underwater target, thereby validating the effectiveness of the cepstrum method. 相似文献