共查询到19条相似文献,搜索用时 218 毫秒
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吊放式反蛙人声呐的水下姿态不稳定性对设备性能带来不利影响,声呐湿端姿态倾斜会使各波束主瓣平面偏离水平面,导致水平面内的发射声波强度损失以及海底、海面混响反射强度的增加,姿态旋转则会造成声呐接收方位失真。文章在推导给出湿端陀螺坐标系与大地坐标系之间姿态变换关系的基础上,基于大地坐标系内的姿态和横滚角,以相控俯仰实现导引方位上的发射波束稳定,在纵倾6°情况下,于波束导引方位可获得2.7 dB的波束稳定增益;以湿端横滚角补偿进行接收波束的方位修正,弥补陀螺航向角修正的精度误差,在纵倾6°情况下,能克服最大0.56°的方位修正误差;将仿真结果和有关试验数据进行了分析比较,验证了相控波束稳定方法的工程可行性。 相似文献
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针对声学多普勒测速仪安装过程中存在的基阵坐标系与载体坐标系之间的不重合问题,以实际工程应用为背景,提出了综合采用测速仪的速度推算航迹及其波束域斜距信息的三维安装偏角精确校准方法。利用航偏角校准精度受纵、横摇偏角影响小的特点,采用载体上的高精度全球定位系统(Global Positioning System,GPS)、姿态装置推算航迹建立航偏角观测方程,实现航偏角校准。在此基础上,利用波束域斜距与纵、横摇偏角之间的几何方程,精确解算纵、横摇偏角。仿真分析了校准算法性能,并通过外场试验数据验证了校准算法的有效性。结果均表明该方法能够实现基阵三维安装偏角的精确校准,有效提高了导航精度,具有较好的工程应用价值。 相似文献
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随着电子技术、计算机技术.特别是高精度GPS定位技术的完善,多波束技术也得到了迅速发展,并广泛应用于海洋工程勘察中,多波束测深系统的优势也越来越明显。本文首先阐述了多波束测深的工作原理,其次,分析了影响海洋工程勘察中多波束测深精度的因素。同时,就多波束测深在海洋工程勘察中的应用进行了深入的探讨,具有一定的参考价值。 相似文献
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提高多波束测深系统的综合精度,不仅需要提高远场精度,近场精度也不可忽视。针对常规多波束测深系统中采用远场近似模型,使得近场精度急剧下降的不足,研究了基于FPGA的多波束实时动态聚焦波束形成(RT-DFBF:Real-time Dynamic Focused Beam-forming)方法。该方法引入相移聚焦波束形成,论证其在多波束测深系统中解决近场问题的可行性,同时深入分析各个影响因素的实时处理情况,提出了一种基于FPGA的实时处理结构,该结构在输入通道为80个、采样率为28kHz、波束数为128个的条件下完成RT-DFBF。水池实验结果验证了该方法的实时性、有效性和实用性,具有重要工程应用价值。 相似文献
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建立了舰船消磁系统舰磁干扰量模拟法的S矩阵数学模型,该模型可以用来模拟产生任意地磁场作用下和舰船任意姿态时消磁系统电流变化关系。提出了利用不同主航向上舰船消磁系统电流与横摇角、地磁场和感应干扰量的变化关系来测量和分析S矩阵元素的方法,为解决舰船消磁系统快速抗干扰和跨纬度区调整问题奠定了理论基础。 相似文献
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在常规单站SAS系统中,多子阵技术是提高测绘率的一个有效方法,针对发射站固定的双站SAS模型,多子阵技术同样可以用来解决测绘率与降空间采样率的矛盾,但是当"停-走-停"假设不再成立时,将引入相位误差项,降低双站SAS的成像质量,针对该问题在原有多子阵逐点成像算法的基础上,研究了发射站固定的双站SAS基阵运动引起的相位误差,提出了多子阵双站合成孔径声纳带相位补偿的逐点成像算法,在建立多子阵双站SAS数学模型的同时,形成了新的多子阵双站SAS系统方案设计。并给出了改进的波束形成逐点算法和仿真实验。改进的逐点算法并未改进运算量大小,新方法能够改善成像效果,仿真实验验证了该方法的有效性。多子阵双站合成孔径声纳成像的逐线算法有待进一步研究。 相似文献
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为更好地实现智能稳定平台隔离扰动的性能,本文针对平台载体运动姿态的预测问题展开研究.在对平台载体横滚运动时间序列进行混沌特性判定的基础上,使用加权一阶局域法对载体运动姿态进行多步预测.针对预测过程中误差累积的问题,提出在姿态预测的同时对误差序列进行预测,并通过误差预测值实时修正姿态预测值.文中给出了两种误差补偿的多步预测方法,通过试验水池的实测数据仿真分析表明,误差补偿的加权一阶局域多步预测方法提高了预测精度,抑制了误差的累积;进一步通过相对均方误差等指标进行评价,指出预测方法中LPC法误差补偿的多步预测效果最优,具有一定的实用价值. 相似文献
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Bjastad T. Aase S.A. Torp H. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(7):1340-1351
Parallel beamforming is a commonly used method for increasing the frame rate in ultrasound imaging systems. By receiving in several directions for each transmission, the frame rate is increased. However, this method also introduces blocklike artifacts in the B-mode image, due to the reception offsets when compared with the transmission direction. The synthetic transmit beam technique (STB) has been previously proposed as a compensation technique when addressing these artifacts. Previous work by Hergum et al. investigated the performance of this method in regard to the case of 2 parallel beams in tissue mimicking phantoms without aberrations. This study is a continuation of that work in which this method is tested in an aberrating environment using 4 parallel beams. Several quantitative and qualitative performance aspects of this method have been investigated such as lateral shift invariance, beam-to-beam correlation fluctuations, speckle- tracking performance, improvements from higher order STB interpolation and beam profile shape preservation, as well as perceived image quality improvements. The results were obtained from simulations, in vivo measurements, and in vitro measurements. The results showed that aberration amplified the image artifacts for regular parallel beamforming, which resulted in more shift variance, lower beam-to-beam correlation, higher speckle- tracking error, and more variation in beam profile shape. Compared with regular parallel beamforming, STB resulted in a significantly better image quality and a higher score in all measuring methods. The improvements from using STB were largest in cases involving aberration. Using STB, the variation in beam-to-beam correlation was reduced from 30% to 1%, and the standard deviation of the speckle-tracking error was reduced from 8% to 1.5%. 相似文献
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With conventional optical interferometry flying-height testing, a stationary measurement beam and a two-axis moving stage are used to measure slider-disk spacing at different points on the slider. Pitch angle or roll angle is calculated on the basis of the measurement results. We report on a scanning differential-heterodyne interferometer, which measures the continuous flying-height variation along the edge of a slider with two continuously scanning laser beams. Pitch angle or roll angle can be obtained directly from the scanning measurement. The system can also measure points individually to obtain the absolute flying height at different locations on the slider. Experiments were performed to demonstrate the concept of scanning measurement. The flying-height variation along the slider edge was measured by continuous scan and by point-to-point moving. The measurement results from continuous scan coincided with those of conventional methods. 相似文献
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Calibration of a Novel MEMS Inertial Reference Unit 总被引:3,自引:0,他引:3
《IEEE transactions on instrumentation and measurement》2009,58(6):1967-1974
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Laser-induced ultrasonic bulk wave tomography is used for density variation determination of powder metal compacts. A laser beam is used to excite ultrasonic energy, and the signals passing through the specimen are received by an air-coupled transducer. The density variations of powder metal compacts can be determined directly by the cross-sectional tomographic images of slowness obtained by using a filtered, backprojection algorithm based on measured time of flights. Interpolations with respect to sample and projection angles are used to generate the input data required for displaying a well-balanced, reconstructed image to reduce the aliasing distortions caused by insufficient input data. Results of presintered cylindrical ferrous powdered samples show that this novel approach makes the reconstruction process more cost effective than the very tedious, time-consuming, and inaccurate metallographic methods, thus making it a potentially powerful tool for studying manufacturing processes through significant parameters to obtain a more uniform density distribution. 相似文献
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Xiang Zhao Joseph L Rose Huidong Gao 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(2):360-369
Laser-induced ultrasonic bulk wave tomography is used for density variation determination of powder metal compacts. A laser beam is used to excite ultrasonic energy, and the signals passing through the specimen are received by an air-coupled transducer. The density variations of powder metal compacts can be determined directly by the cross-sectional tomographic images of slowness obtained by using a filtered, backprojection algorithm based on measured time of flights. Interpolations with respect to sample and projection angles are used to generate the input data required for displaying a well-balanced, reconstructed image to reduce the aliasing distortions caused by insufficient input data. Results of presintered cylindrical ferrous powdered samples show that this novel approach makes the reconstruction process more cost effective than the very tedious, time-consuming, and inaccurate metallographic methods, thus making it a potentially powerful tool for studying manufacturing processes through significant parameters to obtain a more uniform density distribution. 相似文献
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在海水性质变化剧烈地区利用重构声速剖面进行多波束测深时,传统的经验正交函数(Empirical Orthogonal Functions,EOF)方法在阶次选取时未顾及声速浅水的复杂性和深水的平稳性的特点。针对传统EOF方法存在计算量大、精度低等问题,给出了一种声速剖面EOF重构中分层阶次的确定方法。根据常梯度声线跟踪计算深度,在满足0.25%倍水深限差的要求下,统计有效波束比,采用自适应方法确定出合理的阶次。实验结果表明,该方法相较于传统EOF重构声速剖面测深的阶次选取方法,降低了运算量,提高了精度。 相似文献