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采用数据融合算法完成高精度外弹道测量对各测元时间同步有着严格的技术要求。在分析时间不同步对融合弹道测速精度的影响基础上,分析了引起无线电测速时间不同步的因素,并构建了有效的数学修正模型。针对融合弹道速度异常超差现象,依据对测速误差理论模型公式和无线电测速原理分析结果,提出基于各测量设备测速数据解算模型的积分点移位和传播延迟修正模型算法,并应用于潜射弹的数据融合同步修正。工程应用结果表明,融合弹道偏差优于0.04 m/s,较修正前精度提高了4倍以上。由于陆基无线电测量系统的测距、测角具有类似的时间不同步特征,因此该模型也可作为多测元融合弹道解算过程中的一般方法推广使用。 相似文献
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A local outlier factor algorithm based on bidirectional neighbor correction was proposed to solve the problems of existing outlier detection algorithms such as difficulty in parameter selection,poor efficiency and low accuracy.The bidirectional neighbor searching algorithm was used to reduce the neighbor search time.Then the bidirectional neighbor pruning algorithm was used to reduce the number of parameters and unnecessary calculations.And the correction factor based on bidirectional neighbors was used to improve the calculation accuracy.Experimental results show that the proposed algorithm has better performance in parameter selection and time efficiency than other outlier detection methods.The correction factor improves the accuracy of the algorithm,in the synthetic data set and UCI data set. 相似文献
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在蜂窝无线定位中,由于非视距(non-line-of-sight, NLOS)误差是影响定位精度的主要因素之一,所以如何减轻NLOS误差影响成为当前无线定位研究的热点。本文针对NLOS环境下的定位跟踪问题,提出一种基于扩展卡尔曼滤波(extended Kalman filter ,EKF)的定位跟踪算法。该算法首先在最小二乘准测下推导出估计测量值中NLOS误差的直接计算公式,然后使用约束加权最小二乘(constrained weighted least squares, CWLS)方法计算出每一个测量值中所含的NLOS误差,最后利用NLOS误差估计值去修正EKF滤波,以便适应NLOS环境下的定位跟踪,并获取高的定位精度。这种方式不依赖于特定的NLOS误差分布,也无需视距(line-of-sight, LOS)和非视距识别。数值结果表明该算法相比较于经典EKF算法和基于NLOS迭代的EKF算法可以快速有效地抑制定位误差,并且可以在极为恶劣的NLOS环境下满足FCC的定位要求。另外,复杂性实验表明该算法可适用于实时跟踪。 相似文献
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Qingyu Chen Li Chen Haibin Wang Longsheng Wu Yuanqing Li Xing Zhao Mo Chen 《Journal of Electronic Testing》2016,32(6):695-703
Bit faults induced by single-event upsets in instruction may not cause a system to experience an error. The instruction vulnerability factor (IVF) is first defined to quantify the effect of non-effective upsets on program reliability in this paper; and the mean time to failure (MTTF) model of program memory is then derived based on IVF. Further analysis of MTTF model concludes that the MTTF of program memory using error correcting code (ECC) and scrubbing is not always better than unhardened program memory. The constraints that should be met upon utilizing ECC and scrubbing in program memory are presented for the first time, to the best of authors’ knowledge. Additionally, the proposed models and conclusions are validated by Monte Carlo simulations in MATLAB. These results show that the proposed models have a good accuracy and their margin of error is less than 3 % compared with MATLAB simulation results. It should be highlighted that our conclusions may be used to contribute to selecting the optimal fault-tolerant technique to harden the program memory. 相似文献
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压电晶体(PZT)光学移相器作为移相干涉仪(PSI)的关键部件,其移相误差直接影响被测波面的相位复原精度。分析了压电晶体移相器在移相过程中导致干涉图旋转的原因——类进动,其本质是移相器在伸长的同时其参考镜端面法线方向绕着伸长方向产生旋转。利用典型的Hariharan五步移相算法。得出了类进动现象所导致的波面相位复原误差计算公式,给出了在测试孔径上的误差分布图。对影响误差大小的主要因素如干涉条纹的宽度、旋转的角度和测试口径等进行了具体分析,由此推导出在移相干涉仪光学调整过程中控制干涉图旋转误差的准则。 相似文献
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Thermal response curves used to calculate the peak junction temperature of power semiconductors are normally derived by experimental identification of the parameters of a known model. Unfortunately the model, developed many years ago, is inappropriate for large surges of short time duration, as they are encountered in present day power conditioning systems. An alternative model is derived, the limits of its accuracy are estimated, and a correction factor is described. A verification of the accuracy of the two methods is also presented. For pulse widths shorter than the thermal transit time, which is in the order of 300 μs, the peak junction temperature can be more accurately calculated with an expression derived in the present work, which takes into consideration the active volume in which the heat is generated, than with the transient thermal response curve. A correction factor, a function of the width of the pulse, inserted in this equation, further improves its accuracy 相似文献
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靶场通常采用夜间静态拍星的方式检测光电经纬仪的静态测角总误差。受大气折射率变化的影响,俯仰方向测角数据通常采用大气折光差经验公式进行修正。不同地区和时间的大气环境差异使得该经验公式存在较大误差,导致拍星解算得到的俯仰方向测角误差偏大,且影响俯仰方向测角误差因素的进一步分离。为此,提出了一种基于多台光电经纬仪同步拍星数据相关性分析的大气折光差修正方法。基于经纬仪拍星方位角和俯仰角测量残差模型推导得到了大气折光差修正误差模型。根据该误差模型,利用分布在同一区域不同点位的多台光电经纬仪拍星俯仰角残差数据,采用最小二乘法拟合得到大气折光差的修正系数并修正俯仰角测量残差数据。实测数据表明:采用该方法对俯仰角测量残差进行大气折光差修正后,光电经纬仪俯仰角测角总误差显著降低,且由垂直轴倾斜误差修正错误引起的方位角和俯仰角残差特性得以显现。文中提出的方法无需使用探空气球等获取大气参数,即可对同一地域分布的多台光电经纬仪拍星俯仰角残差数据进行修正,修正后的数据可用于进一步分离其他误差因素,具有较强的工程应用价值。 相似文献
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A time error correction method for improving the accuracy of asynchronous CMOS (Complementary Metal Oxide Semiconductor) imager sensor (CIS) is proposed. By adding a time error measurement unit in each pixel, the time error can be recorded, and then is sent out together with the address-events. Besides, in the external processing circuit, the correction will be accomplished before making time-stamping. For the sake of clarifying the influences on the image accuracy, different scale of the pixel array, event collisions, accuracy of time-stamping and illumination are adopted in the simulation. The simulation results of the Matlab Simulink show that, in an 8?×?8 asynchronous CIS without time error correction, when the illumination is 103?~?105 lx, the error of the image accuracy is from 0.4 % to 28 %. With the decrease of the time-stamping accuracy, the expansion of pixel array, the increase of event collisions and the strengthening of illumination, the error would deteriorate further. As to the model of asynchronous CIS with time error correction, when the accuracy of the time-stamping is 10 ns, the time error can be controlled within 20 ns. For the same illumination, the maximal error of image is 0.31 %. 相似文献
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We construct a Hamiltonian formulation for coupled-wave equations that describes the envelope functions of the electric field in an almost-periodic distributed-feedback waveguide with gain or loss. From the Hamiltonian, we can derive that the determinant of the fundamental matrix of the waveguide is always unity. A perturbation formula for the eigenvalues of the coupled-wave equations is simply derived using the Hamiltonian formulation. The Hamiltonian also provides the basis for the numerical calculation of the eigenvalues using the variational method 相似文献
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<正> 一、引言 本文提出了在积分变量较小的区域用三次函数插值代替二次函数插值的方法计算扩展电阻修正因子;进一步简化了修正因子的计算公式;并用TASC编译程序对用BASIC语言编写的,程序进行编译;从而使修正因子的计算精度有较大的提高,计算速度提高了约30倍。 相似文献
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Gonçalves SI de Munck JC Verbunt JP Bijma F Heethaar RM Lopes da Silva F 《IEEE transactions on bio-medical engineering》2003,50(6):754-767
In vivo measurements of equivalent resistivities of skull (rho(skull)) and brain (rho(brain)) are performed for six subjects using an electric impedance tomography (EIT)-based method and realistic models for the head. The classical boundary element method (BEM) formulation for EIT is very time consuming. However, the application of the Sherman-Morrison formula reduces the computation time by a factor of 5. Using an optimal point distribution in the BEM model to optimize its accuracy, decreasing systematic errors of numerical origin, is important because cost functions are shallow. Results demonstrate that rho(skull)/rho(brain) is more likely to be within 20 and 50 rather than equal to the commonly accepted value of 80. The variation in rho(brain)(average = 301 omega x cm, SD = 13%) and rho(skull)(average = 12230 omega x cm, SD = 18%) is decreased by half, when compared with the results using the sphere model, showing that the correction for geometry errors is essential to obtain realistic estimations. However, a factor of 2.4 may still exist between values of rho(skull)/rho(brain) corresponding to different subjects. Earlier results show the necessity of calibrating rho(brain) and rho(skull) by measuring them in vivo for each subject, in order to decrease errors associated with the electroencephalogram inverse problem. We show that the proposed method is suited to this goal. 相似文献
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The Gauss-Laguerre quadrature is proposed as a numerical method for calculating the correction factor integrals that occur in spreading resistance calculations. The method is very efficient in terms of computation time and memory storage, requiring only 33 integrand values for each integral evaluation. The accuracy of the method has been investigated for a variety of graded structures, and found to be better than 5%. As a test of its practical utility, the method has been used in the correction of the spreading resistance profile of a practical buried layer structure, and it has been found that the CPU time taken to correct the entire profile of 57 data points is 1.0 min on an IBM 1130 System with a 16K word (16 bit) memory or 0.4 sec on a UNIVAC 1100/10 Multiprocessor System with a 393K word (36 bit) memory. These times are a factor of 6 to 8 less than those required by using the previously proposed adaptive Simpson's rule to compute the correction factor integrals. 相似文献
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《Electron Devices, IEEE Transactions on》1986,33(2):182-187
A test is made of a recent proposal by Lewyn and Meindl for approximation of MOS inversion layer charge and substrate capacitance. Included in the test are the charge sheet formula and a new formula derived here which includes the pinning of the depletion layer width in strong inversion. Comparison with numerical calculation shows the Lewyn-Meindl result for charge density is less accurate than the charge sheet result over the entire subthreshold region. Similar inaccuracy is expected in MOS current-voltage curves in the subthreshold region and near pinch-off. The new formula is better than the other two over the entire bias range. A comparison of dc and ac substrate capacitances shows the new result to be better than both of the other formulas. In inversion, however, the percent error in dc capacitance is large. This large percent error corresponds to a small absolute error because the dc capacitance goes to zero in strong inversion. The ac capacitance error in strong inversion is ∼5 percent because of neglect of the ac inversion layer redistribution. Percent error curves for all three formulas are presented as a function of band bending and reverse bias. 相似文献
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Analysis of transient responses between coupled dipole antennas by using a simple equivalent circuit
Transient responses between two dipole antennas were analyzed by using a simple equivalent circuit of a dipole antenna. This equivalent circuit is composed of a lossless transmission line and two shunt resistances representing electrical discontinuities at a feed point and tips of the dipole antenna. A closed-form formula for the induced load voltage in the time domain was derived. Since the damping factor due to radiation from antennas is included in this expression, this formulation gives better results than those given by the conventional transmission-line approximation. Measured time histories support the validity of theoretical results. 相似文献
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在二自由度快速控制反射镜系统设计中,为提高系统的控制带宽,应尽量降低工作方向上的低阶固有频率,提高非工作方向上的高阶固有频率。该课题以某深切口柔性铰链快反镜系统作为研究对象,首先对系统前四阶固有频率的振型运动方向进行了分析,并针对传统刚度计算方法不适用于第三阶振型方向的问题,重新推导了第三阶振型方向上的刚度计算公式;其次,利用能量法和卡式第二定理对深切口柔性铰链上的工作刚度进行了推导,并进行了非线性拟合化简,得出的简化计算公式计算结果与有限元仿真结果误差不超过8.9%,证明了推导的铰链工作刚度理论公式的准确性;然后,将第三阶振型方向刚度计算公式和柔性铰链刚度计算公式代入固有频率计算公式,并进行有限元验证,结果表明理论公式计算结果与有限元仿真结果误差不超过1.7%,证明了新的三阶振型方向上的刚度计算公式的准确性。最后利用遗传算法,对系统前四阶固有频率进行了多目标优化设计,到达设计要求,所求出的优化结构较初始结构有明显优化,工作方向刚度减小19.04%,非工作方向刚度提高297.83%和77.09%。此外还对其进行了有限元仿真验证,结果证明一、二阶固有频率减小8.08%、5.40%,三、四阶固有频率提高了112.59%、16.80%。证明优化结构较初始结构有较大提高,能有效提高系统控制带宽。 相似文献