共查询到18条相似文献,搜索用时 56 毫秒
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构造了基于剩余飞行时间指数函数的扩展目标罚函数,给出了对常值机动目标最优的扩展弹道成型制导律簇。利用无量纲化方法和伴随技术,研究了含有一阶动力学滞后的制导系统在目标常值机动、随机机动和终端落角约束作用下的无量纲位置和角度脱靶量随无量纲末导时间变化特性。采用直接法对伴随法仿真结果进行了验证。研究结果表明,当末导时间分别为制导系统动力学滞后时间常数的15倍、20倍左右时,落角约束和目标常值机动引起的位置和角度脱靶量均趋近于零;随着指数n的增大,导航系数也越大,无量纲位置和角度脱靶量振荡加剧,收敛时间也加长。目标随机机动引起的位置和角度脱靶量随着末导时间的增大维持在某个稳定的值,并不趋近于零,而且指数n越大,其脱靶量的稳定值也越大。 相似文献
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飞秒激光跟踪仪通过PSD探测脱靶量实现目标跟踪,脱靶量零位是跟踪激光指向反射靶球的中心时反射激光在PSD上输出的光斑位置,跟踪时以脱靶量零位作为基准计算目标脱靶量,因此如何准确标定脱靶量零位是仪器实现精确测量的前提。文中在分析角反射器特性的基础上,结合仪器自身特点提出了一种基于角反射器的飞秒激光跟踪仪跟踪脱靶量零位标定方法。分析了脱靶量零位误差对仪器指向精度的影响;建立了跟踪脱靶量标定误差模型;根据仪器结构设计和轴系几何误差对脱靶量零位标定方法进行了仿真,结果显示,其误差小于17.8 m,当目标距离仪器10 m时,仪器的指向误差小于1.1,该结果对系统误差补偿模型建立奠定了基础。最后,基于实际装置对仪器的脱靶量零位进行了标定,为后续仪器的动态测量提供了跟踪基准。 相似文献
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激光跟踪仪是一种用于大尺寸空间精密几何坐标测量的重要光学测量仪器。PSD是激光跟踪仪实现对合作目标精密跟踪的脱靶量传感器件,其探测精度直接影响跟踪测量性能。首先,简要介绍了激光跟踪测量系统及基工作原理,然后根据系统需求提出了脱靶量精密探测方案。重点讨论了I/V变换、信号放大、滤波、参数匹配等硬件设计方法以提高PSD输出微弱电流信号的稳定性,研究提出了基于FPGA和有限状态机的去极值平均滤波算法和扩展除法运算算法分别用于降低噪声干扰与提高测量精度;数据表明在4mm4mm的区域内脱靶量探测稳定度优于2m。采用该方法实现激光跟踪仪对合作目标的动态跟踪,很好地满足了激光跟踪仪的精密快速跟踪需要。 相似文献
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针对红外成像导引头复杂战场环境适应性测试,提出了一种采用数字图像注入式的闭环半实物仿真试验方法,并分析了闭环注入式仿真试验系统的组成及工作原理。由于仿真测试时红外成像导引头的传感器被图像仿真计算机和图像注入接口设备取代,导致数字图像生成及脱靶量计算环节存在延迟和误差,使伺服控制系统的性能与实际工作情况可能不一致,从而影响仿真试验结果精度和置信度,因此,在建立导引头伺服控制系统模型的基础上,研究了仿真时间延迟、脱靶量误差对伺服控制系统的影响。研究结果表明:由于脱靶量误差对跟踪精度的影响仅为1.33%,如果将时间延迟控制在56.5 ms之内,开展闭环注入式仿真试验是可行的,该结果可为下一步开展红外成像导引头闭环注入式仿真试验提供理论支持。 相似文献
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Orthogonal frequency division multiplexing (ofdm) systems have gained interest, especially in the case of bad propagation channels with severe multipath propagation and long delays. We will describe an ofdm system model and focus our attention on the estimation of the channel transfer function. Two different methods are presented which are analyzed and illustrated with regard to their mean squared error (mse). Then we will investigate the effects of an improper estimation on multilevel signal constellations. It reveals that avoiding signal points with high energy is very essential. Thus, we present a coding scheme which uses trellis shaping. Our simulations with ofdm over multipath channels give additional gains over those which are known for the additive white Gaussian noise (awgn) channel. 相似文献
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An extended combinatorial analysis framework for discrete-time queueing systems with general sources
《Networking, IEEE/ACM Transactions on》2003,11(1):95-110
The paper considers a general class of discrete time systems with batch arrivals and departures. Such models appear frequently in the teletraffic analysis of computer and communications networks. Our arrival models are assumed to be quite general. They could be independent and identically distributed (i.i.d.) in successive slots, periodic, Markovian, or described by the moving average time-series model, etc. Our solution framework is novel and unifying and it uses a combination of multidimensional generating functions and combinatorial analysis utilizing extensions of classical ballot theorems. In general, we provide an explicit analytical expression as an infinite sum to obtain the system stationary probability distribution avoiding classical root-finding methods, matrix analytical methodologies, and spectral decomposition approaches. We provide a number of analytical and numerical examples including: i.i.d. models with Poisson and Binomial arrivals; multiserver queueing systems fed by Markovian sources; queues fed with a discrete moving average source of the first and second order; an i.i.d. discrete Pareto batch arrival model. Closed-form analytical expressions are obtained for the stationary distribution of the system queue lengths and numerical examples are also provided when appropriate. 相似文献
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针对增程单兵火箭弹由于弹道低伸和末段弹道时间短的弹道特点对激光末段制导形成的局限,研究捷联激光制导导引头在末段全弹道上的目标捕获域和目标捕获率。建立低伸弹道上激光半主动导引头目标捕获域模型,在不同的火箭弹发射角条件下,对导引头在末段全弹道上的目标捕获域与最小锥形视场进行仿真,分析最小目标捕获域边界由双曲线变为椭圆时的弹道点和视场角,得到导引头的最佳半视场角为5.9。考虑弹道扰动的影响,通过蒙特卡罗方法计算末段弹道上不同弹道点的导引头目标捕获率,得到在弹道上导引头的最佳起始探测弹道点。为增程单兵火箭弹的制导化提供参考。 相似文献
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为了减少MIMO无线通信系统的射频链路硬件成本和降低系统复杂度,针对采用排序逐次干扰抵消(OSIC)接收的MMSE V-BLAST系统,通过对增广信道矩阵进行次优排序和QR分解分析,提出了一种新颖低复杂度的发射天线选择算法.与其它方案不同的是,本文算法综合考虑了排序、干扰抵消和噪声对天线选择性能的影响.仿真结果表明,该算法的性能比其它算法的性能有很大改善. 相似文献
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This paper studies the effect of chip waveform shaping on the performance of band-limited multicarrier direct-sequence code-division multiple-access (MC-DS-CDMA) systems. The performance criterion is the average multiple access interference at the output of a correlation receiver. A criterion based on the elementary density function is introduced for the performance comparison of various chip waveforms. It is demonstrated that the performance of MC-DS-CDMA systems is quite insensitive to the chip waveform shaping. Moreover, the optimum chip waveform for MC-DS-CDMA systems is practically the same as that of a single-carrier DS-CDMA system. 相似文献
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Error spectrum shaping (ESS) quantizers are analyzed in the context of realistic FIR reconstruction filters and nonzero probability of saturation. Conditions for stable operation are derived, and a suboptimal but effective and computationally efficient design method is proposed. Excellent agreement is obtained between the analysis and simulations. Even under these more stringent constraints, ESS quantizers are shown to achieve significant signal-to-quantization-noise ratio (SQNR) gains when quantizing oversampled Gaussian sources 相似文献
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Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD 相似文献