Clutter Suppression Properties of Weighted Pulse Trains

A common but troublesome requirement on radar sensors is the detection of a target in the interference from undesired scatterers, or clutter. Systems with coherent processing of pulse trains are uniquely suited for the purpose because, with pulse trains, it is possible to concentrate the receiver output for particular values of Doppler and thus suppress the clutter by Doppler filtering. This paper discusses to what degree the effectiveness of the method can be enhanced by tapering, or weighting, of the pulse amplitudes. The general results are illustrated by computer-plotted response functions for weighted pulse trains. The clutter suppression efficiency of weighting is calculated both for unilateral weighting in the receiver and for bilateral weighting in both receiver and transmitter. The significance of additional phase weighting is discussed and the results for pure amplitude weighting are compared with publishedwork on phase and amplitude weighting.     

带有落角约束的一般加权最优制导律

以期望的落角方向为坐标轴定义了落角坐标系,在落角坐标系中建立了线性化的运动关系方程。应用Schwarz不等式,分别研究了控制系统为一阶惯性环节和无惯性环节情况下带落角约束的任意加权最优制导律,得到了制导律的一般表达式。对于无惯性环节控制系统以及加权函数为一般初等函数类型的一阶惯性环节控制系统,当加权函数的逆的一次到三次积分都能求出解析表达式时,均可以得到解析形式的最优制导律。对于不同的制导目的,应用本文结果可以方便地设计相应的制导律。对于某些特定的加权函数,所得制导律推广了现有文献的结论,并给出了指数权函数下满足落角约束的最优制导律的仿真结果。     

Range Dependent Waveform of an Active Weighted Pulse Compression Receiver

This paper presents the output waveform of a correlation techniquewhich incorporates time domain amplitude weighting and matchedfiltering. This scheme may be used in pulse compression radars wherefine target detail is desired over an increment of range, the rangewindow. Analytic expressions describing the amplitude, phase, andfrequency modulation of the output waveform are obtained for thecosine-squared weighted spectrum, truncated Taylor weighted spectrum,and cosine-cubed weighted spectrum with weighting mismatchas a parameter. The effects of such mismatches on the amplitude,phase, and frequency modulation of the compressed waveform areplotted. However, the methods used to obtain these results are generalenough to obtain output waveforms of other weighting functions similarlymismatched.     

高阶柔性结构系统振动控制中加权函数的选择

 总结了混合灵敏度H_∞控制算法中加权函数阵的选择方法,提出了一种新的选择加权函数矩阵的思想。以某悬臂梁为研究对象,将混合灵敏度H_∞控制方法应用在高阶柔性结构的振动主动控制问题中,完成了两输入两输出结构振动控制的控制器设计和算法仿真。结果表明,通过本方法选择加权函数矩阵,可在满足鲁棒稳定性的前提下,使外部干扰得到有效抑制,减振效果良好。     

学科间信息传递的参数化空间散乱数据插值法

耦合信息传递是实现耦合系统求解的关键技术之一,本课题研究了参数空间散乱数据插值方法.为了避免三维插值空间平整性导致的插值误差,将三维耦合界面进行参数化处理,在参数空间中构造插值函数进行插值传递.针对径流式叶片的特点,进行了温度插值传递.从插值效果看,这种基于参数空间的数据插值方法保证了较高的插值精度.比较了反距离加权平...     

Some Results on Digital Chirp

Generating chirp waveforms by means of phase coding yields a simple, cost-effective mechanization. The coding process, however, introduces phase errors whose effect must be included in the design. An approximate analysis is presented, valid for moderate to high compression ratios, which allows error effects on compressed pulse amplitude and sidelobes to be calculated in a simple manner. The anaylsis provides criteria for selecting the coding bit width (sample rate), weighting network bandwidth, and phase-coder quantization interval and transition times. Weighting functions for maximizing the signal-to-noise ratio (SNR) or for producing desired close-in sidelobe performance are derived, as is an exact expression for the transmitted spectrum. Numerical results are presented for Gaussian and the maximum-SNR weighting. The results indicate that performance will be satisfactory for many applications.     

基于μ理论的飞机俯仰姿态控制

针对飞机飞行条件变化引起的模型不确定性问题,基于μ控制理论设计鲁棒的俯仰姿态控制系统.首先,根据干扰抑制原理将俯仰姿态控制系统设计转化为μ综合的一般框架,合理地选择加权函数确定广义被控对象,通过引入虚拟的不确定块将鲁棒性能问题转化为广义系统的鲁棒稳定性问题.然后,利用D-K迭代算法求解得到14阶的μ控制器,基于平衡截断...     

舰载飞机着舰精确轨迹跟踪控制研究

根据着舰运动及Ｈ∞控制方法概念对用Ｈ∞控制方法设计舰载飞机自动着舰导引系统进行了研究;并按着舰导引系统的性能要求,确定了Ｈ∞控制综合模型的结构,给出了权阵的选取准则。以ＡＤ－４飞机为例进行了仿真验证,仿真结果表明,所设计的自动着舰导引系统能满足着舰要求,并有效地提高了导引系统着舰轨迹跟踪精度及抗气流扰动的能力。     

模糊数学用于飞机总体参数的优化设计

一、引言 飞机总体参数设计是飞机全局性的综合设计,是整个飞机设计工作战略性的一步,它是围绕如何达到使用技术要求这个目标来进行的。使用技术要求对设计飞机的主要性能指标提出了起码的限度值。然而,这一阶段的设计工作是粗略的、不精密的。     

测轨时序差分观测权阵的解析表达式

基于相关权逆阵和二次差分矩阵的对应关系,利用Delta函数的性质,推导了时序差分组合的相关权矩阵公式,并利用M atlab对解析表达式进行了数值验算。该公式可以直观地反映出差分组合观测量的统计相关信息。     

基于遗传算法的直升机鲁棒飞行控制器设计

以旋翼机驾驶品质要求 ADS-33为设计目标,采用 H∞ 混合灵敏度方法设计直升机在低速飞行时的鲁棒控制器,设计中利用遗传算法优化加权阵参数,找到同时满足频域和时域性能要求的控制器。以 UH-60 A直升机为对象,所设计的直升机飞行控制系统不仅具有鲁棒稳定性,而且满足 ADS-33D水平 1操纵品质要求。     

极点配置的H_∞技术在直升机控制器设计中的应用研究

极点配置的 H∞ 设计方法不但能满足系统的 H∞ 性能要求 ,而且能使闭环极点配置在希望的范围内 ,因而使系统具有满意的阻尼比 ,同时也避免了过快的控制器动态对设备产生的冲击。针对直升机 H∞ 控制器设计中遇到的问题 ,如控制器结构的选择、加权矩阵的选择以及如何考虑不确定性等进行了研究。通过对 CH-4 7直升机设计结果的数值仿真 ,表明所设计的系统达到了 ADS-33水平 1的性能要求和鲁棒稳定性要求     

极点配置的H_∞技术在直升机控制器设计中的应用研究

 极点配置的 H∞ 设计方法不但能满足系统的 H∞ 性能要求 ,而且能使闭环极点配置在希望的范围内 ,因而使系统具有满意的阻尼比 ,同时也避免了过快的控制器动态对设备产生的冲击。针对直升机 H∞ 控制器设计中遇到的问题 ,如控制器结构的选择、加权矩阵的选择以及如何考虑不确定性等进行了研究。通过对 CH-4 7直升机设计结果的数值仿真 ,表明所设计的系统达到了 ADS-33水平 1的性能要求和鲁棒稳定性要求     

Two freedom linear parameter varying μ synthesis control for flight environment testbed

To solve the problem of robust servo performance of Flight Environment Testbed(FET)of Altitude Ground Test Facilities(AGTF) over the whole operational envelope, a two-degree-offreedom μ synthesis method based on Linear Parameter Varying(LPV) schematic is proposed, and meanwhile a new structure frame of μ synthesis control on two degrees of freedom with double integral and weighting functions is presented, which constitutes a core support part of the paper. Aimed at the problem of reference command's rapid change, one freedom feed forward is adopted, while another freedom output feedback is used to meet good servo tracking as well as disturbance and noise rejection; furthermore, to overcome the overshoot problem and acquire dynamic tuning,the integral is introduced in inner loop, and another integral controller is used in outer loop in order to guarantee steady errors; additionally, two performance weighting functions are designed to achieve robust specialty and control energy limit considering the uncertainties in system. As the schedule parameters change over large flight envelope, the stability of closed-loop LPV system is proved using Lyapunov inequalities. The simulation results show that the relative tracking errors of temperature and pressure are less than 0.5% with LPV μ synthesis controller. Meanwhile, compared with non-LPV μ synthesis controller in large uncertainty range, the proposed approach in this research can ensure robust servo performance of FET over the whole operational envelope.     

MTI Improvement Factors for Weighted DFTs

The use of the discrete Fourier transform (DFT) to enhance the detection of moving targets in ground clutter is examined. The improvement factor, defined as the signal-to-clutter ratio at the DFT processor output compared with that of the input, is given as a function of normalized clutter spectral width for various weighting functions on the DFT input. The effect of quantization of the weights on the improvement factor is also examined.     

适用于混合网格的约束最小二乘重构方法

为强化边界条件对计算流体力学(CFD)计算中流场重构过程的影响,基于三维任意多面体混合网格,对一种约束最小二乘法进行了研究。通过对不同边界类型的透明化处理,统一了约束方程组的形式,从而简化了该方法的应用。为了充分吸收消去法和加权法各自求解约束方程组的优点,提出了混合采用两种方法的思路。针对层流平板研究了加权法中加权系数如何取值问题,数值实验表明加权系数取到5基本已经足够大。最后通过亚声速层流平板和跨声速湍流ONERA-M6算例对比了混合法、加权法与原始最小二乘法,计算结果表明:约束最小二乘法相比原始最小二乘法的流场重构更加准确,特别是对边界质量较差网格的计算优势更为突出;混合消去加权法相比单独采用加权法的计算结果也有所改善。     

MTI Loss with Coherent Integration of Weighted Pulses

A moving target indicator (MTI) preceding a coherent integrator causes a degradation in the signal-to-noise ratio (SNR). This negative effect can be reduced by weighting of the MTI output pulses before the integration process. Two examples are given which show the improvement in SNR and detection probability as a result of this weighting.     

面向声源定位的改进广义互相关时延估计方法

面向以数字微机电系统(MEMS)麦克风作为声传感器的声源定位阵列,完成了前端麦克风阵列的电路设计和以现场可编程逻辑门阵列(FPGA)为核心的数据采集系统的开发,并对麦克风输出的脉冲密度调制信号进行了降采样处理.针对传统的广义互相关算法在低信噪比下时延估计误差较大的问题,提出了一种改进PHAT加权函数的方法.在同等条件下对基于不同加权函数的广义互相关算法进行了MATLAB仿真验证,实验结果表明,在低信噪比条件下该方法相较于传统的广义互相关算法,时延估计误差更小且抗噪性能更强.     

MTI Weightings

A comparison is made between optimum weighting, which maximizes Pd for a given ?, and several MTI weightings. It is shown that a special case of the optimal weighting is approximately equal to the MTI weighting which maximizes the MTI improvement factor.     

转子后总压旋态误差的研究

总压测量时,测点气流的真实总压是p~*(不考虑探针的干扰),而探针感受到的压力是p_(?)转子后旋态使气流方向有大幅度变化(如图1,在近场尾迹中可达40°),因此一般p_(?)不一定与真实压力恒等,测试系统最后得到指示压力P_(?)工程上一般要求总压的质量平均值p_m~*,而在指示端得到的是指示压力的时间平均值芦p_(H(?)),故旋态误差为