Transverse vibration of the blade for unmanned micro helicopter using rayleigh-ritz method

A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural frequencies and mode shapes of the blade for the helicopter are studied by using beam characteristic orthogonal polynomials by the Rayleigh-Ritz method. The variation of natural frequencies with the speed of rotation and the mode shapes at different rotational speeds are plotted. The using of orthogonal polynomials for the bending shapes enables the computation of higher natural frequencies of any order to be accomplished without facing any difficulties.     

Novel non-coherent integration method using binary phase-coded radar signal

The m series with 511 bits is taken as an example being applied in non-coherent integration algorithm. A method to choose the bi-phase code is presented,which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power increasing times of larger target sidelobe is less than the power increasing times of smaller target mainlobe because of the larger target’s pseudo-randomness. Smaller target is integrated from larger target sidelobe,which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic,a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6 . 5 dB by the proposed method.     

心电图信号处理技术及小波变换方法

给出了心电信号处理的两种方法。第一种方法是运用合成技术,它可以保证波形的完整,而且便于实现。第二种方法是运用小波分析。小波适用于分析非平衡信号,适宜于对心电图数据进行预处理和特征提取。本文应用Mallat算法对心电图信号进行了多尺度分解。     

心电图信号处理技术及小波变换方法

给出了心电信号处理的两种方法。第一种方法是运用合成技术 ,它可以保证波形的完整 ,而且便于实现。第二种方法是运用小波分析。小波变换适用于分析非平稳信号 ,适宜于对心电图数据进行预处理和特征提取。本文应用Mallat算法对心电图信号进行了多尺度分解     

高阶混沌振子的微弱信号频率检测新方法

采用高阶Rossler混沌振子及比例微分控制方法相结合,将含有待检信号的Rossler混沌振子从混沌态控制到周期态,然后利用谱分析的方法检测待检信号的频率.该方法突破了以往Duffing方程检测信号频率需要使用较多振子的局限,利用比例微分控制理论将Rossler系统控制到稳定的周期态,从而提取待检信号的频率,较大提高了检测精度和检测稳定性.通过数值仿真,验证了该方法的有效性.     

基于高阶统计量的非高斯噪声中的信号检测方法研究

信号检测方法是信号处理的一个重要研究方向,以前的信号检测方法多是基于高斯噪声的讨论,对非高斯噪声中的信号检测较少,本文针对未知协方差非高斯噪声中的确知信号的检测,提出一种基于高阶累积量的检测方法,并且论述了广义匹配滤波器的设计及相关接收检测原理,最后进行了计算机仿真并给出了仿真对比实验结果。     

基于时间序列相似性度量的瓦斯报警信号辨识

提出了基于时间序列相似性度量的瓦斯报警信号自动识别技术.基于动态时间弯曲（DTW）距离对从山西某高瓦斯煤矿2010年瓦斯监测数据库中提取的150组数据采集周期为9～70s的采掘工作面瓦斯含量超限报警时间序列进行聚类分析,获得了7种典型的瓦斯超限报警时间序列模式;以此为数据源,采取分段形态度量方法,提取并筛选出3个重要指标,建立了瓦斯报警时间序列形态特征库,并提出了基于分段形态度量的瓦斯报警信号快速辨识算法.对另外150组瓦斯报警时间序列进行辨识,实验表明,准确率达92%以上.尤其是通过联合分析瓦斯报警时刻前后的k0和k1值可以快速辨别瓦斯超限原因是炮后瓦斯还是突出警报,统计表明,k0〉0.1,k1〉0时,100%发生煤与瓦斯突出.     

一种叶片裂纹检测的稀疏共振解调算法

针对强相干噪声干扰下叶片振动信号中裂纹故障微弱特征的提取问题,提出了一种基于稀疏共振解调的诊断方法。首先,利用从中心集化多分辨分析处理机组上取得的原始振动信号进行子空间重构;其次, 对小波子空间信号进行希尔伯特包络解调,选取故障特征频率及其倍频成分能量占优的子空间;再次, 根据周期性故障稀疏模型,采用梳形滤波器分离故障特征频率及其倍频成分,构造故障分量参考信号;最后,结合故障参考信号对子空间重构信号进行小波降噪, 从而提取与叶片裂纹相关的微弱特征。在出现叶片裂纹故障的发电机组增压风机故障诊断案例分析中,仅采用多尺度分解无法在时域上得到周期性冲击故障特征。而采用所提出的基于稀疏共振解调方法进行信号处理后,强相干噪声得到了有效抑制, 从而突出了故障特征。     

基于CFD的大型风力发电机组叶片气动性能研究

为了研究大型风力发电机组叶片的气动性能,提出了基于CFD技术的叶片气动性能分析方法.该方法采用RANS方程结合SST湍流模型,以实现对大型风机叶片二维翼型气动性能和三维气动性能的分析预报.在此基础上,采用二维方法分析了NACA64-618翼型-180°～180°攻角下的气动性能,获得了其失速攻角,与试验数据的比较证明了该方法的准确性;建立了2MW大型风机三维叶轮模型,采用三维方法分析了其气动性能,与GHBladed软件计算结果比较证明了三维方法的可行性.最后,对2MW风机翼型进行了优化,改善了其气动性能.研究方法对于大型风机叶片的设计,优化及新翼型的开发具有重要参考价值.     

基于信号统计分析的变速旋转机械故障诊断系统

机械振动信号的统计特征对于研究机械振动具有重要意义，旋转机械故障的非线性影响其振动信号的统计特征，本文设计了以单片机为核心的统计分析系统用于对故障前与故障后的振动信号的概率密度函数、幅值增值等统计征的测定，并据此进行故障诊断，本系统克服了基于谱分析的诊断系统的时间空间复杂度高，谱线分辨率受限，受样速度高，对变速机械振动信号的不适应和造价高等特点，适用于诸如数控机床主轴，飞行器旋翼等多种变速旋转机械的实时故障诊断。     

Improved method for SAR echo signal simulation using two-dimensional frequency domain transformation

The echo signal simulation of Synthetic Aperture Radar (SAR) is the basis of the research on SAR signal processing, and the large computation cost is the primary shortcomings of the frequently-used echo signal simulation method. Using the theory that Stolt transformation can simulate the so-called space-varying property of range migration, the IωKA algorithm becomes an impressive fast echo signal simulation method for the extended scenes in the two-dimensional frequency domain, and the computational cost and operation time is cut down sharply. According to the analysis, the key to the IωKA algorithm is the interpolation for the Stolt transformation, and the signal before interpolation in the IωKA algorithm can be seen as a band-limited signal in the strict sense, which is greatly different from that in the ωKA algorithm and may has a great effect on the selection of the interpolation algorithm and the interpolation performance. By preprocessing, the signal before interpolation in the IωKA algorithm is transformed into a baseband band-limited signal in the strict sense, which improves the interpolation performance, reduces the complexity of the interpolation, and enlarges the application range of the algorithm. Experimental result shows that if the error introduced by the simulation is regarded as noise, the error level of our method is much less than the system noise. Also, Compared with the other 2-D frequency-domain simulation methods, this method has a small amplitude error and phase error, and could be applied to the whole strip mode SAR with varieties of squint angles and wide-beam.     

Seismic signal recognition using improved BP neural network and combined feature extraction method

Seismic signal is generally employed in moving target monitoring due to its robust characteristic. A recognition method for vehicle and personnel with seismic signal sensing system was proposed based on improved neural network. For analyzing the seismic signal of the moving objects, the seismic signal of person and vehicle was acquisitioned from the seismic sensor, and then feature vectors were extracted with combined methods after filter processing. Finally, these features were put into the improved BP neural network designed for effective signal classification. Compared with previous ways, it is demonstrated that the proposed system presents higher recognition accuracy and validity based on the experimental results. It also shows the effectiveness of the improved BP neural network.     

短时、临近、雷电和预警制作的多任务平台

为提高地市级气象台制作各种预报和预警产品的效率,分析表明短时预报、临近预报、雷电预报和灾害性天气预警信号的制作过程和内容具有类同的特点.在有限硬件条件下,用集约化、多任务、多功能的设计理念,借助计算机语言,建成地市级气象台集短时预报、临近预报、雷电预报和灾害性天气预警信号制作于一身的多功能平台.该平台集合4项预报业务的制作分发任务,减少重复设计;采用3种编辑方式和2种输入方式,使操作省力而简单;同时配置2种传输方式,提高了程序的网络环境适应性.业务应用表明,该平台可以使每项预报产品从开始制作到最后发送出去比手工操作节约时间达到75%～80%;并说明,用小系统、数据交换和业务流程可组合成"大系统."     

降低OFDM信号峰均比的边带信息检测方案

对于每个子载波只受到QPSK符号调制的正交频率复用系统,提出了两种边带信息检测方案,此边带信息是部分传输序列次优算法降低正交频率复用信号峰均比所引入的．这两种方案利用了QPSK符号的特点,在发射端通过QPSK符号相位旋转把边带信息嵌入信号中,然后在接收端通过求模、减法以及比较运算把边带信息检测出来．这两种方案计算复杂度很低,具有较高检测可靠性能．     

Investigation on full vehicle height control algorithm using feedback linearization method

Aiming to improve the control accuracy of the vehicle height for the air suspension system, deeply analyzing the processes of variable mass gas thermodynamics and vehicle dynamics, a nonlinear height control model of the air suspension vehicle was built. To deal with the nonlinear characteristic existing in the lifting and lowering processes, the nonlinear model of vehicle height control was linearized by using a feedback linearization method. Then, based on the linear full vehicle model, the sliding model controller was designed to achieve the control variables. Finally, the nonlinear control algorithm in the original coordinates can be achieved by the inverse transformation of coordinates. To validate the accuracy and effectiveness of the sliding mode controller, the height control processes were simulated in Matlab, i.e., the lifting and lowering processes of the air suspension vehicle were taken when vehicle was in stationary and driving at a constant speed. The simulation results show that, compared to other controllers, the designed sliding model controller based on the feedback linearization can effectively solve the "overshoot" problem, existing in the height control process, and force the vehicle height to reach the desired value, so as to greatly improve the speed and accuracy of the height control process. Besides, the sliding mode controller can well regulate the roll and pitch motions of the vehicle body, thereby improving the vehicle''s ride comfort.     

测量技术中的混沌方法

提出了一种在极不稳定的混沌系统中进行信号测量的方法．将敏感元件作为混沌电路的一部分,在初值一定的条件下,利用混沌系统的参数敏感性,敏感元件的参数随待测信号变化并使系统的混沌轨道变化,定义了轨道距离,通过测量混沌轨道的距离即可得到待测信号．经仿真验证了此方法是可行的．     

明渠湍流泥沙运动的大涡数值模拟

基于大涡模拟思想建立了水流泥沙运动的三维数学模型,探讨了不同子网格应力模型在明渠湍流泥沙运动模拟中的适用性,所选用的子网格应力模型包括标准Smagorinsky模型、剪应力改进型Smagorinsky模型和RNG模型;探讨了泥沙重力作用项数值离散格式对计算结果的影响;并对近底泥沙浓度分布规律进行了研究.研究表明:在采用修正迎风格式对泥沙重力作用项进行数值离散时,能较合理地预报泥沙浓度的分布;所选用的三类子网格应力模型均适用于明渠湍流泥沙运动的模拟,并能合理地预报时均流速及悬移质含沙量的垂线分布规律;达到统计平衡状态时,泥沙主要集中于近床面附近,且近底泥沙浓度在平面上呈现"条带"分布特征.     

Investigation on experimental method of low-impedance materials using modified Hopkinson pressure bar

To increase the detectability of split Hopkinson pressure bar (SHPB) of low-impedance materials, modifications were conducted on traditional SHPB apparatus with a PMMA tube to output transmitted signal, and weak signals were further amplified by semiconductor strain gauges. Experiments on soft rubbers and cushioning foam materials were carried out. In order to analyze the accuracy of the experimental results, the stress equilibrium issues involved in the assumptions of SHPB were investigated. First, by way of re-constructing loading process of incident wave, the stress-strain curve was obtained, along with the stress equilibrium ratio of specimen. Secondly, the influences on the accuracy of stress-strain curves were investigated through the elastic modulus comparisons. And the results illustrate that the bilinear incident wave from experiments can ensure the stress equilibrium deformation of specimen after 2 normalized times, much sooner than ramp incident waves. Moreover, it even facilitates specimen deformation with a constant strain rate. The results confirm that the detectability of the modified SHPB can be down to tens kPa with enough accuracy level.     

传感器输出信号传输的一种新方法

介绍将传感器输出信号传输给显示仪表的一种新方法.采用耦合、解耦将传感器输出信号迭加在为传感器提供电源的电源线上,使传感器与仪表之间仅需二根线即可实现信号的传输与电源的提供.     

二次谐波加权重构的77GHz FMCW雷达心率监测方法

针对呼吸及其谐波强干扰下的心率估计问题,提出了一种利用心跳二次谐波信号加权重构的心率监测方法,并运用77 GHz调频连续波雷达实现了心率的精准测量.在胸壁位移信号多分辨率分析的基础上,依据各层能量分布特性,对心跳二次谐波范围内的子频带进行加权处理,以凸显心跳二次谐波最可能出现的频率范围,这不仅避免了呼吸及其谐波的强干扰...