基于主成分分析的DEM粗差检测

为探讨误差的空间分布特性对数宁高程模型(DEM)粗差检测率的影响,建立了独立粗差模型和相关粗差模型,并模拟了不同粗差率(0.2%～3.0%)的数据.将随机分布的粗差加入DEM中,采用基于主成分分析的粗差检测算法进行了试验.结果表明,无论粗差是否空间相关,随粗差率增大,检测率均下降.对于独立分布的粗差,当粗差率小于1.0%时,基本可以定位所有污染数据;而对于空间相关的粗差,当粗差率等于1.0%时,检测率不足50%.可见,粗差的空间相关性及较大的粗差率均会降低基于主成分分析的粗差检测算法的检测率.     

Outlier Rejecting Multirate Model for State Estimation

IntroductionMeasured data is often contaminated by noisein state estimation.Kalman filter is a powerfultool for signal extracting.It is especially efficientin estimating spatially inhomogeneous signal whenthe noise is Gaussian.Due to process noise or non-stationary environment,the measured data is usu-ally corrupted by outliers.The performance is de-graded seriously.Generally,there are two kinds ofapproaches to handle this problem.Outlier can bedetected based on renovation[1],then be replace…     

Outlier Rejecting Muitirate Model for State Estimation

Wavelet transform was introduced to detect and eliminate outliers in time-frequency domain. The outlier rejection and multirate information extraction were initially incorporated by wavelet transform, a new outlier rejecting multirate model for state estimation was proposed. The model is applied to state estimation with interacting multiple model, as the outlier is eliminated and more reasonable multirate information is extracted, the estimation accuracy is greatly enhanced. The simulation results prove that the new model is robust to outliers and the estimation performance is significantly improved.     

小波分析在GPS动态监测数据粗差探测中的应用

文章分析了GPS监测数据序列中粗差的不确定性,提出了采用小波分析检测成片粗差,并通过实例进行应用分析,在此基础上进而对原变形数据序列中包含大量粗差的情况进行探测。实例分析表明,合理选择小波函数进行分析可以准确探测出粗差所在位置．解决了传统方法每次只能探测单个粗差的不足。     

一种新的异类多传感器系统误差融合估计算法

为解决由测向测时差无源被动传感器与主动传感器组网探测时异类多传感器系统误差估计问题,提出了一种新的异类多传感器系统误差融合估计算法.首先,通过对主被动传感器进行组合并构建异类传感器系统误差量测模型,实现了各组合传感器系统误差的实时估计;其次,通过建立多传感器融合估计结构,对多传感器系统误差的组合估计信息进行融合并反馈,获得了各传感器系统误差的全局融合估计.蒙特卡罗仿真结果表明:该算法能够对组网探测系统中各主、被动传感器的测向测时差及测距系统误差进行有效的融合估计,具有较高的工程应用价值.     

A Robust Interacting Multisensor State Fusion Based on Adaptive Outlier Controlling Multirate Model

An adaptive outlier controlling multirate model based on Hong’s multirate kinetic model was represented in order to resist the outliers and utilize their useful information. Wavelet transform was introduced to detect and control the outliers. The multirate information extraction and the controlling of outliers were properly integrated to establish an adaptive outlier controlling multirate model. The proposed model was applied to multisensor state fusion with interacting multiple model (IMM), and a robust interacting multisensor state fusion algorithm was established based on adaptive outlier controlling multirate model. The Monte-Carlo simulation shows that it could improve the accuracy of fusion estimation by 70% compared to Hong’s algorithm and at least 14% to Xiao’s algorithm.     

Robust Spectral Estimation of Track Irregularity

Because the existing spectral estimation methods for railway track irregularity analysis are very sensitive to outliers, a robust spectral estimation method is presented to process track irregularity signals. The proposed robust method is verified using 100 groups of clean/contaminated data reflecting he vertical profile irregularity taken from Bejing-Guangzhou railway with a sampling frequency of 33 data every 10 m, and compared with the Auto Regressive (AR) model. The experimental results show that the proposed robust estimation is resistible to noise and insensitive to outliers, and is superior to the AR model in terms of efficiency,, stability and reliability.     

High accuracy NURBS interpolation for five-axis machine of table-rotating/spindle-tilting type

In this paper, the definition of NURBS curve and a speed-controlled interpolation in which the feed rate is automatically adjusted in order to meet the specified chord error limit were discussed. Besides those, a definition of linear interpolation error of post-processed data was proposed, which should be paid more attention to because it will not only reduce quality of the surface but also may cause interference and other unexpected trouble. In order to control the error, a robust algorithm was proposed, which successfully met a desired error limit through interpolating some essential CL data. The excellence of the proposed algorithm, in terms of its reliability and self-adaptiveness, has been proved by simulation results.     

轮机英语教学中的纠错策略

语言教学者的纠错策略一直是语言教学研究的热点问题,第二语言教学中也出现了基于不同错误类型的纠错方法。本文以错误分析理论为依据,探讨了轮机英语教学中常见错误的应对策略,包括对错误应持的态度,纠正错误的原则、策略和技巧,以及实施补救性教学的方法,并建议轮机英语教师遵循IMO的Model Course倡导的交际法原则,在轮机英语教学过程中为学生提供有益的纠错和补救性教学,改进教学效果。     

双摄像头环境下交叉口控制延误提取的误差统计

对双摄像头环境下控制延误提取的过程进行了介绍,主要对控制延误提取的误差指标进行了验证。以曹安路-绿苑路交叉口西进口道为参数提取的场景,首先介绍了控制延误参数提取的原理;然后对获取的单个车辆的行程时间值与真实的行程时间值进行对比,使用平均误差指标得到系统提取的单辆车进行比较,得到行程时间值的误差值接近0,使用塞尔指标验证了课题研究中所提取的行程时间与实际的行程时间,结果表明可以认为检测得到的值与真实值相同。之后通过相关的处理,获取按周期统计间隔得到的车均信控延误值,考虑所获取的车均延误值的大小,选用平均相对误差指标作为周期延误参数误差统计的指标,使用k—S验证了延误参数的平均相对误差指标符合正态分布,最后使用t检验验证了课题研究中所提取的周期控制延误平均相对误差指标的误差值小于10％,从而证明了参数提取方法的有效性。     

A STEP-BY-STEP INTEGRAL METHOD FOR ACTIVELY CONTROLLED STRUCTURES

Introduction　　 Since 1 970 s,the researches in active controlofcivil engineering structures have been developedfor30 years[1] .It is now at the stage where full-scale active systems are installed in actual struc-tures and perform well for the purposes intend-ed[2 ,3 ] .Although a significant progress has beenmade,the true potential of active vibration controlremains non- exploited fully[4] .For example,manyof the current operating systems are designed pri-marily on the basis of the classical…     

柔索索力主频阶次误差及支承条件误差

为研究柔索索力测试中拉索自振频率阶次和支承条件对索力测试误差的影响规律,利用动平衡法推导了考虑弯曲刚度的柔索自振方程和自振频率公式,采用瑞利能量法分析了弹性支承条件和附加质量对拉索自振频率的影响.研究发现频率阶次对索力计算公式的影响符合二次抛物线分布特征,附加质量使拉索的自振频率减小,传感器等测试用的质量块的影响可以忽略不计,弹性支承引起的误差与弹性链杆刚度成线性关系,而且与主频的阶次有关.分析和试验结论对大跨度柔索承重结构如斜拉桥和悬索桥的索力测试具有指导意义.     

液力变矩器性能参数的计算误差及其修正方法

为提高液力变矩器数值模拟的精度,采用CFD(computational fluid dynamics)方法对液力变矩器的变矩比、效率和泵轮容量系数等性能参数进行了计算,对计算误差进行了分析,并提出了相应的误差修正方法.通过分析补偿油液流动对泵轮容量系数计算误差的影响,提出了针对泵轮容量系数误差的修正方法.结果表明:数值计算模型中,忽略摩擦损失和补偿油液流动的影响,将引起变矩器性能参数的计算误差;针对摩擦损失提出的误差修正方法,使算例中变矩器的变矩比和效率的最大相对误差均由16.2%减小到13.9%;按照泵轮容量系数误差的修正方法,泵轮容量系数的最大相对误差由13.9%减小到7.3%.     

三齿轮联动双曲柄环板式针摆行星传动中针摆传动误差分析的新思路

传统的分析减速器整机传动误差的方法通常是以误差独立作用原理为基础,采用微分法和原始误差等效作用法求解,它没有考虑误差的相关性,也不清楚各时刻误差的变化情况.使用不同于传统理论计算的方法,在建立存在各种误差时针摆啮合的坐标系基础上,将针摆啮合传动的过程从数学的角度来定义,并建立可以求出每一时刻输出转角的误差值的数学模型,同时对减速器中的针摆传动部分的传动误差进行了分析.这种方法吸取了实验法的一些优点,同时又克服了它的不足.     

Robust expected violation criterion for constrained robust design problems and its application in automotive lightweight design

Metamodeling techniques are commonly used to replace expensive computer simulations in robust design problems. Due to the discrepancy between the simulation model and metamodel, a robust solution in the infeasible region can be found according to the prediction error in constraint responses. In deterministic optimizations, balancing the predicted constraint and metamodeling uncertainty, expected violation (EV) criterion can be used to explore the design space and add samples to adaptively improve the fitting accuracy of the constraint boundary. However in robust design problems, the predicted error of a robust design constraint cannot be represented by the metamodel prediction uncertainty directly. The conventional EV-based sequential sampling method cannot be used in robust design problems. In this paper, by investigating the effect of metamodeling uncertainty on the robust design responses, an extended robust expected violation (REV) function is proposed to improve the prediction accuracy of the robust design constraints. To validate the benefits of the proposed method, a crashworthiness-based lightweight design example, i.e. a highly nonlinear constrained robust design problem, is given. Results show that the proposed method can mitigate the prediction error in robust constraints and ensure the feasibility of the robust solution.     

悬臂浇注施工斜拉桥的误差控制方法

在预应力混凝土(PC)斜拉桥悬臂施工中,为了减小索力及线形误差,分析了误差原因及其控制现状,提出了模型误差及悬浇效应误差的控制方法。结合三维实体等参元和板壳单元的优点,构造了适用于复杂桥梁结构空间分析的实体退化单元,建立了离散钢筋模型。根据挂篮牵索锚固点处的变形协调条件,推导出牵索索力随混凝土浇筑的增量计算公式,建立了悬浇过程中各工况下挂篮前端标高控制的计算公式。应用结果表明:在悬浇施工过程,牵索索力控制精度达到了3%,成桥索力控制精度达到5%,悬臂端标高误差控制在1 cm内,因此,提出的控制方法可实现PC斜拉桥悬浇过程各工况下索力及线形的准确预测。     

Robust optimization for the correlated MIMO downlink with imperfect channel state information

To reduce the performance deterioration induced by imperfect channel state information (CSI) in cor-related multiple input multiple output(MIMO) downlink, the linear transmit/receive filters should be optimized to be robust to imperfect CSI. A sub-optimization algorithm based on minimizing sum MSE conditional on available imperfect CSI estimates subject to a per-user power constraint is proposed. The algorithm adapts the existing MMSE algorithm from uncorrelated single-user MIMO system with perfect CSI to correlated MIMO downlink with imperfect CSI. Simulation shows that the suboptimal algorithm can effectively mitigate the performance loss induced by imperfect CSI and has a good convergence performance. In addition, the effect of spatial correlation on the performance of the proposed algorithm is also simulated.     

Joint distortion model for progressive image transmission using error correcting arithmetic codes

A novel joint source channel distortion model was proposed, which can essentially estimate the average distortion in progressive image transmission. To improve the precision of the model, the redundancy generated by a forbidden symbol in the arithmetic codes is used to distinguish the quantization distortion and the channel distortion, all the coefficients from the first error one to the end of the sequence are set to be a value within the variance range of the coefficients instead of zero, then the error propagation coming from the entropy coding can be essentially estimated, which is disregarded in the most conventional joint source channel coding （JSCC） systems. The precision of the model in terms of average peak-signal-to-noise has been improved about 0.5 dB compared to classical works. An efficient unequal error protection system based on the model is developed, and can be used in the wireless communication systems.     

Joint Distortion Model for Progressive Image Transmission Using Error Correcting Arithmetic Codes

A novel joint source channel distortion model was proposed, which can essentially estimate the average distortion in progressive image transmission. To improve the precision of the model, the redundancy generated by a forbidden symbol in the arithmetic codes is used to distinguish the quantization distortion and the channel distortion, all the coefficients from the first error one to the end of the sequence are set to be a value within the variance range of the coefficients instead of zero, then the error propagation coming from the entropy coding can be essentially estimated, which is disregarded in the most conventional joint source channel coding (JSCC) systems. The precision of the model in terms of average peak-signal-to-noise has been improved about 0.5 dB compared to classical works. An efficient unequal error protection system based on the model is developed, and can be used in the wireless communication systems.