Bias compensation for the bearings-only pseudolinear target track estimator

The bearings-only pseudolinear target track estimator is known to suffer from severe bias problems. This paper presents a bias analysis for the pseudolinear estimator and develops a method of bias compensation, resulting in a closed-form reduced-bias pseudolinear estimator. The reduced-bias estimator is then incorporated into an instrumental variable estimator to produce asymptotically unbiased target motion parameter estimates. Unlike batch iterative estimators, the proposed instrumental variable estimator has a closed-from solution and therefore avoids the convergence problems associated with iterative estimators. The performance of the proposed instrumental variable estimator is illustrated by way of simulation examples and is shown to be almost identical to that of the computationally more demanding iterative maximum likelihood estimator.     

机载多传感器跟踪航迹数据融合研究

随着机载传感器的增加和性能的提高,使目标探测和跟踪信息更加全面,精度也大大提高,但机载显示和火控需求的参数是唯一的,所以需要对不同传感器探测和跟踪的目标信息进行融合.本文针对机载传感器特点和飞机平台参数需求,对多传感器跟踪生成的目标航迹数据融合进行了研究,并给出了相应算法.     

基于定点航拍图像序列的运动目标跟踪方法

定点航拍图像序列不仅包括目标物的运动信息,同时包括外界环境干扰或自身抖动信息。针对航拍图像序列的背景抖动,对前后帧进行Fast特征点检测匹配,并对当前帧进行仿射变换至前帧的参考坐标系中;针对航拍图像序列中的运动目标,采用Kalman滤波来预测运动信息,设置置信度区间减少Meanshift目标检测迭代的次数。仿真表明:结合Fast特征点的背景运动补偿与改进的Meanshift目标跟踪方法,可有效地补偿外界扰动或自身抖动对航拍图像序列的影响,并对目标物进行快速的跟踪。     

红外动态场景中小目标轨迹模拟系统的设计

传统的红外搜索跟踪系统的室内检测通常使用安放有若干平行光管的检测架,检测架上的平行光管处于不同方位角和俯仰角。这种方法往往精确度较低、体积庞大,且移动不灵活,不适合短距离的室内试验。设计并实现了一种小目标轨迹模拟系统,该系统以高精度步进电机驱动小目标圆盘运动,黑体温度辐射源用来提供目标温度。PC机通过RS-232串口连接步进电机,由VB编写的软件界面设定步进电机运行的速度、方向及运行角度值,给出目标运行坐标轨迹,通过测角精度算法转化为方位与俯仰角。将被测试搜索跟踪系统给出的方位与俯仰角实测值与算法得到的理论值分析比较之后,即可得出被测试搜索跟踪系统精度。文中详细介绍了该小目标轨迹模拟系统的设计与实现,并给出了实验结果与分析。     

MEMS: the path to large optical crossconnects

Continuous growth in demand for optical network capacity and the sudden maturation of WDM technologies have fueled the development of long-haul optical network systems that transport tens to hundreds of wavelengths per fiber, with each wavelength modulated at 10 Gb/s or more. Micro-electromechanical systems devices are recognized to be the enabling technologies to build the next-generation cost-effective and reliable high-capacity optical crossconnects. While the promises of automatically reconfigurable networks and bit-rate-independent photonic switching are bright, the endeavor to develop a high-port-count MEMS-based OXC involves overcoming challenges in MEMS design and fabrication, optical packaging, and mirror control. Due to the interdependence of many design parameters, manufacturing tolerances, and performance requirements, careful trade-offs must be made in MEMS device design as well as system design. We provide an overview of the market demand, various design trade-offs, and multidisciplinary system considerations for building reliable and manufacturable large MEMS-based OXCs     

Probability of maintaining target track for nonmanoeuvring targets approaching a uniformly scanning search radar

A lower bound for the scan period that maximises the probability of maintaining target track for a uniformly scanning radar is determined. The value is orders of magnitude greater than common scan periods, and therefore this is not a reasonable optimality criterion. The result is valid for all target cross-section fluctuation models.     

纳米硬度计在MEMS力学检测中的应用

纳米硬度计是一种能提供10^3～10^-2μm尺度材料或结构微力学性能检测的先进仪器。采用纳米压痕技术，研究薄膜材料的弹性模量和硬度随压痕深度的变化规律以及薄膜厚度测量、微桥弯曲变形测量的方法。采用纳米划痕技术，研究薄膜的表面粗糙度、临界附着力和摩擦系数测量的方法。该仪器能广泛应用于MEMS的力学检测，并有望成为这一领域内的标准力学检测设备。     

纳米硬度计在MEMS力学检测中的应用

纳米硬度计是一种能提供 10 3～ 10 2 μm尺度材料或结构微力学性能检测的先进仪器。采用纳米压痕技术 ,研究薄膜材料的弹性模量和硬度随压痕深度的变化规律以及薄膜厚度测量、微桥弯曲变形测量的方法。采用纳米划痕技术 ,研究薄膜的表面粗糙度、临界附着力和摩擦系数测量的方法。该仪器能广泛应用于MEMS的力学检测 ,并有望成为这一领域内的标准力学检测设备     

应急通信:下一代网络面临的又一挑战

下一代网络需要对应急通信提供支持,但是其中又有许多问题需要解决,包括优先呼叫处理、紧急呼叫的认证和鉴权,以及紧急呼叫定位等。因此．对于应急通信的支持是下一代网络面临的又一个挑战。     

手机病毒：又一种安全威胁

本文首先介绍了一种可向手机乱发短消息的蠕虫病毒－VBS,然后介绍了手机病毒的危害性和已发现的一些手机病毒情况,指出了黑客对手机攻击的方式。文章最后阐述了手机病毒发作的特征及处理方法,介绍了国际上手机毒工作的研究情况。     

共同的目标：印制电路板设计工具

设计自动化会议(DAC)是EDA(电子设计自动化)行业的主要活动.这是制造商展出其产品、设计师纵览最新技术、所有行业参与者学习和讨论最新设计方法的最佳机会.在其存在的大部分时间里,DAC一直专注用于IC开发的工具和方法.你可以找到印制电路板设计工具,不过它们属于少数,而且在提供IC和印制电路板两类工具的制造商的展台上处于次要地位.似乎IC设计方法和工具引导着EDA的进展,而印制电路板设计在产品的技术方案中虽是必不可少的,但却是起着低级功能.     

Design of Compliant Mechanisms: Applications to MEMS

Compliant mechanisms are single-piece flexible structures that deliver the desired motion by undergoing elastic deformation as opposed to jointed rigid body motions of conventional mechanisms. Compliance in design leads to jointless, no-assembly (Fig. 1), monolithic mechanical devices and is particularly suited for applications with small range of motions. The compliant windshield wiper shown in Fig. 1 illustrates this paradigm of no-assembly. Conventional flexural mechanisms employ flexural joints that connect relatively rigid links as depicted in Fig. 2. Reduced fatigue life, high stress concentration and difficulty in fabrication are some of the drawbacks of flexural joints. Our focus is on designing compliant mechanisms with distributed compliance which employs flexural links (see Fig. 3) and have no joints (neither pin nor flexural joints) for improved reliability, performance, and ease of manufacture. Distributed compliant mechanisms derive their flexibility due to topology and shape of the material continuum rather than concentrated flexion at few regions. This paper focuses on the unique methodology employed to design jointless mechanisms with distributed compliance. The paper also illustrates a compliant stroke amplification mechanism that was recently designed, fabricated and tested for MEMS application.     

正从实验室走出的MEMS

微机电系统(MEMS : MicroElectro-Mechanical System)是一种集成微传感器、微执行器、信号处理和控制电路、通信接口和电源等部件,实现感应和控制物理环境的芯片级设备。MEMS在经过25年的发展后,目前正在走出实验室,逐渐成为一个新兴的工业领域。MEMS的应用范围正在不断扩大,从汽车气囊到打印机、电信设备等,这个芯片级设备的出现,正在促使产品真正迈向低成本、高性能。虽然MEMS技术所具有的优点是无可置疑的,然而将这些先进的技术思想转换成新产品的开发进程却还是太慢了。其原因之一是设备本身的多样性和复杂性:对于MEMS的组装,…     

微电机械系统在光通信中的应用:现状和未来

随着波分复用(WDM)网络的发展，光纤通信系统现已发展成一种复杂的多波长通信系统。由于光通信容量的愈益增加，人们寄希望于创新技术去实现光通信系统的巨大潜力，而微电机械系统(MEMS)则是解决WDM网络中关键技术的最有竞争力的候选技术。其应用包括大尺寸光开关结构(如光交叉连接器件、光插／分多路传输器)和传输网络用各种类型的有源和无源光学组件(如可调谐激光器和滤波器、色散补偿装置、放大增益匀衡器、偏振控制器及其他器件)。本文讨论了光通信用MEMS技术的开发现状、希望、面临的挑战及未来发展前景。重点讨论了基于MEMS的光交叉连接器。     

Mechanical reliability challenges for MEMS packages: Capping

This paper presents our effort to predict reliability problems for MEMS packages. MEMS devices are vulnerable to the external loads subjected to it. As such, MEMS devices need to be protected. Protections can be generated by capping the device: a piece of silicon is placed on top of it to create a cavity above it. Parametric finite element models are combined with dedicated verification experiments to address the reliability of four different capping concepts. The results gain a better understanding of MEMS capping issues, with failure modes as cavity deflection, cap fractures, and moisture penetration.     

半导体硅片键合:MEMS制造工序中的成熟技术

新型MEMS应用领域的发展为现有的制造技术带来了很大的挑战,并促使了满足新加工要求的制造能力的发展。根据目前MEMS制造中普遍采用的不同的晶圆键合方法及其主要工艺参数要求,开发了一种新型的晶圆键合技术。     

A three-scale approach to the numerical simulation of metallic bonding for MEMS packaging

In this work we present a numerical, multi-scale approach to estimate the strength of a wafer-to-wafer metallic thermo-compression bonding. Following a top-down approach, the mechanical problem is handled at three different length scales. Taking into account control variables such as temperature, overall applied force over the wafer and contact surface roughness, it is shown that the proposed approach is able to provide an estimate of the sealing properties, especially in terms of bonding strength.