MEMS加速度计信号光电检测与电容检测的噪声分析

在高精度MEMS扭摆式加速度计电容检测和光电检测实现原理的基础上,分析了该加速度计热机械噪声和电学噪声特性.该加速度计结构在品质因数Q=1和Q=85时,热机械噪声分别为2.4μgn/根号Hz和0.28 μgn/根号Hz.对于电学噪声,电容检测的电学噪声为3.27 μgn/根号Hz,光电检测在只考虑电学噪声时能分辨的最小加速度可达0.05 μgn.对比得出对于扭摆式加速度计结构,光电检测具有比电容检测更小的系统总噪声.     

体硅电容式双轴微加速度计的信号检测新方法

在研究体硅电容式双轴加速度计结构部分,分析差分电容检测方法的基础上,提出了一种适合该加速度计的新型信号检测方法,此方法可有效地将两轴的混叠信号分别进行输出。通过HSPICE软件仿真验证了该方法的可行性。且依据0.5μmCMOSN阱工艺参数对总体电路进行模拟仿真,5V单电源供电,微加速度计单轴灵敏度为50mV/gn,频响为2.3kHz,量程为±50gn。     

差分电容硅微加速度计检测电路研究

针对硅微加速度计中微小差分电容检测,提出了一种基于调制解调方法的闭环检测电路,介绍了该闭环检测系统的原理框图和实现途径。分析了基于单路载波的前置电容-电压( C-V)转换电路,证明了基于相关芯片的解调方法的有效性,其解调效率仅对开环输出有影响;基于双路反馈电路的静电力平衡回路有效提高该检测系统的线性度。结合硅微加速度计参数和电路设计参数,对加速度计系统进行了仿真,仿真结果显示系统稳定,刻度系数为0.9 V/gn 左右,带宽700 Hz左右。结合表头进行的精密转台实验结果表明该加速度计系统刻度系数0.88 V/gn,量程可达±13 gn。     

高gn值微加速度计的设计

设计了一种新型四梁压阻式MEMS高gn(gn=9.8m/s2)值加速度计,其量程为0~150 000gn,抗冲击200 000gn,横向灵敏度小于6%。根据设计指标及强度条件对结构参数进行了优化设计,并进行应力分析、抗冲击分析、横向效应分析以及灵敏度分析。同时,利用有限元分析软件,对模型进行了静态应力分析和模态分析,给出了具体的分析结果,并与理论值加以比较,从而使该高gn值加速度计的结构分析和设计更加合理。     

基于MEMS电容式加速度计的闭环读出电路设计

设计了面向圆片级封装的一种闭环加速度计读出电路.在基于电容式微加速度计结构的读出电路设计中考虑了寄生电容对整个系统的影响.用MATLAB SIMULINK对所设计的读出电路进行了建模仿真.在仿真过程中分析了噪声、圆片级封装与普通封装的寄生参数及实际工艺中流水结构的不对称性的影响并进行了比较.结果表明,所设计传感器及读出电路的非线性误差在量程±20 gn范围内小于0.5％;圆片级封装的稳定时间在2 ms,小于普通封装的稳定时间;基于圆片级封装的对称性梳齿结构的输出电压灵敏度为328 mV/gn.     

基于∑-△M的五阶MFLR数字微加速度计闭环控制系统

为了进一步抑制加速度计信号带宽范围内的噪声,提出并设计了一种基于∑-△M的五阶多反馈谐振式（MFLR）微机械加速度计闭环控制系统,该系统通过增加额外的内部负反馈对量化噪声进行再一次整形.微机械加速度计结构为一种全差分式结构,在结构层厚度为60 μm、基底层厚度为400μm的SOI硅片上,经过光刻、溅射、深度反应离子刻蚀等工艺步骤加工而成.整个闭环控制系统的Matlab/Simulink模型首先被建立,然后采用“单位圆分析法”进行系统参数的设定,系统仿真显示：当输入幅值1gn、频率128Hz的加速度信号时,加速度计的噪声为-136.2 dB,与传统五阶MF结构的∑-△M闭环控制系统相比,在0 ～500 Hz信号带宽范围内的噪声降低了7.9dB.最后整个系统在四层PCB电路板上进行了功能性验证和测试.     

基于电容桥的差动电容检测方法

数字闭环石英挠性加速度计系统主要由石英挠性加速度计表头和数字检测电路组成,其极限精度取决于差动电容检测电路的灵敏度。针对数字闭环石英挠性加速度计前端差动电容检测的需求,给出了一种基于电容桥的差动电容检测方法。利用数字电路产生高频方波进行单载波调制,同时利用交流电容桥结构对载波信号进行处理,并设计后续的差分放大电路对载波信号进一步处理最终实现对微弱差动电容变化的检测。经过实验验证,检测电路对电容的检测最终实现最小分辨率约为1. 8 f F(对应加速度变化1μgn)。     

新型双轴电容式加速度传感器设计

为了实现多轴加速度检测,设计了一种新型双轴电容式加速度传感器.由内、外2个质量块组成,分别由4组折叠梁支撑.传感器通过固定梳齿和活动梳齿之间的距离变化引起两者电容值发生变化,最终测得加速度.通过ANSYS仿真分析得出:传感器的位移灵敏度为0.0845μm/gn(X轴)和0.1381μm/gn(Y轴).结构的一～三阶谐振频率分别为1.34,1.71,14.48kHz.由于各阶模态频率相差很大,避免了跨轴信号的干扰.     

静电刚度式谐振微加速度计设计

运用梁的横向振动特性分析了梁振动频率与平行板电容形成的静电刚度的关系,并以此设计了静电刚度式谐振微加速度计。在加速度作用下,检测质量产生的惯性力使电容器极板发生位移来改变电容结构的间隙大小,从而使谐振频率发生变化,通过检测频率变化量来测量输入加速度的大小。根据加速度计的工作原理说明检测过程中梁的机械刚度保持不变,只与产生静电刚度的电容间隙变化相关,减小了检测信号对机械误差与残余应力的依赖性。运用加工参数进行理论计算得出加速度计的灵敏度为21．17Hz／gn,在CoventorWare2005中进行仿真表明：加速度计的固有频率为23．94kHz,灵敏度约为20Hz／gn,与理论设计值相近。     

一种低噪声MEMS加速度计设计与制作

为了提高微加速度计的噪声性能,研究了一种基于绝缘体上硅(SOI)技术的单轴MEMS加速度计的设计和加工方案。该微加速度计采用大面积质量块的电容式检测结构,通过增加检测质量,在保证灵敏度的前提下,有效地降低了微加速度计的机械布朗噪声,增强了信噪比。另外,该微加速度计采用一种基于Al保护层的MEMS SOI工艺技术制造,有利于提高微加速度计的整体精度水平。测试结果表明:微加速度计的本底噪声为20μgn/√Hz,灵敏度为2.5 V/gn。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.