新型三轴压阻式硅微加速度计的研究

微惯性系统以及其他高精密场合往往需要高精度三轴加速度计来检测三个垂直方向加速度矢量。针对类似需求,介绍了一种四边八梁结构式三轴压阻式硅微加速度计,利用硅衬底上单一质量块和惠斯通半桥结构可同时实现三个轴向上的加速度高精度测量。另外设计了微加速度计在高过载环境下的硅一玻璃防护结构和体硅加工工艺,并通过ANSYS仿真和试验验证了加速度计结构的合理性,还对微加速度计相关性能进行了测试,测试结果表明,该微加速度计具有较高的测量精度和较好的线性度,满足设计要求。     

解耦硅微陀螺仪的结构误差分析和系统性能测试

为了研究对称解耦的硅微陀螺仪的性能,对其结构误差进行了分析,并对其系统性能进行了测试.利用全解耦硅微陀螺仪的简化运动模型,分析了由弹性梁梁宽误差导致的机械耦合误差,并推导其公式.利用有限元方法,对机械耦合误差进行了仿真.仿真结果表明,当悬臂梁的加工误差在0～0.4μm间变化时,机械耦合误差变化范围为0～62.88°/s;同时仿真结果和计算结果比较显示,机械耦合误差的仿真结果基本与理论公式的计算结果相符,证明理论分析的正确性.对机械耦合误差进行了测试,测试结果表明,全解耦硅微陀螺仪的机械耦合误差仅为31°/s,相比课题组前期的半解耦硅微陀螺仪缩小了13.9倍.系统性能实验结果表明,由于机械耦合误差的减小,全解耦硅微陀螺仪的零偏温度系数仅为57.68°/（h.℃）,相比课题组前期的半解耦硅微陀螺仪缩小了9.42倍.     

基于正弦激励的压电加速度计模型参数辨识

针对压电加速度计常规校准无法完全满足实际机械动态量测量要求的问题,采用基于加速度计模型参数校准的方法。参数未知的线性二阶微分方程用来表示加速度计动态特性,利用绝对法振动校准加速度计频率响应数据,采用最小二乘算法确定了未知的参数的值,同时利用蒙特卡罗法确定了参数值的不确定度。最后对加速度计进行了瞬态冲击加速度校准,计算辨识所得模型在相同冲击激励下的预测输出。结果表明:瞬态冲击加速度校准与计算辨识模型结果相差不超过1%。     

基于路面识别的电磁混合式悬架自适应模糊控制EI北大核心CSCD

为改善不同路面等级上主动悬架动态性能与馈能特性适应性差的问题,设计了一种基于路面等级识别的电磁混合式悬架自适应模糊控制。采用天牛须搜索(beetle antennae search, BAS)算法优化了神经网络权值阈值,建立了BAS-BP(beetle antennae search-back propagation)路面识别模型;设计了自适应模糊PID(proportional integral derivative)控制器,针对不同路面等级设计了三种目标函数并引入了主动力反馈调整论域;仿真分析了悬架动态性能与馈能特性,并进行了台架试验。仿真结果表明,相比于模糊PID控制,自适应模糊控制的悬架系统在A级、B级路面簧载质量加速度均方根值分别降低了13.28%、13.84%,在B级、C级、D级路面轮胎动载荷均方根值分别降低了9.09%、16.07%、15.54%,并实现了42.8 W的振动能量回收。试验结果表明,与仿真分析相比,各路面等级上时域、频域的相对误差均在16%以内,验证了仿真结果的正确性和系统的实用性。     

某型号卫星控制力矩陀螺隔振装置设计和试验技术研究EI北大核心CSCD

针对某型号卫星控制力矩陀螺(control moment gyroscope,CMG)在轨工作产生的微振动对星载光学遥感载荷成像产生扰动的问题,文章对CMG扰振特性及卫星基频分析,建立了CMG隔振系统模型,基于CMG扰振特征频率完成了系统错频及隔振装置参数化优化设计,并通过地面单机级及整星级微振动试验对有限元建模结果进行验证。试验结果表明,在主要扰振方向上,主要扰振频点处最佳可实现97%隔振效果,系统的固有频率在仿真与敲击实验对比中误差低于3 Hz,对其他型号卫星的微振动隔振装置优化设计具有参考价值。     

过载振动复合条件下的加速度计不对称性误差

为研究过载-振动复合条件下加速度计不对称性引入误差的影响,建立了包含加速度计模型不对称性的振动整流误差数学模型,并给定相关参数进行仿真分析。分析结果表明,当过载大于等于振动加速度幅值时,可忽略加速度计不对称性引起的振动整流误差;在给定的仿真情况下,当过载小于振动加速度幅值时,加速度计不对称性引起的振动整流误差小于全部振动整流误差的1%。     

过载振动复合条件下的加速度计不对称性误差分析

为研究过载-振动复合条件下加速度计不对称性引入误差的影响,建立了包含加速度计模型不对称性的振动整流误差数学模型,并给定相关参数进行仿真分析.分析结果表明,当过载大于等于振动加速度幅值时,可忽略加速度计不对称性引起的振动整流误差;在给定的仿真情况下,当过载小于振动加速度幅值时,加速度计不对称性引起的振动整流误差小于全部振...     

有源噪声控制次级声源的非线性建模

基于电动扬声器的顺性、磁力因子和音圈自感三个非线性参数,建立了基于电力声类比线路方法的次级声源非线性时域模型.采用该模型对次级声源总谐波失真(THD)进行仿真,并与测试结果进行比较,结果表明在较低频率范围、较大输入信号幅值的情况下,该非线性模型是可行的.将该模型引入有源噪声控制系统,并以滤波-XLMS算法为例,对采用次级声源理想模型、线性时域模型和非线性时域模型的控制系统分别进行仿真,结果表明采用非线性模型系统的降噪量远低于采用其他模型的系统,并且非线性失真度大小对降噪量也具有明显的影响.     

微细铣削振动信号特征参数的主成分分析

铣削振动是描述微细铣削加工状态的重要特征参数. 利用微小型车铣加工中心、压电加速度计和多通道电荷放大器建立了微细铣削振动测试系统,分别提取了不同铣削方式和铣削转速条件下微细铣削振动信号的时域特征参数和频域特征参数. 针对特征参数数量繁多且变化趋势不一致的特点,引入主成分分析方法,利用主成分分别对时域和频域特征参数进行替换,定量描述出振动信号的能量和差异,以及主频带位置和能量分散程度之间的关系. 分析结果表明,通过时域与频域特征参数主成分的综合运用,应用较少的参数即可描述微细铣削振动信号的主要特征,显著降低了原始数据维数; 主成分分析结果可用于铣削方式和铣削转速等微细铣削加工参数的优化.     

硅微谐振式加速度计的温度效应及补偿

零偏和标度因数稳定性是衡量加速度计性能的两个重要参数.为了降低硅微谐振式加速度计的温度敏感性,对其温度影响机理进行了深入研究.通过温度实验发现,硅微谐振式加速度计的零偏和标度因数与设计理论参数有较大区别,且都具有较大的温度灵敏度,分别为0.72 g/℃和1.5℃-1.对弹性模量和谐振器应力与谐振器频率的关系进行了理论计算和FEA仿真验证,其中弹性模量引起的谐振频率-温度灵敏度为-0.7 Hz/℃,谐振器应力引起的谐振频率-温度灵敏度为180 Hz/℃.阐述了加工过程中键合应力产生的原因以及键合应力与谐振器残余应力的关系,发现谐振器应力是造成加速度计输出随温度漂移的主要因素.提出了一种隔离残余应力的隔离梁的设计方案,可使零偏温度灵敏度降至-35 Hz/℃,为温度补偿指明了方向.     

一种摆式加速度计结构模态分析

利用ANSYS软件对一种单轴摆式加速度计的结构进行了有限元分析,得出了各阶模态下加速度计结构的固有频率和振型,找到了处于该型加速度计通频带之内的模态频率。然后,对加速度计进行了结构优化,使各阶模态频率处于通频带之外,为加速度计的结构改进提供了理论依据。     

基于窄脉冲冲击激励的压电加速度计动态校准

论述了目前加速度计校准的方法以及主要不足之处,并以压电加速度计为例,采用冲击激励法对其进行了动态校准,详细说明了校准所使用的装置和校准过程,采用单自由度的质量弹簧系统来描述加速度计的数学模型,利用系统辨识的方式得到了数学模型的参数,分析了加速度计动态校准的结果并且与绝对法振动校准进行了比较与分析。     

Photon and neutron dose discrimination using low pressure proportional counters with graphite and A150 walls

A graphite-walled proportional counter with low neutron sensitivity was used in combination with a tissue-equivalent proportional counter (TEPC) to separate the photon and neutron components in mixed radiation fields. Monte Carlo (MCNP4C) simulations of the photon and neutron responses of the two detectors were done to obtain correction factors for the sensitivity differences. In an alternative method the radiation components were determined using constant-y(D)-values for typical photon and neutron energy distributions. The results show no significant difference between the two methods and the measured neutron dose-equivalent agrees within +/-50% with Bonner sphere determined values. The experimental data were obtained in measurement campaigns organised within the EVIDOS-project.     

Assessment of an instrumented Charpy impact machine

The dynamic responses of the standard Charpy impact machine were studied experimentally using strain gauges and accelerometer attached to the striker and the rotary position sensor fixed at the rotating axis and numerically with the finite element analysis. The fracture propagation was simulated with the cellular automata finite element approach developed earlier. A series of low velocity as well as full capacity Charpy tests were analysed. It was found that the strain gauge signal recorded close to the tup edge and the acceleration recorded at the back of the striker do not match. The energy calculated with the strain gauge data agrees well with the dial reading, while the energy calculated with the accelerometer signal is never near it. Frequencies close to the first natural \hbox{frequency} of the Charpy sample have high modal magnitudes in the acceleration signal but are effectively damped in the strain gauge response. Vibrations of the striker arm have highest modal magnitudes in the rotary position sensor. A low-pass filter is used to obtain the striker movements. The finite element analysis partly supports the experimental observations but also suggests that acceleration at the tup edge suffers higher oscillations than strain.     

力平衡式三轴微加速度计的设计与分析

设计了一种具有单一检测质量的力平衡式三轴微加速度计．采用硅-硅键合工艺形成作为单一检测质量块的硅片组合。利用全差分电容检测法实现对加速度三轴分量的检测．通过提高检测质量的重心，有效增加了X、Y轴的灵敏度．利用ANSYS仿真软件对该微加速度计进行了模态及静力学分析，提出了优化设计参数．3个检测模态（1阶、2阶和3阶模态）的频率分别为1．329kHz、1．345kHz和2．174kHz．通过优化设计，提高了3阶模态和4阶模态的频率差距，降低了其他高阶模态的干扰．在100g（g为重力加速度）的Z向加速度作用下，悬臂梁所受的最大应力为46MPa。小于单晶硅的弯曲极限值70-200MPa．静力学分析表明，加速度计的悬臂梁结构参数能够满足加速度计的力学性能要求．     

分度头检测加速度计时横向效应对线性度的影响

对分度头检测加速度计静态特性相关的几何物理问题进行了分析,结果表明,传感器在分度头上的安装偏差角和传感器自身固有的横向效应都会影响检测精度。用分度头对加速度计进行静态特性的检测,横向效应包含在测量结果的非线性中。用非线性和横向效应都很小的加速度传感器作为试样,在分度头上人为安装有00、50和150的偏角时,检测到的非线性随偏角的增加而变大,与理论分析一致。利用高分辨分度头寻找能降低悬臂梁压阻式加速度传感器横向效应的基准面,以此基准面封装成的传感器的横向效应和非线性的综合效果小于0.05%。     

Performance analysis and simulation of automobile air conditioning systemAnalyse de la performance et simulation d'un système de conditionnement d'air automobile

Performance analyses of separate components of an automobile air conditioning system have been carried out under various operating conditions. The air conditioning system consists of a laminated type evaporator, a swash plate type compressor, a parallel flow type condenser, a receiver drier and an externally equalized thermostatic expansion valve. A computer program for performance analysis of the laminated type evaporator has been developed on the basis of the overall heat transfer coefficient and pressure drop which were obtained experimentally. A computer program for performance analysis of the parallel flow type condenser, using an empirical equation for the heat transfer coefficient, has been developed, which demonstrates that the predicted condensing capacity agrees very well with the experimental data. Then, a model for combining the performance analysis programs of separate components of an automobile air conditioning system is proposed, which simulates very well the performance of the integrated automobile air conditioning system. Further, the effects of condenser size and refrigerant charge on the performance of the integrated automobile air conditioning system are discussed.     

Evaporative condenser control in industrial refrigeration systems

This paper is a result of a research project which focused on optimization of an existing industrial refrigeration system for a large two-temperature level cold storage distribution facility located near Milwaukee, Wisconsin. This system utilized a combination of single-screw and reciprocating compressors (each operating under single-stage compression), an evaporative condenser, and a combination of liquid overfeed and direct expansion evaporators. A mathematical model of the existing system was developed. The model was validated using experimental data recorded from the system. Subsequently, the model served as a tool to evaluate alternative system designs and operating strategies that lead to optimum system performance. The methods, analysis, and results presented in this paper focus on evaporative condenser sizing and head pressure control. Operating system head pressures that minimize the energy costs of the system were found to be a linear function of the outdoor wet-bulb temperature. A methodology for implementing the optimum control strategy is presented. Simulation results for the annual performance of the refrigeration system investigated in this project show a reduction in annual energy consumption by 11% as a result of the recommended design and control changes.