六轴硅微静电加速度计的悬浮回路设计

传统的静电加速度计在空间微弱加速度测量方面可以获得极高的分辨率。提出了一种采用静电悬浮、可实现六轴加速度测量的微静电加速度计。敏感组合件采用玻璃-硅-玻璃三层键合结构、体硅加工工艺;检测质量采用"回"字形结构,以提高加速度计的径向量程和刚度。利用有限元软件分析了大气环境下检验质量的气模阻尼特性,对六自由度静电悬浮回路进行了建模与分析,提出了实现六轴加速度检测的控制方案。给出了静电悬浮回路的仿真结果,评估了六轴加速度计的性能。     

基于静电悬浮转子的硅微陀螺技术

设计了一种转子采用五自由度静电悬浮的微机械陀螺。微陀螺基于玻璃-硅-玻璃键合的三明治结构、环形转子、体硅工艺、电容式位移检测方案;采用公共电极施加高频激励信号,基于隔离网络和频分复用的方法实现检测电极与加力电极的复用以简化陀螺结构;通过有源静电悬浮系统约束环形转子沿五自由度的运动,并提供足够的支承刚度;转子的转速控制基于三相可变电容式电机驱动方式,借助于检测转子与定子旋转电极的电容变化获得转子速度以实现转速闭环控制。目前已加工出基于深反应离子刻蚀工艺的微结构,采用基于DSP的数字控制器实现了环形转子的五自由度稳定悬浮。     

硅微静电加速度计的支承刚度特性

静电加速度计通过降低带宽和量程在空间微重力环境下可以实现极高的分辨率。设计了一种采用玻璃-硅-玻璃"三明治"结构、平行六面体状检验质量、体硅加工工艺的三轴硅微静电加速度计,推导并讨论了静电支承回路的典型刚度特性与控制参数之间的关系式。采用基于DSP的数字控制器,实现了敏感质量的六自由度稳定支承,在大气环境下测试了静电支承回路的主要性能。分析与测试结果表明,在支承系统频带内,支承刚度特性与控制器参数及气膜阻尼系数密切相关;同时,改变预载电压可以在较大范围内在线调整加速度计的量程和支承刚度等指标。     

静电悬浮式惯性仪表中的微位移检测技术

静电陀螺仪、空间静电加速度计等基于静电悬浮的惯性仪表在高精度的惯性导航和空间微重力测量领域得到广泛应用。近年来，对基于MEMS工艺的悬浮式微惯性传感器的研究引起了广泛的重视。介绍了静电悬浮式惯性仪表中采用的差动电容式微位移检测电路的原理，分别对静电陀螺、静电加速度计和MEMS微陀螺、微加速度计的电极配置方案和位移检测的接口电路进行了分析，并对不同的位移检测方案进行了比较.     

静电加速度计悬浮质量块质心偏移量在轨标定

高精度静电加速度计已广泛地应用于航天任务中,用于测量作用于航天器的非引力加速度。如果静电加速度计悬浮质量块的质心与航天器的质心安装有偏差时,重力梯度力、姿态耦合产生的干扰加速度,静电加速度计控制系统引入的干扰加速度等干扰力会夹杂在测量数据中。针对这一问题,研究了航天器小质量特性变化情况下,当静电加速度计处于动态设计良好并进入稳态后,利用静电加速度计、陀螺仪和磁强计作为敏感元件,基于非线性卡尔曼滤波理论的静电加速度计悬浮质量块质心偏移量的在轨标定。仿真结果表明,该方案的精度J向可以达到0．1mm,Y和Z向能达到0．04mm。     

静电悬浮转子微陀螺及其关键技术

静电悬浮转子微陀螺具有比振动式微陀螺精度高的潜在优点，并可同时测量二轴角速度和三轴线加速度。介绍了静电悬浮转子微陀螺的研究现状。对该静电悬浮转子微F1螺／加速度计的工作原理、特点进行了分析，并对实现高精度静电悬浮转子微陀螺／加速度计晌关键技术如静电稳定悬浮、微位移检测控制、静电恒速旋转驱动、微机械加工和真空封装技术等进行了探讨。指出这一新颖MEMS陀螺是高精度多轴集成微惯性传感器技术发展的一个重要方向，具有广阔的应用前号和较大的发展潜力。     

硅微机械陀螺仪的新进展及其方案分析

介绍了国外硅微机械陀螺仪的新进展，综述了梳状驱动振动陀螺仪、压电棒式振动陀螺仪、电磁驱动音叉陀螺仪、振环陀螺仪、静电悬浮转于陀螺仗和微机械加速度计陀螺仪的结构、原理及性能。关键词     

硅微振梁式加速度计抗温漂的微结构及工艺设计

针对硅微振梁式加速度计输出频率随环境温度漂移的问题,提出了抗温漂的硅微结构设计方法及相关工艺,降低了环境温度对输出的影响,在室温条件即可达到一定精度。通过建立"硅-玻璃"和"玻璃-陶瓷"耦合模型,分析了造成硅微振梁式加速度计温度漂移的原因。然后提出了"抗温漂耦合设计"的微结构和"半粘结封装"的封装工艺,降低了耦合模型中的理论温漂。利用加工出的原理样机进行实验,结果显示,采用抗温漂结构设计及封装工艺的原理样机,输出频率的温漂系数为-3.5×10-6/℃,室温下零偏稳定性为72.0μg。实验验证了抗温漂理论的可行性,可以满足室温下高精度硅微振梁式加速度计的设计要求。     

硅微谐振加速度计交流检测信号解耦技术

硅微谐振加速度计以高精度的频率信号输出及潜在的敏感结构与处理电路实现一次集成的优势,成为硅微传感器研制的热点之一。针对交流检测信号耦合效应对硅微谐振加速度计性能的重要影响,在分析硅微谐振加速度计工作机理的基础上,从结构和电路两方面研究了交流检测信号耦合效应的来源,分析了耦合效应对检测电路和闭环控制精度的影响。采用双质量块结构方案和电路优化设计所研制的硅微谐振加速度计,基频为15 kHz,标度因数为36 Hz/g,量程为±30 g。试验证明耦合效应对仪表性能的影响降低到0.3 mg以内。     

硅微隧道式加速度计的输出反馈控制电路设计

为提高硅微隧道式加速度计的灵敏度,必须设计出高灵敏度的输出和反馈控制电路。在电路设计中,通过采用行之有效的措施来降低噪声和干扰可达到提高灵敏度的目的,如：将隧道式加速度计敏感单元的参考地设置为同一的大地;采用能抑制隧道式加速度计敏感单元和半导体器件所产生的1/f噪声的低噪声运算放大器;在电压信号放大过程中,尽量抑制干扰和噪声;且在电压反馈电路设计中,保护敏感单元不受损坏等措施。测试结果为标定因数1.2659V/g,其非线性度小于1%,可见在提高线性度的基础上也提高了灵敏度。     

基于遗传算法的加速度计免转台标定方法

针对现有的加速度计标定方法依赖于昂贵的仪器设备,导致标定成本高,提出一种低成本、操作简单的加速度计免转台标定方法。该方法通过对原始数据进行预处理,将标定问题转化为优化问题,采用遗传算法进行最优化求解得到补偿参数。通过对比试验得到:两种方法的标定相对误差在0.5%(标度因素)、3%(零偏);两种方法标定后通过加计姿态角提取的水平角误差在0.2°左右。结果表明,加速度计通过该方法经过补偿后,能够得到与传统转台标定方法相同数量级的测量精度,该方法可以有效替代传统标定方法,简化标定步骤,降低标定成本,具有重要的理论及使用价值。     

离心机上辨识陀螺加速度计二次项系数的优化试验设计

提出了一种在带有反转平台的精密离心机上标定陀螺加速度计误差模型二次项系数K 2的D-最优试验方案。应用该D-最优试验方案,通过重复试验,能够在测试点最少的情况下获得高测试精度,实现陀螺加速度计误差模型系数的最优(D-最优的)辨识。推导了测量随机误差、试验方案的测试点、测试点的重复测试次数以及误差模型系数方差之间的关系式。精度分析的结果表明,应用D-最优试验方案,采取重复试验的方法,能够有效地减小二次项系数K的估计量的方差,从而提高K的辨识精度。     

Non-Newtonian end effects in falling ball viscometry of concentrated suspensions

In a Newtonian fluid contained in a cylinder, a small ball initially at rest released just below the surface would accelerate to achieve a steady-state velocity within one cylinder diameter. After traversing the center section of the cylinder, the ball would begin slowing down within one cylinder diameter of the bottom. This behavior is also observed in suspensions where the size of the suspended particles is small relative to the containing cylinder. However, in concentrated suspensions of larger suspended particles, balls released near the upper surface travel faster than the steady state velocity. In addition, the length of the upper surface end effect, where the falling ball decelerates to the steady state velocity, and the lower end effect zone, where the ball decelerates to rest at the bottom, is many times longer than in a Newtonian single-phase liquid. These non-Newtonian end effects are reduced if the suspended particles are polydisperse in their size distribution.     

Numerical modeling of deposition-release mechanisms in long-term filtration: validation from experimental data

A numerical phenomenological filtration model based on the combination of existing modeling approaches for simulating the transport of suspended particles in saturated porous medium is presented. The model accounts for the decreased physical straining with the distance from the inlet and the amount of deposited particles in the deposition kinetics. The particle release flux is a function of the local shear stress exerted by the flow on the pore surfaces. The proposed model is validated by interpreting a series of experimental data, realized in a laboratory sand column. The results show that the present model allows simulating the presence of a plateau in the breakthrough curves in the light of the shear stress conditions, and the spatial profile of deposited particles in the porous medium in the light of the straining profile.     

斜拉索模态试验参数研究

试验模态分析是斜拉桥索力测试中广泛应用的方法。该方法的关键之一是采取合理的试验方案获取可靠的响应信号以识别出正确的索振动频率。本文通过试验,详细讨论了斜拉索模态测试中若干试验参数,如激振类型、激振位置、传感器位置以及频率分辨率对试验结果的影响;比较环境激励与锤击激励的效果,验证了环境激励的方法也可以准确识别索的频率;最后给出了较为合理的斜拉索模态试验方案,用该方案确定的索力与理论计算结果相差不超过 1. 5%。     

采用GRIN透镜的数字式光纤加速度计系统设计

为使测量加速度计的传感器小型化，且不受电磁干扰，根据GRIN透镜在1／4波节处具有入射光线与出射光线成中心对称的特性^[1]，首次提出并研制了采用GRIN透镜制成的微型光纤加速度计。闭环负反馈电路设计技术被应用于该加速度计中，使之成为一个具有调宽脉冲再平衡性能的新颖加速度测量系统。对该系统进行的数字仿真和精度定量分析表明：该光纤加速度计具有测量线性范围宽，精度高的特点，可广泛应用于惯性测控系统中。     

Nonlinear Oscillations of a Nonresonant Cable under In-Plane Excitation with a Longitudinal Control

The nonlinear oscillations of a controlled suspended elastic cable under in-plane excitation are considered. Active control realized by longitudinal displacement of one support is introduced in order to reduce the transverse in-plane and out-of-plane vibrations. Linear and quadratic enhanced velocity feedback control laws are chosen and their effects on the cable motion are investigated using a two degree-of-freedom model. Perturbation analysis is performed to determine the in-plane steady-state solutions and their stability under an out-of-plane disturbance. The analysis is extended to the bifurcated two-mode steady-state oscillations in the region of parametric excitation. The dependence of the control effectiveness on the system parameters is investigated in the case of the first symmetric mode and the range of oscillation amplitudes in which the proposed control ensures a dissipation of energy is determined. Although control based only on in-plane response quantities is effective in reducing oscillations with a prevailing in-plane component, addition of out-of-plane measures has to be considered when the motion is characterized by two comparable components.     

Empirical model for estimating vertical concentration profiles of re-suspended,sediment-associated contaminants

Vertical distribution processes of sediment con-taminants in water were studied by flume experiments. Experimental results show that settling velocity of sedi-ment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants, especially near the bottom where particle diameter is similar in size to vortex structure.Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment.The smaller the initial sediment concentration was,the more time it took to achieve a uniform concentration distribution for suspended sediment. A con-taminants transportation equation was established depending on mass conservation equations.Two mathematical estima-tion models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment:equilibrium par-tition model and dynamic micro-diffusion model.The ratio of time scale between the sediment movement and sorption can be used as the index of the models.When this ratio was large,the equilibrium assumption was reasonable,but when it was small,it might require dynamic micro-diffusion model.     

Solution of some variational problems of two-phase gas dynamics

The problem of constructing an optimal-profile nozzle for a two-phase medium is considered in the one-dimensional approximation. A problem of this type to find an optimal-thrust nozzle was considered by Kraiko, Starkov, and Sternin [1]. In contrast to their study, a more complete model of the two-phase medium is used in the present paper, and the nozzles are optimized with respect to the efficiency, gas velocity, and velocity of the suspended particles. The problem is solved using the formalism of optimal control theory [2, 3]. The change in the vapor concentration and phase transitions are taken into account. A method of numerical solution of the problem is proposed. It has been realized on a computer. The method can be used to solve similar problems for a more complicated model of the two-phase medium.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 52–58, January–February, 1982.