Vibration sensitivity analysis of the ‘Butterfly-gyro’ structure

The ‘Butterfly-gyro’ is simple to manufacture with single sided electrostatic excitation and capacitive detection, and it is considered as one kind of the microgyroscope with high sensitivity due to its unique structure. This paper provides the sensitivity analytical model by solving the dynamic equations of motion and the design guidelines for microgyroscope with high sensitivity. Using Coriolis Effect and Newton’s second law, the dynamic equations are built. The sensitivity analytical model, including the denotations of Q factors and the resonant frequencies, is built. The approximate analytical expressions of Q factors and the resonant frequencies are derived by rational assumptions. Based on the sensitivity analytical model, the parametric analysis is carried out, and the design guidelines of high sensitivity are also deduced. Finally, Q factor, frequency split and other factors influencing the sensitivity are discussed in details to enhance its sensitivity. Results presented are valuable in the design and parameters optimization of the microgyroscope with high sensitivity.     

Modeling of angular-rate bandwidth for a vibrating microgyroscope

A new analysis on the angular-rate bandwidth characteristics of a vibrating microgyroscope is proposed. Employing a dynamic model for a vibrating microgyroscope, the frequency response of the vibrating microgyroscope is analyzed with respect to an input angular rate. A microgyroscope, in which an inertial mass vibrates on a substrate plane, is designed and fabricated by surface micromachining technology using polysilicon structures on an insulation layer. The fabricated microgyroscope was operated in a vacuum environment of 100 mtorr, and showed the sensitivity of 5 mV s/° with the noise level of 1 mV. Bandwidth characteristics of the microgyroscpes were also investigated by comparison with the simulation on the bandwidth model, and the validity of the proposed dynamic model was evaluated.     

Structural topology optimization on dynamic compliance at resonance frequency in thermal environments

This paper [r] carries out topology optimization to minimize structural dynamic compliance at resonance frequencies in thermal environments. The resonance response is the main dynamic component, minimization of which could possibly change structural dynamic characteristics significantly. A bi-material square plate subjected to uniform temperature rise and driven by harmonic load is investigated in pre-buckling state. The compressive stress induced by thermal environment is considered as pre-stress in dynamic analysis, which could reduce stiffness of the structure and alter the optimal topology. Sensitivity analysis is carried out through adjoint method efficiently. As natural frequencies are constantly changing during the optimization, the associated sensitivity should be calculated in which multiple-frequency case is briefly discussed. Mode switching may occur during the optimization, and mode tracking technique is adopted. Numerical results show that the topology is mainly determined by the excited modes, and could be altered by the location of the applied load if different modes are excited. The natural frequencies become larger in optimal design and the dynamic compliance decreases in nearby frequency band. The critical buckling temperature increases as optimization proceeds, indicating the structure is always in pre-buckling state.     

硅微陀螺仪的误差分析

以z轴硅微陀螺仪为研究对象,对加工误差产生的误差信号进行了分析.由于加工误差,使得陀螺仪结构不对称,主要表现为支承梁不对称、梳齿间距不等,产生了不等弹性、阻尼不对称以及力不平衡这三种现象.以动力学方程为基础,分析了不等弹性和阻尼不对称产生的误差信号;以静电理论为基础,分析了驱动梳齿和敏感梳齿间距不等时产生的误差信号.分析结果表明,这些误差信号包含了正交耦合误差和与有用信号同相位的误差信号.最后,介绍了一种减小正交误差的方法,并进行了仿真.     

Robust optimization of an automobile rearview mirror for vibration reduction

An automobile outside rearview mirror system has been analysed and designed to reduce vibration with a finite element model. Modal analysis is conducted for the calculation of natural frequencies. Harmonic analysis is utilized to estimate the displacements of the glass surface under dynamic loads. The model is verified with the vibration experiment for the parts and the assembled body. The structure of the mirror system is optimized for robustness defined by the Taguchi concept. At first, many potential design variables are defined. Final design variables are selected based on the amount of contribution to the objective function. That is, sensitive variables are chosen. The signal-to-noise (S/N) ratio in the Taguchi method is replaced by an objective function with mean and standard deviations of the quality characteristics. The defined objective function is appropriate for structural design in that the vibration displacements are minimized while the robustness is improved. Received: January 21, 2000     

于二次谐波检测的电容式微惯性器件频率响应测试方法研究

针对电容式微惯性器件信号微弱、耦合噪声大的特点,提出了一种基于二次谐波检测的频率响应测试方法,详细介绍r该测试方法的基本原理,设计了基于此方法的频率响应测试系统,分析了测试系统中存在的误差,以本实验室研制的电容式微陀螺为测试对象,对该方法和传统的一次谐波检测方法进行了对比,结果表明,该方法能够有效地减小电路中耦合噪声对测试结果的影响,提高频率响应测试精度.     

驱动微梁形状对微陀螺仪耦合误差的影响分析

为研究微陀螺驱动微梁在加工误差下的微梁形状变化对正交耦合误差、模态耦合以及检测信号的影响,建立了驱动微梁在对角线梁宽误差下的有限元分析模型,采用有限元仿真分析和解析计算相结合的方法研究了U型梁一端梁长的变化对微陀螺正交耦合误差、模态耦合以及检测信号的影响.研究发现,当U型梁一端的梁长为另一端长度的二分之一左右时该类加工误差会引发非常严重的正交耦合误差和模态耦合现象,并对检测信号产生极大影响;当U型梁退化为直梁或者为等长梁的时候,对检测信号的干扰很小、正交耦合误差为零、模态耦合程度最小,而且两者的变化规律呈现正相关.适当地加大单自由度微陀螺驱动模态和检测模态的频率差不仅可增加微陀螺的带宽还可减小耦合的影响.     

温度对液滴指纹图水质识别的影响分析

研究水本身温度和环境温度的变化对液滴指纹图产生的影响,可为液滴分析仪仪器化设计提供参考。在环境温度保持在27℃左右时,对注射器中水的温度由57℃降至31.3℃期间,连续采集了16组液滴指纹图,比较各组液滴指纹图,光纤信号和电容信号的最大变化分别为0.17%和1.23%,与系统误差相当,说明水本身温度对液滴指纹图几乎无影响;以纯水在不同温度下的折射率、表面张力和介电常数值,计算了环境温度对纯水液滴测量信号的影响大小,计算结果表明:环境温度由18℃升至30℃时,光纤信号和电容信号的变化分别为0.64%和3%,对电容信号的影响较大。     

硅微Z轴谐振陀螺仪闭环伺服控制系统设计

根据自行设计的硅微Z轴谐振陀螺仪的工作原理,提出了闭环伺服控制系统模型,在对开环检测模型分析的基础上设计了闭环伺服控制系统,并用Matlab软件对闭环伺服系统的频域和时域特性进行了仿真分析,选取了合适的校正环节及优化参数,使系统有较高的稳定裕度和较好的动态特性.通过实验调试实现了初始检测电容差引起的信号以及正交信号的反馈抑制控制,达到了较高的控制精度.     

Nonlinear thermal–mechanical vibration of flow-conveying double-walled carbon nanotubes subjected to random material property

The present study deals with the dynamic response variability of nonlinear thermal–mechanical vibration of the fluid-conveying double-walled carbon nanotubes (DWCNTs) by considering the effects of the temperature change, geometric nonlinearity and nonlinearity of van der Waals (vdW) force. The nonlinear governing equations of the fluid-conveying DWCNTs are derived based on the Hamilton’s principle and theory of thermal elasticity. The Young’s modulus of elasticity of the DWCNTs is assumed as stochastic with respect to position to actually describe the random material property of the DWCNTs. By utilizing the Monte Carlo simulation, the nonlinear coupled governing equations of the fluid-conveying DWCNTs become deterministic. Then we adopt the harmonic balance method in conjunction with Galerkin’s method to solve the nonlinear coupled deterministic differential equations for many different sample functions. Some statistical dynamic response of the DWCNTs such as the mean values and standard deviations (SDs) of the amplitude of the displacement are calculated, meanwhile the effects of the temperature change and flow velocity on the statistical dynamic response of the DWCNTs are investigated. It is concluded that the mean value and SD of the amplitude of the displacement increase nonlinearly with the increase of the frequencies in both low and high temperatures. Furthermore, the mean value of the amplitude of the displacement for any fixed frequency decreases due to the temperature change in low temperature; on the contrary, it increases under the temperature change in high temperature.     

Automated structural design and analysis of advanced composite wing models

The design of a composite wind tunnel model has demonstrated the ability to tailor the response of a composite structure to provide desired static and dynamic characteristics. This was possible because the strength and stiffness properties of composite structures can be controlled through selection of materials and lamination patterns. To take maximum advantage of the capability, efficient computer procedures are being developed for the design and analysis of composite structures. A finite element procedure and a direct Rayleigh-Ritz procedure, specialized for the preliminary analysis of wing-type structure, are discussed. The use and accuracy of these procedures have been demonstrated on a low cost, low risk basis in the design and analysis of a composite wind tunnel model and in test-theory correlation for static and dynamic response. Material selection, intermediate design decisions, fabrication, testing for natural modes and frequencies, and testing for influence coefficients for the wind tunnel model are discussed.     

复合材料层合板非线性热振动分析

采用有限元方法研究复合材料层合板结构在线性温度场作用下非线性热振动特性．采用特征值屈曲分析方法,判断了结构在线性温度场作用下的临界屈曲分歧点,计算了结构的一阶弯曲固有频率,分析了铺层角度及铺层层数对结构临界屈曲温度分布和结构固有频率的影响,总结了其对复合材料层合板结构热振动特性影响的一般规律．这些结论对复合材料结构设计、抗热设计有一定的指导意义．     

基于电容传感器的飞机滑油磨粒检测系统设计

飞机发动机的异常摩擦、磨损会在滑油中产生大量的磨粒,对滑油磨粒的有效检测可以为发动机的故障诊断提供可靠信息。设计了一个弧状极板式电容传感器,但传感器中电容变化量非常小,传统方法难以检测,采用交流电桥式电容检测方法。系统以AD9833为DDS信号发生器给交流电桥施加激励信号,经C/V转换、差分放大、相敏解调以及低通滤波等处理后得到实时电压变化。可实现弱信号的精确检测,且能有效克服杂散电容和寄生电容的影响。多次实验结果均表明：该检测系统具有灵敏度高,稳定性好等特点。     

Influence of environmental temperature on the dynamic properties of a die attached MEMS device

Die attach is one of the major processes that may induce unwanted stresses and deformations into micro-electro-mechanical systems (MEMS). The thermo-elastic coupling between the die and package may affect the performance of MEMS under various temperature loads, causing unreasonable effects of the output signal, such as zero offset, temperature coefficient of offset (TCO), nonlinearity, ununiformity and hysteresis, etc. A complete characterization of these effects is critical for a more reliable design. This work presents experimental studies of the temperature effects on the dynamic properties of MEMS. Microbridges and strain gauges with different dimensions were used as test structures. They were surface-micromachined on test chips and the chips were die attached on organic laminate substrates using epoxy bonding as well as tape adhering. The material and dimension of the substrate were specially defined to amplify the magnitude of the coupled deformation for the convenience of investigation. Modal frequencies of the microbridges under a set of controlled environmental temperature before and after die attach were measured using a laser Doppler vibrometer system. The average initial residual strain was also measured from the strain gauges to help analyze the dynamic behavior. Nonlinear TCO of the frequencies were observed to be as large as 2,500–5,000 ppm for the epoxy-bonded samples, in contrast with much smaller values for the tape-adhered and unpackaged ones. The frequencies recovered to their original values beyond the curing temperature of the epoxy. A distributed feature was also observed in frequencies of the microbridges with the same length but at different locations of the chip with a maximum relative difference of 20%. The process of thermal cycling and wire bonding was also applied to the samples and caused tender shifts of the frequencies. The experiments reveal major factors that are related to the temperature effects of die attached MEMS and the results are useful for improving the reliability of a package–device co-design.     

Analysis of a milling machine structure for ribbing of the cross-arm

The dynamic characteristics of a milling machine structure are studied using a computer aided technique for numerical analysis and a model technique for experimental analysis. The solid cross-arm is replaced by a hollow ribbed cross-arm with five transverse ribs positioned in three different ways: (i) equispaced throughout the cross-arm; (ii) equispaced in half of the cross-arm adjacent to the column; and (iii) equispaced in half of the cross-arm away from the column.

The natural frequencies and corresponding mode shapes are determined analytically and experimentally. A comparison is made between the different cases. The analysis is carried out on a -scaled perspex model of the Elliot Universal Milling Machine structure. The knowledge of the dynamic characteristics is utilized in improving the structural design of the milling machine by saving material and increasing the dynamic rigidity of the structure.     

Dynamic analysis of a bulkhead flat car underframe structure

A dynamic analysis of the underframe (U/F) structure of a 100-ton bulkhead flat car was performed. Center plate accelerations and side bearing forces were obtained from the dynamic analysis of the car system using random track irregularity inputs. In this analysis the carbody was treated as two rigid elements connected by springs. The objective of this study was: (a) to investigate the effect of bulkheads on the natural frequencies and mode shapes of the U/F structure; (b) to evaluate the maximum dynamic stresses and stress ranges for a few selected critical members of the U/F structure; (c) to determine the influence of the bulkheads and structural damping, in both the original and new (statically optimized) U/F structure designs: (d) to compare the calculated dynamic stresses in a few selected members, with increased static stresses based on dynamic load factors for specified design loads; (e) to modify the design of the U/F structure according to the results of the dynamic analysis; and (f) to discuss the fatigue life of the U/F structure, based on the calculated stress ranges.     

校车车身模态分析

建立某校车有限元模型,用Abaqus对该校车车身骨架进行有限元动态分析,计算出车身骨架的振型和对应模态值,分析其动态特性,为骨架的设计和优化提供参考.     

Robust optimization of structural dynamic characteristics based on adaptive Kriging model and CNSGA

Dynamic characteristics greatly influence the comprehensive performance of a structure. But they are rarely included as objectives in traditional robust optimization of structures. In this study, a robust optimization model including both means and standard deviations of dynamic characteristic indices in the objective and constraint functions is constructed for improving the structural dynamic characteristics and reducing their fluctuations under uncertainty. Adaptive Kriging models are employed for the efficient computation of dynamic characteristics. An intelligent resampling technology is proposed to save computational costs and accelerate convergence of Kriging models, which takes full advantage of the test points for precision verification, the sample points within the local region of the biggest relative maximum absolute error and the near-optimal point to improve the global and local precision of Krigings. The high efficiency of proposed intelligent resampling technology is demonstrated by a numerical example. Finally, an efficient algorithm integrating adaptive Kriging models, Monte Carlo (MC) method, constrained non-dominated sorting genetic algorithm (CNSGA) is proposed to solve the robust optimization model of structural dynamic characteristics. Kriging models are interfaced with MC method to efficiently compute the fitness of individuals during CNSGA. The implementation of proposed methodology is explained in detail and highlighted by the robust optimization of a cone ring fixture with lots of circumferentially distributed holes in a large turbo generator aimed at moving its natural frequencies away from the exciting one. The comparison of the optimized design with the initial one demonstrates that the proposed methodology is feasible and applicable in engineering practice.     

Mixed elements in the optimal design of plates

The theory of design sensitivity analysis of structures, based on mixed finite element models, is developed for static, dynamic and stability constraints. The theory is applied to the optimal design of plates with minimum weight, subject to displacement, stress, natural frequencies and buckling stresses constraints. The finite element model is based on an eight node mixed isoparametric quadratic plate element, whose degrees of freedom are the transversal displacement and three moments per node. The corresponding nonlinear programming problem is solved using the commercially available ADS (Automated Design Synthesis) program. The sensitivities are calculated by analytical, semi-analytical and finite difference techniques. The advantages and disadvantages of mixed elements in design optimization of plates are discussed with reference to applications.     

一种评价硅微陀螺性能的电路分析方法

硅微机械陀螺批量生产后,传统的微陀螺测试方法耗费时间比较长,需要专用设备,测试系统比较复杂,工作量很大.基于双正弦载波调制的测控电路,经过大量的电路调试工作,首次利用电路分析方法,提出了三种评价硅微陀螺性能的指标.运用此评价指标,对五个硅微陀螺进行了性能评价,性能由高到低依次是G05、G04、G03、G02、G01,并用零偏稳定性指标对G05 、G01进行了验证,G05零偏稳定性67°/h, G01零偏稳定性104°/h.结果表明,电路分析方法可以快速评价硅微陀螺性能,效率高,准确率高.最后,运用电路分析方法进一步优化了微陀螺的结构设计以及改进了相关的制造工艺.