Present Status and Prospect of High-Frequency Electro-hydraulic Vibration Control Technology

Electro-hydraulic vibration equipment(EHVE)is widely used in vibration environment simulation tests,such as vehicles,weapons,ships,aerospace,nuclear industries and seismic waves replication,etc.,due to its large output power,displacement and thrust,as well as good workload adaptation and multi-controllable parameters.Based on the domestic and overseas development of high-frequency EHVE,dividing them into servo-valve controlled vibration equipment and rotary-valve controlled vibration equipment.The research status and progress of high-frequency electro-hydraulic vibration control technology(EHVCT)are discussed,from the perspective of vibration waveform control and vibration controller.The problems of current electro-hydraulic vibration system bandwidth and waveform distortion control,stability control,offset control and complex vibration waveform generation in high-frequency vibration conditions are pointed out.Combining the existing rotary-valve controlled high-frequency electro-hydraulic vibration method,a new twin-valve independently controlled high-frequency electro-hydraulic vibration method is proposed to break through the limitations of current electro-hydraulic vibration technology in terms of system frequency bandwidth and waveform distortion.The new method can realize independent adjustment and control of vibration waveform frequency,amplitude and offset under high-frequency vibration conditions,and provide a new idea for accurate simulation of high-frequency vibration waveform.

Output Waveform Analysis of an Electro-hydraulic Vibrator Controlled by the Multiple Valves

The existing research of the electro-hydraulic vibrator mainly focuses on system stability, working frequency width and output waveform distortion. However, this high frequency performance of the electro-hydraulic vibrator is difficult to be improved greatly due to fast insufficiently frequency response of the servo valve itself and limited compensation capability of the control structure in the vibrator system. In this paper, to realize high frequency vibration, an improved two-dimensional valve （here within defined as a 2D valve） as a main control component is adopted to the parallel connection with a servo valve to control the electro-hydraulic vibrator, Because the output waveforms of this electro-hydraulic vibrator are incapable to be verified through timely feedback as in the conventional electro-hydraulic servo system, the analysis to the output waveform becomes crucial to the design and control of the electro-hydraulic vibrator. The mathematical models of hydraulic actuation mechanism and the orifice area of the parallel valves connection are established first. And then the vibration process is divided into two sections in terms of the direction of the flow, the analytical expression of the excited waveform is solved. Based on relationships exist between working states and the control parameters the analytical results, the vibration boundary positions and the are derived. Finally an experimental system was built to validate the theoretical analysis. It is verified that this electro-hydraulic vibration system could achieve high working frequency, up to 2 000 Hz. The excited waveform is similar to the sinnsoidal waveform. And the ascent and decent slopes of the waveforms are somewhat asymmetrical. This asymmetry is not only caused by the change of the direction of the elastic force but also dependent on the bias position of the vibration. Consequentky the distortion of effective working waveform is less tha~ 10%. This electro-hydraulic vibrator controlled by the multiple valves could not only greatly enhance the working frequency but also precisely control the vibration characteristic variables such as waveform shape.

Vibration Measurement of Pedestrian Bridge Using Double Magnetic Suspension Vibrator Based on Wavelet Analysis

Aiming at the problem of pedestrian bridge vibration measurement,a vibration measurement system of pedestrian bridge with dual magnetic suspension vibrator structure was designed according to absolute vibration measurement principle. The relationship between the magnetic repulsion force of vibrator and its displacement was obtained by the experimental method and the least square fitting method. The vibration equations of two magnetic suspension vibrators were deduced respectively,and the measurement sensitivity of the system was deduced. The amplitude-frequency characteristic of the system was studied. A simulation model of vibrator measurement system with double magnetic suspension vibrator was established. The analysis shows that the sensitivity of the vibration measurement system with double magnetic suspension vibrator is higher than that with single magnetic suspension vibrator. The four vibration waveforms were measured,that is,no one passes through a pedestrian bridge,there are cars running under the pedestrian bridge,single pedestrian passes through the pedestrian bridge and multiple pedestrians pass through the pedestrian bridge. The multi-scale one-dimensional wavelet decomposition function was used to analyze the vibration signals. The vibration characteristics were obtained using one dimension wavelet decomposition function under four different conditions. Finally,the vibration waveforms of four cases were reconstructed. The measured results show that the vibration measurement system of pedestrian bridge with double magnetic suspension vibrator structure has high measurement sensitivity. The design has a certain value to monitor a pedestrian bridge.

APPLICATION OF FRF ESTIMATOR BASED ON ERRORS-IN-VARIABLES MODEL IN MULTI-INPUT MULTI-OUTPUT VIBRATION CONTROL SYSTEM

The FRF estimator based on the errors-in-variables （EV） model of multi-input multi-output （MIMO） system is presented to reduce the bias error of FRF HI estimator. The FRF HI estimator is influenced by the noises in the inputs of the system and generates an under-estimation of the true FRF. The FRF estimator based on the EV model takes into account the errors in both the inputs and outputs of the system and would lead to more accurate FRF estimation. The FRF estimator based on the EV model is applied to the waveform replication on the 6-DOF （degree-of-freedom） hydraulic vibration table. The result shows that it is favorable to improve the control precision of the MIMO vibration control system.

Design and Analysis of Axial Thrust Roller-Exciting Vibrating Table and Its Motor-Control System Based on Co-simulation

Aiming at improving the mechanical vibrating equipment,the axial thrust roller-exciting vibrating tables and its motor-control system based on co-simulation were put forward. First, the structures of vibrating table and its surface equations and boundary conditions were established through reversal process. Second,waveform distortion influenced by random and harmonic waves was analyzed by equivalent parametric transition. These two steps were both technological challenge and contribution for the vibrating table.Finally, based on research above, a proportion integration differentiation( PID) motor-control system was built to show its rapid operation and convenient control. All the results show that not only does vibrating table have lower waveform distortion than traditional ones,but its control system narrows down the fluctuation and improves anti-interference performance. Hence,it provides a more extensive selection for efficient and practical mechanical vibrating table.

Comparison of Tongue and Lip Trills with Phonation of the Sustained Vowel /<i>ε</i>/ Regarding the Periodicity of the Electroglottographic Waveform and the Amplitude of the Electroglottographic Signal

Aim: The aim is to compare the vocal fold vibration seen during lip and tongue trills with that seen during phonation of the sustained vowel /ε/, in terms of the periodicity of the EGG waveform and the amplitude of the EGG signal, in professional voice users. Study design: This was a quasi-experimental study. Methods: We used electroglottography (EGG) to compare the vocal fold vibration seen during tongue and lip trills with that seen during phonation of the sustained vowel /ε/, in terms of the EGG waveform periodicity and signal amplitude, in 10 classically trained, professional singers. The participants produced the sustained vowel /ε/ and performed tongue and lip trills at the same frequency and intensity. The periodicity of the waveform and the amplitude of the signal were visually analyzed by three blinded, experienced readers. To confirm the visual analysis results, we measured the jitter and shimmer of the signal and the frequency of variation in vocal fold vibration during the trill exercises. Results: The EGG waveform was classified as periodic for the sustained vowel phonation task and as quasi-periodic for the trill exercises, the vibration pattern repeating at approximately 24 Hz. Conclusion: The vibration of the vocal folds was modified according to the supraglottic movement in trills exercises.

Application of Waveform Factors in Extracting Fault Trend of Rotary Machines

Vibration intensity and non-dimensional amplitude parameters are often used to extract the fault trend of rotary machines. But,they are the parameters related to energy,and can not describe the fault trend because of varying load and conditions or too slight change of vibration signal. For this reason,three non-dimensional parameters are presented,namely waveform repeatability factor,waveform jumping factor and waveform similarity factor,called as waveform factors jointly,which are based on statistics analysis for the waveform and sensitive to the change of signal waveform. When they are used to extract the fault trend of rotary machines as a kind of technology of instrument and meter,they can reflect the fault trend better than the vibration intensity,peak amplitude and margin index.

爆破振动强度、波形与频谱研究综述:预测及主动控制

岩石钻孔爆破不可避免地会产生爆破振动效应及危害,准确预测爆破振动效应并进行主动控制具有极大的现实意义。论文综述了近40年来,国内外研究人员在爆破振动预测及主动控制方面取得的研究成果。在爆破振动速度峰值(PPV)预测方面,经验模型预测方法体现出了较大的便捷性,但预测精度与效果较差,将概率统计理论引入经验模型预测方法,提高了PPV预测精度;而基波叠加预测方法可实现对振速、频率和持续时间的综合预测,但是该方法对振动基波的测试精度要求较高,同时亟须在行业内建立对爆破振动采集设备的定期标定与校核机制;人工智能预测方法极大提高了PPV预测精度,同时为多因素影响下的爆破振动效应预测提供了新思路,但需要建立在海量真实有效实测数据的基础上,目前还缺乏充实的振动测试样本数据库;PPV预测理论模型及数值模拟预测法对理论与专业知识、数值模拟技术等要求高,限制了两种方法在工程的普遍应用。在爆破振动速度主动控制上,可以确定合理的延期时间,采用毫秒延迟干扰减振法来降低PPV,但目前多为单一防护对象所提出的延期时间建议值;从调整爆破振动频谱结构的角度,通过主动改变延期时间调控爆破振动频率成分,可避开建(构)筑物自振频带,减小爆破振动危害,然而目前仅仅停留在理论层面或模型试验尺度条件下,缺乏大规模的现场应用实例。最后,对未来爆破振动预测及控制方面重点研究内容进行了展望。

连续振动载荷在线复现控制技术研究

提出一种主从分布式振动试验方法,建立了连续振动载荷在线复现控制技术,研制了系统样机。其中,提出一种信号分帧处理与重构技术,解决了长时连续振动载荷的在线波形复现难题;提出一种基于多量级样本库构建与加权平均的传递函数动态估计方法,抑制了系统非线性对控制精度的影响;采用谱误差反馈修正方法,改善了系统的频域控制精度。开展了“1主2从”联台试验,结果表明:时域和频域控制精度良好,整体延迟时间在亚秒量级,全程总均方根值误差在1%以内,为主从分布式振动试验提供了关键技术支撑。

掏槽爆破作用下振动波形预测及影响分区确定

为研究隧道掘进过程中掏槽爆破对既有建筑物的影响,构建地表质点爆破振动波形预测函数,引入基于爆破振动波形理论的影响区域划分方法。基于等效球形药包理论,结合萨道夫斯基公式和爆破振动频率预测公式,将拟合系数与等效振源强度函数中的工程参数建立联系,构建适用于实际工程的爆破振动波形函数。依托现场监测数据,验证引入方法的可靠性。最后,分别以质点峰值振速、振动位移作为标准划分爆破振动影响区域。根据计算结果,掌子面在邻近被保护对象水平距离D=50 m时应采取相应的控制爆破措施。

减震沟爆破降振机理的试验研究

降低爆破振动危害是爆破安全中广泛关注的重要课题,研究减震沟的降振机理对指导爆破工程安全具有一定理论价值。以混凝土为振动传播介质,固定埋深的炸药爆炸后,测试有无减震沟条件下不同距离爆破振动参数。通过波形分析其传播衰减过程,利用MATLAB工具包对爆破振动波进行时频分析。结果表明:随着距爆心水平距离的增加,切向、径向、垂向峰值振动速度均逐渐减小,且符合萨道夫斯基公式的指数式衰减;减震沟过滤了爆破振动的低频成分,有效地阻隔爆破振动产生的P波,显著降低爆破振动的能量强度,控制爆破振动危害。

隧道爆破振动中掏槽段的波形预测方法

为探讨隧道爆破振动响应的分布特征,对掏槽爆破诱发的爆破振动波形展开预测。基于等效的球形爆源理论,引入一种地表爆破振动波形的预测方法,首次将频率的影响纳入爆破振动波形的预测研究中,推导得到等效球形爆破荷载作用下的地表爆破振动波形的符号表达式。以此为基础,构造形式简洁的爆破振动波形预测函数。依托具体隧道爆破的现场监测数据对预测函数的可靠性进行验证。结果表明:理论波形与实测波形在爆破振动曲线总体趋势上表现出良好的一致性。二者对应的质点峰值速度与振动周期基本相同。这种对比结果可验证该文引入方法的可行性。

微差爆破降震效果影响因素分析

依托单段实测爆破振动信号,借助Matlab软件编程,分析了特性各异的子信号在不同微差时间下叠加信号的时频特征,通过引入"降幅率"和"振速比例"的概念,提出了微差爆破叠加信号各特性随微差时间、起爆顺序及子信号特性的变化规律。分析发现,使叠加信号达到一定降幅率的时差并非某一具体时差点,而是多个间断的时差区间,其主频随微差时间的不同呈阶跃锯齿型变化;合理微差时间下,两单段信号的振动特性越相近,干扰降震效果越明显;若装药已定,优先起爆小药量的段别所达到的降震效果更佳。现场试验数据显示,研究结果基本符合微差爆破的现实运作规律。

基于单段波形叠加的爆破振动信号时频分析

基于实测的单段爆破振动信号,利用Matlab7.0编制程序在0～120ms内每隔单位毫秒进行两段波形叠加,研究不同微差间隔下的叠加信号振速峰值和主频的特征;并根据RSPWVD可以看作信号能量在时域和频域分布的明确的物理意义,从能量的角度探讨不同微差间隔下叠加信号的能量分布规律。结果表明:叠加信号降振率的最大值并非出现在单段爆破振动信号1/2周期的微差间隔处;叠加信号的主频不是连续变化的,具有一定的阶跃性,其持续时间随间隔时间的延长而增加;叠加信号的能量随着微差间隔延长具有明显的规律性,可尝试从能量的角度并考虑建(构)筑物对不同频率的选择放大作用对干扰降振进行研究。

基于波形预测小波包分析模型的降振微差时间选择

从计算机模拟的角度,利用波形预测的小波包分析模型进行了段微差时间间隔的优化选择研究。算例表明:不同的微差段数,有合适的微差时间间隔范围,在该范围选择不同的微差时间间隔,具有不同的结果;随着微差段数的增加,段微差时间间隔的选择范围变窄,且选择范围出现更细的划分。这说明在实施微差爆破过程中,段微差时间间隔应当选择更高的精度,才能满足相应的干扰降振要求。

基于叠加原理的隧道爆破近区振动规律研究

为了改善隧道近区振动强度预测的准确性,以线性叠加理论的假设条件为基础,建立了符合现场实际的隧道近区振速计算模型。以北京兴延高速公道浇花峪右线隧道,里程为YK28+190到YK28+354范围内实测数据验证模型的可行性,并对隧道近区振动规律进行研究。研究表明:(1)基于波形叠加的爆破振动预测模型适用于隧道近区振动预测;(2)随着单孔装药量的增加,平行于掌子面的隧道截面上能量密度增加,振速等值线的强度增大,轮廓形态出现变化,中心测线振速的增长幅度大于两边,在爆破近区这种现象尤为明显;隧道已开挖区垂直掌子面的测线方向上,随着离爆源的距离增加,振速的衰减速度逐渐变小。(3)随掏槽孔孔数目的增多,相同数值的等值线外移,且等值线逐渐平缓;平行于掌子面的隧道截面上,振速的增加幅度逐渐减小。

爆破振动全历程预测及主动控制研究进展

爆破振动为爆破公害之首,工程上需要对其进行控制.基于爆破振动全历程预测的爆破振动控制方法是一种主动的控制方法,且具有良好的应用前景,本文阐述了爆破振动全历程预测的研究进展与应用,并对各种预测模型的优缺点进行了比较.介绍了两种典型的爆破振动主动控制方法——干扰降振法和频谱控制法的理论试验研究及其在工程中的应用,并重点分析了爆破振动控制在电子起爆条件下的优势及一些应用实例.最后指出了今后需要进一步研究的问题.

多点激励振动试验控制技术进展

多点激励振动试验由于能更加真实地模拟实际振动环境而被越来越多的人所重视,成为振动环境试验发展的趋势。阐述了多点激励振动试验系统基本控制原理,并对时域波形复现的关键技术迭代算法和驱动信号重叠连接,以及频谱再现的关键技术反馈修正算法和时域随机化技术进行了介绍。最后对多点激励振动试验控制技术进行总结与展望。

磁悬浮效应检振系统设计

为了设计一种高效、高灵敏度的检振系统,在构建了磁悬浮球模型及控制系统的基础上,通过对系统的结构和运行参数分析,推导了外界振动下的系统动力学方程,并将其等效成表征质量-弹簧测振系统的常系数二阶微分方程,使等效阻尼系数和刚度系数与质量-弹簧系统的参数有一定的对应关系。在磁悬浮球质量分别为126.5g和198.5g的条件下,对振动频率为50Hz的激振器的位移波形及通过频谱分析得到的自功率谱进行了测量,对激振器不同位置的影响进行了实验比较。实验结果表明,该检测方法克服了一般测振系统无法克服的摩擦,提高了测量灵敏度,而且只要改变控制参数即可达到改变阻尼系数的目的,实现容易。

基于磁悬浮技术惯性式振动测量方法研究

磁悬浮球作为质量块实现惯性式振动测量,测量磁悬浮球与测振系统壳体的相对位移即可得到被测振动体的振动参数。由于磁悬浮球不与任何物体接触、无机械摩擦、无机械间隙误差,与传统惯性式振动测量方法相比具有灵敏度高、测量上限频率高,直接输出振动位移信号,通过微加工技术可实现体积小等优点,控制电路还可提供各类所需阻尼函数,但低于10 H z测量频率时需加大测试装置尺寸。在构建磁悬浮球模型及控制系统的基础上,通过对系统的结构和运行参数分析,推导了磁悬浮测振系统动力学方程,并将其等效成表征质量-弹簧测振系统的常系数二阶微分方程,使等效阻尼系数和刚度系数与质量-弹簧系统的参数有一定的对应关系。通过标准激振器产生不同的振动信号,测量结果验证了该方法正确。测试系统灵敏度:986 mV/g,测量频率范围:20 H z^5 kH z。该方法无需粘贴传感器、性价比高、操作方便。