ACTIVE VIBRATION SUPPRESSION VIA LINEARIZING HYSTERESIS OF PIEZOCERAMIC ACTUATORS

A novel active vibration control technique on the basis of linearized piezoelectric actuators is presented. An experimental apparatus consisting of a cantilever beam to which are attached strain patches and piezoceramic actuators to be used for active vibration suppression is described. A dynamical model of the cantilever beam using Lagrange＇s equation and two coordinate systems are presented. Based on the Lyapunov＇s direct method, an active vibration controller with hysteresis compensation is designed. The controller is designed so that it guarantees the global stability of the overall system. The controller developed is assessed experimentally.

Mechanical properties of disc-spring vibration isolators based on boundary friction

To ascertain the influence of the boundary friction on mechanical properties of disc-spring vibration isolators a load-displacement hysteresis curve formula of disc-spring vibration isolators is derived on the basis of the energy conservation law as well as considering the effect of the boundary friction.The formula is validated through the finite element analysis and static load tests.On this basis the effect of the boundary friction on the bearing capacity is researched. Then the dynamic performance of disc-spring vibration isolators is studied by dynamic tests.The experimental results indicate that the boundary friction can promise a larger damping with a ratio of 0.23 for disc-spring vibration isolators.Compared with the loading frequency the loading amplitude has a greater impact on the energy consumption dynamic stiffness and damping of vibration isolators.This research can provide valuable information for the design of disc-spring vibration isolators.

Random vibration of hysteretic systems under Poisson white noise excitations

Hysteresis widely exists in civil structures,and dissipates the mechanical energy of systems.Research on the random vibration of hysteretic systems,however,is still insufficient,particularly when the excitation is non-Gaussian.In this paper,the radial basis function(RBF)neural network(RBF-NN)method is adopted as a numerical method to investigate the random vibration of the Bouc-Wen hysteretic system under the Poisson white noise excitations.The solution to the reduced generalized Fokker-PlanckKolmogorov(GFPK)equation is expressed in terms of the RBF-NNs with the Gaussian activation functions,whose weights are determined by minimizing the loss function of the reduced GFPK equation residual and constraint associated with the normalization condition.A steel fiber reinforced ceramsite concrete(SFRCC)column loaded by the Poisson white noise is studied as an example to illustrate the solution process.The effects of several important parameters of both the system and the excitation on the stochastic response are evaluated,and the obtained results are compared with those obtained by the Monte Carlo simulations(MCSs).The numerical results show that the RBF-NN method can accurately predict the stationary response with a considerable high computational efficiency.

Direct scaling of residual displacements for bilinear and pinching oscillators

The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the event.An attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5%initial damping,directly in terms of easily available seismological,site,and model parameters.None of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not available.The statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude,epicentral distance,site geology parameter,and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models,as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model alone.The proposed scaling model is applicable to horizontal ground motions in the western U.S.for earthquake magnitudes less than 7 or epicentral distances greater than 20 km.

Microscopic dynamic observation of adhesion hysteresis friction and exploration of the influence of different pressures on friction transmission

The mechanism of adhesive friction between viscoelastic materials is a key question.In this study,the friction process of the adhesive interface between a friction lining and a wire rope is dynamically observed in real time to analyze the adhesion hysteresis friction intuitively and quantitatively.The adhesion is determined by the state of motion,while the relative displacement of the wire rope and lining is used to find the magnitude of the adhesive friction.The hysteresis friction is reflected by the internal deformation of the lining.The magnitude of the hysteresis friction is determined by the displacement difference(Ax)in the sliding direction of two marked points at different distances from the contact surface.The results show that the adhesion friction is proportional to the loss modulus and the hysteresis friction is proportional to the ratio of the loss modulus to the square of the storage modulus(E"/(E'^(2))).The frictional vibration first decreases and then increases with the increase in pressure.The K25 lining has the highest adhesion hysteresis friction and minimal frictional vibration.The result provides a simple and intuitive method for research into the friction transmission and vibration of viscoelastic materials.

DYNAMICAL ANALYSIS OF AUTOMOBILE HYSTERESIS NONLINEAR SYSTEM

This paper adopts free interface modal synthesis method to divide the whole automobile model into many sub-structures and establish dynamical equations of automobile nonlinear coupled system. The Monte Carlo method is used to simulate the spectrum of the random excitation of the road and the engine. Based on the automobile dynamical equations, a simulation is carried out within time domain and frequency domain on the characteristic of vibration due to the excitation of automobile wheel and the engine. The results are verified by bench experiment to make the research more practicable. In order to do research of rubber hysteresis’ influence on automobile dynamic property, Poincare diagrams and amplitude frequency characteristic curves were drawn with automobile linear and nonlinear models. The results show that the nonlinear dynamical model concerning rubber hysteresis not only can improve the simulation accuracy, but also is beneficial to find some complex nonlinear dynamical behaviors of vehicles.

基于粒子群算法的钢丝网垫隔振器参数识别

目的 证明粒子群优化算法对钢丝网垫隔振器参数识别的有效性和准确性。探究不同的加载条件对钢丝网垫元件力学性能的影响。方法 对钢丝网垫元件进行正弦加载试验,获取试验响应数据。以双折线模型对钢丝网垫的力学性能进行描述,建立隔振器的参数识别方程,应用粒子群算法和试验响应数据识别出模型参数,并研究不同加载条件下识别参数的变化规律。结果 用识别出的参数计算绘制的迟滞回线和试验结果吻合较好。改变激励幅值和频率,钢丝网垫的一次刚度、三次刚度、滑移刚度、等效阻尼均发生规律性变化,而改变钢丝网垫所受静载,曲线变化极为微小。结论 研究证明了粒子群优化算法对钢丝网垫隔振器参数识别的有效性和准确性,是一种有工程应用价值的参数识别方法。

液压蓄能式竖向隔震装置性能试验及隔震参数分析

提出一种由液压油缸和蓄能器组成的新型竖向隔震装置,用于建筑结构竖向隔震.首先,介绍液压蓄能式竖向隔震装置的工作原理,并建立了非线性刚度模型和阻尼耗能模型.其次,开展了频率相关性、位移幅值相关性的反复加载试验,测得液压蓄能式竖向隔震装置的竖向刚度和阻尼耗能性能参数.试验结果表明,隔震装置的竖向刚度呈现非线性变化,理论值和实测试验值误差在±3%以内;隔震装置的滞回曲线饱满,具有较强的耗能性能,阻尼特性为速度相关型,试验结果与理论计算值吻合.最后,利用有限元方法建立不同竖向刚度和阻尼系数的竖向隔震结构数值分析模型,研究了在竖向地震作用下,隔震装置参数对结构隔震效果的影响.结果表明,隔震结构竖向刚度降低会导致竖向位移响应增大,而竖向加速度响应减小;通过调节阻尼调节阀可有效控制隔震结构在地震作用下的竖向位移,从而实现良好的隔震效果.

带限位隔振系统的主共振响应及隔振性能研究

针对舰船设备带限位隔振系统中普遍存在的非线性特性,文中建立包含分段线性刚度和分段线性阻尼的限位隔振系统数学模型,采用平均法对主共振响应进行解析求解,推导出系统力传递率方程,综合分析了限位器各参数对系统幅频特性和隔振性能的影响规律,通过扫频试验进行验证。结果表明:限位器阻尼对系统振动性能具有积极意义,大阻尼限位有效减小了幅频响应峰值,降低了力传递率,减小甚至避免了跳跃和滞后现象的产生;对于任意一组系统参数都存在一个最优刚度比,使得相对位移幅值最小、隔振性能最好,同时保证了跳跃区间相对较小;适当增大限位间隙可以减小跳跃区间,进一步改善系统的振动性能。

直流偏磁下磁控电抗器铁芯矢量电磁振动特性

在交直流共同激励的工作方式下,磁控电抗器(magnetically controlled reactor,MCR)受直流偏磁的影响,其电磁特性及振动特性会发生极大的变化。为了精确模拟材料在直流偏磁下的磁化及振动特性,首先基于电工钢片的矢量磁致伸缩逆模型和磁特性测量曲线,采用速度可控粒子群优化(velocity-controlled particle swarm optimization,VCPSO)算法提取并优化模型参数,对磁控电抗器铁芯电工钢片的磁滞和磁致伸缩特性进行分析,并对比实验和仿真曲线,验证磁化特性仿真的准确性;其次,结合矢量磁致伸缩逆模型与MCR有限元模型,模拟MCR铁芯在不同直流偏磁下的矢量电磁振动特性,并分析MCR铁芯位移波形的谐波分量。最后,搭建MCR振动测试系统,验证模型仿真的准确性。研究结果可为磁控电抗器铁芯振动的相关研究提供参考。

基于双线性池化引导特征融合的轴承故障诊断算法

为了深入优化滚动轴承在变负载驱动环境下特征提取不充分、轴承故障特征表征不足的问题,提出了基于双线性池化引导特征融合的轴承故障诊断算法。对读取到的原始信号数据进行预处理,通过去除直流分量、噪声滤波、抗混叠滤波、时域窗函数等操作,提高信号处理后的振动谱图质量;对预处理后的信号数据进行傅里叶变换,计算出变换后的幅值和频率数据,并绘制对应的振动谱图;利用通道注意力和空间注意力改进Res2Net网络,提取不同关注点下的视觉特征,并基于双线性池化方法进行多特征融合;利用全连接和softmax函数构建分类头,实现轴承故障分类。结果表明:所提出的方法在凯斯西储大学轴承数据集以及德国Paderborn数据集中的精确率分别为98.22%、97.94%,在轴承故障诊断中,所提算法不仅在理论上融合了自动化控制理论与控制工程原理,而且在实践中验证了其在轴承故障诊断中的有效性,为实现轴承故障的早期预警和智能诊断提供了新的技术途径。

一起内部振动引起GIS超声波局放异常分析

针对一起500kVGIS局部放电带电检测中超声信号异常引起的检修事件,通过对异常电压互感器展开外观检查、解体前局放试验、解体检查等,结合家族性缺陷数据以及装配工艺等因素,综合判断异常是设备内部装配工艺不良导致磁滞振动引起了超声局放信号,并针对后续设备运维工作提出了建议措施。

不同循环荷载频率下软黏土动力特性试验研究

通过开展饱和重塑软黏土GDS动三轴试验,研究了不同频率、循环荷载动应力比和初始有效应力作用下土体不排水累积轴向应变、累积孔压及回弹模量演化规律,并探明相关作用机理。研究结果表明:循环荷载动应力比、初始有效围压和频率对土体累积轴向应变、累积孔压及回弹模量影响较大。土体累积轴向应变、累积孔压与动应力比、初始有效应力呈正相关,与回弹模量则呈负相关。低循环应力比下,频率越高,软黏土产生的轴向累积应变与孔压越大,试样回弹模量越小;当动应力比过大时,软黏土试样则呈现相反的规律。根据上述规律,提出在不排水循环条件下,土颗粒吸收振动所产生的能量导致吸附于表面的强弱结合水发生转化,且在不同频率交通循环荷载下,软黏土变形受到了频率产生能量与黏土滞后效应的共同影响。研究结论可为交通工程中软土地基的变形计算提供重要参考。

考虑滞回效应的螺栓连接组合结构非线性随机振动分析

针对具有滞回效应的螺栓连接组合结构,结合虚拟激励法和多谐波平衡法实现了随机振动响应频域功率谱分析。首先,对于随机激励作用下的组合结构,以Jenkins模型进行本构建模。其次,将随机激励表达为复指数级数,将响应谱分析转化虚拟响应的向量运算,提出了扩展虚拟激励法(extended pseudo excitation method, E-PEM)。最后,对虚拟响应求解中频域本构的计算困难,引入时频变换处理;将非线性迭代转换为优化问题并利用信赖域方法求解,有效解决了传统牛顿法的收敛困难。以二自由度和组合梁模型为对象,研究了结构的随机振动响应谱特性,并同蒙特卡罗模拟法对比验证E-PEM的正确性,同时对结构特有的非线性随机振动机制进行了讨论。结果表明:建立的E-PEM为一般非线性结构随机振动频域分析提供了一个可借鉴的求解思路。

非线性隔振器阻尼特性研究

对一类迟滞非线性隔振器进行研究 ,提出了动力模型的建模方法 ,用此方法建立了钢丝绳隔振器的动态模型。由所建模型重构恢复力 -位移回线并与试验回线比较 ,结果表明 :理论回线与试验回线吻合好。用此模型研究这类隔振器的非线性阻尼特性 ,研究表明 :这类隔振器的阻尼随振幅和频率变化 ,阻尼成分丰富 ,既有粘性阻尼 ,又有干摩擦阻尼和“高阶”阻尼。该模型能很好地描述这类非线性隔振器的阻尼特性 ,这为设计多个宽频工作区来兼顾缓冲、隔振奠定了动力学基础。文中提出的建模方法适用于有非线性特性的隔振、减振器材的建模和刚度及阻尼特性的研究。

一类迟滞非线性振动系统建模新方法

用理论和试验相结合的手段研究一类迟滞非线性振动系统的动力建模， 提出一种新的建模方法， 用此方法建立非线性模型用来描述这类系统的动态特性。该模型用非线性刚度和非线性阻尼机理构造， 刚度和阻尼机理由理论和试验推出， 模型中的参数由试验数据辨识。用所建模型重构恢复力——位移迟滞环， 结果表明， 该模型能很好描述这类非线性振动系统的特性， 模型中各参数的重要性得到展示， 提出的建模方法实用且有效。

金属橡胶材料的动态力学模型

提出了用等效粘性阻尼理论和试验相结合,建立金属橡胶材料动态力学模型的一种新方法。用此方法,把金属橡胶材料的阻尼耗能机理等效为粘性阻尼,金属橡胶的恢复力由高阶非线性多项式和等效的粘性阻尼力叠加而成。模型中考虑了振幅和频率的影响,参数可通过试验数据辨识出来,用所建模型可以重新构造其它振幅和频率下的恢复力与位移的滞后曲线,得到了金属橡胶材料阻尼特性在振幅和频率影响下的变化规律。

一个新的非线性迟滞隔振系统动力学模型

提出了一个新的非线性迟滞隔振系统的动力学模型,并导出了系统动力学模型的实用表达式。该模型由非线性刚度和非线性阻尼构造,迟滞非线性阻尼力被表示为位移的函数,从而使数值计算变得简单易行,试验中的测量工作减少。模型中的各个参数物理意义明晰,各阶刚度系数能很好地反映系统中存在的线性和非线性特性,而阻尼函数能很好地反映系统的迟滞和耗能特性,运用阻尼函数还可对隔振系统中可能存在的干摩擦阻尼、粘性阻尼及高阶阻尼等各种阻尼成分进行有效的识别。

并列双圆柱流致振动的不对称振动和对称性迟滞研究

对雷诺数Re=100间距比s/D=2.5和5.0的并列双圆柱流致振动进行了数值模拟研究,其中圆柱质量比m*=2.0,折合流速Ur在2.0～10.0之间,两圆柱仅能做横流向振动.研究发现,当间距比s/D=2.5时,在折合流速4.0<Ur<4.8区间内,两圆柱流致振动响应出现不对称振动现象,在折合流速4.4<Ur<4.8区间内,两圆柱流致振动响应出现对称性迟滞现象;而当间距比s/D=5.0时,圆柱流致振动响应与单圆柱涡激振动响应相似,没有出现不对称振动和对称性迟滞现象.在不对称振动区间内,两圆柱的升、阻力参数也出现了不相等的情况.此外,当两圆柱不对称振动时,圆柱间隙流稳定地偏斜向其中的一个圆柱;相应地,尾涡也出现了宽窄不等的模式.窄尾流圆柱的振幅和升、阻力均较宽尾流圆柱的大.通过对比不对称振动现象发生前后的尾涡模式,对新现象的产生机制进行了阐述.

双线性双滞后环系统非线性振动

研究含双线性双环滞后单自由度系统非线性振动的响应特点。先用平均法得到主共振情况下系统的幅频响应方程。然后讨论了外激励振幅变化对幅频响应的影响。给出了模式变化的临界参数条件,找到了四种不同类型的幅频响应并分析了其特点。在四种响应中,只有一种能充分发挥滞后环的耗能作用,适于减振设计。