Multi-objective optimal design of inerter-based vibration absorbers for earthquake protection of multi-storey building structures

In recent years different inerter-based vibration absorbers (IVAs) emerged for the earthquake protection of building structures coupling viscous and tuned-mass dampers with an inerter device. In the three most popular IVAs the inerter is functioning either as a motion amplifier [tuned-viscous-mass-damper (TVMD) configuration], mass amplifier [tuned-mass-damper-inerter (TMDI) configuration], or mass substitute [tuned-inerter-damper (TID) configuration]. Previous work has shown that through proper tuning, IVAs achieve enhanced earthquake-induced vibration suppression and/or weight reduction compared to conventional dampers/absorbers, but at the expense of increased control forces exerted from the IVA to the host building structure. These potentially large forces are typically not accounted for by current IVA tuning approaches. In this regard, a multi-objective IVA design approach is herein developed to identify the compromise between the competing objectives of (i) suppressing earthquake-induced vibrations in buildings, and (ii) avoiding development of excessive IVA (control) forces, while, simultaneously, assessing the appropriateness of different modeling assumptions for practical design of IVAs for earthquake engineering applications. The potential of the approach to pinpoint Pareto optimal IVA designs against the above objectives is illustrated for different IVA placements along the height of a benchmark 9-storey steel frame structure. Objective (i) is quantified according to current performance-based seismic design trends using first-passage reliability criteria associated with the probability of exceeding pre-specified thresholds of storey drifts and/or floor accelerations being the engineering demand parameters (EDPs) of interest. A variant, simpler, formulation is also considered using as performance quantification the sum of EDP variances in accordance to traditional tuning methods for dynamic vibration absorbers. Objective (ii) is quantified through the variance of the IVA force. It is found that reduction of IVA control force of up to 3 times can be achieved with insignificant deterioration of building performance compared to the extreme Pareto optimal IVA design targeting maximum vibration suppression, while TID and TMDI achieve practically the same building performance and significantly outperform the TVMD. Moreover, it is shown that the simpler variant formulation may provide significantly suboptimal reliability performance. Lastly, it is verified that the efficacy of optimal IVA designs for stationary conditions is maintained for non-stationary stochastic excitation model capturing typical evolutionary features of earthquake excitations.     

Benefits of the inerter in vibration suppression of a milling machine

This paper investigates the benefits of the inerter in improving vibration suppression of milling machine tools. The traditional method for repressing the cutting vibration of milling machines includes applying passive mechanical networks that consist of masses, dampers, and springs. However, because the mass element is not a genuine two-terminal network element, the achievable performance of the passive mechanical networks might be restricted. The inerter was invented to substitute the mass element and has been successfully applied to many mechanical systems, such as vehicles and buildings. This paper extends the application of the inerter to a milling machine and discusses the resulting vibration suppression improvements. We first built a model of the milling machine via experiments, followed by applying three basic suspension layouts to the model and illustrating how the inerter can help reduce system vibration. Lastly, we conducted experiments to verify the effectiveness of the inerter in improving the manufacturing performance of the milling machine.     

A comparative study of vibration isolation performance using negative stiffness and inerter dampers

Two types of passive devices, namely, negative stiffness damper (NSD) and inerter damper (ID), have been receiving growing interest in vibration isolation and suppression, because both can produce negative-slope force-displacement relationships that are similar to those associated with active control forces. Despite such a similarity, these two passive dampers possess obvious differences in their mechanical behaviors. This study aims to illustrate the similarity and difference between these two dampers in vibration isolation applications with respect to the H₂ and H_∞ performance. The comparative study indicates that both dampers can reduce the H_∞ norm effectively; the negative stiffness devices can reduce the H₂ norm as well, whereas the H₂ norm cannot converge under the influence of inerter. This finding explains why a tuned-inerter damper, i.e., an inerter connected in series with a spring with proper frequency tuning, is more commonly adopted in vibration isolation. The pros and cons of both devices were further discussed.     

Adaptive vibration control of a flexible structure based on hybrid learning controlled active mass damping

Natural disasters such as earthquakes and strong winds will lead to vibrations in ultra-high or high-rise buildings and even the damages of the structures. The traditional approaches resist the destructive effects of natural disasters through enhancing the performance of the structure itself. However, due to the unpredictability of the disaster strength, the traditional approaches are no longer appropriate for earthquake mitigation in building structures. Therefore, designing an effective intelligent control method for suppressing vibrations of the flexible buildings is significant in practice. This paper focuses on a single-floor building-like structure with an active mass damper (AMD) and proposes a hybrid learning control strategy to suppress vibrations caused by unknown time-varying disturbances (earthquake, strong wind, etc.). As the flexible building structure is a distributed parameter system, a novel finite dimension dynamic model is firstly constructed by assumed mode method (AMM) to effectively analyze the complex dynamics of the flexible building stucture. Secondly, an adaptive hybrid learning control based on full-order state observer is designed through back-stepping method for dealing with system uncertainties, unknown disturbances and immeasurable states. Thirdly, semi-globally uniformly ultimate boundedness (SGUUB) of the closed-loop system is guaranteed via Lyapunov’s stability theory. Finally, the experimental investigation on Quanser Active Mass Damper demonstrates the effectiveness of the presented control approach in the field of vibration suppression. The research results will bring new ideas and methods to the field of disaster reduction for the engineering development.     

A review of the inerter and inerter-based vibration isolation: Theory,devices, and applications

The inerter has garnered much attention in the past two decades owing to its unique mechanical characteristics. As a substitution of the capacitance element based on the electrical-mechanical analogy, the inerter has outstanding advantages. Extensive investigations have been conducted for the development of inerter-based vibration isolation system. This paper provides a retrospective perspective and an update on the inerter's progress for vibration isolation in different fields. The advantages of inerter compared with mass element are analyzed and revealed. Some existing reviews and highly-cited papers are summarized to outline the inerter development progress. Thereafter, the inerter is reviewed in detail from the perspective of network analogy and synthesis, mechanical domain, and power flow transmission. The devices improvement and control approach are summarized. Finally, the significance of inerter research, the challenge in current studies, and promising inerter application fields are presented and discussed. This paper is closed by conclusions, which highlight the necessity of inerter research, current challenges, and future research directions.     

Substructural control of fuzzy nonlinear flexible structures

It is advantageous to use the substructural and/or decentralized techniques in structural control to save on computations and time. In this paper, a generalized substructural approach is presented in the control of fuzzy nonlinear flexible structures with discrete sensors/actuators. The substructural control scheme is developed using the static condensation technique together with the LQG control method. The subcontrollers and subobservers designed at substructure levels are used to assemble the global controller and observer for the whole structure. Nonlinear effects are included in the structural formulations and a fuzzy methodology is adopted for handling the imprecision present in the structure modeling. The nonlinear and fuzzy schemes are applied to one structural control problem to illustrate the accuracy and capability of the substructural control technique.     

Novel fluid inerter based tuned mass dampers for optimised structural control of base-isolated buildings

This work studies the advantageous features of the fluid inerter device for optimised structural control of buildings. Experimental data are first presented to characterise the fluid inerter dynamics, and validate the simplified analytical formulations. Building on these observations, the device is modelled as an inerter in parallel with a nonlinear dashpot representing a power law damping term. The latter dissipative effects are mainly induced by the pressure drops occurring in helical channels due to the fluid viscosity and density. Then, novel passive vibration control schemes are implemented for the earthquake protection of base-isolated buildings by combining the fluid inerter with a tuned mass damper system. To account for the uncertain nature of the earthquake input, the base acceleration is modelled as a Kanai–Tajimi filtered stationary random process. The optimal fluid inerter parameters, namely inertance and damping, are identified numerically by minimising stochastic performance indices relevant to displacement, acceleration, and energy-based measures of the structural response. The nonlinear damping behaviour of the fluid inerter is fully incorporated in the optimal design procedure via the statistical linearisation technique. Nonlinear response history analysis under an ensemble of 44 natural earthquake ground motions is carried out to assess the seismic performance of the system. Since inertance and damping are coupled characteristics in a real fluid inerter, design guidelines are finally outlined to determine the actual geometrical and mechanical properties of the device to achieve targeted parameters resulting from the optimisation procedure.     

基于软件复用的CRM系统的柔性化设计应用发展研究

在同行业内部,客户关系管理软件系统有许多相似之处。鉴于此,提出了一种基于软件复用的CRM系统的柔性化设计技术。在开发行业内客户关系管理系统时,先依据需求划分出通用模块,采用多层次极限编程的方法加以实现,可以提高开发过程对需求变化的适应性、提高软件的复用率,并且经过测试和使用过的模块能有效地提高系统的稳定性、可扩展性和可维护性。     

基于有限元法的转台振动特性研究

转台结构作为一种精密的半实物仿真设备,广泛应用于现代科技领域中。其振动特性将直接影响到它的动态精度,因此对转台振动特性的研究具有重要的工程意义。本文对转台结构的关键部件进行处理,利用有限单元法建立整个系统的振动模型,并研究了单轴转台的模态特性。     

Design of inerter-based multi-actuator systems for vibration control of adjacent structures

Distributed multi-actuator systems can provide effective solutions for mitigating the vibrational response of large structures. In this paper, we present a computational strategy to design inerter-based multi-actuation systems for the seismic protection of adjacent structures. The proposed approach allows considering both interstory and interbuilding Tuned Mass-Inerter Damper (TMID) actuators, and aims at simultaneously reducing the vibrational response of the individual buildings and avoiding the interbuilding impacts. The tuning procedure is based on an H_∞ cost-function and uses a constrained global-optimization solver to compute parameter configurations with high-performance characteristics. To illustrate the main features of this work, two different Tuned Inerter Damper (TID) multi-actuator schemes are considered for the seismic protection of a particular multi-story two-building system. A multi-actuator Tuned Mass Damper (TMD) system is also designed and is taken as a reference in the performance assessment. The obtained results demonstrate the flexibility and effectiveness of the proposed design methodology, and clearly show the superior performance and robustness of the TID actuation systems.     

电力系统安全运行策略与方法研究

选择合理的黑启动路径对电力系统大停电后快速、有效的恢复至关重要。经过对一系列赋权方法的研究与考量,选取可变熵模型确定黑启动指标的权重,该模型具有一定柔性,克服了经典熵权法权重分配差别过大、权重无法体现评价矩阵微小变化等问题。使用所得权重对灰关联法进行改进,构建黑启动方案关联系数矩阵,融合客观权重和关联系数实现方案的综合排序。利用所提方法对天津电网黑启动路径数据进行了评估,结果不仅证明了可变熵模型的合理性,也验证了结合灰色关联度的这套评估方法的有效性。     

一种基于频率变化线的飞机振源分析方法

对于飞行试验中非平稳振动信号,进行时频分析后仅可定性的观察到频率值随时间发生变化的趋势,为了确定振源机理,需要进一步寻求频率变化与飞行参数变化之间的相关性.提出了一种把所关注频率值的变化曲线从时频分析图中提取出来的方法,以定量的研究引起频率值变化的原因.针对某型机平飞状态出现的垂尾尖部振动较大现象,运用此方法提取频率变化线,通过与发动机参数的对比与拟合,确认了该振动产生的振源来自发动机的高压转子.     

基于智能代理的供应链柔性决策支持系统

传统的决策支持系统(DSS)的决策机制和系统结构缺乏足够的柔性,难以适应处于动态变化环境条件下供应链系统的决策支持。智能代理技术的运用在很大程度上提高了传统的DSS的结构柔性和决策柔性。本文建立了基于智能代理的供应链柔性决策支持系统(IA-SCFDSS)及其柔性决策机制和决策流程。     

Robust input shaping control for multi-mode flexible structures using neuro-sliding mode output feedback control

Input shaping provides an effective method for suppressing residual vibration of flexible structure systems. However, it is not very robust to parameter uncertainties and external disturbances. In this paper, a closed-loop input shaping method is developed for suppressing residual vibration of multi-mode flexible structure systems with parameter uncertainties and external disturbances. The proposed scheme integrates both input shaping control and discrete-time neuro-sliding mode output feedback control (NSMOFC). The input shaper is designed for the reference model and implemented outside of the feedback loop to achieve the exact elimination of residual vibration. In the feedback loop, the discrete-time NSMOFC technique is employed to make the closed-loop system behave like the reference model with input shaper, where the residual vibration is suppressed. The selection of switching surface and the existence of sliding mode have been addressed. The knowledge of upper bound of uncertainties is not required. Furthermore, it is shown that increasing the robustness to parameter uncertainties does not lengthen the duration of the impulse sequence. Simulation results demonstrate the efficacy of the proposed closed-loop input shaping control scheme.     

基于关键链技术的航天型号项目柔性组织过程管理研究

航天型号项目研制是科研院所参与国家重大科技创新的重要活动之一,研制任务具有时间紧、难度大、变量多、经费少等特点。分析和掌握航天型号项目研制过程本身的规律,以科研院所承担的航天型号项目为例,通过梳理项目管理流程和约束条件,并对技术、进度、质量、经费等管理要素进行融合分析,采用权变管理理论、柔性组织理论、风险管理理论等科学管理理论和关键链技术、系统管理方法、统筹分析方法、故障树分析法等多种研究方法,强化流程控制和风险管理,构建面向产品全生命周期的航天型号项目管理体系,从而提升航天任务的研制能力,推动科研院所高质量创新发展,圆满完成空间在轨各项工程任务。     

基于信任的合同柔性改善项目管理绩效研究

发承包双方间的信任关系及合同柔性作为关系治理与合同治理的核心，被视为工程项目管理绩效保障的重要因素。然而，信任、合同柔性作为多维度概念，其深层影响关系并未得到充分解释。本文从信任、合同柔性以及项目管理绩效相互作用剖析入手，构建信任、合同柔性、项目管理绩效结构模型，并依据调查问卷的统计分析结果得出以下结论：诚信信任与能力信任正向影响合同柔性，且正向影响项目管理绩效。制度信任与合同柔性及项目管理绩效的关系并不显著。合同柔性的使用与项目管理绩效间存在显著正相关关系。最后，基于研究结论提出了相关管理启示。     

基于遗传算法的柔性作业车间等量分批调度问题研究

针对柔性作业车间等量分批调度问题的复杂性,文中采用遗传算法进行求解.引入等量分批的策略,并提出了染色体的两级编码方法,设计了两种交叉和变异操作方法,以防止操作中非法解的产生,提高求解效率.对比整批调度和等量分批调度的生产周期,仿真结果表明,等量分批调度可缩短生产周期,验证了本文采用算法的可行性和有效性.     

An intelligent propagation distance estimation algorithm based on fundamental frequency energy distribution for periodic vibration localization

Earth surface vibrations generated by passing vehicles, excavation equipment, footsteps, etc., attract increasing attentions in the research community due to their wide applications. In this paper, we investigate the periodic vibration source localization problem, which has recently shown significance in excavation device detection and localization for urban underground pipeline network protection. An intelligent propagation distance estimation algorithm based on a novel fundamental frequency energy distribution (FBED) feature is developed for periodic vibration signal localization. Contributions of the paper lie in three aspects: 1) a novel frequency band energy distribution (FBED) feature is developed to characterize the property of vibrations at different propagation distances; 2) an intelligent propagation distance estimation model built on the FBED feature with machine learning algorithms is proposed, where for comparisons, the support vector machine (SVM) for regression and regularized extreme learning machine (RELM) are used; 3) a localization algorithm based on the distance-of-arrival (DisOA) estimation using three piezoelectric transducer sensors is given for source position estimation. To testify the effectiveness of the proposed algorithms, case studies on real collected periodic vibration signals generated by two electric hammers with different fundamental frequencies are presented in the paper. The transmission medium is the cement road and experiments on vibration signals recorded at different propagation distances are conducted.     

基于矢量有限元方法的谐振腔的模拟设计

做了基于矢量有限元法的谐振腔通用计算模拟器的模拟设计。该模拟器包括前处理、有限元求解和后处理三部分。首先在前处理中进行三维实体建模和网格划分,然后运用有限元方法生成矩阵并求解该矩阵,在后处理中计算谐振腔的任意本征频率,本征值及电磁场分布。通过分别对几种不同介质加载下的谐振腔进行仿真求解,并将计算结果与商业仿真软件HFS...     

相控阵超声换能器的谐振频率匹配研究

利用压电陶瓷换能器等效成LC电路的方法,推导出发出最大能量时的谐振频率。通过改变电路的参数值可得到不同的频率值,结果表明电路等效法是高效的方法。