LVP Modeling and Dynamic Characteristics Prediction of A Hydraulic Power Unit in Deep-Sea

A hydraulic power unit （HPU） is the driving ＂heart＂ of deep-sea working equipment. It is critical to predict its dynamic performances in deep-water before being immerged in the seawater, while the experimental tests by simulating deep-sea environment have many disadvantages, such as expensive cost, long test cycles, and difficult to achieve low-temperature simulation, which is only used as a supplementary means for confirmatory experiment. This paper proposes a novel theoretical approach based on the linear varying parameters （LVP） modeling to foresee the dynamic performances of the driving unit. Firstly, based on the varying environment features, dynamic expressions of the compressibility and viscosity of hydranlic oil are derived to reveal the fluid performances changing. Secondly, models of hydraulic system and electrical system are accomplished respectively through studying the control process and energy transfer, and then LVP models of the pressure and flow rate control is obtained through the electro-hydraulic models integration. Thirdly, dynamic characteristics of HPU are obtained by the model simulating within bounded closed sets of varying parameters. Finally, the developed HPU is tested in a deep-sea imitating hull, and the experimental results are well consistent with the theoretical analysis outcomes, which clearly declare that the LVP modeling is a rational way to foresee dynamic performances of HPU. The research approach and model analysis results can be applied to the predictions of working properties and product designs for other deep-sea hydraulic pump.

PARAMETER IDENTIFICATION OF DYNAMIC MODELS USING A BAYES APPROACH

The Bayesian method of statistical analysis has been applied to the parameter identification problem. A method is presented to identify parameters of dynamic models with the Bayes estimators of measurement frequencies. This is based on the solution of an inverse generalized evaluate problem. The stochastic nature of test data is considered and a normal distribution is used for the measurement frequencies. An additional feature is that the engineer's confidence in the measurement frequencies is quantified and incorporated into the identification procedure. A numerical example demonstrates the efficiency of the method.

A novel method of dynamic characteristics analysis of machine tool based on unit structure

A novel approach,which can be used for dynamic characteristics analysis of machine tools based on unit structure(US),is reported in this paper.The concepts of unit structures for design of machine tools are defined.In order to satisfy the dynamic characteristics requirement of high natural frequency and light-weight of US,a design method of multi-disciplinary optimization of NSGA-II about unit structures driven by natural frequency and mass is developed.Through analyzing the unit structures,key factors affecting the natural frequency and mass are extracted,and the mathematical models of natural frequency and mass about unit structures are also established by using central composite design and response surface model.The goal of high natural frequency and light-weight is reached by using the multi-objective genetic algorithms.The Pareto optimal set is also obtained.The dynamic behavior of US is investigated by the experimental modal analysis.To show the efficiency of the proposed novel method,the example of YKW51250 gear shaping machine bed is used.Through optimization of NSGA-II about US of YKW51250 machine bed,the natural frequency of YKW51250 gear shaping machine bed is increased by 30.4%and its mass decreased by 5.2%comparing with the original design.By studying the dynamic characteristics of the simplified machine tools bed,useful laws are obtained,and these laws can be used in primary design of NC machine tools structures.The optimal method based on US can be also applied to the dynamic optimal design of machine tools and other similar equipments.

Experimental investigation on dynamic response and damage models of circular RC columns subjected to underwater explosions

Reinforced concrete(RC) columns are widely used as supporting structures for high-piled wharfs.The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharfs antiknock security.In this study,the dynamic response and damage model of circular RC columns subjected to underwater explosions were investigated by means of scaled-down experiment models.Experiments were carried out in a 10.0 m diameter tank with the water depth of 2.25 m,under different explosive quantities(0.025 kg-1.6 kg),stand-off distances(0.0 m-7.0 m),and detonation depths(0.25 m-2.0 m).The shock wave load and dynamic response of experiment models were measured by configuring sensors of pressure,acceleration,strain,and displacement.Then,the load distribution characteristics,time history of test data,and damage models related to present conditions were obtained and discussed.Three damage models,including bending failure,bending-shear failure and punching failure,were identified.In addition,the experie nce model of shock wave loads on the surface of a RC column was proposed for engineering application.

DISOPE distributed model predictive control of cascade systems with network communication

A novel distributed model predictive control scheme based on dynamic integrated system optimization and parameter estimation （DISOPE） was proposed for nonlinear cascade systems under network environment. Under the distributed control structure, online optimization of the cascade system was composed of several cascaded agents that can cooperate and exchange information via network communication. By iterating on modified distributed linear optimal control problems on the basis of estimating parameters at every iteration the correct optimal control action of the nonlinear model predictive control problem of the cascade system could be obtained, assuming that the algorithm was convergent. This approach avoids solving the complex nonlinear optimization problem and significantly reduces the computational burden. The simulation results of the fossil fuel power unit are illustrated to verify the effectiveness and practicability of the proposed algorithm.

Identification of Artificial Neural Network Models for Three-Dimensional Simulation of a Vibration-Acoustic Dynamic System

Industrial noise can be successfully mitigated with the combined use of passive and Active Noise Control (ANC) strategies. In a noisy area, a practical solution for noise attenuation may include both the use of baffles and ANC. When the operator is required to stay in movement in a delimited spatial area, conventional ANC is usually not able to adequately cancel the noise over the whole area. New control strategies need to be devised to achieve acceptable spatial coverage. A three-dimensional actuator model is proposed in this paper. Active Noise Control (ANC) usually requires a feedback noise measurement for the proper response of the loop controller. In some situations, especially where the real-time tridimensional positioning of a feedback transducer is unfeasible, the availability of a 3D precise noise level estimator is indispensable. In our previous works [1,2], using a vibrating signal of the primary source of noise as an input reference for spatial noise level prediction proved to be a very good choice. Another interesting aspect observed in those previous works was the need for a variable-structure linear model, which is equivalent to a sort of a nonlinear model, with unknown analytical equivalence until now. To overcome this in this paper we propose a model structure based on an Artificial Neural Network (ANN) as a nonlinear black-box model to capture the dynamic nonlinear behaveior of the investigated process. This can be used in a future closed loop noise cancelling strategy. We devise an ANN architecture and a corresponding training methodology to cope with the problem, and a MISO (Multi-Input Single-Output) model structure is used in the identification of the system dynamics. A metric is established to compare the obtained results with other works elsewhere. The results show that the obtained model is consistent and it adequately describes the main dynamics of the studied phenomenon, showing that the MISO approach using an ANN is appropriate for the simulation of the investigated process. A clear conclusion is reached highlighting the promising results obtained using this kind of modeling for ANC.

考虑系统稳定边界的同步调相机励磁与升压变参数联合优化

现有提升调相机动态无功特性的参数优化方法侧重于电磁参数的优化,这给生产企业带来较高的工艺要求和较大的成本压力。针对该问题提出考虑系统稳定约束的调相机励磁系统及升压变参数联合优化方法,分析其对电磁参数优化的可替代性。首先,推导了基于Park模型下调相机的无功频域特性,与6阶实用模型下的无功频域特性对比,基于调相机的Park模型可提升调相机动态无功特性的分析精度。然后,提出根据调相机并网系统的稳定边界确定参数的优化区间,采用频域灵敏度方法确定重点参数,并基于人工鱼群算法进行参数优化。最后,通过仿真结果表明,励磁系统与升压变参数的联合优化,可获得与仅优化电磁参数时相近的调相机动态无功性能,验证了电磁参数优化的可替代性,从而降低调相机的制造成本,扩大同步调相机的应用场合和范围。

人体分布式动力学模型及其参数识别

建立人体动力学模型获取人体自振频率是土木工程、机械工程、交通工程、航空航天、康复医学等许多领域的共性科学问题,以往研究最常采用的弹簧-质量块-阻尼器集中质量模型,与实际人体质量、刚度沿身高的分布式特性并不相符。本研究提出含有生物自驱力的人体分布参数动力模型,理论上推导了自振频率的表达式,并据此提出了基于步态测试技术的频率识别算法。组织了247名测试者进行步态试验,识别了每位测试者的人体刚度和自振频率,进一步研究了识别参数的概率分布特征,并通过与以往研究结果对比、不同年龄段统计分析等,多角度验证了所提模型的合理性和适用性。

Nonlinear dynamic analysis of cantilevered piezoelectric energy harvesters under simultaneous parametric and external excitations

The nonlinear dynamics of cantilevered piezoelectric beams is investigated under simultaneous parametric and external excitations. The beam is composed of a substrate and two piezoelectric layers and assumed as an Euler-Bernoulli model with inextensible deformation. A nonlinear distributed parameter model of cantilevered piezoelectric energy harvesters is proposed using the generalized Hamilton＇s principle. The proposed model includes geometric and inertia nonlinearity, but neglects the material nonlinearity. Using the Galerkin decomposition method and harmonic balance method, analytical expressions of the frequency-response curves are presented when the first bending mode of the beam plays a dominant role. Using these expressions, we investigate the effects of the damping, load resistance, electromechanical coupling, and excitation amplitude on the frequency-response curves. We also study the difference between the nonlinear lumped-parameter and distributed- parameter model for predicting the performance of the energy harvesting system. Only in the case of parametric excitation, we demonstrate that the energy harvesting system has an initiation excitation threshold below which no energy can be harvested. We also illustrate that the damping and load resistance affect the initiation excitation threshold.

液压圆柱滑阀K-K型节流槽流量面积参数模型

针对K-K型节流槽流量系数复杂时变及结构参数强耦合的特征,采用流量面积参数模型(FAPM),开展了液压圆柱滑阀K-K型节流槽阀口流量压降特性研究。首先,推导出K-K型节流槽阀口面积的数学模型,并将其等效为3个单阶K型节流槽阀口面积的组合形式;其次,基于计算流体动力学(CFD)和响应面模型(RSM),建立了极限饱和流量下K-K型节流槽的FAPM模型;最后,通过对FAPM模型的分析,得到组合型节流槽阀芯结构与流量压降的映射关系。研究结果表明:当入口体积流量大于7.31 L/min时,满足极限流量饱和条件,此时流量系数与入口体积流量无关;当入口体积流量分别为20、30、50 L/min时,FAPM模型预测的K-K型节流槽阀口压降与CFD仿真值的平均误差均控制在7%以内。该模型完成了对K-K型节流槽阀芯结构的近似表达,并可应用于其他类型的组合型节流槽。

双制动片参数差异对制动系统动力学特性影响研究

为探究双制动片参数差异对制动系统动力学特性的影响,以双自由度制动片振动模型为基础,建立双制动片制动系统动力学模型。调整两制动片之间参数差异,分析制动片时变振动信号,得到相应相位图、分岔特性图,以此探讨两制动片间参数差异对制动系统稳定性影响,并探究不同制动策略下制动系统的振动特性。结果表明:双制动片参数差异对制动系统动力学特性有明显影响;在制动片之间存在一定质量、摩擦模型参数、制动片径向/切向刚度差异的情况下,制动系统振动呈现混沌特性,可以通过调整双制动片关键参数差异来抑制混沌振动。该研究可以为双制动片系统的制动策略优化与减噪抑振提供一定参考。

冻融循环及各向异性对原状黄土动力特性的影响研究

【目的】为了研究冻融循环作用和各向异性对西宁地区原状黄土力学特性及变形的影响,【方法】借助冻融循环试验箱和GDS双向动态三轴仪,开展冻融循环试验和施加半正弦波形式的循环荷载动力特性试验,采用修正H-D模型分析冻融循环次数、与沉积方向呈不同角度对西宁地区黄土动力特性参数的影响。【结果】结果显示:(1)随着冻融循环次数的增加,动剪切强度呈现出先减小后增加的趋势;黄土Gd-1增长阈值呈现出先增大后减小的趋势;黄土阻尼比λ呈现出先增加后减小的趋势。(2)与沉积方向呈不同角度的土样动剪切强度具有差异性,即由大到小为0°>60°>90°>45°;Gd-1增长阈值由大到小为45°>90°>60°>0°;黄土阻尼比λ由大到小为45°>90°>60°>0°。【结论】结果表明:(1)随着冻融循环次数的增加,土体结构强度和刚度均表现出先减弱后增强的趋势,土体抵抗变形消耗的动能则呈相反趋势。(2)各向异性影响黄土的动剪切强度、刚度及阻尼比,与沉积方向呈45°土体动剪切强度最低,刚度最弱,土体发生变形消耗动能最多。(3)冻融循环作用影响土体在不同方向的力学特性,随冻融循环次数的增加,与沉积方向呈45°时土体各向异性表现明显,其结构损伤程度最大。

船用橡胶隔振器参数反演及预测模型应用

以BE型橡胶隔振器为研究对象,根据隔振器的额定参数,通过ABAQUS与ISIGHT联合仿真反演橡胶材料的超弹本构参数和黏弹本构参数,利用反演参数建立橡胶隔振器的预测模型。结果表明,预测模型垂、纵、横3个方向静刚度和3个方向动刚度的误差均小于7%;使用此预测模型研究橡胶隔振器频率、振幅和预载荷对动刚度的影响时,仿真结果与同类橡胶器件的试验结果基本一致;将此预测模型应用于系统级振动模拟时,仿真结果能较好地吻合振动试验结果。

某电厂1000 MW汽机基础动力参数优化设计研究

以某电厂2×1000 MW汽轮发电机组为工程背景,开展汽机基础动力参数优化设计研究。针对汽机转子动力响应过大而不利于汽机正常工作的问题,采用ANSYS软件建立汽机基础结构整体有限元模型,依次开展汽机基础动力特性和强迫振动响应分析,分别讨论增加短柱、短柱宽度和L型梁高度对汽机基础动力响应产生的影响。结果表明:在汽机基础有限元建模中可采用增加附加质量及刚域的方式模拟转子和静子的刚度、质量贡献;分别增设梁间短柱和增加横梁高度,能够有效降低转子动力响应;研究结果可为汽机基础精细化建模与降低汽机转子振动响应提供参考。

基于寿命特征参数研究的电磁阀可靠性寿命研究

本文提出了高铁某系统电磁阀基于寿命特征参数影响的运用可靠性评估方法。通过对电磁阀的使用环境进行模拟复现,设计加速应力试验,缩短试验周期。最终确定电磁阀的寿命特征参数为响应时间。利用响应时间评估电磁阀的可靠性寿命。结果表明,动车组电磁阀在工作条件下,约13~20年可靠性会降低,并给出了修程修制优化建议。

铝合金平面薄壁件动态特性研究与建模

针对三类常见的铝合金材料(6061/7050/7075)薄壁件,基于锤击实验的方法,开展了考虑切削路径频响函数模态参数的识别研究,获得了其动态特性影响因素,并构建了考虑切削振动的薄壁件动态特性模型。研究结果表明:6061/7050铝合金薄壁件固有频率随切削路径向工件中线靠近而增加,7075铝合金薄壁件则变化不明显。该文所构建模型可有效预测薄壁件加工路径上模态参数的变化。

联合搜索零序电压变化量的小电阻接地配电网故障测距

针对小电阻接地配电网单相故障后保护直接作用于跳闸,供电可靠性低的问题,提出一种基于零序电压变化量的故障测距方法。首先建立了考虑分布与集总参数相结合的配电线路故障分析模型,分析了零序电压沿线分布规律,推导了故障位置与故障区段首、末端零序电压、电流的关系,根据双端推算零序电压在故障点处差值最小原理来构建故障精确测距方程,采用进退-黄金分割法联合搜索求解故障距离。利用电磁暂态仿真软件搭建改进型IEEE34节点小电阻接地配电网故障仿真模型,同时在10 kV配电网真型故障试验平台进行验证。结果表明,所提方法测距精度高、定位速度快、鲁棒性强,具有良好的应用效果。

矮塔斜拉桥动静力特性对结构参数敏感性影响分析

目的 为优化矮塔斜拉桥结构设计参数,以槎马特大桥为背景,研究桥梁结构参数及结构体系对矮塔斜拉桥动、静力性能影响。方法 采用ANSYS及Midas civil软件建立全桥三维动、静力有限元模型,基于结构参数敏感性分析的摄动原理,研究各参数下关键截面静力性能的敏感性系数;改变结构构件刚度及结构体系,研究结构参数对矮塔斜拉桥动力特性影响。结果 斜拉索刚度对内力及动力特性影响均较小;墩梁支承方式对动力特性影响较小,但对内力影响较大。当主梁刚度和桥墩刚度分别增加为原刚度的2.744倍和2.125倍时,同阶自振频率最大差值均达到了22%。结论 矮塔斜拉桥主要呈现梁桥动力特性,主梁抗弯及抗扭性能受主梁刚度和桥墩刚度影响较大。

FRC/钢嵌入式T型接头疲劳试验及可靠性分析

为了研究FRC/钢嵌入式T型连接接头疲劳特性,采用真空成型工艺(VARTM)及缝合技术制作T型连接接头,利用Letry疲劳试验机对接头开展拉-拉疲劳试验。根据疲劳试验结果,研究了T型接头在拉-拉疲劳载荷作用下初始损伤特性及损伤演变规律;基于两参数Weibull分布模型,开展T型连接接头疲劳可靠性分析,拟合得到接头在不同应力水平下的疲劳寿命分布规律,给出接头在不同应力水平下疲劳可靠度函数,以及接头在指定可靠度下应力/寿命双对数曲线关系式(R-lnS-lnN曲线)。结果表明,ln ln[1/R(N)]与lnN呈现良好的线性关系,T型接头疲劳寿命服从Weibull分布;疲劳寿命可靠度双对数方程建立了可靠度、疲劳寿命以及疲劳应力的关系,可指导接头疲劳可靠性设计和工程应用。

自复位消能摇摆模块复合钢框架协同抗侧机理与抗震加固设计方法

该文采用自复位消能摇摆模块对既有抗弯钢框架进行加固,以减小其震后残余位移、提升其地震抗倒塌性能、避免其因层间变形集中而发生薄弱层倒塌破坏。基于分布参数连续体模型,揭示了自复位消能摇摆模块与钢框架结构的协同抗侧机理,分析了自复位消能摇摆模块抗弯刚度及抗侧刚度对结构层间变形模式、摇摆模块和钢框架内力需求的影响。提出了利用自复位消能摇摆模块加固既有抗弯钢框架基于位移的抗震设计方法,给出了具体设计流程。基于提出的设计方法对某三层抗弯钢框架进行加固设计。静力推覆分析和动力分析结果表明,自复位消能摇摆模块可有效减小既有抗弯钢框架结构的震后残余变形、使结构获得均匀的层间变形模式。加固后的结构在设计地震下可达到预期设计目标。