新型机电惯容器抗振性能仿真与实验研究

针对传统滚珠丝杠式机电惯容器换向时存在的惯性逆效应,提出一种可稳态切换的新型滚珠丝杠式机电惯容器设计方法.首先,介绍了新型机电惯容器的结构与工作原理,依据滚珠丝杠式惯容器与旋转电机的动力学模型,建立了机电惯容器的动态模型;其次,基于新机电相似理论,仿真分析外接不同电容下的机电惯容器力学性能输出,研究电机电感与电阻对力学...     

摩擦力对滚珠丝杠惯容器频响特性的影响

为建立更精确的惯容器模型和完善惯容器设计理论与方法,设计丝杠旋转式滚珠丝杠惯容器,搭建惯容器试验台架,研究非线性因素对惯容器的影响。采用系统识别的方法,将时域响应试验数据转化为频域响应数据,得到惯容器的频响特性曲线,以惯容器Malcolm线性模型为试验研究的比较对象,分析无背隙情况下摩擦力对滚珠丝杠惯容器频响特性的影响。结果表明:低频下,滚珠丝杠惯容器摩擦力占据主导地位,导致惯容器相位跌落、幅值增大;随着频率和惯容系数的增大,摩擦力对惯容器的影响相对减小,惯容器实际性能与理论性能逐步接近。     

基于量子遗传支持向量机的流体惯容预测模型

为进一步研究惯容器的实现形式与力学性能特征,研制了新型流体惯容器装置。首先,在单通道伺服激振台架上进行力学性能测试,分析其非线性因素及对力学输出的影响机理;然后,考虑采用基于统计理论的支持向量机方法建立流体惯容器的力学输出预测模型,分别研究了不同激振频率、不同位移输入条件下的流体惯容器力学性能输出;最后,利用全局搜索能力较优的量子遗传算法优化径向基函数的方差与惩罚因子,并将构建的预测模型与试验输出结果相对比。结果表明:利用支持向量机构建的流体惯容器力学输出预测结果与试验吻合良好,采用量子遗传算法优化的预测模型具有更高的预测精度,其方差降幅最大可达到61.36%,说明构建的预测模型正确合理,可为准确掌握流体惯容器动力学特性提供新思路。     

基于液压活塞式惯容器的车辆悬架性能研究

阐述了液压活塞式惯容器的基本结构、工作原理与承载力大的特点,建立了考虑摩擦力、寄生阻尼力和油液弹性效应的惯容器非线性力学模型。在数控液压伺服激振台上对液压活塞式惯容器进行了力学性能试验,基于试验结果,利用Matlab参数辨识工具箱对非线性力学模型中的参数进行辨识。在此基础上建立了包含液压活塞式惯容器非线性因素的车辆惯容器 弹簧 阻尼器（inerter-spring-damper,简称ISD）悬架动力学模型并进行了仿真分析。结果表明,当考虑液压活塞式惯容器非线性因素时,车辆ISD悬架系统的车身加速度均方根值增加5%,而轮胎动载荷与悬架动行程均方根值均有所减小,降低了车辆的行驶平顺性。     

可控惯容器非线性建模分析与参数辨识测试

为研究可控惯容器的非线性,依据机电相似理论,进一步推广得到机电液相似理论,并基于该理论研制了流体式可控惯容器装置,建立其理想模型和非线性等效模型,利用台架试验对其部分参数进行辨识,仿真分析其力学输出特性。结果表明,非线性因素对所设计的可控惯容器力学输出性能影响较大,一般情况下不可忽略。在液体的压缩性不可忽略时,低频振动下主要由惯容器所产生的惯性特性对振动起到抑制作用;高频激励下主要是液体弹性特性对振动起到抑制作用。研究结果进一步验证了机电液相似理论的正确性。     

惯容器模型结构探索

针对惯容器模型的实现装置种类少及实现方法单一的问题,从设计理论角度出发,探讨惯容器模型结构及其实现方法。基于惯容器是一种被动式两端点机械网络元件,可以利用不同的机械零件加以实现的特点,通过研究齿轮齿条式、滚珠丝杠式这一类封装飞轮惯性为特征的惯容器,提出了以封装质量惯性为特征的一类惯容器;针对这两类惯容器均为平动元件,无法进行转动机械网络综合这一问题,进一步提出了扭转惯容器的概念,并找到了实现装置;阐明了装置的基本设计原理。研究发现,惯容器以多种形式存在于平动机械系统中,扭转惯容器客观存在于转动机械系统中。     

重载滚珠丝杠副可靠性试验及分析

1．试验系统构成 对于重载滚珠丝杠副,实际使用时主要考察其在正常使用条件下的疲劳寿命,因此可靠性试验系统中不需要测量精度和预紧力的仪器。试验中重载滚珠丝杠副的疲劳寿命情况,主要通过测定反向间隙以及观察疲劳点蚀进行判定,因此重载滚珠丝杠副可靠性试验系统的主要功能是测定滚珠丝杠副的反向间隙、摩擦力矩等。     

基于虚实映射模型的惯容惯质系数测试与验证

为测试实际惯容器的惯质系数并验证惯容器动力学模型，以低频简谐力为激励，基于滚珠丝杠惯容器开展了台架实验。实验表明，滚珠丝杠惯容器惯质系数接近理想，但其易受安装预紧力的影响，过大与过小的安装预紧力均为不当安装，使测试惯质系数严重偏离理论惯质系数。为判断惯容器安装预紧力是否合适，且便于惯容器的运行维护，建立了惯容器虚实映射模型并开展实验测试与验证。结果表明，所建立的虚实映射模型可有效判断安装预紧力的大小，为调整惯容器安装预紧力提供指导，进而为惯容器使用过程中的运维保障提供技术支持。     

滚珠丝杠副转速对摩擦力矩波动影响的分析与测试

根据赫兹接触理论分析了丝杠副滚珠接触的弹性变形量以及由弹性变形所造成的弹性势能。对滚珠进入丝杠滚道的受力过程进行了分析,认为滚珠进入滚道所引起的摩擦力矩变化的波动量与丝杠转速有关,当滚珠速度小于临界速度时,丝杠的摩擦力矩波动较大;当滚珠速度大于临界速度时,丝杠的摩擦力矩波动呈减小趋势。实验数据验证了丝杠在不同速度下摩擦力矩波动随转速变化的分析结果。     

考虑反向器影响的滚珠丝杠副摩擦力矩计算模型

基于赫兹接触和弹性碰撞理论,分别对滚珠丝杠副反向器入口和出口处滚珠的微观动态行为和受力平衡状态进行分析,揭示滚珠进出反向器时的碰撞和预紧受压对摩擦力矩的影响机理,建立同时考虑反向器入口及出口处影响的滚珠丝杠副摩擦力矩计算模型,并对某型丝杠进行了不同工况下的试验测试。对比分析表明,滚珠进出反向器产生的摩擦力矩是丝杠副摩擦力矩的重要组成部分,计入反向器的影响可以大幅提高摩擦力矩计算精度;其中反向器入口处因滚珠的连环碰撞使得其对摩擦力矩影响较大,而出口处的影响则相对较小。利用模型计算所得摩擦力矩,在不同转速及轴向载荷下均与实测值吻合良好,表明模型具有较高的计算精度。     

Positioning and tracking of a linear motion stage with friction compensation by fuzzy logic approach

In this paper, the development of a fuzzy controller that compensates for nonlinear friction in a linear motion stage is presented. The experimental work and instrumentation set up is presented for this research. Based upon a nonlinear friction model, friction parameters were estimated from experimental results. Simulation and experimental validation on a ball-screw mechanism is presented, showing the effectiveness of the proposed controller. Furthermore, it is shown that the proposed fuzzy control scheme offers several implementation advantages such as smaller control effort, and reduced effect of measurement noise. Moreover, the fuzzy logic methodology displays superior performance when compared to a conventional PID controller. It also shows good and robust tracking with respect to system parameters variation.     

Nonlinear dynamic characteristics of geared rotor bearing systems with dynamic backlash and friction

Effects of the friction and dynamic backlash on the multi-degree of freedom nonlinear dynamic gear transmission system, which incorporate time varying stiffness, are investigated. Firstly, the relationship between gear central distance error and backlash is deduced and the dynamic backlash is defined, subsequently a multi-degree of freedom nonlinear dynamic gear transmission system is developed with dynamic backlash, friction and time varying stiffness. The nonlinear dynamic system is solved by the Runge-Kutta method. The results show that the friction force may enlarge the displacement magnitude and affect the high frequency parts significantly in frequency domain at low speed. But the RMS of the steady response is reduced on the effect of friction. The difference between the constant backlash and the dynamic backlash models is also discussed. The system may enter into previous chaotic motion due to the effect of dynamic backlash. Finally, no impact motion, single-side impact motion and double-side impact motion are also predicted in the new dynamic backlash model.     

Dynamic analysis of planar mechanical systems with clearance joints using a new nonlinear contact force model

We investigated the dynamic behavior of planar mechanical systems with clearance joints. First, the contact effect in clearance joint was studied using a new nonlinear contact force model, and the rationality of this model was verified by the results of numerical simulations, which are based on a journal and bearing contact model. Then, the dynamic characteristics of a planar slider-crank mechanism with clearance were analyzed based on the new nonlinear contact force model, and the friction effect of clearance joint was also considered using modified Coulomb friction model. Finally, the numerical results of the influence of clearance size on the acceleration of slider are presented, and compared with the published experimental results. The numerical and experimental results show that the new nonlinear contact force model presented in this paper is an effective method to predict the dynamic behavior of planar mechanical system with clearance joints, and appears to be suitable for a wide range of impact situations, especially with low coefficient of restitution.     

基于正交切削的铝合金切削力理论计算方法

基于传统正交切削力学模型,采用Johnson-Cook材料本构和失效模型,建立同时考虑前刀面和后刀面双摩擦因素的切削力理论计算模型。采用双摩擦切削力模型模拟7050航空铝合金切削力的计算,获得了与试验结果非常吻合的切削力理论计算值。用本文模型计算了不同Johnson-Cook材料本构参数下的切削力,获得了与文献仿真值非常一致的结果。双摩擦切削力模型引入的后刀面摩擦分量,在航空铝合金切削仿真中,占主切削力的比重较少(约占12.5%),但不可忽略。     

基于能量等效的行波型超声波电动机解析模型

提出一种基于能量等效的行波型超声波电动机稳态特性分析计算的解析模型.首先通过能量等效原则将压电复合定子环简化成复合等直梁模型,综合考虑压电复合定子的转动惯量和剪切变形的影响,利用铁木辛柯梁振动理论得到电动机定子振动的频率方程和强迫振动稳态解:其次,对电动机定、转子接触面的滑动状况进行分析,利用弹性接触理论确定了定、转子接触面的力传递模型和效率表达式,通过把定、转子接触面的摩擦损耗和转子的输出功率视为定子强迫振动的等效阻尼损失,由此建立电动机的机械特性和输出功率表达式;最后,仿真和试验分析了不同电动机结构和材料参数以及定子预压力、驱动频率和摩擦层厚度等对电动机振动特性和机械特性的影响,试验证明了该模型的有效性和适用范围.     

Dynamic simulation of a displacement-controlled total knee replacement wear tester

This paper presents a dynamic finite element method (FEM) model of a commercial displacement-controlled total knee replacement (TKR) wear tester. The first goal of the study was to validate the model, which included both the wear tester and the TKR components. Convergence simulations and experimental testing were performed. These included a novel experimental determination of the coefficient of friction and an evaluation of predicted joint contact areas by comparing simulation results with experimental data collected using pressure-sensitive film. The second goal of this study was to develop a procedure for implementing force-based testing protocols on a displacement-controlled TKR wear tester. A standard force-based cyclic wear-testing protocol was simulated using the FEM model and resulting displacement waveforms were extracted. These were used as control inputs to the physical wear tester and an experimental wear test was performed. Reaction loads on the tibial components were measured and compared with the simulated results. The model was capable of accurately predicting the tibial loads throughout the test cycle, verifying the model's contact mechanics. The study demonstrated the use of computational modelling to convert a force-based testing protocol into displacement-based control parameters for use in a displacement-controlled mechanical testing system.     

热连轧机工作辊水平-垂直非线性振动特性及抑制

基于振动情况下轧制界面水平-垂直方向摩擦力模型和动态轧制力模型,考虑轧机的结构和工作辊轴承座与牌坊立柱间的摩擦力等因素的影响,建立了热连轧机工作辊水平-垂直系统的非线性振动模型。运用平均法求解得到幅频特性方程,分析外扰力和非线性参数等因素对系统幅频特性的影响,为抑制轧机工作辊水平-垂直振动提供理论指导。通过分析李雅普诺夫指数和位移分岔图,发现系统随外扰力幅值变化表现出周期、倍周期和混沌等不同运动状态。最后,通过分析工作辊轴承座与牌坊立柱间有无衬板间隙这两种情况下的幅频特性及衬板间隙对系统振动的影响规律,提出一种抑制工作辊水平振动和垂直振动的方法,仿真和实验结果均表明该方法有效。     

Stochastic modeling of friction force and vibration analysis of a mechanical system using the model

The squeal noise generated from a disk brake or chatter occurred in a machine tool primarily results from friction-induced vibration. Since friction-induced vibration is usually accompanied by abrasion and lifespan reduction of mechanical parts, it is necessary to develop a reliable analysis model by which friction-induced vibration phenomena can be accurately analyzed. The original Coulomb’s friction model or the modified Coulomb friction model employed in most commercial programs employs deterministic friction coefficients. However, observing friction phenomena between two contact surfaces, one may observe that friction coefficients keep changing due to the unevenness of contact surface, temperature, lubrication and humidity. Therefore, in this study, friction coefficients are modeled as random parameters that keep changing during the motion of a mechanical system undergoing friction force. The integrity of the proposed stochastic friction model was validated by comparing the analysis results obtained by the proposed model with experimental results.     

基于机电惯容的漂浮式海上风力机无源振动控制

机电惯容是一种新型惯容装置,可利用电路网络实现高阶机械阻抗,具有性能和空间上的优势。由于海上风力机的机舱空间有限,研究了位于浮式平台中的机电惯容系统对漂浮式海上风力机载荷的影响。根据直流电机的特性,电机轴的转矩输出与电机回路中的电流呈线性关系,因此针对所建立的机电惯容,重点研究了所有由单个电阻、电容、电感组成的电路网络对漂浮式风力机减振性能的影响。为了降低优化过程中的复杂度,首先建立了3自由度(Degree of freedom,DOF)漂浮式海上风力机模型,随后优化了含有电路网络模型的输入输出传递函数的H2范数,得到电路网络最优参数。最后,基于美国可再生能源实验室的5 MW基准风力机模型对优化结果进行了仿真分析。仿真结果表明,在不考虑装置工作行程的情况下,所建立的机电惯容调谐质量阻尼器(Mechatronic inerter tuned mass damper,MITMD)系统可以有效减少风力机系统的结构载荷。相较于减振装置位于机舱中的情况,建立在平台中的MITMD系统可以同时减轻塔基和塔顶转轴处的载荷。MITMD的控制效果以运动位移为代价,因此在实际应用中需要折中考虑减振效果和装置...