Dynamic Modeling and Experimental Verification of an RPR Type Compliant Paralle Mechanism with Low Orders

Efficiency of calculating a dynamic response is an important point of the compliant mechanism for posture adjustment.Dynamic modeling with low orders of a 2R1T compliant parallel mechanism is studied in the paper.The mechanism with two out-of-plane rotational and one lifting degrees of freedom(DoFs)plays an important role in posture adjustment.Based on elastic beam theory,the stiffness matrix and mass matrix of the beam element are established where the moment of inertia is considered.To improve solving efficiency,a dynamic model with low orders of the mechanism is established based on a modified modal synthesis method.Firstly,each branch of the RPR type mechanism is divided into a substructure.Subsequently,a set of hypothetical modes of each substructure is obtained based on the C-B method.Finally,dynamic equation of the whole mechanism is established by the substructure assembly.A dynamic experiment is conducted to verify the dynamic characteristics of the compliant mechanism.

An Operational Modal Analysis Experimental Technique for Self-propelled Gun

The experimental modal analysis of the selected self-propelled gun was completed to obtain its modal frequency distribution and modes by using an operational modal analysis experimental technique.The result obtained by the method was compared with that obtained by the traditional method.It indicates that the two results are in good agreement.

Design and Experiment of Triangular Prism Mast with Tape-Spring Hyperelastic Hinges

Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like configuration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stiffness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The finite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the influence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stiffness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and finite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.

EXPERIMENT RESEARCH ON DYNAMIC LOAD IDENTIFICATION TECHNOLOGY BASED ON GENERALIZED ORTHOGONAL POLYNOMIAL THEORY (GOPT)

A dynamic load identification model of structural system based on the gener-alized orthogonal polynomial theory is provided, and the least Square discrete algorithm foridentifying the dynamic load is supplied. The main key is that the convolution relationsbetween the input and output of the system in time domain are transformed into linear oP-erators in generalized orthogonal domain. The new theory is fully tested and verified bythe dynamic analysis l 'modal test and dynamic load identification teSt of a simulation speci-men- It is shown that the method has some advantages, such as the simple dynamic cali-bration test, the high identification accuracy, especially for the transient load with shortsampling. These are very useful in engineering applications.

应用模态分析软件MODAL3．0对机构进行试验模态分析

对模态分析软件ＭＯＤＡＬ３．０的主要功能和特点进行了介绍。论述了机构模态试验的特点、方法与步骤，应用ＨＰ３５６２Ａ动态信号分析仪和ＭＯＤＡＬ３．０对一弹性连杆机构进行了试验模态分析，试验分析结果与数值计算结果一致，获得了一些有意义的数据和结论。

Modal喷气涡流纺纺纱工艺研究

研究喷气涡流纺纺纱工艺(纺纱速度、喷嘴气压、前罗拉钳口到喷嘴的距离、导引针到锥面体尖端的距离)对Modal成纱性能的影响。改变纺纱工艺参数进行单因子实验,并通过正交实验得出最佳纺纱工艺:喷嘴气压0.55 Mpa,前罗拉钳口到喷嘴的距离14 mm,导引针到锥面体尖端的距离1.5 mm。

基于振动速度与噪音的横梁动态特性优化

针对某型小五轴高精密数控机床加工精度不高的问题,对其横梁的动态性能进行研究.采用锤击模态测试实验与有限元模拟计算相结合的方法,对横梁的固有频率进行研究;测量主轴不同转速下的振动速度和振动噪音,通过赋权处理,建立振动评价指标方程,得到优化目标;对所研究横梁进行形状优化.试验与仿真所得固有频率最大误差为5.76%;基于主轴振动情况确定83~117 Hz的频率范围,作为横梁设计时需要避开的低阶固有频率范围.经过形状优化后,横梁的一阶固有频率为139 Hz,相较于原横梁增加了约20.870%,横梁的动态性能得到改善.

MODAL ANALYSIS OF A CHASSIS FRAME OF A HEAVY LECTRA HAUL

The chassis frame of a heavy lectra haul is analysed by both modal experiment method and finite element method (FEM ) . The first ten order modal parameters of the chassis frame have been obtained satisfactorily. These parameters have important reference value in designing the chassis frame properly and provide a necessary basis for the fault diagnostics of the truck.

敷设约束阻尼层的工字梁振动特性研究

本文提出了一种计算带约束阻尼层梁振动响应的方法。以工字梁为研究对象,开展了室内振动试验,测得了不同位置的振动响应。并基于有限元法同步建立了数值仿真模型,利用模态应变能法准确计算了结构的自振频率和模态损耗因子。基于上述结果,利用模态叠加法进行谐响应分析,得到了约束阻尼层工字梁的振动响应结果。将振动响应的实测值与仿真值进行对比,验证了模型的准确性。分析了设计参数(阻尼层厚度、约束层厚度)对构件自振频率、模态损耗因子及加速度总振级的影响。研究结果表明:各板件的振动响应有着相似的变化规律,腹板加速度总振级最大,底板次之,顶板最小;总体上阻尼层厚度对工字梁前5阶自振频率影响不大,而随着约束层厚度的增大,构件前5阶自振频率先减小后增大;增大阻尼层厚度和约束层厚度都能持续增大构件的模态损耗因子,进而有效降低加速度总振级,且对腹板的减振效果好于顶板和底板。

基于单高速相机3D-DIC的涡轮叶片全场振动测量

采用成本较低、结构紧凑且使用便捷的单高速相机三维数字图像相关方法(single-camera high-speed three-dimensional digital image correlation,简称SCHS 3D-DIC)对涡轮叶片的振动特性进行试验研究。首先,介绍了测量装置和原理,以悬臂铝板为对象开展验证试验,结果证明了该测量系统的准确性与有效性;其次,开展了叶片的全场振动特性测量,得到了其三维形貌、模态特性、全场位移与应变分布,获得了叶片在振动载荷作用下的高应变区域位置及应变分布特点。研究表明,SCHS 3D-DIC方法相比常规双高速相机3D-DIC方法具有更高的视场利用率,适合于细长型的涡轮叶片的振动测量试验。

沉积层海底界面Scholte波水池实验

海底界面Scholte波具有衰减小、传播距离远等特点,可应用于水下目标探测与海底参数反演。在实际海洋环境中,海水与弹性海底之间的沉积层会对Scholte波的激发和传播产生显著影响。该文利用缩比原理设计并开展水池实验研究,将实际海洋环境按1:5000的比例缩比至实验室水池尺度,利用声压场Scholte波识别方法在包含沉积层的实验环境下对Scholte波的激发与传播规律进行探究。实验结果表明,该实验条件下,1 mm厚度的沉积层时海底界面依然有Scholte波激发,但沉积层的存在会增大其衰减;而厚度超过1 mm的沉积层会导致Scholte波无法激发。根据缩比原理,实验环境对应为声源频率10 Hz、水深3000 m、沉积层厚度5 m的实际海洋环境,即在上述实际海洋环境中,海底界面Scholte波仍可以正常激发,而厚度大于5 m的粉沙质沉积层会导致Scholte波无法激发。

如何开展“虚实融合+多模态感知交互”的智能实验?——以中学化学智能实验为例

现代信息技术的进步推动了虚拟仿真实验的发展,然而当前的虚拟仿真实验普遍缺乏实际操作感,且交互方式相对单一,不仅影响了学生的实验体验,而且不利于培养学生的动手能力。为此,文章首先参考虚实融合、多模态感知交互的相关研究成果,构建了“虚实融合+多模态感知交互”的智能实验模型,并设计了智能实验系统和流程以从技术上实现此模型。之后,为验证此模型的有效性,文章以钠与水的反应为实验内容,开展了“虚实融合+多模态感知交互”的中学化学智能实验。在此实验中,文章开发了中学化学智能实验原型系统,并通过对比实验比较了实验效果,结果发现:在相同的实验操作时间段内,无论是实验任务完成质量还是完成效率,使用原型系统的智能实验都优于使用NOBOOK在线仿真实验教学平台的仿真实验,参加智能实验的学生脑力负荷更小且更好地掌握了知识与操作技能。文章的研究可为虚实融合和多模态感知交互在智能实验教学中的融合应用提供理论指导,并可为人工智能赋能实验教学创新研究提供实践参考。

基于模态分析的双定子电励磁场调制电机弹性模量调整方法

准确获得电机结构的模态分析结果是研究电磁噪声的前提条件。该文以一台双定子电励磁场调制电机为研究对象,首先,利用有限元软件对影响其模态分析的弹性模量展开研究,探索弹性模量变化对各阶固有频率的相对影响率大小,找到外定子、电枢绕组、机壳和端盖的弹性模量变化对模态分析结果的影响规律,由此明确参数调整的方向性。然后,采用锤击法进行模态实验,并获得外定子、外定子组件以及整机模态实验结果与仿真结果二者误差的大小。最后,根据二者误差大小及参数调整的方向性,选择合适的弹性模量调整值将其误差均调整到4%以内,从而得到精确的模态仿真结果,进而有利于后续该电机电磁噪声的分析。

自走式果园割草机切割器的设计与试验

山地丘陵果园障碍物密集、地形复杂,一般的切割器无法实现高效除草作业。本文结合传统果园行距、株距较小等特性,实地调研青岛山地丘陵地带果园地势起伏情况、杂草类型等,设计符合山地作业需求的自走式果园割草机切割器。通过对刀盘进行模态分析以及运动学仿真,验证其结构合理性以及作业可靠性,并在青岛果园对切割器割草性能进行实地试验验证。结果显示实地作业的平均割茬高度为24.15 mm,割幅利用系数为98.96%,漏割损失率为1.54%。试验证明所设计的切割器能提高山地丘陵地形果园除草管理效率,降低除草劳动强度,满足果园除草的作业要求,对助力推动林果生产机械化的进一步提高具有重要意义。

滚珠丝杠进给系统刚柔耦合动力学建模与时变动态特性分析

数控机床运行过程中,多轴滚珠丝杠进给系统的刚度和惯量会随着各轴位姿的变化而变化,致使其动态特性呈时变的特点。多轴滚珠丝杠进给系统时变动态特性的高保真建模与分析已成为数控机床轮廓误差精准预测的瓶颈难题之一。针对这一难题,提出基于拉格朗日方程与Ritz级数法的滚珠丝杠进给系统刚柔耦合动力学建模与分析方法。以某型号五轴加工中心的两轴滚珠丝杠进给系统为具体对象,重点考虑丝杠本体轴扭方向的连续弹性体变形影响,采用拉格朗日方程建立滚珠丝杠进给系统的刚柔耦合动力学模型,并采用Ritz级数法对方程求解,得到动力学模型的数值解。利用所建立的动力学模型分析进给轴位姿对两轴进给系统固有频率和模态振型的影响,发现各阶固有频率和模态振型随进给轴位姿的变化规律与对应阶次的主导轴有关。随着主导轴进给台由固定端移动至支撑端,对应阶次的固有频率逐渐减小,对应阶次的振型中丝杠本体的弹性振动幅值逐渐增大。此外,两轴进给系统的低阶模态振型主要由承载轴主导,高阶模态振型主要由附属于承载轴的子轴主导。最后,通过模态实验对所提方法进行应用验证,证明所建立动力学模型的准确性。研究结果对数控机床轮廓误差的精准预测具有重要参考价值。

基于多模态交互的智能座舱唱歌系统研究

目的以汽车智能座舱唱歌娱乐系统为研究对象,结合多模态交互设计方法,提供一个以用户体验为中心的设计框架,以实现在汽车智能座舱中进行唱歌娱乐时的安全、高效和舒适的人机交互设计。方法基于用户的汽车出行生活调研,结合情境感知技术,提出了基于多模态交互的车载信息娱乐系统的设计模型。结果多模态交互方式的融合使人车交互更加自然和轻松,并赋予智能座舱乘客情感化的使用场景。研究结果表明:多模态交互设计对提升用户体验、辅助驾驶、增加竞争力以及智能座舱产品平台的开放性和可扩展性具有重要意义。结论欢唱娱乐功能已经成为智能座舱产品中不可或缺的一部分,对智能座舱产品的设计具有重要意义。

周期变半径薄圆环模态实验研究

针对变半径法向等厚薄圆环的面内振动模态问题,依据振动测试理论,提出了定测量点、变激振点的实验方法,以简化实验操作流程。利用激光多普勒测振仪和LMS振动测试系统进行测振实验,得到了变半径圆环前八阶振动的固有频率和振型,并将结果与有限元仿真及现有文献相关结论对比,验证了实验方法的可行性。归纳了半径变化周期p和模态阶数n不同关系时结构固有频率的分裂规律,并总结了法向厚度h和半径变化幅度Δ对圆环固有频率的影响。

基于响应面法的柔性钻削加工机床的整机结构优化

柔性钻削加工机床的整机静动刚度对保证其加工精度至关重要,为提高柔性钻削加工机床的整机综合性能,建立整机的有限元模型进行静动态特性分析,选取主要部件的关键尺寸为设计变量,基于响应面法和多目标尺寸参数优化方法确定整机的结构优化方案,利用LMS动态测试系统完成整机的模态参数识别。研究结果表明:优化设计后,机床整机质量减少7.2%,最大变形量减小了23.1%,一阶固有频率增加33.6%。整机的静动刚度均有不同幅度提升,研究结果对提升整机的综合性能具有一定的指导意义。

子午线轮胎横向弯曲振动模态的数值与实验研究

为进一步研究子午线轮胎胎面在300 Hz以上发生的横向弯曲振动特性,本研究参照被广泛使用的轮胎模态命名约定,通过建立205/55 R16子午线轮胎有限元模型,对胎面在0~500 Hz上的面内振动、面外振动和横向弯曲振动进行计算,获得对应阶数下的固有频率及模态振型。通过锤击实验对对象轮胎进行模态分析,获得0~500 Hz胎面振动模态,有限元模型的准确性得到验证。此外还通过对有限元模型施加旋转角速度,讨论轮胎频率分裂现象,并进一步得到转速与固有频率之间的关系。工作为研究轮胎在各个频段的振动特性和诊断车辆的NVH(Noise,Vibration,and Harshness)故障提供一种可供借鉴的思路和方法。

Finite element modal analysis and experiment of rice transplanter chassis

The vibration problem during the operation of rice transplanters is the most common phenomenon.In order that the static and dynamic characteristics of the rice transplanter chassis can meet the requirements of more stable operation,the research took the 2ZG-6DK rice transplanter as the research object to carry out a vibration reduction optimization study.In the research,the Pro/Engineer 5.0 software was first used to model the chassis of the rice transplanter.The constructed finite element model was revised by using the structural parameter revision method and the mixed penalty function method.The model was imported into ANSYS Workbench to solve the modal frequency and vibration shape of the rice transplanter chassis.Based on the MAC(modal assurance criterion)criterion,modal tests were carried out to verify the accuracy of the finite element theoretical analysis.Through the analysis of the characteristics of the external excitation frequency,the chassis is structurally optimized to avoid resonance caused by the natural frequency of the chassis falling within the road excitation frequency range.The final optimization results showed that the first four orders of modal frequencies of the chassis were adjusted to 32.083 Hz,33.751 Hz,42.517 Hz,and 50.362 Hz,respectively,in the case that the chassis mass was increased by 6.714 kg(8.8%).They all avoid the range of road excitation frequency(10-30 Hz)so that the rice transplanter can effectively avoid the resonance phenomenon during operation.This study can provide a reference for the design and optimization of the chassis structure of transplanter.