空间敏感载荷用超精密驱动系统刚柔耦合振动分析

作为实现空间敏感载荷精密定位的关键部件,超精密驱动系统不仅需要具备亚毫米级的输出行程,同时还应达到微纳米级的分辨精度。提出了一种利用柔顺放大机构与智能材料作动器联合驱动的方案。对柔顺放大机构在传动过程中可能因微振动而影响输出精度的问题,利用伪刚体模型法、假设模态法和拉格朗日方程构建了柔顺放大机构的刚柔耦合动力学模型;并基于该模型仿真研究了作动频带内柔顺放大机构的动力学响应特性。结果表明:随着驱动频率的增加,放大机构弹性振动加剧;但在整个作动频带内,弹性振动与刚体运动的幅值比在5 Hz驱动频率下仅为0.61%;进一步结合试验测试证明了所设计的驱动系统可以忽略柔顺放大机构产生的弹性振动的结论,表明该驱动系统具备超精密定位的潜力。     

车载平台刚体动力学模型分析

车载火控系统平台装置主要包括光束控制系统、激光器和支撑平台。将整个系统视为刚体，建立刚体动力学模型，并主要对平台在地基的各种振动激励，激光器的脉冲振动以及光束控制系统在力矩、加速度的荷载下进行计算分析．     

柔顺停歇机构伪刚体模型的运动学和动力学分析

针对柔顺停歇机构的柔性构件在运动中产生的大变形、大挠度等几何非线性行为,采用伪刚体模型法来分析该类非线性大变形系统.首先,基于大挠度理论对大变形柔性梁进行屈曲分析,运用第一、第二类椭圆积分模拟初始状态为直梁的柔性梁,用多项式拟合得到其载荷—位移关系式.结合边界条件与受力特性,得到柔性梁的等效非线性弹簧伪刚体模型.在此基...     

含非线性大变形构件的柔顺机构建模与分析

柔顺机构的大范围运动引起柔性构件产生几何非线性大变形,使得机构的建模与分析变得困难。分别采用椭圆积分法和绝对节点坐标法(ANCF)建立柔顺机构的力学模型,获得了机构运动过程中柔性构件的变形和驱动力的变化规律。以一种固定—导向柔顺梁为例,仿真与实验结果验证了以上方法的有效性;以一种柔顺双稳态机构为例,仿真结果验证了ANCF法对复杂柔顺机构动力学特性分析的有效性;通过以上两种方法的建模与分析过程对比,ANCF法对柔顺机构建模与分析更具有适应性。     

三自由度并联包装机构动力学建模与分析

目的为了提高一种三自由度并联包装机构动态性能,对其进行动力学建模与仿真研究。方法首先建立机构三维模型并进行位置反解计算,而后应用凯恩法列出动力学方程。在对支链模态分析基础上依托多体动力学仿真软件ADAMS与有限元软件Ansys,将各连接杆件由刚体转换为柔性体进行刚柔耦合动力学分析。结果通过动力学建模求得了驱动杆在广义坐标下的驱动力。由模态分析求得支链的第1阶到第6阶固有频率分别为88.656,108.95,119.96,125.33,131.07,138.77 Hz,以及机构在各个阶次下的振型。得到了机构动平台质心运动位移、速度、加速度,以及关节驱动力、力矩变化曲线。结论并联包装机构中刚度薄弱环节位于球铰连接两端,在各阶模态振型中,振动相对位移较大位置位于动平台和支链中部滑块;连接杆件会对动平台运动性能、关节驱动力产生一定的影响。分析结果为并联机构进一步优化提供了理论依据。     

新型Nano-CMM二维定位平台"共平面"结构研究

介绍了一种新型纳米三坐标测量机二维定位平台的结构设计.打破了传统二维定位平台堆栈的结构形式,引入了"共平面"的导向模式.经理论研究计算,能实现近零阿贝误差,满足微纳米级定位平台的要求.     

考虑三维圆柱铰间隙碰撞的空间机构柔性多体动力学分析方法

三维圆柱铰的动态性能对空间机构的运动精度和动力学特性有着重要的影响。基于多体动力学方法和刚体有限元方法,提出考虑三维圆柱铰的间隙碰撞和动态接触作用的空间机构柔性多体接触动力学方法。采用圆柱-圆柱的线接触力学模型和切片法,计算圆柱-圆柱的接触变形量和接触力,建立三维圆柱铰的轴销与轴套之间的间隙碰撞作用和三维动态接触关系。以等效刚体单元和Timoshenko梁单元描述柔性杆件的刚性有限元模型,建立柔性连杆和三维圆柱铰的具有多刚体系统的统一形式的动力学方程。计算分析了含三维圆柱铰的空间机构的运动精度和动力学特性,获得空间机构的位移响应,三维圆柱铰的相对运动轨迹和动态作用力等动力学响应。采用三维圆柱-圆柱动态线接触方法,能有效地预测空间机构系统的三维圆柱铰持续接触、间隙碰撞状态和摩擦作用下的动力学特性。计算结果表明三维圆柱铰的间隙碰撞作用对空间机构的运动精度和动态特性的影响较为显著。动力学模型和计算结果对复杂工况下高精度多间隙的空间机构的动态设计和动力学研究具有重要的理论意义。     

四自由度全柔顺并联机构刚度分析

利用动力学方程求出4 CRU型全柔顺并联机构支链的刚度,并用ANSYS软件仿真结果验证此种方法的正确性,为求全柔顺并联机构整体刚度提供了依据;本文基于4 CRU并联机构的运动特性,采用传统柔性并联机构的构成方式设计了具有全柔顺特性的新型4 CRU的全柔顺并联机构;利用动力学方程对全柔顺支链刚度进行计算;采用ANSYS软件建立4 CRU型全柔顺机构支链模型,并对其刚度进行仿真实验对比研究;仿真结果与计算结果基本上一致,验证了分析方法的正确性.     

高速轧辊磨床微进给机构动力学分析

以高速轧辊磨床微进给机构为研究对象,利用HYPERMESH建立各零部件的有限元模型,并在ANSYS中采用弹簧阻尼器单元COMBIN14建立各结合部的动力学模型,从而建立微进给机构整体有限元模型,进行了模态分析和谐响应分析,得到微进给机构前10阶模态,识别了微进给机构的薄弱环节,从而为微进给机构的设计改进提供依据。     

微/纳米传动平台的模态试验及优化设计

微/纳米传动平台中,柔性机构的弹性势必导致平台高速、高加速带来的残余振动。采用拉格朗日方法,建立了平台的动力学模型,得到了平台前5阶固有频率的解析式;分析了平台固有频率与柔性板簧厚度、长度的相互关系,得到了固有频率随柔性板簧厚度、长度的变化规律。应用有限元方法,分别仿真得到了前6阶固有频率和模态阵型;以固有频率为优化目标,建立了平台的优化模型。采用动态测试系统,分别对优化前、后的平台进行了模态试验分析;通过对比分析,得到了提高平台动态性能的方法,且模态试验结果表明,调整柔性板簧厚度、长度的方法是有效的、可行的。     

X Y parallel compliant stage with compact configuration

This paper presents a piezo-driven compliant stage for nano positioning with two degree-of-freedom parallel linear motions. Nano positioning is one of the most important factors in completion of nanotechnologies. It can be accomplished by flexure-based compliant stages driven by piezo-actuators. For compact configuration, the compliant stage is stacked by two-layered compliant mechanisms. The upper layer contains a motion guide mechanism, and the lower layer two displacement amplification mechanisms. The motion guide mechanism consists of four prismatic-prismatic parallel compliant joint chains for two translational motion guides. The displacement amplification mechanism is adopted by a flexure-based flextensional amplification mechanism driven by a stack-type piezo actuator. Due to the parallel compliant joint chains, the stage has the same dynamics in the x and y axes. In this study, through design and analysis, the mechanisms were machined via wire electro-discharge machining and are were then integrated with two stack-type piezoelectric elements for actuation, and two capacitive sensors for ultra-precision displacement measurement. Finally, experiments were carried out to demonstrate the performance of the compliant stage.     

3-RPRR类平面全柔性并联机构拓扑优化设计

针对全柔性并联机构的构型设计不能满足精密定位和微纳制造领域的需求,为提高全柔性并联机构的整体刚度、抗振性和抗干扰性,基于3-RPRR并联机构原型,采用型综合法,设计出与并联机构原型空间运动特性一致的3-RPRR类平面全柔性机构及其支链.运用拓扑优化的方法,得到铰链最优配置的3-RPRR类平面全柔性并联机构及其支链.采用Hyperworks/Radioss软件分别对这2种3-RPRR类平面全柔性并联机构进行静力学及模态分析,仿真结果表明:在实现相同运动特性的前提下,优化后的3-RPRR类平面全柔性并联机构不仅节省材料,而且在刚度、抗振性和抗干扰性方面更优.     

Design optimization of a spatial hybrid mechanism for micromanipulation

Traditional parallel manipulators suffer from errors due to backlash, hysteresis, and vibration in the mechanical joints. The hybrid mechanism is built through the reconfiguration of parallel-serial structure. In this paper, a new 3SPS + RPR spatial hybrid mechanism which has three degrees of freedom (DOF) and can generate motions in a microscopic scale is proposed. As a reliable compliant hybrid mechanism which provides micro/nano scale micromotion with high accuracy, it can be utilized for biomedical engineering and fiber optics industry. The detailed design of the structure is first introduced, followed by the kinematic analysis and performance evaluation. Based on the kinetostatic model, the joint and link compliances of the passive constraining leg are investigated. Second, a finite-element analysis of resultant stress, strain, and deformations is evaluated based upon different inputs of the three piezoelectric actuators. Finally, the genetic algorithms and radial basis function networks are implemented to search for the optimal architecture and behavior parameters in terms of global stiffness/compliance, dexterity and manipulability. The proposed analysis and optimization methodology is intuitive and effective that offers a constructive way for design optimization of the family of parallel/hybrid manipulators.     

Laser Induced Coffee-Ring Structure through Solid-Liquid Transition for Color Printing

Metallic micro/nano structures with special physicochemical properties have undergone rapid development owing to their broad applications in micromachines and microdevices. Ultrafast laser processing is generally accepted as an effective technology for functional structures manufacture, however, the controllable fabrication of specific metallic micro/nano structures remains a challenge. Here, this work proposes a novel strategy of laser induced transient solid-liquid transition to fabricate unique structures. Through modulating the transient state of metal from solid to liquid phase using the initial pulse excitation, the subsequent ultrafast pulse-induced recoil pressure can suppress the plasma emission and removal of liquid phase metals, resulting in the controllable fabrication of coffee-ring structures. The solid-liquid transition dynamics, which related with the transient reflectivity and plasma intensity, are revealed by established two temperature model coupled with molecular dynamics model. The coffee-ring structure exhibits tunable structure color owing to various optical response, which can be used for color printing with large scale and high resolution. This work provides a promising strategy for fabricating functional micro/nano structures, which can greatly broaden the potential applications.     

生物质材料对微纳塑料吸附性能的研究进展

废弃塑料在江河湖海中呈累积趋势，老化分解产生的微纳塑料严重污染水质，威胁生态环境和居民饮用水安全。传统处理方法，如物理絮凝、生物降解等，存在处理周期长、吸附效率低等问题。天然生物质含有大量的羟基、羧基等活性基团，对生物质进行物理处理或化学修饰改性能够改善孔隙结构和提高比表面积，可作为吸附微纳塑料的绿色材料。本文从微纳塑料的常规处理方法和基本特征出发，简要概况了不同类型微纳塑料对植物、动物和人体的潜在影响和危害，系统介绍了生物质材料(生物质炭、纤维素、甲壳素等)在微纳塑料吸附领域的研究现状，分析总结了生物质材料对微纳塑料的吸附行为、规律和作用机制，最后展望了生物质材料吸附微纳塑料的未来发展前景。      

Nonlinear size-dependent modeling and dynamics of nanocrystalline arc resonators

International Journal of Mechanics and Materials in Design - The adequate modeling of the micro/nano arc resonators' dynamics is vital for their successful implementation. Here, a...     

Prediction of anisotropic behavior of nano/micro composite based on damage mechanics with cell modeling

New advanced composite materials have recently been of great interest. Especially, many researchers have studied on nano/micro composites based on matrix filled with nano-particles, nano-tubes, nano-wires and so forth, which have outstanding characteristics on thermal, electrical, optical, chemical and mechanical properties. Therefore, the need of numerical approach for design and development of the advanced materials has been recognized. In this paper, finite element analysis based on multi-resolution continuum theory is carried out to predict the anisotropic behavior of nano/micro composites based on damage mechanics with a cell modeling. The cell modeling systematically evaluates constitutive relationships from microstructure of the composite material. Effects of plastic anisotropy on deformation behavior and damage evolution of nano/micro composite are investigated by using Hill's 48 yield function and also compared with those obtained from Gurson-Tvergaard-Needleman isotropic damage model based on von Mises yield function.     

Spatio-temporal carrier dynamics in ultrashort-pulse laser irradiated materials

A space and time-dependent quantum-kinetic theory has been formulated based on previous theoretical approaches to study the spatio-temporal microscopic carrier dynamics in laser excited semiconductor materials that accounts for the effects of inhomogeneous excitation and structural inhomogeneities due to bulk filamentation damage and micro/nano structuring. The approach involves extensive computational effort.     

Mesenchymal Stem Cells Differentiation on Hierarchically Micro/Nano‐Structured Titanium Substrates

Surface topography of a biomaterial plays an essential role in the regulation of cell adhesion, proliferation, and differentiation. To investigate the influence of hierarchically micro/nano‐structured substrates on the differentiation of mesenchymal stem cells (MSCs), a series of micro‐, nano‐, and micro/nano‐structured titanium substrates were fabricated via dual acid etching and/or anodic oxidation. The morphologies of titanium substrates were characterized by field emission scanning electron microscopy (FE‐SEM) and contact angle measurement, respectively. The differentiation of MSCs adhered to different substrates was investigated in vitro. Compared to native titanium, micro/nano‐structured titanium substrates improved the alkaline phosphatase (ALP) production and mineralization of MSCs. More importantly, micro/nano‐structured titanium substrates demonstrated great potential to induce the differentiation of MSCs, which was revealed by the expressions of osteocalcin (OCN) and osteopontin (OPN). The study provides a potential alternative to generate hierarchically micro/nano‐structured titanium‐based implant for enhanced osseointegration.     

微纳马达行为控制与驱动燃料研究

人造微米马达是一种通过特定工艺制备而成的微米尺寸器件,在特定刺激下,能够实现各种各样的机械运动。微纳马达发展至今,取得了很多重大的突破和进展,科学家们通过多种材料制备了能在不同化学燃料中运动的微纳马达。主要对微纳马达行为控制与驱动燃料进行研究。