Enhanced haptic model for real-time human-computer interaction

为提高软组织变形仿真的精度与实时性,根据人机工程学的最新研究成果,提出了一种基于叠加白噪声的增强力触觉模型.该模型中每层各个弹簧变形量之和的叠加对外等效为软组织表面变形,与之相连的弹簧弹性力的合力等效为软组织表面接触力.利用力触觉交互设备构建了力触觉交互实验系统,实现了虚拟医用弯钳对胆囊按压以及虚拟医用直钳对心脏拉拽的手术仿真.实验结果表明:该模型不仅计算简单,而且能够保证变形计算具有较高精度;同时在交互过程中,力触觉感觉平稳、模拟效果逼真,满足虚拟手术仿真实时交互需要.     

具有简单孔洞结构柔性体的力/触觉框架模型

针对具有简单孔洞的柔性体提出了一种基于框架结构的力/触觉变形模型。此模型以外力接触端为公共端,根据内部孔的位置和形状构建框架。整体框架由一个或多个钢架组成,每根钢架可为单杆件或多杆件结构。当外力作用时,运用虚功原理和Bernoulli-Euler定理求得钢架节点和虚拟固定端的变形位移,从而得到框架的变形,通过框架变形插值求解柔性体全局变形。实验结果表明,该模型方法简单,实时性好,在具体的虚拟建模力反馈工作中可操作性强。     

柔性多体系统碰撞动力学研究

摘 要：针对工程中常见的柔性多体系统碰撞过程,详细的分析了柔性多体系统的接触碰撞条件,基于非线性等效弹簧阻尼模型建立了柔性体的碰撞模型,并基于库仑摩擦模型考虑两体碰撞时的切向摩擦作用。在此基础上把柔性体碰撞模型综合到柔性多体系统动力学方程中,建立了含接触碰撞的柔性多体系统动力学模型,此模型适用于一般含碰撞的多体系统。仿真算例以柔性梁在重力场中的接触碰撞过程为对象进行动力学仿真,研究柔性梁碰撞前、碰撞过程及碰撞后的动力学特性和动态响应,以及碰撞过程碰撞力的变化规律,并与刚性梁在重力场中的接触碰撞过程进行详细的比较和分析,结果表明基于非线性等效弹簧阻尼模型建立的柔性多体系统碰撞动力学模型可以有效的分析接触碰撞过程的动力学性能,验证了模型的有效性和正确性。     

基于虚拟样机技术的曲轴多体动力学仿真

基于虚拟样机技术和柔性多体动力学理论,综合运用三维建模,有限元分析以及多体动力学仿真等技术,建立包括曲轴柔性体以及随曲轴一起转动的零件刚性体在内的整个曲轴系统的虚拟样机模型,通过进行曲轴系统在发动机真实工况下的柔性多体动力学仿真计算,得到了各构件之间相互作用力,继而得到曲轴在一个工作循环周期内的实时动力学响应,为曲轴的优化设计奠定了基础.     

折叠式高空作业车臂架系统的动力学建模

用柔性多体动力学的理论分析折叠式高空作业车臂架系统的动态特性。把高空作业车的臂架模拟成柔性机械臂,采用柔性多体动力学理论和拉格朗日方程建立高空作业车臂架系统的柔性多体动力学方程,通过对高空作业车臂架运动微分方程的推导和数值求解,对高空作业车各臂架的运动情况进行分析。分别建立高空作业车臂架的刚性模型和柔性模型。仿真得出两种模型的变形曲线,结果表明,考虑各个臂杆柔性变形的影响是非常必要的,同时研究成果为折叠式高空作业车臂架及工作台的振荡控制和轨迹精确控制研究打下基础。     

抗压内LET柔性铰链的建模及分析

针对内LET(Lamina emergent torsion)柔性铰链存在轴向刚度低这一问题,基于倒置原则提出了一种抗压内LET柔性铰链.首先,综合考虑各柔顺片段的变形特点,设计了抗压内LET柔性铰链的结构;其次,利用等效弹簧刚度模型推导了该铰链的弯曲等效刚度及抗压等效刚度,并用有限元分析实例验证了2种理论计算模型的正确性;最后,将内LET柔性铰链和抗压内LET柔性铰链弯曲变形及压缩变形的有限元仿真结果进行比较.结果表明,在外形尺寸一致的情况下抗压内LET柔性铰链的弯曲刚度是内LET柔性铰链的1.195倍,而抗压刚度却是其24.532~28.141倍.在弯曲刚度无明显变化的前提下,抗压内LET柔性铰链的抗压刚度大幅提升,该铰链的结构设计完全符合预期要求.     

苏州纳米所在柔性可穿戴电子及其应用方面取得新进展

正当前人工智能快速发展,各种类人功能智能机器人层出不穷,触觉感知是人类和未来智能机器探索物理世界的基础性功能之一,发展具有触觉功能的仿生电子皮肤柔性感知器件,并实现器件与柔软组织间的机械匹配性具有重要的科学意义和应用价值。受指纹能够感知物体表面纹理的启发,中国科学院苏州纳米所张珽研究团队在前期研究基础上,采用内外兼具金字塔敏感微结构的柔性薄膜衬底及单壁碳纳米管导电薄膜,设计与制备了具有宽检测范围(45～2500Pa)、高灵敏度(3.26kPa-1)的叠层结构柔性振动传感器件。并建立了其摩擦物体表面时振动频率与物体表面纹理粗糙度的模型。该     

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...     

基于非线性气弹耦合模型的风力机柔性叶片随机响应分析

为准确模拟柔性叶片在紊流风速下的气弹响应,研究叶片振动对气动载荷与气弹响应的反馈,构建包含多体系统动力学模型与气动模型的柔性叶片非线性气动弹性力学模型。在将细长柔性叶片离散为多刚体系统基础上,运用计算多体系统动力学理论和Roberson-Wittenburg的建模方法,结合叶素动量理论,采用Kaimal模型模拟脉动风速,建立风力机柔性叶片的气弹耦合方程。算例以美国可再生能源实验室(NREL)研制的5 MW近海风力机为研究对象,分析叶片的振动和叶根的挥舞与摆振力矩,研究柔性叶片振动对气动载荷影响。结果表明,叶片达到一定长度后,模拟风力机气弹响应问题时,其振动影响不可忽略。     

球轴承柔性多体动力学分析与接触振动研究

结合有限元法和柔性多体动力学方法,提出球轴承柔性多体接触动力学模型和动力学分析方法。综合考虑钢球与内外圈滚道的游隙、柔性多体接触、套圈弹性变形、摩擦、离心力和转速等关键因素,建立球轴承的柔性多体接触动力学模型。研究了球轴承的柔性多体动力学特性和接触振动响应,计算出球轴承钢球公转一周时的接触力变化、套圈中心的相对振动位移、加速度、套圈弹性变形、截面接触应力和径向接触应力等接触振动响应,揭示了球轴承的支承钢球数目奇偶交替时的变柔性接触振动本质。提出的球轴承动力学模型与计算结果为以系统振动为目标的球轴承动态设计和球轴承系统设计提供理论指导和参考数据。     

Snapping algorithm and heterogeneous bio-tissues modeling for medical surgical simulation and product prototyping

This paper presents a novel technique for modeling soft biological tissues as well as the development of an innovative interface for bio-manufacturing and medical applications. Heterogeneous deformable models may be used to represent the actual internal structures of deformable biological objects, which possess multiple components and non-uniform material properties. Both heterogeneous deformable object modeling and accurate haptic rendering can greatly enhance the realism and fidelity of virtual reality environments. In this paper, a tri-ray node snapping algorithm is proposed to generate a volumetric heterogeneous deformable model from a set of object interface surfaces between different materials. A constrained local static integration method is presented for simulating deformation and accurate force-feedback based on the material properties of a heterogeneous structure. Biological soft tissue modeling is used as an example to demonstrate the proposed techniques. By integrating the heterogeneous deformable model into a virtual environment, users can both observe different materials inside a deformable object as well as interact with it by touching the deformable object using a haptic device. The presented techniques can be used for surgical simulation, bio-product design, bio-manufacturing, and medical applications.     

Snapping algorithm and heterogeneous bio-tissues modeling for medical surgical simulation and product prototyping

This paper presents a novel technique for modeling soft biological tissues as well as the development of an innovative interface for bio-manufacturing and medical applications. Heterogeneous deformable models may be used to represent the actual internal structures of deformable biological objects, which possess multiple components and non-uniform material properties. Both heterogeneous deformable object modeling and accurate haptic rendering can greatly enhance the realism and fidelity of virtual reality environments. In this paper, a tri-ray node snapping algorithm is proposed to generate a volumetric heterogeneous deformable model from a set of object interface surfaces between different materials. A constrained local static integration method is presented for simulating deformation and accurate force-feedback based on the material properties of a heterogeneous structure. Biological soft tissue modeling is used as an example to demonstrate the proposed techniques. By integrating the heterogeneous deformable model into a virtual environment, users can both observe different materials inside a deformable object as well as interact with it by touching the deformable object using a haptic device. The presented techniques can be used for surgical simulation, bio-product design, bio-manufacturing, and medical applications.     

A Novel Twist Deformation Model of Soft Tissue in Surgery Simulation

Real-time performance and accuracy are two most challenging requirements in virtual surgery training. These difficulties limit the promotion of advanced models in virtual surgery, including many geometric and physical models. This paper proposes a physical model of virtual soft tissue, which is a twist model based on the Kriging interpolation and membrane analogy. The proposed model can quickly locate spatial position through Kriging interpolation method and accurately compute the force change on the soft tissue through membrane analogy method. The virtual surgery simulation system is built with a PHANTOM OMNI haptic interaction device to simulate the torsion of virtual stomach and arm, and further verifies the real-time performance and simulation accuracy of the proposed model. The experimental results show that the proposed soft tissue model has high speed and accuracy, realistic deformation, and reliable haptic feedback.     

轴向冲击下薄壁圆柱壳的屈曲行为的实验研究

由于薄壁圆柱壳比厚壁圆柱壳的不均匀性更大，薄壁圆柱壳的轴向动力屈曲比厚壁复杂得多。了解轴向冲击下薄壁圆柱壳的屈曲行为，有助于进行吸能构件设计。介绍了采用落锤实验进行圆柱壳的动力屈曲行为研究中，超薄壁圆柱壳的一些特殊屈曲行为，在实验中观察到随着径厚比的增加，折屈边数有相应增加的趋势，存在过渡区。经吸能特性分析，随着圆柱壳径厚比的增加，平均压垮载荷和一个基本变形单元能量吸收量增加，有效压缩距离和一个基本变形单元的初始长度增加，但有效压缩距离与基本变形单元长度之比保持不变；在壁厚相同的条件下，能量吸收量与圆柱壳半径成正比。     

两端并圈多股弹簧的冲击响应研究

针对实际工作中的多股簧是两端并圈,且主要用作往复运动中的复进簧来承受冲击载荷的问题,推导了两端并圈多股簧的中心线数学模型,通过CATIA软件生成了两端并圈多股簧的三维几何模型,进一步建立了两端并圈多股簧的有限元冲击模型并利用ABAQUS软件进行冲击响应计算。计算结果表明：多股簧受冲击载荷时,使各簧圈产生振动,弹簧上各质点的运动以纵波的形式向固定端传递,并会在固定端和受力端反射,因此弹簧上各质点的位移和速度不再沿轴向呈线性分布;受力端变形大,固定端基本没有变形,当冲击载荷超过极限值时,就会使多股簧的簧圈产生压并现象;实际设计多股簧时,必须进行冲击响应分析,合理选择多股簧的刚度,避免压并现象的发生。     

Vibrational spectroscopic analysis of silicones: a Fourier transform-Raman and inelastic neutron scattering investigation

An inelastic neutron scattering spectrum of a poly(dimethylsiloxane) (PDMS) is reported, and a spectrum simulated using a monomer molecular unit as a model for comparison. FT-Raman spectra of a series of PDMS derivatives are reported and structure spectra correlations are shown to exist for the estimation of (a) PDMS average chain length, (b) ratio of the number of monofunctional units to quadrifunctional units in silicone resins, and (c) the percentage weight of PDMS in silicone emulsions.     

钢斜撑+钢桁架+钢筋混凝土管柱竖向混合结构 抗震性能试验研究

传统钢桁架+钢筋混凝土管柱形式的空冷支架结构体系在地震高烈度区已不能满足百万千瓦机组火电厂对结构使用性能的要求。该文提出钢斜撑+钢桁架+钢筋混凝土管柱的新型空冷支架结构体系,并对其抗震性能进行试验研究。选取原型结构的1/4,并按照1/8缩尺比制作试验模型,进行动力特性测试、拟动力试验与拟静力试验,探讨该结构体系的滞回性能、变形性能以及破坏模式等。结果表明:钢斜撑+钢桁架+钢筋混凝土管柱空冷支架结构体系的荷载-位移滞回曲线饱满,结构的耗能能力与变形能力较强,能够满足高烈度区大容量机组的抗震要求。     

Molecular model of drawing polyethylene and polypropylene

Morphological studies of plastic deformation of single crystals, thin layers, and bulk samples together with mechanical, X-ray and infra-red data revealed the existence of three stages in cold drawing of crystalline polymer: the plastic deformation of the original spherulitic structure, the discontinuous transformation of the spherulitic into fibre structure by micronecking, and the plastic deformation of the fibre structure. The initial material, which has low strength and high ductility, consist of stacks of parallel lamellae with few interlamella links. It deforms plastically by stack rotation, sliding of lamellae, phase change and twinning of crystal lattice, chain slip and tilt until the predeformed lamellae reach the position of maximum compliance for fracture by micronecking. The micronecks transform every single lamella into microfibrils of between one and three hundred angstroms in width, consisting of folded chain blocks broken off the lamella primarily by chain slip in the boundary layers between adjacent mosaic blocks. The chains bridging the crack are partially unfolded during the micronecking process. They connect in axial direction the blocks in the microfibril as intrafibrillar tie molecules. The number of microfibrils per cm of crack length increases with molecular weight. The draw ratio of the microfibrils and the axial separation in the microfibril of the originally adjacent crystal blocks increase with the average distance between microfibrils and, hence, decrease with increasing molecular weight. The concentration of micronecks in every stack of lamellae in a thin destruction zone produces a bundle of microfibrils of rather uniform draw ratio. Such a fibril measuring a few thousand angstroms in width includes the interlamella ties of the original sample as interfibrillar tie molecules connecting adjacent microfibrils. The concentration of micronecks also provides the conditions for a nearly adiabatic heating of the generated fibril by the transformation work in the destruction zone. The local temperature rise imparts so much mobility to the chains in the crystal blocks that during subsequent cooling to ambient temperature, the long period becomes adjusted to this temperature. The more or less random distribution of destruction zones in the neck makes the transformation from spherulitic to fibre structure appear to be a gradual process in spite of the discontinuous transformation in the micronecks. The plastic deformation of the new fibre structure can proceed only by longitudinal sliding of microfibrils past each other, a process limited by interfibrillar tie molecules. Hence, high molecular weight samples with many interlamella links exhibit a smaller draw ratio than lower molecular weight material. The three stages are to some extent intermixed in the neck. In the initial neck characterised by a low draw ratio and rather gentle constriction, the transformation into the fibre structure is not complete, so that some of the remains of the original microspherulitic structure are still present in the necked portion. They are destroyed during subsequent drawing which completes the transformation and also deforms the fibre structure. The sharply constricted mature neck, however, yields a high draw ratio which is composed of the draw ratio of microfibrils and of subsequent sliding motion of the microfibrils. The technically important natural draw ratio is the maximum draw ratio obtained with the sample under the conditions of the experiment. It seems to be higher than the draw ratio of the microfibrils.     

A finite element simulator for spine orthopaedics with haptic interface

The human spine is a biomechanical structure that allows complex motions while providing stability and protection for the spinal cord during a variety of loading conditions. In this study, finite element models of spine are developed to investigate clinical problems as well as to predict its biomechanical behaviour. This research proposes a combination of an online real-time FE simulator and an offline nonlinear FEA solver. Haptic feedback is provided in the online FE simulator to enhance the human–computer interaction of the system. Primitive results of spinal deformation can be obtained from the haptic online FE simulator. The offline FEA solver provides detailed deformation and strain/stress information based on the primary simulation results from the online FE simulator.     

A characteristic length for stress transfer in the nanostructure of biological composites

Although it has been widely recognized that stress transfer in the nanostructure of biological composites follows a tension–shear chain, with mineral platelets primarily under tension and protein matrix primarily under shear, some of the critical assumptions of this model has not been thoroughly investigated. For example, an implicit assumption of the tension–shear chain model is that the shear stress in the protein layer between two neighboring platelets is uniformly distributed. Here we derive a characteristic length for stress transfer in a unit cell of biocomposites and show that the assumption of uniform shear stress in protein is valid only if the length of the mineral platelets is below a characteristic value. Numerical simulations have also been carried out to confirm that stress transfer in the staggered biocomposites is most efficient when the length of the mineral platelets is equal to the characteristic length.