海龟柔性前肢仿生推进研究

为探讨水翼法推进方式,进行了海龟柔性前肢仿生技术研究.基于水翼法运动解析,研究了海龟柔性水翼的弦向形变特征、反卡门涡街脱泻及斯特劳哈尔数等,推算出水翼尾涡脱泻的斯特劳哈尔数位于0.2～0.45之间,雷诺数位于3×102～3×104之间;根据海龟水翼粘弹本构特性,研制了半骼式仿生柔性水翼,并对其进行柔性形变和组织模态分析...     

2自由度振荡水翼推进性能分析及实验研究

为了研究仿生水翼推进性能,设计了一种2自由度振荡水翼推进装置.实现了基于升力/阻力模式的2种振荡水翼推进方式.研制了振荡水翼推进性能实验平台,在循环水池环境下完成了不同参数耦合情况下振荡水翼推进性能实验.利用6轴力传感器测量水翼振荡时产生的推力/升力,并将实验结果与数值模拟结果对比,分析不同参数对推进性能的影响.实验结果表明,在升力推进模式下,增加拍旋运动幅值和振荡频率可以提高平均推力;随着位旋运动幅值的增加,平均推力呈现先增大后减小的趋势;随着来流速度的增大,平均推力逐渐减小.在阻力推进模式下,增加拍旋运动幅值和振荡频率均可提高平均推力.     

扑翼的非定常水动力特性数值研究

研究水下推进装置结构优化设计问题,建立了扑翼的简谐运动模型,根据有限体积法和非结构动网格技术,完成了对扑翼运动的非定常建模研究.通过计算得到了扑翼运动的水动力特性及流场的变化规律,提出了扑翼产生的涡的特点及其作用机制.计算结果表明:在简谐运动驱动下,扑翼运动能产生较大的推力,而产生的升力较小;扑翼运动过程中伴随着涡的生成和脱离,尾涡能有效地提高扑翼产生的推力,前沿涡能抑制推力的产生和延缓升力的下降趋势.以上研究为水下推进装置优化设计提供了参考依据.     

湍流模型影响狭长空间内火灾烟气运动的数值研究

为准确地预测狭长空间内火灾引起的烟气运动,本文研究了不同湍流模型的影响.针对某一巷道内的火灾烟气运动,分别采用考虑浮力修正的双方程湍流模型和大涡模拟方法展开计算.计算结果表明大涡模拟方法的预测值与测量值吻合较好,普通的双方程湍流模型虽然进行了浮升力的修正,但计算结果与实验值仍然存在着一定的差距.     

用于丝驱动连续体机器人的实用运动学研究

针对单段及多段连续体机器人运动学问题,提出分段常曲率与粒子群算法相结合的完整正逆运动学分析方法.以双段丝驱动连续体机器人为研究对象,首先设计含平移段的机器人样机;然后利用分段常曲率方法建立驱动空间与关节空间的相互映射,根据齐次变换得到关节空间至工作空间的正映射关系;最后利用线性递减权重粒子群算法实现工作空间至关节空间的逆映射.对双段连续体机器人的运动学进行仿真及逆运动学求解耗时测试,并在研制样机上进行了实验验证.仿真结果说明了所提运动学研究方法的合理性及逆运动学求解的快速性,实验结果显示位置平均误差小于双段连续体机器人本体长度的6.22％,验证了所提运动学的有效性.     

分段式低秩逼近的运动捕获数据去噪方法

运动捕获数据去噪旨在从含有噪声干扰的运动数据中恢复出能够较好表达原始数据特性的帧序列.针对人体运动捕获数据在较短时间段内的帧序列常常具有相同或相似的运动行为语义的特点,提出了一种分段式低秩逼近策略的运动捕获数据去噪方法.该方法首先将含有噪声的运动数据划分为多个连续子区间,接着利用不精确拉格朗日乘子法(IALM)对每个分段子区间的含噪声干扰数据批矩阵进行低秩矩阵逼近和稀疏噪声误差估计,达到分段数据去噪目的;最后利用时序特性组合去噪后的分段低秩逼近矩阵进行整体运动捕获数据去噪恢复.仿真实验结果表明,所提方法能够对含有任意拓扑结构的人体运动捕获数据进行去噪,达到了很好的效果,具有一定的通用性和实用性.     

基于DMD方法的矩形断面涡振模态分析

为探究涡激振动下,矩形断面绕流场的模态演化规律及涡振发生机理,基于雷诺平均SST k-ω模型对宽高比为5∶1的矩形断面的涡激振动进行了二维数值模拟研究.通过CFD/CSD交错迭代求解,结合动网格技术实现了二维流固耦合计算,并与风洞试验结果进行对比分析,验证了数值计算的准确性.随后,对流场的瞬时状态进行可视化分析,以z方向涡量值为基本物理量,基于动力学模态分解(DMD)方法对其静态与涡振态流场模态进行了对比分析.结果表明：在涡振发展的不同阶段,主导流场的模态频率不同,主模态频率会由静态涡脱频率向结构固有频率转变,此主模态的转变表征了流固耦合的内在机制;与静态矩形相比,涡振态矩形由于运动诱导涡的存在,导致其前缘涡与尾缘涡的相位差减小,前缘涡与尾涡而合并时前缘涡占据主导,使得在尾缘脱落的Karman涡相关性减弱,形成了涡振锁频现象.     

摩擦提升机的虚拟样机研究

钢丝绳传动特性是摩擦式提升机设计一个重要的考虑因素.为了研究摩擦提升机提升过程中钢丝绳的动力学特性,为安全运行提供保证,通过虚拟样机技术及其支撑软件ANSYS和RecurDyn,利用相对节点法建立了钢丝绳的多体动力学仿真模型,构建了简化后的摩擦式提升机虚拟样机仿真模型.通过对摩擦提升机虚拟样机的仿真分析,获得了仿真模型的运动学、动力学特性数据,得到了与理论分析相吻合的结果.为设计经济、可靠的多绳摩擦提升机系统提供了有力的工具和实现方法,还可以推广应用到其他挠性传动的分析.     

基于MS-CNN算法的虚拟运动场景人机协同仿真

在目前的人机协同仿真方法中,缺乏运动场景对仿真结果影响的考虑,影响人机协同仿真的准确性,因此提出基于MS-CNN算法的虚拟运动场景人机协同仿真研究.建立虚拟运动场景模型确定运动场景下的运动参数.运用MS-CC算法对虚拟运动场景进行运动识别,提取特征参数.拟定人机协同中的影响因素.最后运用Flexsim、Matlab和VC集成软件来进仿真开发,实现仿真方法的设计.为了验证设计的仿真方法的可行性.设计实验,使用某地工厂的人机协同工作车间内2个月的订单工作数据为基础,使用设计的仿真方法以及文献[3]、文献[4]、文献[5]中的仿真方法进行实验.实验结果证明,设计的仿真方法仿真得出的数值更接近实际数值,能够准确高效实现虚拟运动场景人机协同仿真.     

双足机器人NAO爬楼步态规划

双足机器人的爬楼梯性能是衡量其在复杂环境下行走能力的一项重要指标.本文针对双足机器人NAO爬楼梯步态规划问题,提出一种离线步态规划方法：基于几何法建立机器人爬楼梯逆运动学模型;将运动解耦为前向运动和侧向运动,对于起步、中步和止步三个阶段,采用加速度空间法和几何约束规划法,计算各关节运动轨迹,并基于其逆运动学模型,得到各关节角序列;分别基于NAOSim和NAO进行虚拟样机仿真实验和实物样机验证.实验结果表明,步态规划方法合理有效.     

Shape-optimization of 2D hydrofoils using an Isogeometric BEM solver

In this paper, an optimization procedure, based on an Isogeometric BEM solver for the potential flow, is developed and used for the shape optimization of hydrofoils. The formulation of the exterior potential-flow problem reduces to a Boundary-Integral Equation (BIE) for the associated velocity potential exploiting the null-pressure jump Kutta condition at the trailing edge. The numerical solution of the BIE is performed by an Isogeometric Boundary-Element Method (BEM) combining a generic B-splines parametric modeler for generating hydrofoil shapes, using a set of eight parameters, the very same basis of the geometric representation for representing the velocity potential and collocation at the Greville abscissas of the knot vector of the hydrofoil’s B-splines representation. Furthermore, the optimization environment is developed based on the geometric parametric modeler for the hydrofoil, the Isogeometric BEM solver and an optimizer employing a controlled elitist genetic algorithm. Multi-objective hydrofoil shape optimization examples are demonstrated with respect to the criteria (i) maximum lift coefficient and (ii) minimum deviation of the hydrofoil area from a reference area.     

仿生推进与操纵系统方案设计与运动仿真

以金枪鱼为原型对仿生推进与操纵系统的运动机理进行的详细分析，给出了三节点摆动翼的数学描述，在AutoCAD中对金枪鱼的外型进行简化，完成了系统的方案设计并给出了尾部结构图，利用VB语言编制了模仿鱼类尾部游动的仿真软件，只需改变模型中的各项控制参数即可模拟系统尾部各节的运动状态，文中给出了四种典型运动状态下的仿真结果，将为仿生推进与操纵系统的设计以及确定最佳运动与控制参数提供计算和实验依据。     

Design and development of an autonomous wave-powered boat with a wave devouring propulsion system

This paper describes the design, development, and experiments of an autonomous wave-powered boat with a wave devouring propulsion system (WDPS). The WDPS consists of two fins (hydrofoils) below the bow of the boat. They generate thrust force directly from wave power and reduce roll and pitch motion of the boat in the waves. As described herein, first we performed numerical analysis and a preliminary experiment to design the hull form and the WDPS. Based on the analysis and experimentally obtained results, we designed and developed a prototype autonomous wave-powered boat. We also developed electrically powered systems such as a navigation, control, and wireless communication system for the boat. Moreover, we experimentally tested the performance of the developed boat in a test tank and in a coastal sea area. The experimentally obtained results indicate that the developed wave-powered boat can be a useful tool for ocean observation.     

A fluidelastic model for the dynamics of cantilevered plates with an additional spring support in axial flow

A fluidelastic model has been developed for studying the dynamics of cantilevered plates in axial flow, with an additional spring support at the plate trailing edge. The plate is supposed to be two-dimensional; a nonlinear equation of motion based on the inextensibility condition is used to account for the possible large vibration amplitude. For the fluid-dynamic part, an unsteady lumped vortex model is used for calculating the fluid loads acting on the plate undergoing deformation; the longitudinal displacement of the plate associated with lateral motions is also taken into account. The fluidelastic model is first validated through comparisons with experimental data published for systems without the spring support; it is then used to investigate the dynamics of cantilevered plates in axial flow with an additional spring support at the plate trailing edge. Some interesting results of the dynamics of the fluid–structure system are presented.     

基于 Kane 方法的机器海豚动力学建模及速度优化方法

在利用Kane方法对机器海豚进行动力学建模的基础上, 提出了一种对豚体波拟合推进进行速度优化的方法. 首先, 选取各连杆的关节角和机器海豚头部质心的坐标作为广义坐标, 对具有三个推进关节的机器海豚进行运动学分析,进而得到广义惯性力; 然后,结合对各连杆受力分析得到的广义主动力, 建立机器海豚的动力学方程. 其中, 根据尾鳍攻角所处的不同范围,分别利用升力线理论和阻力模型将尾鳍建模为有限翼展机翼或平板来计算水动力. 在此基础上, 结合豚体波拟合推进, 提出一种通过调节尾鳍关节角规律的幅度和相位来优化平均推进速度的方法. 仿真结果表明了所建模型及优化方法的有效性.     

Instability of the flow in the vicinity of trailing edge of a class of thin aerofoils

A numerical study has been undertaken to investigate the notion of absolute/convective instability in laminar incompressible trailing edge flows past wedge-like shapes with curved boundaries of the form y=α(−x)^m. The effects of various trailing edge shapes m and relative thickness α on the flow separation and the development of instabilities in the vicinity of trailing edge are investigated. The nonlinear viscous-inviscid interaction equations, which have been derived by means of the asymptotic theory of flow separation, are solved first numerically to construct genuine mean velocity profiles representing the correct flow in the vicinity of the trailing edge. The absolute/convective nature of the asymptotically formed velocity profiles via a composite expansion is then ascertained by using a spatio-temporal analysis based on the Briggs-Bers pinching criterion. Although no absolute growth is encountered upstream of the trailing edge of the airfoil shapes considered, in particular the wake region behind the trailing edge of Joukowski type profiles is found to be persistently susceptible to absolute instability. It is found that separation is enhanced as the relative thickness of the airfoil gets bigger. This, in turn, is shown to lead to an additional enhancement of the absolute instability character by both increasing the absolute growth rate as well as the extent of the unstable region. Shedding frequency of the Karman vortex street is also determined behind the trailing edge shapes considered.     

基于图像处理的滑坡后缘裂缝运动轨迹分析

滑坡后缘裂缝运动轨迹分析对于滑坡监测预警至关重要,针对滑坡后缘已有裂缝带,提出了一种基于最大类间算法（OTSU）、Canny算子与目标物体特征识别的滑坡后缘裂缝检测方法,通过对滑坡后缘裂缝图像进行预处理、形态学处理与边缘检测、边缘轨迹比较,获取滑坡后缘裂缝位移情况。经测试,该方法在上位机（基于QT平台开发）上能有效检测滑坡后缘裂缝,并判别理论模型下的运动轨迹,可为滑坡灾害预警提供支撑。     

Dynamic instability of thermal-flying-height-control sliders at touchdown

With the wide application of thermal flying-height control (TFC) technology in the hard disk drive industry, the head-disk clearance can be controlled to as low as ~1?nm. At this ultra-low clearance, the air bearing slider is subject to relatively large interfacial forces, and it experiences more complicated dynamics, compared with the flying case. In this study we conduct a numerical analysis to investigate the dynamics of TFC sliders during touchdown. The general trend of the slider’s motion predicted by the numerical simulation qualitatively agrees with experimental findings. The touchdown process begins with a slight intermittent contact between the slider’s trailing edge and the disk, followed by a partial slider-disk contact at the trailing edge accompanied by a large pitch motion at the 1st air bearing mode; this pitch motion gets suppressed and the slider comes into stable sliding on the disk as the protrusion is further increased.     

Extracting 3D vortices in turbulent fluid flow

This paper presents a computational framework to extract salient patterns, called vortex structures, from 3D turbulent fluid flows. These structures can be characterized as regions of dominating rotational motion in the velocity fields and intensity concentrations in the corresponding vorticity fields. A pointwise linear representation is employed to approximate the kinematics of the flow field, and the fluid motion is classified according to motion analysis or topological patterns. The regions of vortex structures are identified as those dominated by rotational motion or those of focus-type singularity. The 2D vortices, as a special case of 3D vortices, are detected by searching for regions of vorticity concentrations     

Hierarchical Vortex Regions in Swirling Flow

We propose a new criterion to characterize hierarchical two-dimensional vortex regions induced by swirling motion. Central to the definition are closed loops that intersect the flow field at a constant angle. The union of loops belonging to the same area of swirling motion defines a vortex region. These regions are disjunct but may be nested, thus introducing a spatial hierarchy of vortex regions. We present a parameter free algorithm for the identification of these regions. Since they are not restricted to star- or convex-shaped geometries, we are able to identify also intricate regions, e.g., of elongated vortices. Computing an integrated value for each loop and mapping these values to a vortex region, introduces new ways for visualizing or filtering the vortex regions. Exemplary, an application based on the Rankine vortex model is presented. We apply our method to several CFD datasets and compare our results to existing approaches.