电脑刺绣机针杆机构位移仿真方法的研究

电脑刺绣机针杆机构是形成刺绣线迹的主要机构，当刺绣机绣针刺入绣布时，其绣框不运动，当刺绣机绣针离开绣布时，其绣框沿X、Y方向运动，以形成绣花图样，因此对针杆机构进行位移仿真计算是十分重要的。该文以电脑刺绣机针杆机构为研究对象，推导了机构多位移矩阵迭代求解和单一位移精确求解的理论方程，并用上述两种方法对针杆机构进行了位移仿真计算。证实单一位移精确求解方法简便，不用确定多个迭代初值，不用求导，有一定的实用性，可用于电脑刺绣机针杆机构运动学设计。     

基于闭环矢量法的五杆合作机器人运动学建模及仿真

利用闭环矢量法对五杆机构进行正运动学建模,给出了五杆并联机器人的闭环矢量方程,推导了其运动学方程,并用MATLAB软件编写MATLAB函数来求解运动学方程.利用Simulink仿真工具建立了五杆合作机器人的运动学仿真模型,仿真分析得到了运动学仿真曲线.研究过程表明,采用闭环矢量法对五杆并联机器人进行运动学分析既简便又快捷.这种方法对其他复杂平面并联机构的运动学分析具有一定的参考价值.     

平面六杆机构运动学仿真系统研究

研究平面连杆机构动态特性,为提高动态技术性能,采用封闭矢量法分析推导了牛头刨床平面六杆机构运动学求解数学模型.在此基础上,采用软件开发了一套适用于平面六杆机构的运动学仿真系统.在MATLAB平台上进行了牛头刨床主体机构的运动学仿真与动画显示,绘制出了连杆的角度、角速度和角加速度曲线以及滑块和滑枕的位移、速度和加速度曲线.结果证明,该系统不仅分析机构直观方便,通过改变参数后能实现机构优化运动特性,并为设计提供依据.     

基于凯恩方法的机器人动力学建模与仿真

研究机器人动力学的目的是多方面的.机器人动力学模型的重要应用是设计机器人,因为动力学方程可以用来精确地算出实现给定运动所需要的力(矩).用凯恩方法对六自由度关节臂式机器人进行动力学方程的推导,可以减少计算步骤,提高计算效率.经过对推导的动力学方程仿真可以找到现场使用机器人第三个臂出现故障的原因,因此在机器人具体设计、轨迹规划、动力学优化以及实时控制中可以代入具体的参数,从而时机器人的动力学性能进行分析,并具有通用性.     

耦合压力与温度修正算法对流体流场数值仿真

深入研究了目前流体流场的数值仿真问题,由于流体流场中可能存在着马赫数变化很大的流动情形,通常的方法不能较好地计算出准确的结果,因此找出一种能计算任意马赫数流动的算法是非常必要的.使用了一种耦合压力与温度修正算法求解Navier-Stokes方程.是通过连续方程和能量方程推得压力修正值与温度修正值的方程,并将压力修正值方程与温度修正值方程联立求解,而其它求解变量采用分离式求解的思想,求解中对流项差分格式采用了AUSM 格式,并在低马赫数时进行了改进.通过对喷管和圆弧凸包的数值仿真,较好地反映出了流场中的激波现象,计算表明方法能适应任意马赫数范围的流体流动,并且具有一致的计算精度.     

柔性桥式微位移机构位移放大比特性研究

为了分析柔性桥式微位移放大机构的位移放大比特性,利用桥式微位移放大机构的结构全对称性,建立了微位移放大机构的1/4数学模型.采用矩阵法建立了其柔度矩阵,进而推导了桥式位移放大机构的输出位移公式及位移放大比公式.采用ANSYS 11.0软件进行了有限元仿真,并与理论模型进行了分析比较.最后,设计加工了一个实验样件,对理论...     

DGR—5A机器人的动力学及控制

摘要 DGR-5A 机器人是我们自行设计的五自由度全关节型电动机器人.本文讨论了该机器人的动力学及控制问题.为此对机器人的各杆臂建立坐标系并详尽地计算了各杆臂的惯性参数.在推导了该机器人前三个自由度的动力学方程和分析了动力学特性之后,我们提出了一种实时计算量少,易于工程实现的控制方案.最后对该方案进行了仿真研究,仿真的结果是颇为令人满意的.     

基于COMSOL的光子晶体能带结构仿真计算

为更方便、快捷地求解光子晶体能带结构问题,基于有限元数值仿真软件COMSOL Multiphysics系数偏微分方程模块,重新建立了数学模型,直接从亥姆霍兹方程出发,结合布洛赫态,推导出光子晶体偏微分形式的本征方程,充分考虑了布洛赫波矢的传播情况,求解出相应的本征频率从而求解出能带,对一维和二维光子晶体能带结构分别进行仿真计算。仿真计算结果与传统方法结果进行对比分析,验证了此方案的可行性。     

非线性末制导系统参数灵敏度分析

末制导系统参数随着飞行环境及飞行条件的改变而存在摄动,针对这一问题本文提出根据动态灵敏度来分析参数摄动对脱靶量的影响.基于伴随法推导出与系统动态方程相同规模的伴随方程,并通过一次伴随求解计算得到脱靶量对所有可调参数及摄动参数的动态灵敏度,有效的提高了计算效率.传统的直接分析法是将系统状态变量直接对参数变量进行微分,需要对每个参数变量求解一组代数或微分方程,对于状态变量及参数变量较多的情况效率较低.本文基于两种方法对末制导系统的参数灵敏度进行分析,分析结果揭示了参数摄动对脱靶量的影响程度,较小的参数灵敏度为提高系统的鲁棒性提供了依据.     

基于Solid Edge平面四杆机构运动分析与仿真

文章介绍了在Solid Edge环境下,用Visual Basic作为开发工具,实现平面四杆机构运动分析与仿真软件的原理与方法.用二次开发方法建立了平面四杆机构的三维构件模型与装配模型,在运动分析的基础上,对其位移、速度、加速度以及给定点轨迹进行了研究,并给出了列表和线图形式的结果,利用Solid Edge的装配设计关系,实现了平面四杆机构的运动仿真.     

Design and analysis of novel micro displacement amplification mechanism actuated by chevron shaped thermal actuators

This paper presents design and analysis of microelectromechanical system (MEMS) based displacement amplification mechanism actuated using thermal actuators with enhanced performance. The proposed model consists of chevron shaped thermal actuators, an amplification mechanism capable of amplifying displacement 20 times and an electrostatic comb drives for sensing displacements. When voltage is applied to thermal chevrons, displacement is produced which is then amplified 20 times. Steady state static thermal electrical analysis is performed under variable resistivity and voltage bias of 2 V. In-plane reaction forces of magnitude 194.2 and 150.91 µN along X and Y-axis, respectively, thus producing displacement of 0.11 and 2.22 µm along X and Y-axis, respectively. Time domain simulations of device are carried with constant electrical resistivity, variable voltage and convective boundary conditions. Modal analysis of the mechanism is carried out to predict the natural frequencies and associated mode shapes of mechanism during free vibrations. The desired mode is at frequency of 286.160 kHz. Dynamic simulations including direct integration-transient, transient modal and steady state modal analysis are performed on the device for time span of 0.0006 s, under application of 25 g and frequency range of 200–300 kHz. Simulation results prove the viability of the mechanism as an amplification device with enhanced voltage–stroke ratio.

     

Design,modeling and test of a novel compliant orthogonal displacement amplification mechanism for the compact micro-grasping system

In the compact micro-grasping system, the combination of precisely orthogonal movement transformation, displacement amplification and simple structure is important. The typical solution of the combination issue requires bidirectional symmetric input forces/displacements. However, under a certain driving condition, numerous actuators used in micro-manipulation only supply unidirectional input froce/displacement for the driven mechanism, which makes the typical solution infeasible. In this study, a novel compliant orthogonal displacement amplification mechanism (DAM) is proposed to solve the combination issue for numerous actuators used in micro-grasping. The proposed mechanism is a triangulation amplification-based mechanism with undetermined structural parameters. The number of the undetermined parameters and the solution principle are analyzed. The design process is presented. Finite element analysis (FEA) is used to verify the design method. The FEA results show that, for the design examples, the errors evaluating the orthogonal movement transformation are smaller than 0.56 % and 0.15 % respectively, and the displacement amplification ratios are larger than 4.6. The orthogonal displacement amplification is realized. A precise model of the displacement amplification ratio is derived. The dynamic performances of the proposed orthogonal DAM are modeled and FEA verified. Furthermore, a microgripper utilizing the proposed mechanism is presented. The performances of the gripper, including the displacement amplification and the parallel movement of the jaws, are verified by FEA and experiments.

     

基于神经网络的冗余度TT-VGT机器人的运动学求解

应用BP神经网络对冗余度TT-VGT机器人的位姿正解进行训练学习,进而求解机器人 的位姿反解问题．根据网络模型求得机器人的一、二阶影响系数,应用神经网络求解雅可比 矩阵的伪逆．并对七重四面体的变几何桁架机器人进行了仿真计算．     

位移法浅水波方程的解及其特性

不同于传统流体力学,在Lagrange坐标下推导浅水波方程.若将水平位移作为基本变量,则推导出的浅水波数学模型可描述为固体力学的非线性大位移问题.运用不可压缩条件,通过变分原理推导出位移法浅水波方程,给出椭圆函数形式的行波解,并分析孤波解产生的条件.该基础研究建立了在分析结构力学中分析浅水波问题的理论基础,有利于进一步开展水动力学的研究.     

Solution of generalized non-singular Sturm–Liouville systems via an approximation method in a Hilbert space

The approximation method in a Hilbert space is applied to the analysis of a generalized non-singular Sturm-Liouville eigenvalue problem. The variable coefficients in the system equation and the solution are approximated by a suitable linear independent basis, the expansion coefficients are explicitly expressed as a backward recursive formula and the eigenvalues are obtained by solving an algebraical characteristic equation. The computation is simple and straightforward.     

Numerical solution of the two-dimensional Helmholtz equation with variable coefficients by the radial integration boundary integral and integro-differential equation methods

This paper presents new formulations of the boundary–domain integral equation (BDIE) and the boundary–domain integro-differential equation (BDIDE) methods for the numerical solution of the two-dimensional Helmholtz equation with variable coefficients. When the material parameters are variable (with constant or variable wave number), a parametrix is adopted to reduce the Helmholtz equation to a BDIE or BDIDE. However, when material parameters are constant (with variable wave number), the standard fundamental solution for the Laplace equation is used in the formulation. The radial integration method is then employed to convert the domain integrals arising in both BDIE and BDIDE methods into equivalent boundary integrals. The resulting formulations lead to pure boundary integral and integro-differential equations with no domain integrals. Numerical examples are presented for several simple problems, for which exact solutions are available, to demonstrate the efficiency of the proposed methods.     

The large deformation,post-buckling and catastrophic stability of slender cantilever columns

Several solutions, analytical and numerical, exist for the cases of nonlinear bending of beams and post-buckling of columns. However, the solution for the general case of an arbitrarily inclined load does not seem to exist. In this paper, the governing equation of equilibrium for a cantilever of variable cross section under an arbitrarily inclined load is formulated, by using the axial and transverse displacement quantities. The solution is obtained by means of a simple numerical iterative procedure. The results for the post-buckling and non-linear bending of the structure under concentrated tip load, uniformily distributed load and linearly varying load are presented, and compared with the available results, wherever possible. Further, a type of catastrophic behaviour in post-buckling region is observed and studied using the same numerical scheme. The method is general and can be used for any load variation and for any tapered beam-column.     

改进的Marquardt算法研究制膜液三元相图

在制膜液三元相图的计算研究中，非线性方程组解经常出现无意义解。为了避免该问题，本工作以Flory-Huggins理论为基础，推导出浊点线(binodal)方程和旋节线(spinodal)方程，先确定富相中聚合物体积分数为独立变量，然后应用更新雅可比矩阵及其逆的技巧，并应用本工作改进了的Marquardt算法，得出非线性方程组的有意义解。本工作还推导出成膜过程连续相组成迹线(pathline)方程。通过计算绘出了浊点线、旋节线和连续相组成迹线，并用于分析聚合物膜的成膜机理。     

基于ANSYS的速度时程求解方法

针对动力方程数值求解中采用由位移时程求导得到速度时程的方法会造成数值误差的问题,提出在动力方程的求解过程中引入速度变量,并对速度和位移这2个状态变量共同求解的方法,从理论层面证明该方法的可行性.基于ANSYS提出虚拟自由度法（Dummy Freedom Degree Method,DFDM）,并用APDL进行二次开发,达到在数值模拟中直接获取速度时程的目的.工程算例分析结果表明：2个实例表明该方法求解速度时程有效、实用;在直接获得结构速度时程的同时,可将加速度时程的求导阶数降为1阶.