基于连续蚁群算法的3-RPS并联机构正解

为了避免传统数值方法求解并联机构正解问题的弊端,提出了一种将并联机构正解问题转化为目标函数优化问题的求解方法。并联机构正解的核心问题是求解一组多元耦合非线性方程组,以此为依据建立了并联机构正解的目标函数优化模型,并提出了一种简单的连续蚁群算法来求解该优化模型。以求解3-RPS并联机构正解为例进行了仿真分析。结果表明,该算法具有良好的全局寻优功能,能够避免初始值和局部极小值对计算结果的影响,不用计算雅可比矩阵及其逆阵,且计算精度满足并联机构正解的要求。     

一种2PUU+2PUS并联机构的位置与工作空间分析

对2PUU+2PUS并联机构进行了分析研究.运用解析几何中的坐标变换理论,求得了该机构位置反解的显式表达式,给出了求解位置正解的方法,并进行了数值验证;采用CAD变量几何法确定了该并联机构的工作空间边界点,并利用小型CAD软件对工作空间进行了三维可视化描述,从而给出工作空间一种有效的计算方法.     

基于三元非线性方程组的并联机器人运动学研究

到目前为止,对于并联机器人运动学正解的封闭解问题还没有得到完美的解决,现在最为流行的方法是采用广义几何法和方程组的数值解法。然而,这些方法的推导过程非常的复杂,且在求解的过程中还存在解不唯一等的问题。因此,为了避免上述问题,根据多元函数的Taylor公式推导出了一种基于三元非线性方程组牛顿迭代法的并联机器人运动学正解算法,同时,基于其数学原理,也可以得到并联机器人的反解。该算法与其他的方程组数值解法和几何求解法相比,巧妙地绕开了令人头疼的并联机器人运动学正解多解取舍问题,直接获得了工作空间内满足运动连续性的合理解,且迭代次数少,收敛速度快,显示出了极大的优势。     

求十面体变几何桁架机器人位置正解的改进粒子群算法

根据杆长约束条件,给出了求解6-DOF十面体变几何桁架并联机器人机构位置正解的无约束优化模型,并应用粒子群算法(Particle Swarm Optimization,PSO)求解此优化问题.针对PSO直接在整个解空间内寻优时很难求得全部位置正解的问题,提出了求并联机器人机构位置正解的改进粒子群算法--分区搜索粒子群算法(PSO Based on the Regional Search,PSObRS).数值实例表明,PSObRS能求出并联机器人机构的全部高精度位置正解.     

基于共形几何代数求解(4SPS+SPR)+(2RPS+SPR)串并联机构位置正解

提出将共形几何代数引入至串并联机构位置正解求解过程,以(4SPS+SPR)+(2RPS+SPR)串并联机构为例,首先分别针对上下层并联机构选择合理的运动学参数,基于共形几何代数中基本几何元素的表示方法,对机构中相应球面、平面等共形几何表达式进行求交或对偶运算,得到上下层并联机构动平台顶点的共形几何表达.再结合机构中尺寸、几何约束和内积运算,建立上下层并联机构正向位置解的一元高次方程,进而获得上下层并联机构动平台相对于基平台的位姿.在此基础上,基于共形几何代数中刚体运动变换表达式,得到串并联机构动平台顶点的共形几何表达,进而获得串并联机构的位置正解.该方法避免了传统方法中复杂的消元运算,且分析过程几何直观性较强,在简化串并联机构位置正解几何建模方面表现出巨大优势.     

基于ADE-Newton算法的3-RPS并联机构位置正解分析

将智能算法和数值迭代法相结合,构造一种组合式算法——自适应差分进化算法-Newton迭代(Adaptive differential evolution and Newton iteration,ADE-Newton)算法。以3-RPS并联机构为研究对象,详细阐述利用ADE-Newton算法求并联机构位置正解的原理和步骤。为了验证ADENewton算法的有效性和通用性,给出3-RPS并联机构在不同驱动杆长条件下的数值算例。仿真结果表明,ADE-Newton算法能够以较高的效率求得不同驱动杆长条件下的全部高精度位置正解。还比较了ADE-Newton、人工蜂群、粒子群和差分进化算法求3-RPS并联机构位置正解的性能,比较结果显示,ADE-Newton算法的计算效率、收敛精度、稳健性以及可靠性高于对比算法。     

并联机构大范围收敛高效正解法

为提高并联机构正解的效率,以3-RPS并联机构为例,讨论了牛顿迭代法直接用于正解算法的不合理性,并基于牛顿型下降程序,提出一种求解并联机构位置正解的高效解法。该方法通过调整松弛因子,求解并联机构位姿方程的微分初值问题,通过引入符合工作空间的有效约束条件,求出指定杆长动平台的正确位姿。仿真结果表明,该方法摆脱了初值约束,算法具有全局收敛性,且计算速度快,结果准确可靠。     

三移动一转动4-RPUR并联机构及其位置分析

提出一种能实现三维移动和绕Z轴转动(3T1R)的新型全对称4-DOF空间4-RPUR并联机器人机构,并建立其几何模型。应用螺旋理论分析4-RPUR并联机构自由度的数目和性质,证明该机构能够实现3T1R运动,验证了选取各支链中的移动副作为驱动副的合理性。以机构杆长为约束条件,建立机构位置正解分析的非线性方程组,再转化为无约束优化问题,并采用差分进化(Differential Evolution,DE)算法求解该问题。给出机构位置逆解的显式解析表达式,且由该式可知,机构最多存在16组位置逆解。为改进差分进化算法的寻优效率,提出一种加权基矢量变异策略。当种群出现进化停滞而陷入局部最优区域时,采用自适应逃逸操作引入新个体,进而增强种群多样性。新型变异策略与自适应逃逸操作结合,形成具有较强全局优化能力的自适应逃逸差分进化(Adaptive Escape Differential Evolution,AEDE)算法。给出机构位置分析数值算例,应用AEDE算法求得所有高精度位置正解,并应用位置逆解验证位置正解的正确性。还比较了基本DE、粒子群优化和AEDE算法求机构位置正解的性能,结果表明:AEDE算法性能均优于比较算法性能。     

一种新型多自由度混联运动平台的设计与仿真分析

以3-RPS三自由度并联机构为原型,设计了一种新型多自由度混联运动平台,研究其工作空间及动力学性能。采用欧拉法计算分析混联运动平台末端执行器的逆解,采用立体几何法计算分析混联运动平台末端执行器的正解。在MATLAB中采用数值搜索法求解混联运动平台末端执行器的工作空间边界,并将其与3-RPS机构的工作空间作对比。利用ADAMS对混联运动平台进行运动仿真,获得运动平台的动力学仿真数据,为后续实体平台的结构设计、运动控制和误差分析提供可靠依据。     

3-RPS并联平台机构的位置正解与奇异构形分析的数值-符号解

基于Groebner基法和计算机符号处理技术,对3-RSP并联平台机构的位置正解问题进行了符号求解。该法通过对变量排序、建立多项式对的集合、求SP多项式和约简等运算,将一组非线性方程组化简为等价的三角化方程组,得到了封闭形式的解析解。推导了雅可比矩阵和数字一符号表示的奇异位形判别的解析表达式,对该并联机构的可操作性和奇异性进行了分析。同时给出了具体数值实例。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.