新型2UPU/2SPS并联机器人计算机辅助几何分析

提出运用计算机辅助几何法来研究新型4自由度并联机器人的位置和工作空间的问题,利用在CAD软件草图环境下建立的并联机器人模拟机构,基于并联机器人的模拟机构,分析出一种4自由度2UPU/2SPS并联机器人的位置和工作空间.模拟结果表明,计算机辅助几何法的应用不但大大简化了并联机器人机构分析位置和工作空间难度,而且快捷直观,值得推广.     

弧焊机器人工作空间分析与仿真

根据弧焊机器人的结构特点与工作情况,通过对比现有机器人工作空间求解方法,采用蒙特卡洛方法求解多关节弧焊机器人的工作空间,且使用D-H法获得机器人的正运动学方程,运用Matlab进行工作空间仿真.     

基于解析法的2冗余自由度8轴摄影机器人工作空间研究

对设计的2冗余自由度串联PRRPR-S型8轴摄影机器人用解析法研究其工作空间。首先通过固定底层直线运动轴和腰轴的方法,分析去冗余自由度机器人腕关节可达空间的上下侧和内外侧边界;然后不固定底层直线运动轴和腰轴,综合分析机器人工作空间;利用机器人无误差运动学模型,工作空间关键点计算用世界坐标系向工作空间世界坐标系转换,得到实际工作空间关键点坐标;利用多个简单空间覆盖复杂空间的方法来解决隶属度判定问题,并用蒙特卡洛法验证实现多目标点的工作空间隶属度判定仿真。     

焊接机器人的工作空间灵活性分析及优化

针对焊接机器人与焊接工件相对位置安装问题,通过对机器人的工作空间灵活性进行分析.首先,运用D-H法对机器人的运动学进行建模,并通过蒙特卡罗法对机器人的工作空间进行求解;然后借助服务球的概念提出了适合该焊接件的灵活性计算方法,并求解了机器人工作空间中的灵活性;最后分析了各参数对机器人灵活性的影响,并通过遗传算法对灵活性进行优化,得到机器人工作空间中灵活性较高的位姿.该研究为机器人与焊接工件的相对安装位置提供了参考,保证了焊接的可靠性.     

α-Shape算法双机器人协作工作空间研究

机器人协作工作空间是机器人领域的研究热点,但同时也是技术难点.首先以集合形式给出了协作工作空间的定义,基于蒙特卡洛法分别得到主、从机器人工作空间的点云模型;分析了求交集法提取协作空间点的不足,并给出一种通过计算点与点距离并加入一定阈值的判断方法,有效的提取到了协作空间内的点云;运用α-Shape算法分别处理单机器人工作空间与协作工作空间点云数据,对工作空间进行了三维重建,同时给出了基于体积值的参数α的确定方法,并基于此获得了较好的重建效果.最后以六自由度转动关节机器人为例进行了计算和分析,验证了方法的有效性,为指导机器人协作相关技术奠定了重要的理论基础.     

6R型串联机器人工作空间快速求解方法

针对机器人工作空间求解特点,提出了一种基于Matlab中SimMechanics模型并结合蒙特卡洛法的机器人工作空间求解方法.最后与数值法作了实验对比,证明该方法在求解速度上有很大的优势,并且克服了传统方法中对机器人运动学正、反解的依赖.     

3自由度绳索牵引并联机器人的工作空间分析

给出了所设计的平面1R2T三自由度绳索牵引机器人模型,建立了其运动学的逆解模型.在时机器人进行可达工作空间分析的基础上,提出了一种基于矢量封闭原理的可控工作空间;同时在MATLAB环境下采用Monte-Carlo方法对可达工作空间和可控工作空间进行了仿真.仿真结果表明机器人的可控工作空间都落在可达工作空间范围内,验证了可控工作空间分析方法的可行性.该方法也适用于多自由度的绳索牵引并联机器人.     

五自由度教学机器人运动学及工作空间分析

以一种教学五自由度机器人为研究对象,对其进行了运动学分析和工作空间仿真.采用D-H方法推算出运动学方程的变换矩阵,得到运动学正解及利用反变换法获得运动学逆解;根据矢量积方法给出了机器人的速度雅可比矩阵.最后利用包络法分组解法求解了该机器人实际工作空间曲面,为该教学机器人的结构优化、动力学分析和运动控制提供了依据.     

电力铁塔攀爬机器人工作空间的3种求解方法

在对现有的机器人工作空间求解方法分析总结的基础上,分别采用蒙特卡洛法、定步距角法及仿真法求解电力铁塔攀爬机器人工作空间,并从图形效果、分析方法、用时及适用场合4个方面对其进行了比较,选择定步距角法为求解攀爬机器人工作空间的最优方法。通过对工作空间降维提取二维边界曲线并生成三维曲面的方法分析机器人工作空间边界,采用数值法求解了工作空间体积,为机器人结构优化设计、路径规划及运动控制提供了理论依据。     

基于三种方法的油罐清洗机器人工作空间分析

根据油罐清洗机器人的结构特点和各种工作空间求解方法的优缺点,分别采用图解法、蒙特卡洛法和仿真法求解了油罐清洗机器人的工作空间,并从不同角度对3种方法进行了分析比较。结果表明:不同的方法在求解机器人工作空间时适用情况不同,得到的结果也存在误差,在此基础上筛选了不同情况下求解油罐清洗机器人工作空间的优先方法。工作空间的求解为机器人结构优化设计、避障及运动控制提供了理论依据。     

Evaluation of minimum zone flatness by means of nonlinear optimization techniques and its verification

This article deals with the application of some nonlinear optimization techniques for minimum zone flatness. The convergence criteria of the techniques, namely the downhill simplex method and the repetitive bracketing method, are considered. The least-squares method is also applied, and subsequently the three methods are compared from the viewpoint of computational accuracy. A surface profile measuring system and a noncontact sensor are used to obtain three-dimensional data. The measured data are expressed by means of perspective mapping. Subsequently, the relationship among the above three methods is clarified according to accuracy and efficiency of the computation. Furthermore, some examples of the relationship between the manufacturing method and the flatness value, and the technique of a skilled hand are described.     

A comparison of least squares and maximum likelihood methods using sine fitting in ADC testing

ADC test methods require the best possible reconstruction of the input signal of the ADC under test from the acquired, therefore erroneous, ADC output data. The commonly used least squares (LS) fit and the recently introduced maximum likelihood (ML) estimation are competing methods. This paper presents a simulation-based comparative study of these estimation methods with the goal to investigate the behavior of both methods and to determine their limits. Two alternative algorithms for the calculation of the maximum likelihood fit are considered (gradient-based minimization and differential evolution). The main finding is that while for low-INL (linear) ADCs the two methods (LS and ML) give similar results, for practical (almost always nonlinear) ADCs ML is definitely better.     

Comments on the computation of electron wave-propagation in the slice methods

The slice methods developed to calculate dynamical electron diffraction involve an interaction of electrons with each slice and the wave-propagation between the successive slices alternately. Thus an accurate evaluation of the propagation effect, which is mathematically described in terms of a convolution integral, is indispensable. Three main slice methods are examined from the viewpoint of their accuracy and efficiency on the numerical evaluation of the wave-propagation. Some difficulties of two real-space methods are discussed. In conclusion, the FFT multisclie method is the fastest way to obtain the most accurate evaluation of the wave-propagation at present.     

Solving topology optimization problems by the Guide-Weight method

Finding a good solution method for topology optimization problems is always paid attention to by the research field because they are subject to the large number of the design variables and to the complexity that occurs because the objective and constraint functions are usually implicit with respect to design variables. Guide-Weight method, proposed first by Chen in 1980s, was effectively and successfully used in antenna structures’ optimization. This paper makes some improvement to it so that it possesses the characteristics of both the optimality criteria methods and the mathematical programming methods. When the Guide-Weight method is applied into topology optimization, it works very well with unified and simple form, wide availability and fast convergence. The algorithm of the Guide-Weight method and the improvement on it are described; two formulations of topology optimization solved by the Guide-Weight method combining with SIMP method are presented; subsequently, three numerical examples are provided, and comparison of the Guide-Weight method with other methods is made.     

单元分解方法及其应用

单元分解方法是近年来得到广泛发展和应用的无网格方法的一个重要分支。相对于其它无网格方法,它具有更大的灵活性和高精度。本文对现有的单元分解方法进行了综述。阐述了它与其它无网格方法的关系,讨论了单元分解方法的优点和不足。文中还给出了单元分解方法的一般公式及其推导,介绍了用流形方法实现单元分解方法的数值计算,并给出了单元分解方法的算例。最后,介绍了单元分解方法的最新发展状况,并展望了它的发展方向和前景。     

Straightness and flatness tolerance evaluation: an optimization approach

This paper presents an optimization approach that could be used to calculate exact values of straightness and flatness errors as defined by the ANSI Y14.5M standards on geometric dimensioning and tolerancing. The straightness and flatness error evaluation problems are formulated as nonlinear optimization problems with linear objective function and nonlinear constraints. Because of the special structure of the problem, a linear search method is developed that reduces the nonlinear problem to a linear programming problem with only two constraints. Examples are presented to compare the optimization approach with the least-squares method and some exact methods. The results show that the optimization procedures presented in this paper provide exact values of straightness and flatness errors and are superior to the existing methods in terms of computation time.     

高速切削热及温度预测研究进展

切削热和温度问题是研究高速切削加工的一个重要参数指标,对刀具磨损、刀具寿命、表面质量、加工效率和零件精度等都具有很大影响。目前,高速切削热和温度问题主要通过试验法、解析法及数值分析法来进行分析。这些方法各有优缺点,给定状况下切削热问题的最佳分析方法的选择主要取决于方法的可操作性、过程的力学特性、分析的准确性及设施的经济性等因素。从正反两方面简要介绍了上述三种方法的各自特点及其研究进展,并对高速切削过程热及温度预测方法的发展方向进行了初步探讨。     

Comparison of EBSD patterns simulated by two multislice methods

The extraction of crystallography information from electron backscatter diffraction (EBSD) patterns can be facilitated by diffraction simulations based on the dynamical electron diffraction theory. In this work, the EBSD patterns are successfully simulated by two multislice methods, that is, the real space (RS) method and the revised real space (RRS) method. The calculation results by the two multislice methods are compared and analyzed in detail with respect to different accelerating voltages, Debye–Waller factors and aperture radii. It is found that the RRS method provides a larger view field of the EBSD patterns than that by the RS method under the same calculation conditions. Moreover, the Kikuchi bands of the EBSD patterns obtained by the RRS method have a better match with the experimental patterns than those by the RS method. Especially, the lattice parameters obtained by the RRS method are more accurate than those by the RS method. These results demonstrate that the RRS method is more accurate for simulating the EBSD patterns than the RS method within the accepted computation time.     

SFS三维重构技术的发展现状与趋势研究

从明暗恢复形状(SFS)是计算机视觉中三维重构问题的关键技术之一,其原理是利用单幅图像的明暗变化来恢复物体表面的三维形状,应用领域十分广泛.介绍了近些年来SFS方法的发展现状,将SFS算法划分为四种类型:演化和偏微分方程(PDE)方法、最优化方法、局部化方法以及线性化方法.同时,分析了各种SFS算法的特点,并对SFS技...