马鞍形焊缝焊接机器人设计与建模分析

针对目前马鞍形焊缝焊接装备灵活性差,自动化程度低,接头质量稳定性不足等问题,开发了一种新型的管外锚固式四轴焊接机器人. 通过对机器人机构合理简化建立了D-H连杆坐标系,推导了机器人的正逆运动学表达式,并结合机器人关节变量的限位值确定了逆运动学解的唯一性. 通过MATLAB软件对机器人运动学进行了仿真,仿真结果表明,推导的正逆运动学方程模型完全正确. 通过制作样机进行焊接试验,结果表明,焊缝成形致密美观,机器人焊枪末端在x,y,z方向的误差均在±0.35 mm以内,完全满足工程上自动化焊接的需要,为马鞍形焊缝焊接机器人的连续轨迹控制和离线规划提供了依据和算法支持.     

双机器人协同焊接管接头的任务规划及仿真

以船型焊(平焊)焊缝为约束,研究双机器人、管接头、焊枪及焊缝之间的空间位姿矩阵变换关系,建立了双机器人协调焊接坐标系、焊接机器人与夹持机器人的约束关系,对双机器人之间的协调运动做了理论分析。采用D-H变换矩阵法对双机器人协同焊接系统建立连杆坐标系并求解正运动学方程,然后,求出最佳协作空间,根据规划的空间焊缝离散点位置坐标矩阵,利用Matlab求解出机器人逆运动学的各个关节角值。以双机器人协同焊接管接头上的"马鞍形"空间焊缝为例,采用Solidwoks-SimMechanics联合仿真平台进行仿真实验,结果表明,仿真平台能够准确地完成双机器人协同焊接仿真任务规划和分析,验证了所提双机器人协同焊接运动学模型及参数求解的正确性。     

基于雷塞控制系统的五轴焊接机器人的轨迹规划

运用Denavit-Hartenberg方法建立了以旋转关节关节角和移动关节移动分量为变量的基于雷塞系统的五轴焊接机器人运动学模型,对五轴焊接机器人正运动学和逆运动学问题进行了求解分析;采用抛物线过渡的线性插值法对焊接机器人进行了轨迹规划,通过MATLAB Robotics Toolbox工具箱对五轴焊接机器人进行了运...     

水下焊接机器人弧线轨迹平顺运动控制策略

在水下焊接机器人的弧线焊接过程中,为提高焊接质量、改善焊接效率,提出一种弧线轨迹平顺运动控制策略.首先建立焊接机器人的D-H数学模型,推导了机器人的正逆运动学公式,并简化了机器人正运动学公式;然后提出一种6维空间矢量法表示机器人末端的位姿;最后在笛卡尔空间下,采用带抛物线过渡的线性插值方法对机器人的空间位姿进行插补,合理规划了每个路径点对应焊接机器人各个关节的速度、加速度.采用以上控制策略进行水下焊接试验.结果表明,所得焊缝平整光滑,提高了焊接质量,缩短了焊接时间.     

双机器人协调焊接任务规划及仿真

针对复杂曲线焊缝,对一台机器人夹持待焊接的工件,另一台机器人对物体进行焊接的双机器人协调焊接运动问题展开研究,建立了双机器人协调焊接坐标系,采用非主从式运动学轨迹规划,给定待焊接物体上某一点u的位姿,通过点u到焊接机器人和夹持机器人工具末端的两个约束矩阵,分别计算得到焊接机器人和夹持机器人的末端轨迹;焊接过程采用船形焊缝约束,保证焊枪与焊缝在弧焊过程中始终处于接头成形良好的位置,建立双机器人协调焊接Solidworks-SimMechanics仿真平台,并对一个管道直角钢制弯头的协调焊接进行了运动学轨迹规划和仿真.结果表明,建立的平台能精确和有效地对双机器人协调焊接运动进行任务规划和分析,机器人运动轨迹与规划的轨迹一致.     

基于MATLAB Robotic Toolbox的关节型机器人运动仿真研究

在MATLAB环境下对关节工业机器人进行仿真分析。以ER3A-C60机器人为例,分析了它的正运动学、逆运动学和轨迹规划问题。利用Robotics toolbox和D-H参数建模方法,建立该机器人的运动学模型,进行该机器人轨迹规划的仿真,得到机器人关节角、角速度、角加速度随时间变化曲线,验证该机器人参数的合理性.     

集装箱波纹折线焊缝的三自由度焊接机器人逆运动学分析

针对集装箱波纹折线焊缝的焊接难题,设计了一种三自由度焊接机器人.本文在D-H齐次变换矩阵的基础上,对焊接机器人进行运动学逆解.机器人通过3个关节的协调动作,可使固联在末端效应器上的焊枪保持一定的焊接姿态,为保证焊接质量的一致性提供了理论基础.通过Matlab软件仿真,控制各个关节按照给定规律运动,在Matlab环境下实现了恒定焊接速度下的轨迹的跟踪.     

马鞍形焊缝焊接质量控制研究现状

马鞍形焊缝自动化焊接工艺复杂,焊缝定位困难,要保证这种复杂的空间曲线焊缝的焊接质量难度大。从焊接方法、焊接工艺以及焊缝的轨迹跟踪识别几个方面对其焊接质量的控制现状进行了阐述和分析,介绍了常用的自动化焊接方法、复杂空间曲线焊缝的焊接工艺、近年焊缝的定位识别研究进展,并对马鞍形焊缝焊接质量控制问题进行了展望。     

马鞍形曲线自动焊接四轴联动插补算法

介绍了一种马鞍形曲线自动焊接系统的工作原理、系统结构、插补算法和仿真结果.设计了具有τ,γ,ρ,σ四自由度的马鞍形曲线自动焊接系统结构,通过四轴联动控制,控制焊枪运动轨迹和姿态,实现马鞍形曲线焊缝的自动焊接.在对系统运动学模型的分析基础上,利用四轴联动及空间解析几何原理,建立了马鞍形曲线焊接时的轨迹和焊枪姿态控制的数学模型,提出了马鞍形曲线自动焊接四轴联动插补算法.对马鞍形曲线实例进行了算法的仿真分析.结果表明,算法具有理想的轨迹控制精度和姿态控制精度,实现了马鞍形曲线的直接插补.     

工业机器人运动学分析和轨迹拟合研究

为更好地控制工业机器人进行精准的作业,以Puma560工业机器人为例,运用D-H表示法对工业机器人的结构和连杆参数进行分析,建立运动学方程。利用三次多项式插值方法规划出机器人关节角的运动轨迹。在分析了工业机器人运动学模型的基础上,提出了一种通过对机器人轨迹拟合计算表示机器人关节运动精度和机器人运动精度的方法,为后续提高机器人运动精度研究提供了理论依据。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。