基于手眼关系的机器人TCP自标定方法

双目视觉系统和机器人在焊接中的结合使用,可以对焊缝进行实时追踪,以提高焊接质量。而机器人末端工具(焊枪)的中心点(TCP)作为机器人的实际运动轨迹,其标定精度直接影响机器人作业质量。针对该问题,以双目测量为基础,结合手眼关系和成像对称性的特点,提出了一种基于手眼关系的机器人TCP参数快速标定的方法。通过在机器人实验平台上与四点法进行对比实验,验证该标定方法的正确性和有效性。在不增加成本的同时,完成了TCP的快速、正确标定,满足了实际工业生产中机器人末端工具参数的标定需求。     

基于纠偏与示教相结合的机器人自动焊接跟踪

主要分析了一种将纠偏与示教相结合的对焊缝进行跟踪的方法,通过该方法可使机器人实现自动焊接。基于传统的示教机器人,采用激光传感器对示教路径和实际路径的偏差进行测量。根据所测得的偏差及示教路径,通过控制器调整焊枪的位置及方向以实现焊缝跟踪。利用激光传感器和六自由度的机器人进行实验系统的设计,并对本研究的方法进行验证,实验结果证明该方法是有效的。     

成捆圆钢端面标牌自动焊接系统的研究

为实现成捆圆钢端面标牌焊接的自动化,设计一套以双目视觉测量引导的基于工业机器人的标牌自动焊接系统。整个系统主要由工业机器人、双目视觉识别系统、焊钉送料系统、标牌制备系统、末端操作器、控制系统等构成。双目识别系统采用双目相机扫描成捆圆钢端面,得到焊接位置坐标;焊钉供料系统实现焊钉的分料传送,标牌制备系统通过激光打标机将圆钢生产信息制作在标牌上,并将标牌输送到指定位置;末端操作器由工业机器人带动实现焊钉与标牌的抓取、定位焊接以及掰断焊钉尾部等操作;焊接控制系统中工控机与机器人、PLC、双目视觉测量系统等进行通信,完成标牌焊接的自动化流程。     

基于线结构光的型钢自动焊接位置检测技术

摘要： 针对现有H型钢现场焊接过程中多为人工焊接、劳动强度大、操作环境恶劣且人工测量随意性大等问题,提出了一种基于视觉与图像处理的型钢自动焊接位置检测技术。该技术主要基于线结构光测量法来实现对型钢轮廓的检测从而确定焊接位置,利用激光线的位置确定焊缝位置,结合焊接机器人达到自动焊接的目的。先利用张正友标定法获得相机内参数和畸变系数,再通过最小二乘法拟合激光平面的方法实现激光平面的标定,结合两者实现整个测量系统的标定,然后基于OpenCV编程接口实现图像处理,最后利用ABB机器人工具坐标系对该测量方法的检测精度进行评价。针对检测点深度方向坐标误差较大问题提出一种误差拟合方法,应用此方法进行多种型号H型钢测量试验。试验结果表明,采用上述方法标定后的线结构光视觉测量系统测量误差小于1 mm,达到了较高的标定精度,明显降低了坐标误差,能够满足焊接使用要求。 创新点： 利用标准量块提出一种误差拟合方法,可有效降低坐标误差。     

六自由度工业机器人本体标定实验的研究

目前六自由度工业机器人普遍具重复定位精度较高,但绝对定位精度较低的特性,所以为了提高离线编程的精度,需要通过运动学建模、实际测量、参数辨识、误差补偿四步进行机器人本体标定。文中在概括总结现有的工业机器人本体标定技术的基础上,运用MATLAB进行运动学仿真建模,Leica AT960绝对激光跟踪仪系统进行实际测量,SA软件实现参数辨识,外部控制器进行关节补偿,完成本体标定实验。并在此基础上,按照GB/T12642-2013进行标定前后机器人位姿特性检测,通过Robot Check软件处理检测数据,对比前后结果,验证了本体标定实验。     

直角坐标机器人迭代滑模交叉耦合控制器设计

为克服机械惯性、负载扰动以及复杂的轮廓误差模型等因素对三轴直角坐标机器人末端执行器位姿精度的影响,设计了一种迭代滑模交叉耦合控制器。其中:滑模速度控制器用以抑制非周期干扰;迭代学习位置控制器用以减小跟踪误差;轴间变增益交叉耦合控制器用以消除轮廓误差。通过仿真验证了上述复合控制器的性能。结果表明,所设计的迭代滑模交叉耦合控制器具有较高的轮廓精度和较强的鲁棒性。     

基于空间直线约束的焊接机器人手眼标定

视觉传感器与焊接机器人的标定是焊接智能化应用中的重要问题,针对末端夹持线结构光传感器的焊接机器人,提出了一种基于空间直线约束的手眼标定方法.首先任意变换机器人位姿使线结构光传感器投射出的光平面与标定模板相交,然后通过特征点提取算法提取出线结构光与直线的交点,并基于直线约束建立了非线性优化模型,最后结合罚函数法与改进的Powell算法同时求解传感器位置与方向参数.基于上述方法进行了一系列试验,结果表明,该方法通用性强,适合现场标定,有效的提高了标定精度,标定精度在0.2 mm以内.     

平面三自由度欠驱动机器人末端的位置控制

对平面3R欠驱动机器人末端的位置控制问题进行了研究,基于分层模糊控制思想,将欠驱动机器人的末端运动分解为沿x,y轴上的运动,根据两个运动变量分别与各个主动关节耦合的情况,制定简单的模糊控制规则,设计对应的糊控制器,第一个主动关节与第二个主动关节的控制力矩通过对两运动变量控制后的模糊控制器的输出变量进行加权求和得到。最后利用matlab与adams联合仿真以及实验,精确地实现了平面三自由度欠驱动机器人在操作空间中末端点到点的任意位置控制。结果表明,此方法在实现平面三自由度欠驱动机器人位置控制方面具有良好的效果。     

焊接机器人系统标定技术研究现状北大核心

焊接机器人系统的标定是提升焊接智能化水平、提高焊接效率以及保证焊接质量的前提条件。对于焊接机器人系统标定技术的研究,国内外众多学者已开展了大量卓有成效的研究工作。根据标定对象的不同,将焊接机器人系统标定分为焊接机器人本体标定、工具标定、工件标定以及协作系统标定四大类。在简要介绍各自标定原理及具体方法的基础上,提出了现有标定技术的不足和今后的发展趋势,以期促进焊接机器人系统标定技术得到进一步的发展和应用。     

基于神经网络的打磨机器人的力/位混合控制

针对封头打磨机器人在工作过程中末端执行器轨迹跟踪和恒力控制要求与打磨机器人在封头上行走的振动抑制问题,提出一种基于神经网络的力/位混合控制方法。采用力/位混合控制器完成打磨机器人力和位置的同时控制要求。针对打磨机器人平台行走过程产生的振动干扰,设计神经网络鲁棒控制器,通过神经网络对系统参数误差和振动干扰进行抑制。仿真结果显示,该混合控制器不仅能保证打磨机器人末端执行器位置的精确控制和有效的恒力控制,而且对外界振动干扰有很好的抑制效果。     

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).     

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.     

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.     

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。