基于Hermite方法的机器人任务空间二阶平滑位姿路径构造

机器人任务空间的路径构造一直是研究者们重点关注的对象，更加平滑的路径对于机器人运动尤为关键。提出一种机器人任务空间二阶平滑位姿构造方法。位姿路径分为位置路径与姿态路径，用直线和圆弧来表示基本的位置路径，用四元数来表示姿态路径。根据环境给定的过渡区域，基于Hermite方法分别构造位置和姿态路径的过渡曲线，并设计高效易懂的数值积分算法实现位姿路径长度的计算，然后综合数值积分和二分法查找算法实现给定路径长度的插值计算。最后，在MATLAB软件上进行数值仿真分析，验证了所提算法在机器人任务空间二阶平滑位姿路径构造方面的有效性。     

基于特殊正交群的工业机器人姿态插补研究北大核心

针对工业机器人因多姿态插补存在的路径不平滑、运动时间过长、速度波动率大等问题,提出了一种基于特殊正交群的机器人多姿态插补方法。首先,采用特殊正交群将获得的姿态转换为其对应的指数坐标,进而将姿态插值问题转换为对向量插值问题;其次,为保证姿态路径的连续性同时减小姿态路径的曲率对速度影响,利用三次非均匀有理B样条(NURBS)曲线和非支配排序遗传算法(NSGA-Ⅱ)以曲率L_(2)范数和长度为优化目标减小姿态路径的曲率和长度;最后,引入S形加减速对生成的姿态路径进行分段自适应加减速控制,结合弦截法和抛物线(Muller)法提出一种参数密化算法完成姿态插补。研究结果表明:与单位四元数的球面四边形插值(Squad)相比,NURBS插值的姿态路径具有C~2连续性;与标准NURBS曲线插补运动相比,优化插补运动时间缩短8.7%;与弦截法相比,所提算法的绝对平均速度波动率降低73%。     

一种高效的机器人自由曲线运动位姿同步规划方法

针对机器人在自由曲线运动中位姿难以同步的问题,提出一种机器人自由曲线运动的位姿规划方法。该方法采用抛物线边界的三次非均匀B样条曲线拟合任意数目的示教点位置,同时采用四次四元数样条曲线拟合示教点姿态。根据示教点将自由曲线分段,以获得速度规划降速点,减少机器振动。对分段位置曲线及姿态曲线采用复化的辛普森积分求得曲线长度及姿态转角;对位置曲线进行七段S形速度规划,并利用位置规划所得的时间对姿态曲线进行速度规划,从而得到速度连续且时间同步的位置及姿态。实验表明该方法可行、高效。     

基于正弦波加速度曲线的机器人圆弧轨迹规划

针对轨迹规划曲线的平滑性进行研究,提出能够保证C2连续的正弦波加速度曲线对圆弧轨迹曲线进行升降速控制,并采用四元数球面线性插值规划机器人末端平滑的圆弧姿态轨迹。最后在六关节搬运机器人上进行仿真与试验,结果表明:运用正弦波加速度曲线进行升降速控制,不仅能够保证C2连续,而且计算量相对较小,能够较好地满足机器人控制的实时性要求。     

桌面级关节型博弈机器人结构设计与性能分析

为探究适合完成博弈任务的桌面级关节型机器人结构,对5R型关节型工业机器人结构及动力系统、控制系统进行改造。通过倍四元数法分析,得到正确的运动学方程;采用拉格朗日法求取力学平衡方程;利用仿真软件估算工作空间;然后设计了PID控制器保证关节电机的转角精度。经仿真实验表明,改造后的桌面级关节型机器人满足博弈任务。     

基于非均匀B样条曲线的机器人轨迹过渡算法北大核心

针对6自由度工业机器人末端轨迹不光顺、衔接速度慢、运动不平稳的问题,提出了一种基于非均匀B样条曲线的过渡模型和对应规划算法。使用5次非均匀B样条曲线,构建了G^(3)连续的空间轨迹过渡模型;根据轨迹过渡的拐角速度约束以及轨迹长度的相互制约关系,提出了自适应的速度前瞻算法;采用四阶龙格库塔-割线法,实现了样条曲线的插补;最后,利用安川HP20D机器人和Leica激光跟踪仪AT960进行实验,测量机器人末端TCP速度和加速度信息。实验结果表明,该过渡算法提升了多段连续轨迹的衔接速度,减小了速度波动,避免加速度突变,实现了机器人的平稳运动。     

一种基于四元数法的焊接工作站协调控制算法

针对6R串联机器人运动学求解计算量大、传统方法求解困难以及涉及多解和奇异性等问题,在普吕克坐标系下描述了刚体运动,建立其四元数数学模型以及6R串联机器人运动学数学模型,求得6R串联机器人运动学逆解。建立工作站中机器人与变位机的协调联动算法模型,包括位置协调算法、速度协调算法以及姿态协调算法,最终得到机器人与变位机的控制程序。并且搭建焊接机器人工作站进行算法的实验验证。     

线激光视觉测量机器人手眼标定方法研究

线激光视觉测量传感器与工业机器人组成三维测量系统时,法兰盘坐标系与摄像机坐标系之间变换关系求解较复杂。为解决此问题,提出一种基于固定参考点的手眼标定算法。该算法以标定球为靶标,根据标定球球心在机器人基坐标系中坐标不变原则,结合机器人运动学位置约束关系建立了矩阵变换方程,并在旋转矩阵求解中引入四元数,简化计算过程,实现机器人手眼标定。通过试验量化分析测头光平面与标定球相交位置对测量结果的影响,验证了该算法的有效性和实用性     

基于改进DE算法的工业机器人时间最优轨迹规划

为提高工业机器人的工作效率,提出一种进行时间最优轨迹规划的新算法。通过对已知任务轨迹的关键点进行运动学反解,求解与之对应的关节空间位置序列,并采用5次非均匀有理B样条曲线构造关节运动曲线,能够保证机器人各关节位置的准确性,实现各关节运动的速度、加速度以及二次加速度的连续性。通过改进差分进化(Differential Evolution简称DE)算法,充分利用不可行解的信息,加强对边界的搜索,增强了算法的全局搜索能力。与遗传算法以及差分进化算法进行比较,利用该算法进行轨迹规划,结果显示该算法的搜索速度更快,所得的数值结果更小。     

基于双机器人协调焊接标定算法

针对双机器人协调焊接任务,对双机器人工具坐标系（TCF）及基坐标系的标定进行研究,提出一种利用四元数法进行位姿坐标表示的工具标定算法以及"基于公共靶标的三点两步法"的双机器人基坐标系标定方案.根据向量的旋转理论,推导出四元数与旋转矩阵的对应转换关系,简化了TCF标定计算.将标定获得的两初始旋转矩阵差值的F-范数作为优化目标函数,利用拉格朗日乘数法进行优化求解,获得双机器人标定的精确值.最后采用上述标定策略进行了TCF标定及双机器人标定试验.结果表明,该方法可有效减少标定误差、提高标定精度.     

对偶四元数在六自由度飞行模拟器的仿真研究

六自由度平台作为飞行模拟器重要的载体,上下平台的坐标变换至关重要。研究对偶四元数在六自由度运动平台的应用,给出对偶四元数在坐标系转换的换算参数,并在MATLAB/SIMULINK中对六自由度运动平台的反解和经典洗出算法进行了仿真验证,证明对偶四元数在六自由度运动平台具有很好的准确性和可靠性,拓展了六自由度平台坐标变换矩阵的选择范围。     

基于立体视觉焊接变形测量系统标定

应用立体视觉三维测量系统对钢结构上若干待测标志点进行测量,测量前分两步对测量系统参数进行标定.首先应用基于平面模板的方法标定摄像机的固有参数,包括单个摄像机的内部参数和两个摄像机间的位置关系参数.其次使用单位四元数法对摄像机坐标系与设计坐标系之间的位置参数进行标定.为了验证标定结果的准确性,对摄像机内参数标定结果进行了重投影误差估算,重投影误差很小,满足系统测量误差要求.对标定结果进行重建试验,重建结果平均误差小于1 mm,最大误差小于2.5 mm.     

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).