基于点球约束的机器人误差建模与参数辨识

自动化装配对于机器人绝对定位精度提出了更高的要求,机器人理论位姿和实际位姿总存在一定的误差,若绝对定位精度过低,容易导致装配过程中零部件之间发生碰撞,严重影响装配机器人的应用与推广。为此,提出了一种基于点球约束的机器人误差建模与参数识别方法:1)通过在机器人末端安装的6维力传感器反馈末端受力情况,控制机器人以多种姿态使标定锥与靶标球球面重合,记录接触时各关节的位置数据;2)以靶标球球体半径为适应度函数,利用遗传算法辨识误差参数,从而建立完整的误差补偿模型。以自主研制的7自由度装配机器人为研究对象,针对装配机器人的结构特点,由正向递推建立机器人的正运动学方程,应用固定关节法与反变换法获得机器人逆运动学方程;建立机器人的运动学误差模型,预设定误差参数与位姿变换矩阵,通过牛顿迭代法获取了关节变量值,利用遗传算法进辨识误差参数,将辨识结果代入运动学模型中进行验证。采用点球式标定方法采集机器人关节数据,应用遗传算法辨识误差参数,将所得参数代入误差模型中进行实验,结果表明,绝对定位精度提升了76.74%,验证了基于点球约束的机器人误差建模与参数识别方法的有效性,为多自由度机器人标定研究提供了有益参考。

人际关系对大学生锻炼行为的影响:运动氛围与锻炼自我效能感的链式中介效应

基于自我扩散理论,探索校园人际交往中大学生锻炼行为的形成机制。采用人际关系量表、体育锻炼等级量表、运动氛围量表和身体锻炼自我效能感量表,对1308名大学生进行在线问卷调查。借助spss26.0软件包进行独立样本T检验、单因素方差分析、皮尔逊积差相关、Harman单因素共同方差偏差校验,以及Process宏程进行Bootstrap中介效应检验等。结果表明:人际关系与锻炼行为、运动氛围和锻炼自我效能感均呈显著正相关(P<0.01);人际关系显著正向预测运动氛围和锻炼自我效能感(P<0.01),运动氛围正向预测锻炼自我效能感(P<0.01),人际关系、运动氛围、锻炼自我效能感正向预测大学生锻炼行为(P<0.01);运动氛围和锻炼自我效能感在人际关系影响大学生锻炼行为间起到链式中介作用,中介效应数值和占比别为0.076(15.96%)。因此,人际关系可以通过运动氛围和锻炼自我效能感间接预测大学生体育锻炼行为。

Sedimentology and Paleoenvironmental Characteristics of Fine-grained Sediments in Coal-bearing Strata in the Eastern Ordos Basin:A Case Study of the Exploratory Well in the Zizhou Area

The continuously collected cores from the Permo-Carboniferous coal-bearing strata of the eastern Ordos Basin are essential for studying the hydrocarbon potential in this region.This study adopted sedimentological and geochemical methods to analyze the sedimentary environment,material composition,and geochemical characteristics of the coal-bearing strata.The differences in depositional and paleoclimatic conditions were compared;and the factors influencing the organic matter content of fine-grained sediments were explored.The depositional environment of the Benxi and Jinci formations was lagoon to tidal flat with weakly reduced waters with low salinity and dry-hot paleoclimatic conditions;while that of the Taiyuan Formation was a carbonate platform and shallow water delta front,where the water was highly reductive.The xerothermic climate alternated with the warm and humid climate.The period of maximum transgression in the Permo-Carboniferous has the highest water salinity.The Shanxi Formation was deposited in a shallow water delta front with a brackish and fresh water environment and alternative weak reductiveness.And the paleoclimate condition is dry-hot.The TOC content in fine-grained samples was averaging 1.52%.The main controlling mechanism of organic matter in this area was the input conditions according to the analysis on input and preservation of organic matter.

A theoretical and deep learning hybrid model for predicting surface roughness of diamond-turned polycrystalline materials

Polycrystalline materials are extensively employed in industry.Its surface roughness significantly affects the working performance.Material defects,particularly grain boundaries,have a great impact on the achieved surface roughness of polycrystalline materials.However,it is difficult to establish a purely theoretical model for surface roughness with consideration of the grain boundary effect using conventional analytical methods.In this work,a theoretical and deep learning hybrid model for predicting the surface roughness of diamond-turned polycrystalline materials is proposed.The kinematic–dynamic roughness component in relation to the tool profile duplication effect,work material plastic side flow,relative vibration between the diamond tool and workpiece,etc,is theoretically calculated.The material-defect roughness component is modeled with a cascade forward neural network.In the neural network,the ratio of maximum undeformed chip thickness to cutting edge radius RT S,work material properties(misorientation angle θ_(g) and grain size d_(g)),and spindle rotation speed n s are configured as input variables.The material-defect roughness component is set as the output variable.To validate the developed model,polycrystalline copper with a gradient distribution of grains prepared by friction stir processing is machined with various processing parameters and different diamond tools.Compared with the previously developed model,obvious improvement in the prediction accuracy is observed with this hybrid prediction model.Based on this model,the influences of different factors on the surface roughness of polycrystalline materials are discussed.The influencing mechanism of the misorientation angle and grain size is quantitatively analyzed.Two fracture modes,including transcrystalline and intercrystalline fractures at different RTS values,are observed.Meanwhile,optimal processing parameters are obtained with a simulated annealing algorithm.Cutting experiments are performed with the optimal parameters,and a flat surface finish with Sa 1.314 nm is finally achieved.The developed model and corresponding new findings in this work are beneficial for accurately predicting the surface roughness of polycrystalline materials and understanding the impacting mechanism of material defects in diamond turning.

基于注意力胶囊网络的家庭活动识别

本文提出了一种注意力胶囊网络的新框架利用录音识别家庭活动.胶囊网络可以通过动态路由算法来选择基于每个声音事件的代表性频带.为了进一步提高其能力,我们在胶囊网络中加入注意力机制,它通过加权来增加对重要时间帧的关注.为了评估我们的方法,我们在声学场景和事件的检测和分类(Detection and Classification of Acoustic Scenes and Events, DCASE)2018挑战任务5数据集上进行测试.结果表明, F1平均得分可达92.1%,优于几个基线方法的F1得分.

增量式数字阀控缸位置控制系统动态性能分析及实验研究

液压伺服控制系统具有功重比大、精度高和响应快等优点,在工业、农业、轻纺织业和交通运输中应用广泛。液压伺服控制系统多采用伺服阀和比例阀作为控制元件,但伺服阀和比例阀的结构复杂、造价高,对油液质量和清洁度要求高。而增量式数字阀具有结构简单、成本低、抗污染能力强且维护方便等优势,在液压伺服控制系统中具有较好的应用前景。以增量式数字阀控缸位置控制系统为研究对象,首先,对增量式数字阀的结构和工作原理进行分析,建立其位置控制系统数学模型,并基于MATLAB/Simulink仿真平台搭建了其位置控制系统仿真模型;然后,利用仿真分析典型输入信号和不同结构参数下增量式数字阀控缸位置控制系统的动态性能;最后,搭建增量式数字阀控缸位置控制系统实验平台,测试了典型输入信号和不同结构参数下的动态性能。通过仿真与实验相结合,验证了增量式数字阀原理的可行性,分析了增量式数字阀控缸位置控制系统的动态响应能力,并对影响其动态响应能力的因素进行分析,为增量式数字阀的后续结构改进和动态性能优化提供了理论和实验基础。

基于节点块序列约束的局部贝叶斯网络结构搜索算法

针对K2算法过度依赖节点序和节点序搜索算法评价节点序效率较低的问题,提出一种基于节点块序列约束的局部贝叶斯网络结构搜索算法,该算法首先通过评分定向构建定向支撑树结构,在此基础上构建节点块序列,然后利用节点块序列确定每个节点的潜在父节点集,通过搜索每个节点的父节点集构建网络结构,最后对该结构进行非法结构修正得到最优贝叶斯网络结构.利用标准网络将算法与几种不同类型的改进算法进行对比分析,验证该算法的有效性.

相似性与结构平衡论结合的符号网络边值预测

针对传统社会网络中基于相似性的链接预测算法在预测准确率和计算复杂度上难以均衡,且无法直接应用于符号网络的问题,为了实现符号网络中的链接预测与符号预测双重目标,提出一种基于相似性与结构平衡理论的符号网络边值预测方法(PSNBS)。首先,结合符号网络拓扑特征和最优步长的选择,有效融合属性相似性和路径结构相似性,定义了两节点基于结构平衡理论的2-step相似度和3-step相似度。其次,考虑到不同步长的路径对于两节点相似性的不同贡献程度,引入可调步长影响因子,并在此基础上定义了两节点基于平衡论的边值预测得分。得分的绝对值度量了两节点的相似程度,即未来链接建立的概率;得分的正负即为未来链接的符号预测结果。再次,针对边值预测得分为0的特殊情况,引入节点负密度的概念,采用节点的度特征进行符号预测。最后,依据边值预测得分和节点负密度完成链接预测和符号预测。以、和为评价标准,在多个数据集上进行了实验。结果显示了所提算法的有效性和强健性,对于未来链接预测以及已有边的符号预测均能达到较高的预测准确率。此外,与经典的符号预测CN和ICN算法的实验对比分析显示,PSNBS算法符号预测准确率更高。

一种新型SGOI SiGe异质结双极型晶体管

为了改善SiGe异质结双极型晶体管(HBT)的电学特性和频率特性,设计了一种新型的SGOI SiGe HBT。在发射区引入了双轴张应变Si层。多晶Si与应变Si双层组合的发射区有利于提高器件的注入效率。利用Silvaco TCAD软件建立了二维器件结构模型,模拟了器件的工艺流程,并对器件的电学特性和频率特性进行了仿真分析。结果表明,与传统的SiGe HBT相比,新型SGOI SiGe HBT的电流增益β、特征频率fT等参数得到明显改善,在基区Ge组分均匀分布的情况下,β提高了29倍,fT提高了39.9%。

THE 3-D BOUNDARY ELEMENT METHOD OF ROLLER BEARING BY PLATE ELEMENT ANALOGUE

The mill roller bearing is made up of an internal ring, middlerolls and an external ring, the analysis of which is a multi-bodiescontact problem. In this paper, based on the three-dimensionalelastic contact BEM without friction, and using the structuralcharacteristics of roller bearings, middle rolls are de- scribed byelastic plate units of different shapes, which is placed on theinternal ring.

Multi-resolution image segmentation based on Gaussian mixture model

Mixture model based image segmentation method, which assumes that image pixels are independent and do not consider the position relationship between pixels, is not robust to noise and usually leads to misclassification. A new segmentation method, called multi-resolution Ganssian mixture model method, is proposed. First, an image pyramid is constructed and son-father link relationship is built between each level of pyramid. Then the mixture model segmentation method is applied to the top level. The segmentation result on the top level is passed top-down to the bottom level according to the son-father link relationship between levels. The proposed method considers not only local but also global information of image, it overcomes the effect of noise and can obtain better segmentation result. Experimental result demonstrates its effectiveness.

End-to-end rate-based congestion control with random loss:convergence and stability

The convergence and stability analysis for two end-to-end rate-based congestion control algorithms with unavoidable random loss in packets are presented, which can be caused by, for example, errors on wireless links. The convergence rates of these two algorithms are analyzed by linearizing them around their equilibrium points, since they are globally stable and can converge to their unique equilibrium points. Some sufficient conditions for local stability in the presence of round-trip delay are obtained based on the general Nyquist criterion of stability. The stability conditions can be considered to be more general. If random loss in the first congestion control algorithm is not considered, they reduce to the local stability conditions which have been obtained in some literatures. Furthermore, sufficient conditions for local stability of a new congestion control algorithm have also been obtained if random loss is not considered in the second congestion control algorithm.

Supercapacitor characteristic of La-doped Ni(OH)_2 prepared by electrodeposition

Samples of lanthanum-doped nickel hydroxide were prepared by electrodeposition method. The structure and electrochemical properties of the samples were studied by X-ray diffraction and a home-made open three-electrode cell system,respectively. The results show that the deposition process of Ni(OH)2 and La(OH)3 is mainly controlled by electrochemical polarization,which makes it easy to form uniform fine crystals. In addition,La(OH)3 is not a separate phase and lanthanum ions are doped into Ni(OH)2 crystal la...

Fast recursive algorithm for two-dimensional Tsallis entropy thresholding method

Recently, a two-dimensional （2-D） Tsallis entropy thresholding method has been proposed as a new method for image segmentation. But the computation complexity of 2-D Tsallis entropy is very large and becomes an obstacle to real time image processing systems. A fast recursive algorithm for 2-D Tsallis entropy thresholding is proposed. The key variables involved in calculating 2-D Tsallis entropy are written in recursive form. Thus, many repeating calculations are avoided and the computation complexity reduces to O（L2） from O（L4）. The effectiveness of the proposed algorithm is illustrated by experimental results.

铸造铝合金中的组织异质性对其疲劳性能的影响

铸造铝合金材料被广泛应用于发动机部件、结构材料、齿轮箱、底盘等部件,在使用过程中承受交变应力。准确预测铸铝材料的使用寿命对于部件的安全运转极为重要,因疲劳裂纹而导致的漏油等事故可能产生极为危险的后果。铸铝材料的使用寿命可以通过其铸造缩/气孔的尺寸分布或者尺寸最大的缩/气孔的直径结合裂纹扩展速率公式进行预测。缩孔的深度及相对位置对于应力集中具有重要影响。通常情况下,铸造铝合金的组织主要包括铝基体、共晶硅、富铁相及其他一些第二相颗粒。因这些第二相颗粒开裂而产生的微裂纹会导致铸铝材料疲劳寿命的降低。因此,如何通过显微组织合理预测铸铝材料的疲劳寿命对于铸铝材料的使用极为重要。本文回顾了以往研究中铸造缩/气孔和第二相颗粒等组织缺陷对Al-Si-Mg铸造铝合金疲劳寿命的影响。

NUMERICAL SIMULATION FOR SHAPE OF COLD ROLLING ALUMINUM STRIP ON 4-HIGH MILL WITH ROLL SHIFTED

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Congestion control scheme in ATM networks based on fast tracing-queue

One of the more challenging and unresolved issues in ATM networks is the congestion control of available bit rate （ABR）. The dynamic controller is designed based on the control theory and the feedback mechanism of explicit rates With the given method of a chosen parameter, it can guarantee the stability of the controller and closed loop system with propagation delay and bandwidth oscillation. It needs less parameters（only one） to be designed. The queue length can converge to the given value in the least steps. The fairness of different connections is considered further. The simulations show better performance and good quality of service（QoS） is achieved.

Convergence and stability of the Newton-Like algorithm with estimation error in optimization flow control

The Newton-Like algorithm with price estimation error in optimization flow control in network is analyzed. The estimation error is treated as inexactness of the gradient and the inexact descent direction is analyzed. Based on the optimization theory, a sufficient condition for convergence of this algorithm with bounded price estimation error is obtained. Furthermore, even when this sufficient condition doesn＇t hold, this algorithm can also converge, provided a modified step size, and an attraction region is obtained. Based on Lasalle＇s invariance principle applied to a suitable Lyapunov function, the dynamic system described by this algorithm is proved to be global stability if the error is zero. And the Newton-Like algorithm with bounded price estimation error is also globally stable if the error satisfies the sufficient condition for convergence. All trajectories ultimately converge to the equilibrium point.

Exponential stability for cellular neural networks: an LMI approach

A new sufficient conditions for the global exponential stability of the equilibrium point for delayed cellular neural networks （DCNNs） is presented. It is shown that the use of a more general type of Lyapunov-Krasovskii function enables the derivation of new results for an exponential stability of the equilibrium point for DCNNs. The results establish a relation between the delay time and the parameters of the network. The results are also compared with one of the most recent results derived in the literature.

Margin optimization algorithm for digital subscriber lines based on particle swarm optimization

The margin maximization problem in digital subscriber line（DSL） systems is investigated.The particle swarm optimization（PSO） theory is applied to the nonconvex margin optimization problem with the target power and rate constraints.PSO is a new evolution algorithm based on the social behavior of swarms, which can solve discontinuous, nonconvex and nonlinear problems efficiently.The proposed algorithm can converge to the global optimal solution, and numerical example demonstrates that the proposed algorithm can guarantee the fast convergence within a few iterations.