基于轨迹灵敏度的负荷参数辨识范围调整方法

实践表明,参数辨识范围的选取对参数的辨识效果影响很大。在分析负荷模型参数对所吸收功率的轨迹灵敏度的基础上,提出了负荷模型参数辨识范围的调整方法。首先根据动态过程中轨迹灵敏度的大小选择要调整的参数对象,然后进一步依据动态轨迹灵敏度的变化特点调整参数的辨识范围,从而达到提高负荷辨识精度的目的。实际例子充分表明了这种方法的有效性。     

从实测轨迹提取知识时的困难及展望

分析实测轨迹可提供的知识,并按对模型依赖的程度分类。强调在不依赖系统模型的前提下,提炼受扰轨迹信息的重要性。归纳先对实测轨迹降维再提取知识的思路,即利用保稳降维变换将多机轨迹模态的时域识别任务转化为单机的对应问题。采用时频分析方法提取映象单机轨迹的时变特征,并研究轨迹降维及时变因素的影响。指出应该采用可信度校验,在轨迹时变性过强的场合给出提示。指出模型与参数的校核关键是建立随着轨迹动态特征的差异程度而单调变化的指标,进而通过其灵敏度搜索收敛到真值附近。     

具有运动时间约束的机械手最优平滑轨迹规划

为了提高机械手在指定时间内完成运动任务的平滑性,提出一种最优平滑轨迹规划方法.采用七次B样条曲线插值关节位置序列,保证关节加加速度连续且关节启停速度、加速度和加加速度可设定.将运动学约束转化为B样条曲线控制顶点约束,以加加速度平方积分的最小值作为平滑性能指标,采用遗传算法对平滑性能指标和相应的时间节点向量全局寻优,进而规划出最优平滑轨迹,解决了现有平滑轨迹规划方法没有考虑加加速度累积效果和运动学、运动时间约束的问题.实验结果表明,该方法规划的轨迹具有加加速度平滑和加加速度累积最小的特点,与现有的三次样条轨迹相比,可有效降低轨迹跟踪误差.     

Third-order trajectory planning for high accuracy point-to-point motion

This article studies a third-order trajectory planning method for point-to-point motion. All available instances for third-order trajectory planning are first analyzed. To distinguish those, three criteria are presented relying on trajectory characteristics. Following that, a fast preprocessing approach considering the trajectory as a whole is given based on the criteria constructed and system constraints. Also, the time-optimality of the trajectory is obtained. The relevant formulas are derived with the combination of geometrical symmetry of trajectory and area method. As a result, an accurate algorithm and its implementation procedure are proposed. The experimental results show the effectiveness and precision of the proposed method. The presented algorithm has been applied in semiconductor manufacturing equipment successfully. __________ Translated from Journal of Huazhong University of Science and Technology (Natural Science Edition), 2007, 35(12): 58–61 [译自: 华中科技大学学报 (自然科学版)]     

计算机辅助平面尺寸孔轴公差计算

公差设计是平面尺寸链设计中的重点和难点其中有孔轴公差计算,具有较多设计方法且计算量大.针对此问题开发出一套基于Visual C.net的软件程序,集各种设计方法于一身,便于选择最适合的设计方法,并减少了人工计算量.     

基于虚拟仪器的微孔钻削在线监测自动控制系统

为防止微孔钻削过程中钻头折断,开发了基于虚拟仪器的微孔钻削在线监测系统.该系统能够完成主轴电动机电流信号的采集、数据处理、存储显示以及报警退刀等操作.具有硬件结构简单、监测精度高、抗干扰能力强等优点.实验结果表明,应用该系统进行微孔钻削在线监测,可以有效避免微钻头的折断,提高钻头的利用率.     

First-principles study of H2 adsorption on the pristine and oxidized (8,0) carbon nanotube

The effect of oxygen, hydrogen, and (oxygen + hydrogen) molecules adsorption on the structural and electrical properties of (8,0) carbon nanotube (CNT) are investigated through density functional theory. The obtained results indicate endothermical chemisorption of O₂ on the nanotube surface with a large binding energy of about 598 meV and a significant charge transfer of about 0.43 e per molecule. It is discussed that the O₂ chemisorption creates hole carries in the (8,0) carbon nanotube and thus increases the work function of the system. In the case of hydrogen molecule, a weak physisorption on the surface of CNT (∼−5 meV) is identified. The adsorption of H₂ on CNT is also accompanied by hole doping and increment of the work function of the CNT, while the charge transfer between CNT and H₂ is negligible. The band offsets in the H₂-CNT junction are calculated to examine and describe the observed hole doping in this system. The effect of oxygenation of CNT on hydrogen adsorption is also investigated and the most favorable adsorption configuration is found and the related adsorption energy is calculated. It is argued that the oxygenation of CNT enhances the physisorption of hydrogen molecules. It is shown that hydrogen molecule adsorption on the oxidized CNT cancels hole doping and hence decreases the work function of the system.     

平面六杆机构式比例积分型纠偏装置的分析

采用解析法和三维软件Solidworks分析了平面六杆机构式比例积分型纠偏装置的机构自由度、运动方式和运动轨迹,阐明了该类型纠偏装置的纠偏原理.     

涡流检测对比试样的作用

阐述了涡流检测对比试样的作用,通过对比试验说明了试样中两种类型的人工缺陷（通孔和槽形）的优缺点和槽形人工缺陷相位信号与钢管制造过程中容易产生的表面缺陷信号更相似。在普遍采用通孔的情况下,建议在试样上加工槽形人工缺陷与通孔进行对比以提高检测质量。     

Optimal Control Timing Search of Xenon Oscillations in Large PWRs Using a Characteristic Ellipse Trajectory Based on Three Axial Offsets

We have proposed a simplified control procedure for axial xenon oscillations in large PWRs based on a characteristic ellipse trajectory method. However, this procedure cannot guarantee that the desired control rod position can be achieved when the xenon oscillation is terminated. In a previous paper, we proposed an innovative and very simple procedure to generate the trajectory for the predicted oscillation behavior, which can be expressed by trigonometric functions multiplied by an exponential function. By using this prediction capability, it is shown that the optimal control timing can be easily determined to terminate the xenon oscillation at the desired control rod position. The optimal timing is obtained at the intersection or, cross point, of two predicted trajectories, the forward trajectory beginning from the current position and the backward trajectory that is generated based on the desired control rod position. Since the trajectories are calculated by simple trigonometric functions and an exponential function, the prediction takes only a few seconds using a PC.