振动力矩约束条件下空间机构发动机动平衡优化研究

机构动平衡优化以减小机构惯性造成的机构振动为目的。本文在抽象出摆盘发动机的空间多环RRSSC机构学模型基础上,对其进行自由度分析;根据摆盘发动机结构特点与动力学分析,确定出结构设计变量,考虑到以控制摆盘发动机机座振动和降低噪声为其主要目标,给出了以限定振动力矩下降百分比为约束条件的目标函数,建立动力优化数学模型对其进行优化设计,达到最优动力平衡,所得结果对摆盘发动机的减振降噪与性能提高具有一定的理论与实际意义。     

对随机变量的k-阶矩的讨论

文章从随机变量k-阶矩的定义出发,结合已有的定理推导出一些不等式,进而说明一些相关随机变量k-阶矩存在的条件。     

方向盘回正力矩的动态模拟

在车辆动态模拟的研究中,方向盘回正力矩的动态模拟效果直接影响实验驾驶员的操纵行为,从而影响人-车闭环转向控制系统研究的准确性。文章给出了利用力矩电机作为方向盘回正力矩生成部件进行动态模拟的方法,并对控制系统进行了分析。以捷达车作为实验车进行的动态模拟实验证明系统实时性好,满足动态模拟要求。     

基于组合特征的在线商标图像检索系统设计

提出一种基于组合特征的在线商标图像检索系统设计方法,该方法利用颜色直方图匹配、二维傅立叶形状描述子,及二维傅立叶变换形状描述方法与Zemike矩相结合的组合形状描述子,从粗到细、多层次提取商标图像形状特征,用欧氏距离度量形状相似性。用标准MPEG-7的CE2B图像库和1000多张商标图像库进行检索实验,并与现有方法进行比较,表现出其较好的检索性能。     

Principles and Practice of Scaled Difference Chi-Square Testing

We highlight critical conceptual and statistical issues and how to resolve them in conducting Satorra–Bentler (SB) scaled difference chi-square tests. Concerning the original (Satorra & Bentler, 2001 Satorra, A. and Bentler, P. M. 2001. A scaled difference chi-square test statistic for moment structure analysis. Psychometrika, 66: 507–514. [Crossref], [Web of Science ®] , [Google Scholar]) and new (Satorra & Bentler, 2010 Satorra, A. and Bentler, P. M. 2010. Ensuring positiveness of the scaled chi-square test statistic. Psychometrika, 75: 243–248. [Crossref], [Web of Science ®] , [Google Scholar]) scaled difference tests, a fundamental difference exists in how to compute properly a model's scaling correction factor (c), depending on the particular structural equation modeling software used. Because of how LISREL 8 defines the SB scaled chi-square, LISREL users should compute c for each model by dividing the model's normal theory weighted least-squares (NTWLS) chi-square by its SB chi-square, to recover c accurately with both tests. EQS and Mplus users, in contrast, should divide the model's maximum likelihood (ML) chi-square by its SB chi-square to recover c. Because ML estimation does not minimize the NTWLS chi-square, however, it can produce a negative difference in nested NTWLS chi-square values. Thus, we recommend the standard practice of testing the scaled difference in ML chi-square values for models M ₁ and M ₀ (after properly recovering c for each model), to avoid an inadmissible test numerator. We illustrate the difference in computations across software programs for the original and new scaled tests and provide LISREL, EQS, and Mplus syntax in both single- and multiple-group form for specifying the model M ₁₀ that is involved in the new test.     

On Virginia Woolf’s Literary Experimentation

The paper takes the content of Virginia Woolf’s diary and novel as materials to analyze three of her most important theories which are“subjective vision”,“moment of being”and“character as center”to e...     

矩形载流线圈沿一中线折成直角可看作磁偶极子

从磁偶极子的特点出发,用毕奥-萨伐尔定律、安培力公式和力矩的定义,推导出用磁矩表示的矩形载流线圈沿一中线折成直角的远场及其在均匀磁场中所受的磁力和磁力矩,指出此非平面载流线圈可看作磁偶极子.     

再生制动能量的储能方式分析

再生制动是汽车节能的一项重要举措.目前汽车上常采用的4种再生制动能量储能方式是蓄电池储能、超级电容储能、超高速飞轮储能和液压储能.文章在介绍以上4种储能方式特点的基础上,对比分析了它们的技术参数,总结了当前储能方式的各种方案,并对未来发展趋势进行了预测.     

杆摆中的内力分析

对杆摆中的内力、法向内力矩及切向内力的功深入的分析讨论,从而深化对“刚体”及“细杆”概念和刚体的内力的理解,并纠正一些文献中的错误。     

Disturbance rejection control based on acceleration projection method for walking robots

This paper presents a disturbance rejection scheme for walking robots under unknown external forces and moments. The disturbance rejection strategy, which combines the inverse dynamics control with the acceleration projection onto the ZMP （zero moment point）-plane, can ensure the overall dynamic stability of the robot during tracking the pre-computed trajectories. Under normal conditions, i.e., the system is dynamically balanced, a primary inverse dynamics control is utilized. In the case that the system becomes unbalanced due to external disturbances, the acceleration projection control （APC） loop, will be activated to keep the dynamic stability of the walking robot through modifying the input torques. The preliminary experimental results on a robot leg demonstrate that the proposed method can actually make the robot keep a stable motion under unknown external perturbations.