直达滑模控制

用传统到达条件综合而成的滑模控制系统不能保证所有出发于滑动模态邻域的相轨线都能直接到达邻近的滑动模态分支,导致状态转移过程超调,这对于某些控制工程是不允许的.为使滑模控制过程单向收敛,提出了直达滑模控制方法.通过对传统到达条件表述中的不足的分析,介绍了直达函数的定义和直达条件的建立.直达条件是用直达滑模控制法综合滑模控制系统的依据.直达滑模控制系统由指令模态及开关型直达滑模控制组成.与传统到达条件不同,满足直达条件的控制,可保证所有出发于滑动模态邻域的相轨线都能直接到达邻近的滑动模态分支,沿滑动模态趋向零态,状态转移过程快速而无超调.将直达滑模控制应用于示例系统并进行仿真,仿真结果符合对直达滑模控制性能的预期.      

基于Z网络的升降压DC/DC变换器

基本的非隔离型升降压电路存在由二极管反向恢复带来的短路环问题.设计了一种基于Z网络的升降压DC/DC变换器,从电路结构上避免了短路环的存在,分析了Z网络和变换器的初始态阶跃响应,并设计了预充电电路,消除了变换器启动时的电压和电流尖峰,讨论了工作在电感电流连续模式(CCM, Current Continuous Mode)下的3种开关模态并分析了其工作原理,依照效率最优原则对升压和降压模式的开关模态进行简化,从而优化了变换器的控制方法,提出了一种通过合理选择电感电流纹波系数确保变换器工作在CCM模式下的方法,给出了各元器件的设计规则,并通过仿真和实验加以验证,结果与理论分析相吻合.      

Neck-spinning quality analysis and optimization of process parameters for plunger components: Simulation and experimental study

The plunger component is a key part of the plunger pump in the aircraft hydraulic system. Neck-spinning process is commonly used to fabricate plunger components, of which the quality of the spinning process significantly affects the performance of plunger pumps. One of the bottlenecks faced by the industry in the spinning process is to choose a suitable neck-spinning process so as to ensure the quality of plunger components. It is necessary to propose a reliable method to optimize the process parameters which affect the neck-spinning quality of plunger components. In this study, a calculable finite element analysis (FEA) model is established to simulate the three-roller neck-spinning process of the plunger component, which includes six typical slipper structures, two roller structures, and two spinning parameters. The FEA model is then validated by comparing the simulated spinning forces with the corresponding experimental results. The influence of the process conditions on the neck-spinning quality is investigated. And the orthogonal simulation results are analyzed by a combination of range method and fuzzy mathematical analysis method to recommend a reasonable slipper structure, roller structure and neck-spinning parameters. This study provides a promising method to improve the manufacturing quality of the typical plunger components.     

多用户协作式界面

多用户特征是交互桌面的核心特征.多用户围绕交互桌面进行面对面协作过程中体现出一些新的协作方式,这种体现新型协作方式的界面是一种新型界面设计范型,即“协作式界面”.分析了协作式界面的并发操作等6个特征和5种新型协作方式.在设计方面,提出了协作式界面的设计范型,并采用层次状态机对典型协作方式进行了形式化描述与设计.在实现方面,构建了一套体现上述协作特征和协作方式的控件库,基于该控件库实现了2个示例性应用.最后开展了用户实验,并利用李克特量表对实验进行了统计,结果表明,基于交互桌面的协作式界面设计在决策质量、协同标绘效率、协作可视化能力方面都提高了60%以上,效果显著.      

Data Fusion of Multiple Curvature Mode Shapes for Structural Damage Diagnosis

This study aims to develop a reliable method for locating multiple cracks in a beam using data fusion of multiple curvature mode shapes.The identification of multiple damage in beams based on curvature mode shape has become a research focus in recent decades.However,the curvature mode shape method using a single mode carries limited damage information,and fails to reveal all cracks when multiple damage detection is required.To address this limitation,the curvature mode shape method is further enhanced by a data fusion algorithm to fuse damage information in multiple modes.The effectiveness of the method is proved through a numerical case of a beam with multiple cracks.The applicability of the method is experimentally validated by detecting multiple cracks in a composite laminated beam with mode shapes acquired by a scanning laser vibrometer.The results show that the method of fusing multiple curvature mode shapes carries more complete damage information than the traditional one using a single mode,and can successfully locate all cracks in a damaged beam.     

FASTMast伸展机构屈曲模式的理论分析与试验

针对空间站盘绞式（FASTMast）伸展机构在轨工作的承载与变形特点,从理论角度对以伸展机构后屈曲柔性条作为弹性支承的屈曲模式进行了分析。结果表明：在后屈曲柔性条达到临界刚度之前,伸展机构屈曲模式表现为肘关节运动,与伸展机构对角拉索无关;达到临界刚度之后,屈曲模式表现为欧拉屈曲,而后屈曲柔性条的刚度与其截面惯性矩成正比。通过与试验结果的对比,验证了理论分析的正确性,同时也为其它同类机构的设计和试验提供了参考依据。     

三(叠氮乙酰氧甲基)硝基甲烷的合成与性能

以三羟甲基硝基甲烷为原料,经酯化、叠氮化两步反应合成出三(叠氮乙酰氧甲基)硝基甲烷,总收率为83.0%。利用红外光谱、核磁共振、元素分析表征了其结构。探讨了叠氮化反应的影响因素,确定其最佳反应条件为:Na N3摩尔加入量为理论值的1.10倍,混合溶剂中水占总体积的10%~25%,反应时间1 h。测试得到TMNTA的密度为1.45 g/cm3,热分解温度为235.7℃,玻璃化转变温度为-26.23℃,撞击感度H50=44.7 cm(落锤2 kg),爆炸概率4%(摆角66°)。     

基于多余观测分量的整周模糊度可靠性检验方法

针对常规模糊度检验三步法中存在的错误模糊度整数解漏检的情况,分析了错误整周模糊度、观测值残差及多余观测分量矩阵之间的内在联系,阐述了参考星变化对多余观测分量矩阵主对角线元素的影响,进而提出了一种基于多余观测分量的整周模糊度可靠性检验方法。该方法根据多余观测分量主对角线占优原则实现部分卫星的模糊度可靠性检验。对于多余观测分量主对角线不占优的卫星,利用多余观测分量绝对值最大的情况进行整周模糊度可靠性检验,从而完成所有卫星的模糊度可靠性检验。     

毫米波-太赫兹电子回旋器件的几个基础问题

探索和发展更高频率和更高功率水平的电磁波源是电子器件长期以来的重要发展方向.本文介绍了基于电子回旋脉塞原理发展起来的电子回旋器件,该类器件在毫米波-太赫兹波段具有高功率的优势.系统探讨了电子回旋器件所面临的欧姆损耗、模式竞争以及对强磁场的依赖性等几个基础问题,指出在深入研究模式竞争机理的基础上发展高阶模式和高次谐波系统将有助于推动电子回旋器件实现高功率、高效率和高稳定性,这对促进器件向太赫兹频段发展具有参考意义.