直升机传动系统扭转振动特性分析

传动系统扭转振动是直升机研制过程中必须考虑的一个动力学问题。本文通过分析计算，回答在改型设计中“增装的液压泵与交流发电机对原型直升机传动链的扭转振动特性是否会带来不利影响”的问题。采用阻抗匹配法进行分析，导出各子系统的动刚度表达式，对Ｘ型直升机传动系统扭转振动特性进行分析计算，并与原型机进行比较。     

一种新型并联灌注机器人运动学分析和多目标优化

针对大型航天器蜂窝结构灌注需求,提出一种新型串并混联灌注机器人机构,主要对并联机构进行分析研究。首先,对3PSS-PU并联机构进行了运动学分析,建立了运动学反解数学模型和雅可比矩阵;其次,确定了影响机构工作空间主要因素的约束条件,求解出了机构的工作空间;然后,建立了机构的刚度模型,求得机构在运动过程中的刚度变化分布;最后,利用遗传算法,以工作空间和全局刚度为目标对机构结构参数进行优化分析,确定了最终的机构尺寸参数,为蜂窝灌注机器人应用奠定基础。      

Modeling the solar cosmic ray event of 13 December 2006 using ground level neutron monitor data

In order to understand the physics under extreme solar conditions such as those producing ground level enhancements of solar cosmic rays, it is important to use accurate and reliable models. The NM-BANGLE Model is a new cosmic ray model which couples primary solar cosmic rays at the top of the Earth’s atmosphere with the secondary ones detected at ground level by neutron monitors during GLEs. This model calculates the evolution of several GLE parameters such as the solar cosmic ray spectrum, anisotropy and particle flux distribution, revealing crucial information on the energetic particle propagation and distribution. The total output of the NM-BANGLE Model is a multi-dimensional GLE picture that gives an important contribution to revealing the characteristics of solar energetic particle events recorded at ground level. In this work, the results of the NM-BANGLE Model application to the recent GLE of 13 December 2006 are presented and discussed. Moreover, a comparison with the extreme event of 20 January 2005 (GLE69) has been realized.     

Using GPS-SCINDA observations to study the correlation between scintillation,total electron content enhancement and depletions over the Kenyan region

This paper presents the first results of total electron content (TEC) depletions and enhancement associated with ionospheric irregularities in the low latitude region over Kenya. At the low latitude ionosphere the diurnal behavior of scintillation is driven by the formation of large scale equatorial depletions which are formed by post-sunset plasma instabilities via the Rayleigh–Taylor instability near the magnetic equator. Data from the GPS scintillation receiver (GPS-SCINDA) located at the University of Nairobi (36.8°E, 1.27°S) for March 2011 was used in this study. The TEC depletions have been detected from satellite passes along the line of sight of the signal and the detected depletions have good correspondence with the occurrence of scintillation patches. TEC enhancement has been observed and is not correlated with increases in S₄ index and consecutive enhancements and depletions in TEC have also been observed which results into scintillation patches related to TEC depletions. The TEC depletions have been interpreted as plasma irregularities and inhomogeneities in the F region caused by plasma instabilities, while TEC enhancement have been interpreted as the manifestation of plasma density enhancements mainly associated with the equatorial ionization anomaly crest over this region. Occurrence of scintillation does happen at and around the ionization anomaly crest over Kenyan region. The presence of high ambient electron densities and large electron density gradients associated with small scale irregularities in the ionization anomaly regions have been linked to the occurrence of scintillation.     

大变形柔性铰链的静刚度分析及应用

大变形柔性铰链可由弹性较大的橡胶材料制成,而橡胶材料的应变-应力关系不符合胡克定律,其关系可由应变-能量函数关系式导出,为此,采用Mooney-Rivlin模型对形变能量函数进行简化,通过适当选取材料常数的比值,对其非线性的应力-应变关系进行分段线性化,导出圆角型柔性铰链在大变形时转角刚度的近似计算公式.通过有限元仿真对近似计算公式进行了验证.在此基础上,应用大变形柔性铰链构造扑翼式微型飞行器中的柔性胸腔,由转动电机作为驱动器,利用柔性铰链的变形实现翅膀的扇翅运动,实际应用效果表明可有效增大扇翅角并提高能量利用率.     

小突片强化混合研究

测试了亚声速 （Ｍａ＝ ０．３５） 下小突片 （Ｔａｂｓ） 对轴对称收缩喷管射流的强化混合效果, 并探讨了小突片安装个数、后倾角度、堵塞比等因素对强化混合作用的影响。结果表明, 小突片对喷管射流的混合具有显著的强化作用, 不仅使下游流场发生显著变形, 使核心流的衰减显著加快（核心流长度从５Ｄ 降至大约１．５Ｄ）, 还使引射系数显著增加（本文中最大增加到２．７ 倍）。     

齿轮减速器系统可变固有特性动力学研究

考虑到齿轮传动啮合刚度的波动和传动误差的影响以及轴承支撑刚度的作用,对二级齿轮减速器传动系统进行了理论建模和动态响应分析,并与实验结果进行了比较。结果表明,齿轮传动在单齿啮合区和双齿啮合区之间啮合刚度变化较大;减速器系统的动态特性 (固有频率、固有振型、阻尼等 )随啮合周期而发生变化,呈现出一种可变的动态固有特性。故对于系统进行研究时,可分别按单齿区和双齿区平均啮合刚度进行分析,一般可以满足实际工程要求。     

轴系刚度对新型空气动力负载模拟器的影响

新型空气动力负载模拟器是在传统的电液负载模拟器上增加一个位置同步马达,补偿由舵机主动转动产生的位置扰动。理论和实验研究表明 ,由于同步马达与加载马达之间,舵机马达与加载马达之间不可避免地存在机械连接环节 ,即使同步马达与承载马达完全保持位置同步,加载马达轴和壳的相对速度以及多余力矩也不能百分之百被消除。     

卡箍刚度的有限元计算与实验测定

准确确定卡箍刚度对管路系统的振动特性分析具有重要意义。本文针对航空发动机管路系统中不同卡箍的结构特点,建立了计算卡箍刚度的有限元模型。对单管接地卡箍及双管悬地卡箍的刚度系数进行了有限元计算,还对一典型双管悬地卡箍刚度进行了实验测定。通过卡箍刚度计算结果与实验结果的对比表明,本文建立的卡箍刚度计算方法可用于管路系统振动特性分析工程实际之中。      

基于比刚度最大的球铰接杆式支撑臂参数设计

球铰接杆式支撑臂的构型参数设计决定了支撑臂的质量、收拢包络尺寸、刚度和强度等特性。文章提出了一种基于球铰接杆式支撑臂展开后比刚度最大的构型参数设计方法,利用MATLAB和ANSYS联合仿真,分析了不同构型参数组合下支撑臂比刚度的变化规律。结果表明,对于20~100m范围内的球铰接杆式支撑臂,纵梁与横杆的长度比及套筒半径的优选范围随支撑臂总长度增加而增加。当支撑臂总长度分别为20m、60m和100m时,对应的套筒半径优选范围分别为0.3~0.4m、0.5~0.7m和0.6~0.9m。提出了基于比刚度最大的支撑臂参数设计流程。利用提出的设计方法对SRTM任务中球铰接杆式支撑臂进行了构型参数设计,设计结果与ADAM杆构型参数相近,表明设计方法正确、可行。