滚动轴承支承下的转子碰摩故障动力分析、特征提取与智能诊断

针对滚动轴承支承下的转子碰摩故障诊断问题,考虑滚动轴承非线性赫兹接触和轴承径向间隙,建立了含不平衡-碰摩耦合故障的转子-滚动轴承系统动力学模型.应用三维谱图分析碰摩诊断依据和确定频段特征,利用仿真数据获取结构最优的神经网络模型,并对试验碰摩故障数据进行诊断,识别率高达90%以上.计算结果充分表明了建立的动力学模型的有效性,同时,研究结果为有效结合故障机理分析与故障智能诊断提供了新的方法.      

粒子分离器涡流叶片鸟撞击损伤试验

研究粒子分离器涡流叶片受鸟撞击损伤规律,提高粒子分离器抗外物损伤设计能力.通过外物冲击损伤试验方法,研究了模拟鸟撞击粒子分离器涡流叶片的过程.采用瞬态响应测试系统,获得了模拟鸟撞击涡流叶片的应变-时间历程.对采集到的曲线和数据进行了分析.利用三坐标测量仪,测得撞击前后涡流叶片叶型;经过比较计算,得到了涡流叶片的变形.模拟鸟以Ma=0.2速度撞击涡流叶片时,涡流叶片产生了塑性应变,变形很大.      

自适应选择抽取模式的运动估计算法

 提出一种去除运动估计中计算冗余的新方法,该方法与搜索算法结合,通过自适应选择抽取模式去除冗余。首先改进传统的一维梯度下降搜索算法,并提出由梯度下降方向自适应选择不同的抽取模式去除计算运动估计准则时的冗余。实验结果表明,该算法与全搜索以及没有去除计算冗余的梯度下降算法相比,视频质量没有较大影响,但是大大降低了计算量,在视频序列实时处理中有良好的应用前景。     

备件供应保障系统的动力学原理及动态性研究

 针对基层级备件供应保障的供需平衡要求,分析“需求牵引”模式下备件供应保障活动中的反馈控制关系,利用系统动力学分析备件供需系统的动力学数学原理。据此原理建立系统状态空间模型,对备件供应保障系统的动态性进行分析,导出系统达到稳定时关键结构参数的值域,考察物流延迟的存在对系统稳定所产生的影响,并通过系统动力学仿真分析和验证了弱化物流延迟造成的不良影响、恢复系统稳定的条件。在考虑物流延迟的前提下,通过系统动力学仿真对订货周期、订货调整幅度等控制策略进行优化研究。     

Optimization and Sizing for Propulsion System of Liquid Rocket Using Genetic Algorithm

Flight vehicle conceptual design appears to be a promising area for application of the Genetic Algorithm (GA) as an approach to help to automate part of the design process. This computational research effort strives to develop a propulsion system design strategy for liquid rocket to optimize take-off mass, satisfying the mission range under the constraint of axial overload. The method by which this process is accomplished by using GA as optimizer is outlined in this paper. Convergence of GA is improved by introducing initial population based on Design of Experiments Technique.     

On the dynamics of the heliosphere on intermediate and long time-scales

A time-dependent, three-dimensional model of the dynamics of the heliosphere as a result of solar activity and a time-varying local interstellar medium is presented. The model is based on a recent version of the well known ZEUS code and employs parallel processing. It includes the solar and interstellar plasma components as well as neutral atoms, and contains the heliospheric magnetic field in a kinematic fashion. We study the dynamics of the heliosphere due to solar activity on periods of months to years up to the so-called Schwabe (11-year) cycle as well as due to time variations of the local interstellar medium, all of which have drawn increasing attention during recent years, as the significance of their direct or indirect effect on the Earth and its environment is under lively debate.     

Ion dynamics associated with Alfven wave in the near-Earth magnetotail: Two-dimensional global hybrid simulation

Ion dynamics in the near-Earth magnetotail region is examined during periods of fast Earthward flow with a two-dimensional (2-D) global-scale hybrid simulation. The simulation shows that shear Alfven waves are generated at x ∼ −10R_E, where the strong earthward flow is arrested by the dipole field, and propagate along field lines from the equator to both southern and northern polar ionosphere. Non-gyrotropic ion velocity distributions occur where the large-amplitude Alfven waves are dominant. The simulation indicates that the Alfven waves are generated by interaction of the fast earthward flow with the stationary near-Earth plasma. Beam ions are found to be pitch-angle scattered and trapped in the wave field, leading to the non-gyrotropic ion distributions in the high-latitude plasma sheet boundary. In addition, significant particle heating and acceleration are found to occur behind the dipolarization front due to the effect of wave turbulence.     

航天器推进剂晃动与控制系统之间耦合效应的混合型估算方法(英文)

基于等效力学模型理论与计算流体力学技术,提出了一种用于估算航天器中推进剂晃动的力学影响的方法.以计算流体力学技术为依托,建立了晃动的等效力学模型并将其整合为晃动模块,以便在航天器导航控制回路的仿真分析中应用.该模块体现了航天器运动特征参数与推进剂晃动动力响应之间的映射关系,使其在用于分析晃动与控制系统之间的耦合效应时,比直接应用计算流体力学分析软件更为方便.该方法的正确性与优势通过检验算例得到了验证.通过在实例中应用,证明了该方法可方便地用于确定晃动的影响和检验数种防晃设计的有效性.     

带副翼的翼身组合体绕流的 Euler方程解

提出了一种求解带副翼偏转的翼身组合体绕流的Euler 方程计算方法.将对接分区网格与分区求解算法相结合,有效地求解了绕此外形的复杂流动.提出了一种满足通量守恒的内边界耦合条件.数值方法中选用Van Leer 分裂格式离散无粘通量项,并构造了一种限制器(Limiter)函数以保证TVD性质.数值算例表明本文方法是求解带操纵面偏转的翼身组合体绕流的有效方法.     

冗余度机器人动力学容错控制技术研究

就提高冗余度机器人动力学容错能力问题进行了研究.通过优化关节力矩分配椭球,使得该椭球主轴长度的乘积尽可能大,从而动力学容错能力得到改善.基于此,研究了故障状态下的关节力矩再分配算法和实时的动力学容错控制方案.为了减小故障造成的跟踪误差,对PID(Proportional Inteqrated Differential)和变结构控制的仿真效果进行了对比,仿真结果证实了所提算法的有效性和实用性.