Safety margin criterion of nonlinear unbalance elastic axle system

IntroductionAtpresentanewanddevelopingsubject—chaoticdynamicsstartsabroadprospectforanalysisofnonlinearsystem[1～ 5 ].Largerotatingmachineryisatypicalnonlinearnon_autonomoussystem .Thesaferunofrotorsystemisofgreatsignificancetosociallifeandeconomicdevelopment.Thestabilityisthekeytosafeoperation .Thesafestabilityanalysisandcontrolforlargesystemisnotonlyamajorbasicresearchbutalsoisveryimportanttosolvethesafeproblemsinlifeandproduction[6 ,7].Soar,althoughmanymathematicians,mechanistsandengineer…     

求解转子系统突加不平衡响应方法的研究

本文提出并研究了用传递函数分析法求转子系统的突加不平衡响应,讨论了求这一响应的最佳数值积分方法。用本文提出的理论解方法及三种常用的数值积分法:尤拉后差法,纽马克法,及呼伯特法,对一模型转子算例进行了分析计算,结果表明;尤拉后差法最适用于求转子系统的突加不平衡响应。本文提出的传递函数分析法,可以和试验模态分析方法相结合,以求解复杂转子系统的突加不平衡响应。     

Effect of parameters on the rubbing condition of an unbalanced rotor system with initial permanent deflection

A rotor-stator rubbing Jeffcott model of a rotor system with mass unbalance including the mass eccentricity and the initial permanent deflection was set up and the corresponding governing motion equation was derived by d’Alembert principle. Through the analytical method, the rubbing condition was analyzed. Whether the rub would happen and when the rub would happen were well solved. The amplitude of the rotor center was calculated, and the rubbing factor was introduced to determine whether the rub would happen or not for all rotating speeds. Rubbing speeds when rub began to happen were obtained. Parameters such as the mass eccentricity, the initial permanent deflection, damping coefficients, and the phase angle between the mass eccentricity and the permanent deflection were used to analyze their effect on the rubbing condition. Results were obtained and could be used to prevent the rubbing fault or decrease the damage of the rub and diagnose or balance the initial permanent deflection fault.     

照明光瞳非对称性对光刻成像质量的影响

研究了照明光瞳非对称性对光刻成像质量的影响。通过PROLITH软件计算了环形与四极照明条件下,光瞳非对称性对图形位置偏移量、曝光图形内水平线条与垂直线条的宽度差、曝光图形上密集线条与孤立线条之间线宽偏差的影响。研究结果表明,光瞳非对称性主要影响曝光图形的位置偏移量,光瞳非对称性引起的图形位置偏移量与光瞳非对称性的大小成线性关系。根据套刻精度的误差分配原则,计算得到光瞳非对称性的容限为5%。     

非平衡随机效应模型中方差分量的经验Bayes估计

对非平衡单向分类随机效应模型中方差分量找到了其最小充分统计量,在加权平方损失下导出了其Bayes估计,利用多元密度及其偏导数的核估计方法构造了方差分量的经验Bayes(EB)估计,并导出了其收敛速度.文末用例子说明了符合定理条件的先验分布是存在的.     

激光陀螺相邻模零偏差及不平衡电流零偏差性能分析

通过控制参量提高陀螺精度和成品率,是激光陀螺工程技术研究的主要内容之一。引入相邻模陀螺零偏差及不平衡电流零偏差两个参量,对不同等级表陀螺对应参量的研究,发现陀螺性能与该参量具有确定的关系,通过控制这两个参量,可以有效提高陀螺使用精度和成品率。理论研究了两个参数变化的根源,分别为谐振腔参数及锁区的变化,为提高激光陀螺精度提供了一种有效的技术途径,对于进一步提高抖动陀螺精度具有实用价值。     

Chaos in the unbalance response of journal bearings

The behaviour of non-linear systems often yield unexpected phenomena which are extremely sensitive to initial conditions. The hydrodynamic journal bearing is a common machine element which is strongly nonlinear for large excursions within the clearance space. A simple model of a rigid journal, supported hydrodynamically using a short bearing theory is shown to behave chaotically when the rotating unbalance force exceeds the gravitational load. At these values of the force ratio the time history of the response is very sensitive to initial conditions and a spectral analysis demonstrates a significant broadening from the expected peak at the rotational frequency. A once per revolution sampling of the time history (Poincaré plot) revealed an apparent aperiodic pattern. An estimate of the fractal dimension using the Grasberger-Procaccia algorithm resulted in a lower bound of 2.15, a typical result for low dimensional systems with significant dissipative action. The required levels of unbalance are only an order of magnitude greater than acceptable levels for rotating machinery and thus could be achieved with in-service erosion or minor damage. The subsequent non-synchronous response could result in fatigue and potential shaft failure.     

Periodic routing to parallel queues and billiard sequences

In this companion paper of [10] we introduce the combinatorial notion of unbalance for a routing pattern. Using this unbalance we derive an upper bound for the total average expected waiting time of jobs which are routed to parallel queues according to a periodic routing rule. A billiard sequence is obtained with unbalance smaller than or equal to –1, where N is the number of different symbols in the sequence which corresponds to the number of parallel queues in the routing problem.     

静电悬浮球形转子的电场恒速方法

针对静电悬浮球形转子在真空腔中存在转速衰减的问题，研究并改进了一种电场恒速方法，分析了偏心转子的侧向摆动现象及由此产生的不平衡信号的特性，给出了电场恒速力矩的计算公式和限制条件。在此基础上，提出了改进后的球形转子电场恒速控制系统的结构和动态模型。理论分析和计算结果表明：改进后的电场方法能够在不影响系统整体性能的前提下实现各项恒速控制的性能指标。     

有初弯的刚度非对称转子的动力学特性分析及实验研究

对刚度不对称转子在有初始弯曲时的稳定性和动态响应性特性进行了理论分析和实验研究。重点研究了初弯方向与原始不平衡方向间夹角对系统响应特性的影响，提出了识别转子初弯和刚度不对称情形的特征量和诊断方法。研究表明：初始弯曲转子不仅在低转速时的振幅趋于初始弯曲值，而且随初始弯曲与不平衡间夹角的变化和初始弯曲与偏心距比值大小的变化振幅曲线出现很大的差异。特别是在大夹角情形下，夹角对振幅曲线的影响较大。当初始弯曲小于偏心距时，临界前振幅会随着转速升高而下降然后又上升，而当初始弯曲大于偏心距时，临办后振幅会随着转速升高而下降然后又上升。在临界前刚度不对称轩子的幅频曲线有副临界现象，转子运转频率处于两个自然频率间时系统会失稳，不平衡的增大对两类情况的幅频曲线变化趋势影响较大。