钛合金振动攻丝刀具破损监测的研究

对振动攻丝的力学模型进行了研究,找出了钛合金振动攻丝刀具破损失效时的力学特征,并建立了钛合金振动攻丝的振动控制、破损监测和报警停机的自动监控系统。     

具有干摩擦阻尼的叶片组振动的理论与实验研究

通过理论分析与实验研究,讨论带凸肩叶片的振动特性及其干摩擦阻尼效应。提出了适用于凸肩干摩擦的局部非线性特点的一种新的降阶方法,定义了无量纲干摩擦阻尼因子,用于度量干摩擦阻尼效果。最后,按照设计的实验方案,对带凸肩叶片组试件做了振动实验研究。     

复合材料构件发射导弹的动响应分析

通过对复合材料机翼部件的动特性及动响应分析,介绍了计算分析的方法和步骤;对分析结果的进一步处理及指导改进设计。通过对结构的动特性分析,发现在打样设计局部振动现象,可通过改进铺层设计来消除此设计中的薄弱环节。比较外翼、中翼和内翼3种发射导弹的计算情况,给出最严重情况的动力响应值,最后确定其动强度。     

螺桨转子的颤振涡动

本文发展了螺桨转子颤振涡动的分析方法,考虑了桨叶的振动变形及桨轴一支承系统的振动特性、以及螺桨转子的不平衡力,并对运动方程借时域积分法求解,从而使分析结果更为准确。模型螺桨转子的分析计算与风洞试验结果吻合良好。     

结构动特性分析的超单元法

提出一种超单元法,将一个细化的静力学有限元模型转化为反映整体性能的动力学有限元模型。这里定义的超单元具有子结构和协调有限元双重特性。生成了刚性超结点和弹性超结点,以及3刚性超结点和4刚性超结点超单元,从而为构造超单元模型奠定了基础,实现了建模的一致性。算例表明本文提出的超单元法是对动力学有限元模型的精确描述,算法的计算效率高,工程适用性好。     

智能桨叶的实时模型与复合自适应振动控制

研究了智能桨叶的实时模型、控制方法与控制器的实时实现。首先,采用MX滤波器实现了对桨叶动态特性的实时在线模拟,给出了该滤波器的系数与所描述的受控结构模态参数之间的相互关系。接着,提出了一种新的复合自适应控制方法,它综合了自适应前馈控制和反馈控制的特点,实现了对桨叶阻尼和振动响应的控制。最后,在所建立的以高速信号处理器为中心的实时数字仿真系统上,实现了对单频、双频及变频、变幅值谐和激励下桨叶振动的控制,获得了良好的振动控制效果。     

光纤陀螺捷联惯导系统内部减振措施试验研究

振动环境下,光纤陀螺捷联惯性组合的单表输出和导航精度都受到影响。通过采用整体减振措施和单表减振措施两种方法的振动试验,分析其误差产生原因,对两种减振措施的结果进行比较。验证了两种减振措施均能在一定程度上提高振动环境下光纤捷联惯性组合的精度。     

一种新的用于MHD方程逆风格式的Jacobian矩阵分裂方法

针对理想MHD方程,提出了一种新的基于MacCormack算法的雅可比矩阵分裂方法,克服了原有方法稳定性差的问题,并成功地应用于理想MHD方程的求解.控制方程在非结构混合网格上进行空间离散,其中对流项采用本文发展的逆风向量分裂格式,并引入了双曲型磁场散度清除技术,时间推进为显式5步龙格-库塔方法.对MHD激波管流动和带均匀磁场干扰的二维高超声速钝头体绕流流场进行了数值模拟,得到了与参考文献相吻合的数值结果,表明本文发展的数值分裂方法可以有效地捕捉MHD流场的流动特征,并且具有比MacCormack方法更高的稳定性和计算精度.     

航天器非平稳振动环境TVAR时频分析(英文)

Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional time-varying algorithm limits prediction accuracy, thus affecting a number of operational decisions. To solve this problem, a time-varying auto regressive （TVAR） model based on the process neural network （PNN） and the empirical mode decomposition （EMD） is proposed. The time-varying system is tracked on-line by establishing a time-varying parameter model, and then the relevant parameter spectrum is obtained. Firstly, the EMD method is utilized to decompose the signal into several intrinsic mode functions （IMFs）. Then for each IMF, the PNN is established and the time-varying auto-spectral density is obtained. Finally, the time-frequency distribution of the signals can be reconstructed by linear superposition. The simulation and the analytical results from an example demonstrate that this approach possesses simplicity, effectiveness, and feasibility, as well as higher frequency resolution.     

Multi Objective Robust Active Vibration Control for Flexure Jointed Struts of Stewart Platforms via H∞ and μ Synthesis

Active vibration control is needed for future space telescopes, space laser communication and other precision sensitive payloads which require ultra-quiet environments. A Stewart platform based hybrid isolator with 6 hybrid struts is the effective system for active/passive vibration isolation over 5-250 Hz band. Using an identification transfer matrix of the Stewart platform, the coupling analysis of six channels is provided. A dynamics model is derived, and the rigid mode is removed to keep the signal of pointing control. Multi objective robust H∞ and μ synthesis strategies, based on singular values and structured singular values respectively, are presented, which simultaneously satisfy the low frequency pointing and high frequency disturbance rejection requirements and take account of the model uncertainty, parametric uncertainty and sensor noise. Then, by performing robust stability test, it is shown that the two controllers are robust to the uncertainties, the robust stability margin of H, controller is less than that of μ controller, but the order of μ controller is higher than that of H, controller, so the balanced controller reduction is provided. Additionally, the μ controller is compared with a PI controller. The time domain simulation of the μ controller indicates that the two robust control strategies are effective for keeping the pointing command and isolating the harmonic and stochastic disturbances.