锥齿轮传动系统的非线性动力学行为

主要研究了锥齿轮传动转子系统的非线性动力学行为.在滑动轴承或挤压油膜阻尼器中,油膜力是齿轮传动转子系统非线性的一个重要来源,并且与轴承的结构参数、转子的转速和作用力等多个因素有关.首先在刚性转子、齿轮不脱啮等假设条件下,考虑了锥齿轮间的广义位移约束关系,建立在非线性油膜力作用下锥齿轮传动的多转子耦合系统动力学模型.由于油膜力具有强非线性特性,因此采用数值分析方法,结合系统的稳态响应、Poincaré映射和分叉图等多种手段分析系统的动力学行为.通过初步研究得到如下结论:对于不平衡锥齿轮传动的转子系统,在低转速时转子轴心的运动与转速同步;随着转速的增加系统出现2倍周期运动等复杂的分叉现象.这些振动特征可以为这类系统的动力学设计、结构参数优化和运动状态监测等提供必要的理论依据.     

1:1内共振环形桁架天线的稳定性分析

复杂的太空环境易导致环形桁架天线产生大幅非线性振动,严重影响天线的稳定性和结构性能.在大幅的非线性振动中不同模态之间的能量可以相互传递和转换,将引起天线产生内振动.因此内共振在天线的大幅振动中起着重要的作用.本文所研究的环形桁架天线被简化成等效圆柱壳模型,建立其非线性动力学方程.根据有限元模态分析,得出环形桁架天线第四阶模态和第五阶模态的振动频率接近1:1.所以本文利用理论分析和数值计算研究1:1内共振情形下环形桁架天线的局部动力学性质.即系统受到小扰动后平衡点的稳定性.详细研究了两种不同形式下的平衡点的稳定性,即系统特征根为双零和两个负数时的稳定性以及系统特征根为双零和一对纯虚复数时的稳定性.利用中心流形理论、非线性变换、Routh-Hurwitz判据得到平衡点的稳定区域、不稳定区域和临界分岔曲线.最后通过数值模拟验证理论分析.     

间隙引发的变载非线性及其闭环辨识

阐明了齿轮传动位置伺服系统间隙除产生熟知的前向迟滞非线性之外,还将因系统往复运动中加卸载相交替的反向调制致使驱动电机动力学参数同步跳变所出现的变载非线性现象.推导建立了这类非线性在一阶谐波意义下的串联式等效频域模型及其近似计算公式,分析了相应的幅相特性.进一步面向服役中系统提出了直接通过闭环弱自激振荡控制所实现的间隙辨识新方法,给出了控制器的结构及其参数整定策略.此外,文中还给出了含高斯白噪声测量的仿真算例,充分验证了闭环间隙辨识方法的有效性和便捷性.     

基于Lagrange法的刚体与柔体动力学对比研究

对于机器人、航天器和车辆悬架部件等一些多体系统来说,其中一些部件的大尺寸、轻型化趋势使得传统的刚性体建模已经难以准确地模拟实际的工况,将部件所具有的柔性特性加入到多体系统模型中进行柔体动力学仿真,由于考虑了部件弹性变形与大范围刚性运动之间的耦合,故可以得到部件更为真实的动力学行为.文中通过与基于Lagrange法的刚体动力学基本方程进行对比研究,详细说明了柔体动力学方程中上述的耦合作用.以某大型雷达可展开天线为例,分别在刚体和柔体的假设下对其展开运动进行动力学仿真,结果表明采用柔性体仿真更能真实反映其动力学特性.     

环型桁架卫星天线的非线性动力学分析

我国航天工业迫切需要掌握可入轨后展开的大型网架式空间结构技术,而环形桁架可展天线具有应用空间大、结构形式简明的特点,是目前大型卫星天线较为理想的结构形式~([1-3]).本文基于Zhang et al建立的环形天线模型为研究对象并在此基础上建立了天线振动时的非线性常微分运动方程,运用matlab数值模拟方法研究了热激励对系统非线性动力学行为的影响.     

剪叉式过约束双环桁架可展天线机构的构型设计与自由度分析

基于过约束剪叉机构单元,构造了一种剪叉式过约束双环桁架可展天线机构作为星载天线支撑机构.首先,分析了剪叉式过约束双层环形桁架机构的构型机理及过约束特征,并对整体桁架机构进行了单元划分;考虑节点连接件的尺寸,推导出了此剪叉式过约束双环桁架机构的组环几何条件.然后,将双层环形桁架机构进行单元分解,基于图论和螺旋理论绘制了分解后机构单元的旋量约束拓扑图,进而分析了闭环可展开机构单元和整体双层环形桁架机构的自由度,结果表明,双层环形桁架机构的自由度和闭环可展开机构单元的自由度数相同,均只有1个自由度.最后建立了双层环形桁架可展开天线机构的仿真模型,模拟了整个机构的展开过程,验证了整体的可展性.该剪叉式过约束双环桁架可展天线机构所含运动副均为转动副,且整个机构仅具有单个自由度,运动形式简单.     

变截面旋转叶片的非线性动力学研究

将航空发动机叶片简化成变截面旋转悬臂板进行动力学分析.叶片在气动力下变速旋转,其气动载荷用一阶活塞理论表示,同时考虑了叶片的预扭转角、预安装角以及叶片承受的巨大离心力.叶片的非线性位移关系由Von Karman大变形理论得出,利用Hamilton原理建立非线性动力学方程.对所得方程进行Galerkin离散,将偏微分方程转化为常微分方程.考虑1∶3的内共振关系,利用渐近摄动法进行摄动分析,得到四维直角坐标形式下的平均方程.最后对平均方程进行数值模拟,研究了扰动转速对系统非线性动力学行为的影响,得到了不同转速情况下的相图、波形图以及频谱图.结果表明:随着扰动转速的变化,叶片存在倍周期、概周期和混沌等非线性动力学行为.     

航空发动机叶片非线性动力学分析

论文研究了航空发动机叶片的非线性振动问题,将叶片简化为功能梯度材料薄壁悬臂梁,考虑几何大变形的影响,基于一阶活塞气动力理论,利用Hamilton原理建立了叶片的非线性偏微分运动方程.综合运用Galerkin方法、多尺度方法和数值方法对叶片模型进行了非线性动力学分析,通过相图、波形图和频谱图分析了不同气流流速情况下旋转叶片的动态响应.结果表明:随着气流流速的增加,系统呈现倍周期运动和混沌运动等多种复杂动力学行为.     

脉冲推力作用下半被动双足机器人的行走动力学分析

为了提高半被动双足机器人在水平地面上行走的稳定性,研究一种脉冲推力作用下半被动双足机器人的行走动力学行为.以最简单的特殊行走模型为动力学模型,采用支撑腿脚后跟脉冲推力作为双足机器人行走动力源.鉴于系统模型的高度非线性,将连续阶段的非线性微分方程线性化;利用角动量守恒和脉冲推力构造一个二维离散映射;采用离散映射的不动点及其特征值分析系统周期步态的存在性和稳定性;接着讨论系统的倍周期分岔.在理论分析的基础上,通过Matlab软件对半被动双足机器人的行走动力学进行仿真实验. 仿真结果表明,在水平地面上行走的半被动双足机器人具有稳定的周期-1步态和周期-2步态.     

考虑含间隙与润滑平面机构的简化算法

为了更快速、高效地确定含润滑铰间间隙对机构动态特性的影响,文中建立了一种新的计算思路.首先,通过理想机构与含间隙机构的运动学模型求出间隙力,进一步把间隙力以主动力的形式带入动力学方程,得到机构的相应动态特性.然后,以含间隙与润滑的曲柄滑块机构为例,基于二状态接触模型与流体润滑模型,对比分析该模型与干摩擦模型,来进一步验证该方法的正确性与可行性.Simulink仿真数据表明,文中建立的模型能有效地抑制机构的振动,动态特性更接近于理想模型,符合实际情况.     

锥齿轮齿根应力有限元模型和分析

从齿轮加工原理出发,利用渐开线和齿根过渡曲线方程生成轮齿的精确齿形,建立2种等效直齿锥齿轮三维轮齿几何模型,研究渐开线直齿锥齿轮的精确建模方法.分别使用h-单元和p-单元分析计算直齿锥齿轮齿根应力,建立直齿锥齿轮三维轮齿齿根应力有限元计算模型和计算基准.计算结果与ISO国标公式比较,证明模型的正确性、精确性和可靠性.     

Computerized design of advanced straight and skew bevel gears produced by precision forging

The computerized design of advanced straight and skew bevel gears produced by precision forging is proposed. Modifications of the tooth surfaces of one of the members of the gear set are proposed in order to localize the bearing contact and predesign a favorable function of transmission errors. The proposed modifications of the tooth surfaces will be computed by using a modified imaginary crown-gear and applied in manufacturing through the use of the proper die geometry. The geometry of the die is obtained for each member of the gear set from their theoretical geometry obtained considering its generation by the corresponding imaginary crown-gear. Two types of surface modification, whole and partial crowning, are investigated in order to get the more effective way of surface modification of skew and straight bevel gears. A favorable function of transmission errors is predesigned to allow low levels of noise and vibration of the gear drive. Numerical examples of design of both skew and straight bevel gear drives are included to illustrate the advantages of the proposed geometry.     

An accurate model of high-performance manufacturing spiral bevel and hypoid gears based on machine setting modification

Machine setting modification especially considering the tooth contact performance is always vital to design and manufacture for the spiral bevel and hypoid gears. With the application of new manufacture concepts and advanced design methods, a closed-loop complex model is established to execute the high-performance manufacture. Firstly, an optimization model of machine settings modification considering the residual ease-off is established by correlating the tooth flank represented by universal machine settings. Furthermore, a trust region algorithm with control strategies concerning: (i) double Dogleg algorithm for the iteration step and (ii) updating damping efficient for the trust region radius is employed to obtain the target flank. Finally, a closed-loop measurement-modification-manufacturing (3M) model for high-performance manufacture of the spiral bevel and hypoid gear is established. Where, it mainly describes the accurate machine setting modification considering tooth contact performances. Some numerical examples in practical application can verify the accuracy and performance of the proposed model.     

弧齿锥齿轮传动的CAD系统

本文介绍弧齿锥齿轮传动的CAD系统,该系统能自动完成弧齿锥齿轮传动的优化设计、切齿调整计算、接触分析、V-H分析计算、有限元法应力分析以及弧齿锥齿轮工作图的绘制。该系统将弧齿锥齿轮传动的计算机辅助设计(CAD)、辅助制造(CAM)、辅助检验(CAT)及辅助绘图(CAG)集为一体,为弧齿锥齿轮传动提供了一套全新的设计系统。通过在某航空弧齿锥齿轮传动设计中的应用,证实了本系统的有效性。     

仿猫类落地姿态的准零刚度隔振器

对设备加装隔振装置是保证其高效工作的重要方法之一.本文从仿生学的角度,根据猫科动物落地时优秀的抗冲击能力,通过观察其落地动作姿态,利用非线性补偿原理,以空气弹簧作为正刚度结构,设计出一种具有非对称刚度特性的高静低动刚度隔振器.以其为研究对象,建立了动力学模型,利用特定的方法对非对称刚度系统进行分析求解,并与数值结果和有限元仿真结果进行对比.结果表明,在较低阻尼以及较高激励幅值下,还会出现倍周期响应甚至混沌响应.同时,通过将本文设计的隔振结构和单一空气弹簧的隔振性能对比,可以得到隔振效果明显优于单一空气弹簧的结论,从而验证了所设计隔振结构的有效性和可行性.     

Oscillators with nonlinear elastic and damping forces

Generalization to the previous oscillators is done by introducing the nonlinear elastic and damping forces. The mathematical model of the system is a second order differential equation with nonlinear elastic and damping terms whose order is integer and/or noninteger. Cveticanin’s solving procedure is extended for solving such a strong nonlinear differential equation. The approximate solution obtained is a function of initial amplitude and initial phase. A damping coefficient and order of damping interaction with an elastic coefficient and order of elasticity for the generalized oscillators are also determined. Special attention is paid to obtain the relation between initial amplitude and phase, on the one hand, and initial displacement and velocity on the other hand. Correction to the frequency of vibration for the linear oscillators with nonlinear damping and for the pure nonlinear oscillators with linear damping is obtained and analyzed. Analytical results given in this paper are compared with numerically obtained ones and show a good agreement.     

Computer-aided design integration of a reinforced vibration isolator for electronic equipment’s system basedon experimental investigation

Electronic equipment’s system is always manufactured as a superprecision system. However, it will be used in harsh environment. For example, the computer in moving vehicles will be acted by vibrations. The objective of this paper is to provide a systematic investigation to test and computer-aided design of the vibration isolator for protection of electronic equipment’s system in harsh vibration environment. A micro-oil damping vibration isolator is designed and manufactured through coupling the oil and spring by ingenious tactics. The structure of the oil damping vibration isolator can achieve circulating oil damping function with an inner tube and an outer tube (some orifices are manufactured on upside and underside of the inner tube). The dynamics of the key model machine is systematically investigated. Based on the test, a nonlinear dynamic model for the vibration isolator is presented by analyzing the internal fluid dynamic phenomenon with respect to the vibration isolator. The model considers all the physical parameters of the structure. Comparisons with experimental data confirm the validity of the model. In the other, the model is integrated by introducing normalization measure. The normalization model shows the actual physical characteristics of the oil damping vibration isolator by considering quadratic damping, viscous damping, Coulomb damping, and nonlinear spring forces. An approximate solution is deduced by introducing harmonic transform method and Fourier transform method. Therefore, a parameter-matching optimal model for computer-aided design of the vibration isolator is build based on approximate solution. An example confirms the validity of the computer-aided design integration.

Realistic and stable animation of cloth

Researchers have proposed various techniques for cloth simulation in the last decades. The crucial problem in interactive animation for cloth is how to speed up simulation with a stable system. In this paper, we describe a realistic and stable scheme for cloth simulation based on mass‐spring system. This scheme modifies semi‐implicit integration used in cloth simulation system with an efficient damping method. Semi‐implicit integration methods have been widely used in dynamic simulation because of acceptable speed and stability. However, internal damping forces are generated with respect to rotational rigid motions, which are only depending on relative velocities. Undesirable change in global movement of dynamic cloth could result in damping artifact. We replace the internal damping forces with an optimal damping method which is based on iterative spring damping but the limit can be computed directly. The method provides simple damping parameter estimation and guarantees conservation of global movement. As a result, complex clothes can be realistically and stably simulated in real time. Copyright © 2015 John Wiley & Sons, Ltd.     

螺旋锥齿轮球面渐开线齿面形成原理及推论

从螺旋锥齿轮的精确齿面形状出发,详细地论述了球面渐开线齿面的基本 组成。基于球面渐开线理论在螺旋锥齿轮方面已取得的研究成果,分析并总结其特点与不足, 提出了螺旋锥齿轮的球面渐开线齿面形成原理。并对球面渐开线齿面形成过程中的关键环节 产形线、工作齿廓和球面渐开线齿面的基本方程进行了推导和论述,为其设计及加工提出了 一些方案,以便为螺旋锥齿轮的研究提供理论基础和思路。