力传感器模型辨识及动态补偿器设计

力传感器作为测控系统的最前端,其动态特性对测控系统特性有本质影响。为建立有效改善力传感器动态特性的补偿器方法,根据非线性最小二乘法建立了力传感器的动态数学模型,基于零极点配置法设计了力传感器的动态补偿环节。针对以上方法进行了系统辨识实验与动态补偿环节仿真设计。实验与仿真结果表明,非线性最小二乘法能够切合实际地建立非线性系统的辨识模型,零极点配置法所设计的动态补偿环节极大地改善了传感器的动态特性,可以将该补偿方法应用于工程实际当中。     

力传感器模型辨识及动态补偿器设计北大核心

力传感器作为测控系统的最前端,其动态特性对测控系统特性有本质影响。为建立有效改善力传感器动态特性的补偿器方法,根据非线性最小二乘法建立了力传感器的动态数学模型,基于零极点配置法设计了力传感器的动态补偿环节。针对以上方法进行了系统辨识实验与动态补偿环节仿真设计。实验与仿真结果表明,非线性最小二乘法能够切合实际地建立非线性系统的辨识模型,零极点配置法所设计的动态补偿环节极大地改善了传感器的动态特性,可以将该补偿方法应用于工程实际当中。     

机械阻抗方法在振动分析中的应用 Ⅸ 组合结构系统分析(一)

机械阻抗方法的一个重要特点是,在进行结构系统动力分析时,可以将系统分为若干部件(或主系统与子系统)。分别由理论计算或测试识别的方法求出部件的动力特性后,按一定边界条件求出系统动力学方程,并解得组合结构系统的动力特性或动力响应。这就是组合结构系统分析法。本讲第一部分介绍组合结构系统动力特性分析的动刚度法。先从最简单的单座标交联情     

阀控液压马达角位移随动系统动态特性研究

为分析不同控制方法在阀控液压马达角位移控制系统中的应用效果,分别基于PID闭环控制、极点配置法及含有状态观测器的极点配置法对阀控液压马达角位移随动系统动态特性进行对比研究。首先,简要介绍了阀控液压马达系统的工作原理;其次,分别建立了阀控液压马达角位移控制系统的传递函数、方框图及状态空间表达式,并对该系统的时-频域特性与能控-能观测性进行分析;在此基础上,分别基于3种控制方法对阀控液压马达角位移控制系统进行设计,并利用MATLAB/Simulink软件对系统阶跃响应进行了仿真分析,以对比各控制方法在阀控液压马达系统中的应用效果以及状态观测器极点位置对系统动态特性的影响,为改善阀控液压马达系统的动态特性提供理论依据。     

链式结构系统动力特性的灵敏度分析

提出了一种求解链式结构系统的动力特性灵敏度的解析方法。首先根据结构系统振动的传递矩阵法建立了求解系统动力特性(固有频率和模态振型)的方程,在此基础上对系统动力特性的灵敏度进行了分析,导出了系统固有频率和模态振型对结构参数灵敏度的计算表达式。最后通过算例说明了文中模型的合理性和求解方法的有效性,并获得了一些有意义的结论。     

动力总成悬置系统动态特性仿真分析

动力总成悬置系统是汽车振动系统的一个重要子系统,对改善汽车平顺性和舒适性有很大的影响。应用拉格朗日法建立了六自由度动力总成悬置系统的数学模型,并用Newmark法和Simulink仿真模型两种方法对动力总成悬置系统怠速工况进行了仿真分析,两种方法的仿真结果相近,说明模型的正确性,在此基础上对动力总成悬置系统在怠速工况下进行了动特性分析,最后将仿真动特性结果和实测进行了对比,仿真结果和实验结果基本一致,说明其具有工程应用价值。     

随机参数链式结构系统的动力特性分析

以随机参数链式结构系统为研究对象,根据链式扭振系统的传递矩阵法建立了求解系统固有频率的方程,对系统的转动惯量和扭转刚度具有随机性时的系统动力特性进行了分析,利用代数综合法推导出系统特征值随机变量数字特征的计算表达式,并提出基于概率的结构动力特性求解方法。通过算例验证了所建模型的合理性和所提方法的正确性、有效性,并考察了系统物理参数的随机性对其动力特性的影响。     

单自由度行星轮系运动特性的信号流图分析法

依据行星齿轮系运动特性与原理,提出了一种用信号流图法计算复杂行星齿轮传动系统的特性参数。将信号流图的概念引入到单自由度行星齿轮系统的参数计算中,采用该法建立了XP系统、PX系统、T型混联系统、∏型混联系统和E型混联系统的信号流图模型。再利用信号流图的计算规则,获得了各种行星齿轮系的输入与输出及各传动构件的转速关系式,传动系统的转化传动比。该法直观性好,不仅可以做行星齿轮传动的可视化分析,也可以进行功率流的特性分析,为复杂行星齿轮系统运动特性参数计算等方面的研究提出了一种新的方法。     

基于Symlets小波滤波的滚珠丝杠伺服进给系统频响特性辨识

高速、高加速度条件下,滚珠丝杠进给系统所具有的弹性特性会对其频率响应特性造成很大影响.通过分析转矩输入信号和加速度输出信号的幅值和相位关系可以实现对进给系统频响特性的辨识.通过集中质量方法对弹性滚珠丝杠传动系统进行建模,由拉格朗日能量法和状态空间分析对系统的频响特性进行计算.并进一步利用试验方法完成进给系统频响特性的辨识.为了减少量化噪声、白噪声和有色噪声对辨识信号的影响,提出通过Symlets小波滤波方法对有限差分方法得到的加速度信号进行小波滤波处理后,再进行幅值和相位信号的提取和频响函数的拟合.仿真和试验最终证明Symlets小波滤波方法能有效地减少噪声对加速度信号的影响,提取出有效信号,实现对进给系统频响特性更为精确地辨识.     

转子系统动力学分析软件设计

研究基于Riccati变换的整体传递矩阵法进行某压缩机多转子系统稳态不平衡响应计算。结合转子系统动力特性计算方法,开发出分析多转子系统动力特性的通用计算程序。以一些转子系统为对象分析了转子系统的临界转速和相应的振型、应变能,并绘出系统临界转速图谱以及转子系统的稳态不平衡响应。分析结果表明,自主开发的转子系统动力学分析软件运行稳定,操作简单,结果可靠。可以运用其对转子系统进行动力学特性的分析。     

柴油机前端齿轮室总成异响源识别分析与改进

针对柴油机前端齿轮室总成在常用转速下产生异响的问题,采用EEMD小波时频分析方法进行了异响源的识别分析;通过整车定置试验和台架试验分析,提取了异响源的时频特征;通过有限元模型仿真分析,计算了齿轮室总成结构的约束模态频率和振型。综合上述分析结果发现,异响原因是壳体件结构局部刚度不足引起的系统共振。通过改进齿轮室总成结构,提高了固有频率,消除了齿轮室总成异响。     

裂纹对齿轮轮齿结构振动的影响

建立具有裂纹的齿轮轮齿的动力学模型，分析齿轮轮齿发生裂纹后轮齿结构的动力响应及动力特性，并对裂纹出现位置和裂纹尺寸对齿轮结构动力特性的影响进行深入探讨；通过分析计算和有限元数值模拟验证表明，裂纹发生位置对齿轮轮齿振型影响较大，在裂纹发生处振型发生突变；而裂纹大小对其振型和固有频率影响都较大，当裂纹出现后齿轮固有频率发生下降，振型也发生变化，随着裂纹深度的增加，固有频率更加下降，低阶下降显著，而高阶下降缓慢，振型也与无裂纹的情形完全不同。这显示出裂纹对齿轮轮齿结构振动的影响随裂纹尺寸的增加而强烈。     

Analysis of the effects of surface pitting and wear on the vibration of a gear transmission system

A comprehensive procedure to simulate and analyse the vibrations in a gear transmission system with surface pitting, wear, and partial tooth fracture of the gear teeth is presented. An analytical model was developed where the effects of surface pitting and wear of the gear tooth were simulated by phase and magnitude changes in the gear mesh stiffness. Changes in the gear mesh stiffness were incorporated into each gear-shaft model during the global dynamic simulation of the system. The overall dynamics of the system were evaluated by solving for the transient dynamics of each shaft system simultaneously with the vibration of the gearbox structure. In order to reduce the number of degrees-of-freedom in the system, a modal synthesis procedure was used in the global transient dynamic analysis of the overall transmission ststem. An FFT procedure was used to transform the averaged time signal into the frequency domain for signature analysis. In addition, the Wigner-Ville distribution was also introduced to examine the gear vibration in the joint time-frequency domain for vibration pattern recognition. Experimental results obtained from a gear fatigue test rig at NASA Lewis Research Center were used to evaluate the analytical model.     

Identification of Single and Multiple Teeth Damage in a Gear Transmission System

Abstract

The main objective of this article is to identify single and multiple gear teeth damage based on vibration signatures analysis of experimental results and their comparison with those by numerical simulations. In this study, vibration signals are experimentally acquired for the case with no tooth damage to cases with multiple teeth damage using the controllable wear/damage gear sets in the 75-HP gear test rig. Vibration signatures for cases similar to the experimental studies are numerically simulated based on a two-spool rotor-bearing model connected by a set of meshing gears. The effects of the wear on the gear tooth surface are numerically represented by the phase change in the gear teeth mesh stiffness during both gear mesh engagement and disengagement. Results from both experimental studies and numerical simulations are examined and compared in the time domain, the frequency domain, and the joint time-frequency domain using the Wigner-Ville distribution (WVD). Based on results of this comparative study, general conclusions are drawn concerning the identification of single and multiple gear teeth damage and their effects in affecting the global dynamics of the gear transmission system.     

基于道路试验的制动颤振非线性特性分析

为了探究制动器摩擦颤振内在非线性特性,设计平路D档起步和坡道空挡下坡两种试验工况,采集制动器振动信号并进行时域、时频域和相图分析。分析表明:平路D档起步工况下的摩擦颤振具有明显的短时、宽频带和冲击特征,振幅随制动压力变大而增大,持续时间随压降率减小而增长;坡道空挡下坡工况下既会发生短时、宽频带和冲击颤振,也会发生长时、多频率和周期型颤振。在不同的相对运动速度下,会因摩擦-速度非线性发生单周期、倍周期、多耦合周期乃至混沌振动。摩擦颤振存在3种不同的基础频率及其非线性耦合关系,表明颤振机理既有黏滑振动效应,也可能有底盘角系统的模态耦合效应。     

传动比对齿轮时变系统拍击门槛转速的影响

建立了具有时变啮合刚度的二级齿轮系统的动力学方程式。由于齿轮副啮合刚度的影响,动力学方程式代表了一个具有时变系数的线性动力系统。用算符分解算法(AOM)得到了系统的近似解析解,并研究了传动比和时变啮合刚度对拍击门槛转速的影响。根据计算结果分析,时变啮合刚度可以导致拍击;齿轮啮合频率等于派生系统的固有频率引起的共振是产生拍击的原因之一;增大从动齿轮的齿数、或者增大传动比,一般情况下,可导致拍击门槛转速下降;增大低阶模态阻尼,能够增大拍击门槛转速。     

混合动力两级行星机构动力耦合系统动力学建模及分析

以基于双转子电机的混合动力传动系统的两级行星齿轮机构动力耦合系统为研究对象,考虑前后两级行星齿轮机构的齿轮副啮合刚度、中心构件的扭转支撑刚度、连接部分的扭转耦合刚度、各构件惯性等基本因素,详细推导并建立两级行星齿轮耦合系统的纯扭转动力学模型。利用两级行星齿轮机构的有关参数进行特征值问题求解,得到系统整体模型的固有特性,按照振型特点把系统的振动形式划分为三种模式:整体扭转振动模式、前排行星轮振动模式和后排行星轮振动模式。在整体模式下固有频率为单根,系统各构件均以一定幅度做扭转振动;前、后排行星轮模式下固有频率均为二重根,且除了其自身外,其他构件均无振动。归纳分析得到的各振动模式特征与前人有关结论相吻合。同时指出连接部分的耦合刚度对系统振动特性的影响,并作了初步分析。     

应用Hilbert-Huang变换的齿轮磨损故障诊断研究

提出了一种基于H ilbert-Huang变换的齿轮磨损故障诊断的新方法。H ilbert-Huang变换是先把时间序列信号,用经验模态分解方法分解成不同特征时间尺度的固有模态函数,然后经过H ilbert变换获得频谱的信号处理新方法。介绍了该方法的基本原理,并将H ilbert-Huang变换应用于齿轮箱中齿轮磨损故障诊断的研究,通过选取表征齿轮磨损故障的IM F分量进行边际谱和能量谱分析,就可提取齿轮故障振动信号的特征。齿轮故障实验信号的研究结果表明,H ilbert-Huang变换时频分析方法,能有效地诊断齿轮的磨损故障。     

Dynamic characteristics of a planetary gear system based on contact status of the tooth surface

Studies on the planetary gear have attracted considerable attention because of its advantages, such as compactness, large torque-to-weight ratio, vibrations, and high efficiency, which have resulted in its wide applications in industry, wind turbine, national defense, and aerospace fields. We have established a novel dynamic model of the planetary gear transmission by using Newton’s theory, in which some key factors such as time-variant meshing stiffness, phase relationships, and tooth contact characteristics are considered. The influences of gear axial tipping, operating conditions, and the meshing phase on the contact characteristics and the dynamic characteristics were researched systematically. It was found that the contact area of the tooth surface was moved due to the axial gear tipping, which obviously affected the meshing stiffness. With the increase in the inclination angle of the sun gear, the meshing stiffness decreases, which produces an evident influence on the high natural frequency in the planetary transmission system. In terms of the dynamic characteristics of the system, the component of rotating frequency appeared in the dynamic meshing force of the sun gear and the planetary gear. Moreover, the floating track of the center wheel varied significantly and exhibited an oval distribution as the inclination angle of the sun gear changed. When the inclination angle of the sun gear increased, the rotating frequency component increased significantly, but the other meshing frequency components remained unchanged; meanwhile, the deformation of the floating track also increased. If the inclination angle of the sun gear changes, the vibration state of the system and the collision impact could become more serious, and the lifetime of the planetary transmission system will reduce. Furthermore, when the load was increased, we found that the gear-tooth contact zone transformed from line contact to surface contact, the meshing stiffness increased, the effect of high natural frequency on the planetary transmission system became more evident, but its low-order natural frequency remained stable. With regard to the dynamic characteristics of the system, the components of the major frequency at the external gearing remained unchanged, but the rotation frequency of the sun gear and the meshing frequency amplitude increased linearly with the increase in load. In conclusion, the variation in the meshing stiffness of the planetary gear system had minor impact on the low-order natural frequency, but had a significant impact on the high natural frequency of the planetary transmission system due to the phase variation of the gear.     

裂纹齿轮动力特性分析与模拟

建立了齿轮的动力学模型 ,分析了齿轮轮齿发生裂纹后的动力特性 (固有频率、振型等 ) ,并对裂纹出现位置和裂纹尺寸等对齿轮动力特性的影响进行了深入探讨和计算机模拟 ,指出裂纹发生位置对齿轮轮齿振型影响较大 ,在裂纹发生处振型发生突变 ;而裂纹尺寸对其振型和固有频率影响都较大 ,当出现裂纹后固有频率发生下降 ,振型也发生变化 ,随着裂纹尺寸增加 ,固有频率下降更加显著 ,各阶幅值下降大小不一 ,振型也与无裂纹的情况完全不同。这对齿轮的损伤监测和诊断具有重要价值