基于振动分离信号构建和同步平均的行星齿轮箱轮齿裂纹故障特征提取

行星齿轮箱由于行星轮的行星运动导致其振动传递路径存在时变性,其振动响应与常规定轴齿轮箱振动响应有着本质的区别,传统的同步平均并不能直接应用于行星齿轮箱。为解决该问题,国外发展了可有效克服行星齿轮箱变传递路径的加窗同步平均法,详细论述了基于振动分离信号构建和同步平均的行星齿轮箱轮齿裂纹故障特征提取的原理及其实现。该方法首先验证齿轮的啮合齿序特征,根据齿序特征选择合适的窗函数对信号进行加窗截取,再根据重排齿序和加窗截取信号构建目标齿轮振动信号,最后对振动分离信号进行同步平均。行星齿轮箱齿根裂纹故障实测信号分析表明,该方法能有效的对行星齿轮箱进行故障特征提取。     

基于窄带解调的行星齿轮箱故障特征提取

行星齿轮箱由于振动传递路径的时变性导致行星齿轮箱振动信号频谱具有复杂的调制边带,其包含了齿轮的故障信息。结合行星齿轮箱振动分离信号的同步平均和窄带解调法,提出了针对行星齿轮箱的窄带解调方法。对行星齿轮箱振动信号加窗截取,根据行星齿轮箱齿轮啮合齿序特征,将加窗截取信号拼接重构单个齿轮的振动分离信号,克服传递路径时变性的影响;对振动分离信号进行时域同步平均,提高信噪比;最后,对平均后的信号进行窄带解调,提取行星齿轮箱齿轮故障特征和故障位置。通过行星齿轮箱故障实验分析,验证该方法能有效的提取行星齿轮箱故障特征。     

基于振动信号分离的行星轴承故障特征提取

由于行星轴承振动信号传递路径的时变性,且行星齿轮箱中齿轮啮合振动信号较强,导致行星轴承故障特征提取较为困难。为此,提出了一种基于振动信号分离的行星轴承故障特征提取方法。该方法首先采用阶比分析技术将原始振动信号进行等角度采样;每当行星架旋转一周,采用Tukey窗进行加窗截取,按照啮合齿序重新拼接,构造振动分离信号。再采用离散随机分离从振动分离信号中提取行星轴承故障分量;最后进行包络谱分析提取故障特征。行星轴承内圈故障实测信号分析表明,该方法能有效提取行星轴承故障特征。     

行星齿轮箱典型故障对内齿圈齿根应变的作用机理研究

行星齿轮箱由于具有优良的特性被广泛应用于多领域的机械传动系统中,但恶劣的工作条件导致其故障频发,因此开展行星齿轮箱故障诊断方法的研究工作十分必要。传统的基于振动信号的故障诊断方法在识别行星齿轮箱早期微弱故障方面具有局限性,为此提出基于内齿圈齿根应变信号的行星齿轮箱故障诊断方法,并主要开展行星齿轮箱典型故障对内齿圈齿根应变的作用机理研究工作。分析行星齿轮箱内齿圈齿根应变模型的构建方法,将内齿圈齿根应变模型分解为行星轮-内齿圈啮合力模型、内齿圈轮齿的齿形系数模型和齿间载荷分配系数模型;利用行星齿轮箱的纯扭转模型计算行星轮-内齿圈啮合力,利用材料力学理论推导内齿圈轮齿的齿形系数,并对行星轮-内齿圈啮合过程中的齿间载荷分配系数进行分析;研究行星齿轮箱典型故障对啮合刚度的影响,并根据内齿圈齿根应变模型计算得到典型故障下内齿圈齿根应变的变化规律。建模仿真计算分析结果表明,不同类型、不同部位、不同剧烈程度的故障会对行星齿轮箱内齿圈齿根应变信号造成不同影响,利用内齿圈齿根应变信号可有效识别行星齿轮箱的故障行为。     

行星齿轮箱齿轮组合故障振动频谱特征

行星齿轮箱的局部故障容易发展成为组合故障,复合故障频谱特征与局部故障有明显区别。研究太阳轮与齿圈、太阳轮与行星轮、行星轮与齿圈等组合故障频谱结构对行星齿轮箱故障诊断具有重要意义。考虑组合故障对振动信号的调幅-调频作用,以及时变振动传递路径的调幅作用,建立了组合故障振动信号模型,推导了Fourier频谱公式,总结了组合故障的频谱特征规律。推导了太阳轮与齿圈、太阳轮与行星轮、齿圈与行星轮两两组合故障以及太阳轮、行星轮与齿圈三种齿轮同时故障的特征频率计算公式。通过行星齿轮箱实验信号分析验证了理论推导结果,基于Fourier频谱分析诊断了太阳轮与齿圈、太阳轮与行星轮、齿圈与行星轮组合故障。     

行星齿轮箱太阳轮故障动态啮合周期特性

与定轴齿轮箱相比,行星齿轮箱内部齿轮副复杂的相对运动所引发的振动响应更加复杂多样,因而对其关键部件进行故障诊断颇具挑战。当内部轮齿发生故障时,由于故障啮合位置的动态性引起传递路径的时变性,固定在系统箱体上的单个传感器观测到的故障信息强度亦将呈现不规则变化的独特性。若想恰如其分的利用这些故障信息实现简单而有效的诊断,需重点关注故障啮合位置的周期特性,而后基于该周期所观测的信号进行“统筹兼顾”的分析,便可突显出各类故障的差异性。该研究在深入研究行星齿轮系统内部齿轮副的运行规律的基础上,创新性的提出了确定太阳轮故障动态啮合位置周期的方法,并考虑了以下两种情况:行星轮各不相同;行星轮完全相同。基于上述两种情况分别推导出太阳轮和行星架所需的最小旋转圈数的一般性表达式,该表达式可用于计算齿圈固定型的行星齿轮箱中的太阳轮故障啮合位置的运动周期。最后通过实验提出并验证了基于上述周期的故障诊断最小数据长度。     

行星轮系动力学仿真分析与故障诊断

目前行星齿轮箱已经在军用和民用装备中广泛应用,研究行星齿轮箱的故障诊断方法意义重大。为了研究行星齿轮传动的故障机理,揭示其故障特征,本文建立了行星齿轮系统的动力学模型,研究了齿轮裂纹对齿轮啮合刚度的影响,得出了齿轮正常、太阳轮裂纹和行星轮裂纹等三种状态下系统的频率特征,总结了故障特征频率;最后试验验证了仿真结果的有效性,得出的故障特征频率可用于行星轮系的故障诊断。     

考虑信号传递路径的行星齿轮传动太阳轮裂纹故障响应分析

为研究振动信号传递路径对行星齿轮传动系统太阳轮裂纹故障响应的影响，采用有限元法建立齿圈结构动力学分析模型，对比分析了考虑与未考虑传递路径的齿圈振动响应，验证了模型中传递路径的时变效应以及模型的有效性。开展了太阳轮裂纹故障试验，采用快速谱峭度法（Fast Spectral Kurtosis,FSK）对实验信号进行降噪以及故障特征提取，验证了太阳轮裂纹故障仿真结果的准确性。结果表明：仅考虑与太阳轮故障齿啮合的行星轮的传递信号时，故障信号在路径中的传递随距离增加呈现不断衰减趋势；当考虑所有行星轮的传递信号时，故障信号出现调制现象，随传递距离增加呈现衰减或增加趋势。     

基于声发射衰减特性的故障行星轮定位研究

行星齿轮箱是风力机传动装置的重要组成部分,行星轮在低速重载、既自转又公转的复杂环境下容易诱发故障,其故障诊断特别是故障行星轮定位一直是研究重点和难点。建立了行星轮齿轮箱实验装置,模拟了行星轮故障,并利用声发射信号进行故障行星轮定位。实验研究了声发射信号在齿轮内部、齿轮与齿轮之间的传播特性,利用信号的幅值衰减特性简化了故障定位模型。利用信号幅度随信号传播距离增加而呈指数衰减的关系,建立了故障源定位方程组,从而获得故障齿的啮合位置,进一步确定故障行星轮的位置。实验结果表明:利用声发射信号的幅值衰减特性能够较为精确的确定故障行星轮的位置。     

行星轮系动力学分析与响应表示方法研究

集中参数动力学建模是了解行星齿轮故障机理的有效手段,在利用集中参数模型仿真分析时,选择合适的变量表示系统的响应至关重要。针对现有方法不适于太阳轮固定的行星齿轮系统响应表示的问题,提出采用啮合线方向加速度直接叠加表示行星齿轮系统响应的方法,建立行星齿轮的平移?扭转模型;通过啮合线相对位移和啮合力信号及频谱分析,解释了三自由度选择的必要性,并验证了模型的正确性;与两种典型的响应表示方法比较,所提方法在齿轮正常和太阳轮故障时均具有较好的效果,可以有效提取啮合频率及故障频率;通过齿轮正常和太阳轮故障的实验信号频谱分析进一步验证了所提方法的合理性。     

Experimental planetary impact research

Laboratory experiments provided an invaluable tool for simulating cratering processes on planets subject to a wide range of impactor, target, and environmental conditions.     

行星齿轮传动动力学研究进展

围绕行星齿轮传动系统振动和动载荷问题,本文从分析模型、固有特性预测分析、动态响应计算方法与特性、振动抑制和实验研究五个方面综述了近20年来动力学的研究进展,重点阐述了一些可用于指导行星传动动态设计的结论。最后就现有研究中存在的主要问题及研究方向提出了建议。     

Neutron sources for in-situ planetary science applications

There are a number of future European Space Agency (ESA) and NASA planetary science missions that are in the planning or initial study phases, where the scientific objectives include determining the surface composition, measuring planetary surface heat flow and constraining planetary chronology. The University of Leicester is developing instrumentation for geophysical applications that include γ-ray spectroscopy, γ-ray densitometry and radiometric dating. This paper describes the modelling of a geophysical package, with the Monte Carlo code MCNPX, in order to determine the impact that a neutron source would have on in-situ composition measurements, radiometric dating and, in particular, trace element detection. The suitability of 2.54×2.54 cm LaBr₃(Ce) detectors in the geophysical package for in-situ missions was examined. ²⁵²Cf, Am–Be and Pu–Be neutron sources were compared in a trade-off study to determine mission suitability, potential for thermal and electric power production, mass and shielding requirements. This study is linked to a parallel examination of the suitability of radioisotope thermal generators for in-situ planetary science applications. The aim of the modelling was to optimise the source type and detector geometry in order to measure the elemental peaks of interest with a precision of 10% or better based on the Poisson statistics of the detected counts above background.     

Hybridization enhancement using microfluidic planetary centrifugal mixing

DNA microarrays produce their greatest sensitivities when hybridized using concentrated samples and effective mixing; however, these goals have proved elusive to combine. If samples are diluted enough to fill larger chambers, then mixing works well using either pumping or gravity with rotation, although sensitivities will suffer. Various techniques for mixing concentrated samples in small thin chambers have been proposed; however, they often leave streaks or scars, and their reusable components require careful cleaning. Here we introduce a versatile new microfluidics platform, a two-axis centrifuge whose fluidic chambers rotate in a planetary relationship to a radial gravitational field. This paradigm readily overcomes surface and viscous forces even in chambers only 50 microm thin. Thin chambers obviate the need for sample dilution and increase sensitivities and dynamic ranges 10-fold. In comparisons against conventional mixing using the same 10 microg of starting total RNA on 22 000-probe arrays, 10 000 more usable signals rose above the noise. In other experiments, planetary mixing was able to produce comparable results while using only one-tenth the starting sample. The benefits of planetary mixing include sample conservation, shorter hybridizations, less reliance on amplification, and the ability to quantify many gene signals otherwise obscured by noise.     

锥齿行星齿轮传动模态特性分析

根据相对质心的动量矩定理,建立了锥齿行星齿轮传动的多维动力学模型,采用归纳方法研究了模态特性.结果表明:该传动系统的模态可归结为4种典型振动模式,即:轴向平移—扭转、径向平移—扭摆、行星轮及轴向平移振动模式.在轴向平移-扭转振动模式下,中心构件呈现沿轴线方向的平移振动及绕该轴的扭转振动;在径向平移—扭摆振动模式下,中心构件呈现沿径向的平移振动及绕该方向的扭摆振动;在行星轮振动模式下,中心构件均不振动,仅行星轮在振动;在轴向平移振动模式下,中心构件仅呈现沿轴线方向的平移振动,其他方向不存在振动.与上述4种典型振动模式对应的固有频率的重数分别为1,2,N-3及N-2.该研究为锥齿行星传动的动态特性优化奠定了理论基础.     

A MEMS-based gravity gradiometer for future planetary missions

The gradient in the gravity acceleration is of great interest for planetologists when it can be measured with at least 1 E/√Hz. For this purpose several gravity gradiometer designs are considered. A MEMS-based gradiometer made from a single wafer is considered in this article. Using long springs and small attached masses it is possible to reach a sufficiently low Brownian noise level. The proposed readout for this device will be capacitive plates placed in a comb drive configuration. Trapped charges on these plates can cause noticeable errors when there are more than 0.004 electrons/μm². Measurements show that trapped charge mobility goes down with temperature.     

Multilaser Herriott cell for planetary tunable laser spectrometers

Geometric optics and matrix methods are used to mathematically model multilaser Herriott cells for tunable laser absorption spectrometers for planetary missions. The Herriott cells presented accommodate several laser sources that follow independent optical paths but probe a single gas cell. Strategically placed output holes located in the far mirrors of the Herriott cells reduce the size of the spectrometers. A four-channel Herriott cell configuration is presented for the specific application as the sample cell of the tunable laser spectrometer instrument selected for the sample analysis at Mars analytical suite on the 2009 Mars Science Laboratory mission.     

Compact micromachined infrared bandpass filters for planetary spectroscopy

The future needs of space-based, observational planetary and astronomy missions include low mass and small volume radiometric instruments that can operate in high-radiation and low-temperature environments. Here, we focus on a central spectroscopic component, the bandpass filter. We model the bandpass response of the filters to target the wavelength of the resonance peaks at 20, 40, and 60 μm and report good agreement between the modeled and measured response. We present a technique of using standard micromachining processes for semiconductor fabrication to make compact, free-standing, resonant, metal mesh filter arrays with silicon support frames. The process can be customized to include multiple detector array architectures, and the silicon frame provides lightweight mechanical support with low form factor.