高速列车万向轴动不平衡检测的改进变分模态分解法

针对变分模态分解法分离信号的效果严重受到惩罚参数和分量个数的影响,应用信息熵差来改进变分模态分解法。首先分析信息熵差对各模态涵盖信息量变化的捕捉特性,应用捕捉特性分析不同惩罚参数条件下变分模态分解重构信号的信息熵差,应用熵差值的跳动确定若干候选惩罚参数,用这些参数条件下的变分模态分解信号的傅立叶谱来检测万向轴的动不平衡。应用万向轴的动不平衡试验数据对该方法进行试验验证,结果表明,该方法能够检测万向轴动不平衡引起的基频、倍频的故障特征,与VMD方法相比较,该方法解决了参数难选的问题,与EEMD方法相比较,该方法的故障检测力得到显著提高。     

基于DTCWPT和奇异值差分谱的万向轴动不平衡检测方法研究

针对万向轴动不平衡振动信号复杂、提取故障特征难度大等问题,提出了基于双树复小波包(Dual Tree Complex Wavelet Packet Transform,DTCWPT)和奇异值差分谱的动不平衡检测方法。首先采用DTCWPT将万向轴振动信号分解为不同频段的分量,对包含万向轴特征信号的频段构造Hankel矩阵;然后计算奇异值差分谱,以差分谱前五个最大突变点确定奇异值重构个数进行重构;最后求傅里叶谱提取万向轴特征频率幅值。通过线路试验数据对该方法进行验证并分析动不平衡值和万向轴转动频率幅值、运行速度间的关系,结果表明:该方法能够有效凸显万向轴动不平衡特征频率,提高谱线清晰度。转频幅值与动不平衡值呈正相关,动不平衡值增大,转频幅值增大;动不平衡值一致,万向轴转频幅值随运行速度增加而增大。     

改进变分模态分解包络谱分析在自动扶梯轴承故障诊断中的应用

针对滚动轴承故障诊断及特征提取问题,提出了改进适应度函数的变分模态分解包络谱分析方法。首先,通过蜻蜓优化方法及同时兼顾相关系数和峭度的适应度函数确定变分模态分解的分解层数和惩罚因子;然后,采用最优的分解参数对振动信号进行变分模态分解;最后,选择适应度最大的分量进行希尔伯特包络谱分析,提取故障特征。试验台数据验证表明该适应度函数能够显著提高变分模态分解的特征提取和降噪能力,且克服了仅用峭度指标寻优时目标易发生过分解的问题;自动扶梯电机轴承故障案例的分析结果表明,基于改进变分模态分解的包络谱分析方法可有效提取滚动轴承故障信号特征,是一种低信噪比情况下滚动轴承故障特征提取的有效方法。     

高速列车万向轴动不平衡检测的EEMD-Hankel-SVD方法

针对聚合经验模式分解(Ensemble empirical model decomposition,EEMD)的等效滤波特性依然存在模式分量间频带重叠较大的根本缺陷,提出一种高速列车万向轴动不平衡动态检测的新方法。该方法的核心是对万向节安装机座的振动信号进行EEMD分解得到基本模式分量,应用基本模式分量信号来构造Hankel矩阵,对该矩阵进行正交化奇异值(Singular value decomposition,SVD)分解,以奇异值关键叠层作为奇异值的选择准则对信号进行重构,应用重构信号的傅里叶谱来检测高速列车万向轴的动不平衡,消除EEMD分解模式频带重叠对故障特征的淹没和混淆效应,提高了谱的清晰度,凸显了故障特征。应用万向轴动不平衡试验数据对该方法进行试验验证,结果表明,该方法能够有效检测万向轴动不平衡引起的故障特征和万向轴的固有振动特征,与纯EEMD方法相比,该方法在谱的清晰度和故障表征力上得到了显著提高。     

基于FOA的变分模态分解在轴承故障诊断中的应用

变分模态分解(VMD)广泛应用于故障诊断中,从振动信号中提取故障特征是故障诊断过程中的关键部分。针对强背景噪声和脉冲干扰下滚动轴承早期故障特征难以提取的问题,提出了一种新的基于果蝇优化算法(FOA)的变分模态分解的轴承故障诊断方法。首先,利用果蝇优化算法自适应优化VMD的惩罚参数α和分解数K,获取最优参数组合;然后,对信号进行VMD分解,得到K个模态分量;最后,基于峭度最大化准则选取最优模态分量进行包络解调分析,提取出故障特征频率。通过仿真信号分析、实际故障轴承信号验证以及与基于果蝇优化算法的多分辨奇异值分解(MRSVD)方法进行对比,证明了所提方法的有效性。     

万向轴动不平衡检测的二代小波变换奇异值方法

针对第二代小波变换依然存在频率混叠的更本缺陷,提出一种高速列车万向轴动不平衡车载检测的新方法。该方法的核心是对万向节安装机座的振动加速度信号进行第二代小波变换得到不同尺度的分解信号,应用单尺度信号构造Hankel矩阵,对该矩阵进行奇异值正交化分解,以奇异值关键叠层作为奇异值的选择准则对信号进行重构,应用重构信号的傅里叶谱来检测高速列车万向轴的动不平衡,消除第二代小波变换频率混叠对故障淹没缺陷,凸显故障特征。应用万向轴动不平衡试验数据对该方法进行试验验证,结果表明,该方法能够有效检测万向轴动不平衡引起的基频、倍频和分频的故障特征,与传统小波、纯第二代小波变换相比,该方法在谱的清晰度和故障表征力上得到了显著提高。     

基于变分模态分解法和共振解调技术的滚动轴承早期故障检测研究

针对滚动轴承早期故障信号提取困难的问题,基于变分模态分解法和共振解调技术,对滚动轴承早期故障检测进行研究。采用变分模态分解法对滚动轴承振动信号进行分解,计算各分解分量的峭度值,并选取两个最敏感的固有模态分解分量进行重构,然后利用共振解调技术进行解调分析,采用快速傅里叶变换计算出包络谱图。试验结果表明,应用变分模态分解法与共振解调技术更能准确地判断出滚动轴承的早期故障。     

基于GA-VMD的滚动轴承故障特征信号提取方法

针对轴承故障提取困难的问题，该文建立了以包络熵和峭度为综合目标函数的变分模态分解(VMD)参数优化方法。用遗传算法对综合目标函数的最小值进行计算寻优，获得最佳的模态分解个数和惩罚因子的值。利用遗传算法(GA)优化的VMD分解方法获得仿真信号和实测信号的本征模态函数(IMFs),依据相关峭度值最大的方法选取IMF敏感分量，并对其进行Hilbert包络谱分析。分析结果表明，基于遗传算法优化的VMD分解方法能够有效提取故障特征信号。     

基于多特征融合的行星齿轮箱点蚀故障诊断研究

为了识别行星齿轮箱的齿面点蚀故障,通过刚柔耦合仿真获得健康和 3 种不同点蚀程度行星齿轮箱的箱体振动信号。对获得的 4 种状态的箱体振动信号进行变分模态分解后,计算每个本征模态函数分量的能量值、峭度因子和信息熵,基于能量值、峭度因子和信息熵多特征融合构建高维特征向量,采用支持向量机分类器对 4 种状态的行星齿轮箱进行识别。结果表明,基于变分模态分解的本征模态函数分量的能量值、峭度因子和信息熵构建的 15 维特征向量,采用支持向量机分类器能够准确识别健康和 3 种不同点蚀程度齿轮的类型。     

万向传动轴动不平衡动态检测的小波能量主元法

提出一种高速列车万向轴动不平衡车载动态检测的新方法。该方法的核心是:对万向节安装机座的振动信号进行谐波小波包分解,提取前19个小波尺度能量形成特征向量,分别统计动平衡、动不平衡万向轴在不同转速条件下振动信号的特征向量而构成主元分析的训练样本,以累积方差贡献量大于0.8作为主分量个数的确定准则,将特征向量从19维降低到2维,应用第一主元和第二主元联合区分万向轴的动不平衡状态。应用台架试验数据对该方法的有效性进行了测试验证,结果表明:该方法能够有效辨别万向轴的不平衡状态,其准确性高,具有一定的工程适应性。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Robust Impedance Control of Robots Using an Adaptive Interaction Force Observer

For robot interaction control,the interaction force between the robot and the manipulated object or environment should be monitored.Impedance control is a type ...     

Research on key techniques of expendable conductivity temperature depth measuring system

This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.     

CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relationship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.