侵入物高速撞击下铰链式动车组的安全性

为探究侵入物高速撞击下铰链式动车组的安全性,在实物三维扫描重构的基础上,构建一种新的活体三维有限元层叠模型,并在LS-DYNA中进行摆锤侧面碰撞分析验证;通过铰链式动车组与活体在110 km/h速度下的碰撞仿真计算,讨论动车组运行的安全性以及吸能装置的可靠性.结果 显示:活体的有限元层叠模型既能保证计算精度,又能提高计算效率;在110 km/h的碰撞速度下,车体加速度为0.117g,轮对抬升量为0.238 mm,车钩每5 m长度的压缩量最大约为1.89 mm.各项指标都低于EN 15227标准,动车组行车安全性没有受到影响,吸能装置也能可靠工作.     

A decoupled inversion-based iterative control approach to multi-axis precision positioning: 3D nanopositioning example

System inversion provides a nature avenue to utilize the priori knowledge of system dynamics in iterative learning control, resulting in rapid convergence and exact tracking (for nonminimum-phase systems). The benefits of system inversion, however, are not fully exploited in the time-domain ILC approach due to the lack of uncertainty quantification. This critical limit was alleviated in the frequency-domain formulated inversion-based iterative control (IIC) techniques. The existing IIC techniques, however, are for single-input–single-output (SISO) systems only, and the time-domain properties of the IIC techniques are unclear. The contributions of the proposed multi-axis inversion-based iterative control (MAIIC) approach are twofold: First, the IIC technique is extended from SISO systems to multi-input–multi-output systems and is easy to implement in practice. The iterative control law is optimized by using the quantification of the system uncertainty. Secondly, the time-domain properties of the MAIIC law are discussed. The proposed MAIIC technique is illustrated through 3D nanopositioning experiments using piezoelectric actuators. The experimental results clearly demonstrated that by using the proposed technique, precision tracking in all 3D axes can be achieved in the presence of a pronounced cross-axis dynamics coupling effect.     

轨道不平顺影响下高速列车齿轮传动系统的振动特性分析

为了分析高速列车齿轮传动系统在轨道不平顺激励影响下的振动特性变化规律,利用动力学软件SIMPACK建立包含齿轮传动系统的整车动力学模型,分别在大、小齿轮内部布置测点,进行无轨道不平顺和有轨道不平顺工况下的动力学仿真实验,获得高速列车时速250 km/h时大、小齿轮的振动加速度。对大、小齿轮横向、纵向和垂向振动加速度幅值进行频域分析,并对比分析了齿轮传动系统在有、无轨道不平顺工况的振动幅值、频谱分布。结果表明,由于轨道不平顺激励的影响,高速列车齿轮传动系统的横向、纵向和垂向振动加强,振动加速度均增幅明显,其中,垂向振动加速度变化幅值最大。齿轮传动系统的振动频率主要集中在0~400 Hz,小齿轮和大齿轮横向振动受轨道不平顺的影响规律一致,但小齿轮受到纵向振动的影响略小于大齿轮,小齿轮受到垂向振动的影响略大于大齿轮。     

[产品服务]产品服务系统工程特性最终重要度确定方法

提出了一种考虑产品与服务交互的产品服务系统（PSS）工程特性最终重要度确定方法。应用模糊软集合方法解决质量屋在传递信息过程中存在的模糊性和不确定性;利用客户需求改进比率和“买点”对需求基本重要度进行修正,确定需求最终重要度;在工程特性基本重要度的基础上,利用PSS工程特性之间的自相关矩阵、工程特性竞争优先度以及改进比率合成获得工程特性最终重要度。最后以某企业轮式装载机PSS设计为实例,验证了方法的有效性。     

汽车三级分段变刚度双质量飞轮非线性振动研究

分析了三级分段变刚度双质量飞轮（DMF）刚度随扭转角变化的特征,考虑刚度非线性因素建立了搭载DMF的汽车传动系非线性扭转振动模型和对应的微分方程,采用平均法和Runge-Kutta数值积分方法编制算法程序,推导和分析扭转角非线性频率特性近似解析解,并对不同转矩频率下的强迫振动响应进行仿真分析,以进一步探究三级分段变刚度DMF在传动系统中的非线性振动特性。     

基于SK-NLM包络的滚动轴承故障冲击特征增强

非局部均值算法(NLM)是活跃于图像信号处理领域的一种新方法,因其良好的去噪特性,近几年来在滚动轴承故障诊断领域也开始获得应用。NLM利用样本点邻域窗口包含的局部结构为基本单元,通过对相似成分加权运算后取其平均值以达到抑制噪声干扰、突出故障冲击特征的目的。但对于强噪声条件下的低信噪比信号而言,NLM滤波效果并不理想。提出一种结合谱峭度(SK)和NLM权重包络谱的故障诊断方法,首先对原始信号进行SK分析得到最优中心频率及带宽构成最优滤波器,初步消除环境干扰及测量噪声;其次对NLM算法进行改进,不再以滤波信号为分析对象,而是直接利用NLM加权运算得到的信号样本点权值分布曲线作为预处理信号的包络信号,从权重角度使故障冲击得到二次增强,消除SK带通滤波器的带内噪声;最后对权值分布曲线进行包络谱分析,进而得到诊断结果。通过仿真信号、实验室信号及工程实际信号分析对所提方法进行了验证,并与最小熵解卷积(MED)进行了对比。     

振动图像结合CNN的轴承振动信号分析方法研究

本文以强背景噪声下振动信号特征提取和建模分析为研究目标,提出将振动信号转换为振动图像的信号变换方法,以深沟球轴承故障诊断振动信号和轴承质量等级评估振动信号为实验数据集,基于振动图像的卷积神经网络模型（VI-CNN）,并采用正确识别率（CRR）作为模型精度的评价指标。实验结果表明:对于轴承故障诊断和质量等级评估的定性判别,采用VI-CNN对比其他建模方法正确识别率分别为100%和98.16%,模型有更好的稳健性。     

Modeling and vibration characteristics analysis of a DMF rotor system

To analyze the vibration response of a rotor system with circumferential short spring dual mass flywheel (DMF) when the primary flywheel speed changes, the interactions (forces and torques) between the primary flywheel, spring seat, spring, and secondary flywheel are analyzed in detail, and the dynamic analysis model of the DMF rotor system is established considering the influence of clearance and friction between parts in the DMF in this study. The vibration response of the DMF is investigated by numerical method. By analyzing the bifurcation diagram, time history, phase trajectories, Poincaré section, and frequency domain of the relative angular displacement, the variation of vibration form of the system under different excitation frequencies are discussed. Besides, the effects of load, primary flywheel speed amplitude, and spring stiffness on system vibration are also analyzed. Finally, some of the results from the analytical study are verified through the DMF rotor system experiments.

     

Nondestructive measurement of soluble solid content of navel orange fruit by visible-NIR spectrometric technique with PLSR and PCA-BPNN

A relationship was established between the soluble solid content (SSC) of navel orange fruit determined by destructive measurement and visible-near infrared diffuse reflectance spectra in the wavelength range of 350-1800 nm. Multiplicative scatter correction (MSC) and standard normal variate correction (SNV) were applied to the spectra, partial least squares regression (PLSR) and back propagation neural network (BPNN) based on principal component analysis (PCA) were used to develop the models for predicting the SSC of intact navel orange fruit. Thirty-eight unknown samples were used to evaluate the performance of these models. The principal component analysis-back propagation (PCA-BPNN) method with MSC spectral pretreatment obtain the best predictive results, resulting in correlation coefficient, root mean square error of prediction (RMSEP), average difference between predicted and measured values (Bias) of 0.90, 0.68 °Brix and 0.16 °Brix, respectively. Experimental results indicate that PCA-BPNN is a suitable tool to model the non-linear complex system, with additional advantages over PLSR, and the vis/NIR spectrometric technique can be used for measuring the SSC of intact navel orange fruit, nondestructively.