基于Matlab的AR模型参数估计

基于Matlab用时间序列的最小二乘估计和FPE、AIC、BIC准则对AR(n)模型进行参数估计。用实例说明运用Matlab进行AR(n)参数估计,编程简单,分析直观     

时序分析在机床上的应用技术讲座第四讲建模(二)

AR模型的参数估计方法,是线性回归过程,计算简单且速度快,故实际中多采用AR模型。ARMA模型的参数估计则不然,由于｛at｝未知,必须采用非线性回归方法估计参数,比较复杂。下面介绍两种较为简单的ARMA模型参数估计方法。 一、长自回归计算残差法 此法的具体步骤是:第一,按任一种A     

一种AR模型的稀疏模态参数估计方法

基于自回归模型(autoregressive,AR)的模态参数估计方法需要进行阶次估计,阶次确定错误会使结果中包含虚假模态或者遗漏模态。针对这种情形,通过将模态选择的问题转化为带有稀疏约束的振型系数问题,提出了一种基于AR模型的稀疏模态参数估计方法。先假设一个较大的系统阶次,采用基于AR模型的估计方法计算模态参数,然后构造振型系数的稀疏优化模型,多次稀疏求解后用统计和聚类的方法对结果进行校正,最后根据振型系数鉴定对应模态的真假。这种无需提前确定阶次的估计方法既避免了定阶次引起的误差,又能有效地将噪声模态分离,适合复杂环境下的参数估计。在斜拉索桥模型上验证结果表明,该方法具有良好的识别效果。     

基于DSP的AR谱估计的实现

为实现实时在线谱分析,将数字信号处理(DSP)技术应用到AR功率谱分析中.利用Burg算法对AR模型进行参数估计,建立AR模型与数据之间的关系,并通过编程实现模型自动定阶.在旋转机械故障模拟实验平台上对齿轮箱进行实测,通过与B&K公司Pulse Labshop分析系统的FFT谱对比试验.结果表明:AR谱和FFT谱所得结果一致,并且AR谱具有较好的分辨率、谱峰突出等优点,在机械故障诊断中具有较好的前景.     

基于粒子滤波的陀螺随机漂移预测模型研究

陀螺随机漂移是弱的非平稳非线性信号,传统的线性化参数估计方法会导致模型参数不精确。提出采用粒子滤波的方法对陀螺随机漂移时间序列AR模型进行滤波处理,试验结果表明:粒子滤波不仅消除了非线性对陀螺漂移的影响还克服了AR模型的参数估计误差。与UKF滤波方法相比,粒子滤波的随机量不受高斯分布的限制而且滤波结果可以达到或超过UKF。     

基于粒子群优化算法的 AR模型参数估计

利用粒子群优化算法对模型AR（ P）参数进行优化,提高了模型的预测精度。采用AIC准则判断出模型的最佳阶数。该估算方法优于传统的基于最小二乘估计和基于灰色理论估计,为此类模型的参数估计提供了一种新思路。     

基于广义逆矩阵的AR模型参数估计算法

AR(auto-regressive)模型是时序建模分析中常用的时间序列模型。在模型参数的最小二乘估计和定阶的过程中,要求线性方程组必须有解。针对这一问题,文中引入自相关系数矩阵对线性方程组进行化简,并提出基于广义逆矩阵理论的参数估计方法。该算法对线性方程组是否有解没有限制,无需事先判定,从而解决建模过程中线性方程组无解情况下的参数估计问题。实验证明该法可有效地对设备运行状态进行趋势预测,具有一定的工程意义。     

用电镀珩具(铰刀)进行深孔精细加工

先进的深孔精加工技术和高性能价格比的深孔加工装备,能促进我国制造业高速发展.介绍了用电镀珩具进行深孔精加工的方法与应用实例.     

深孔钻削工艺及深孔钻床

所谓深孔,目前尚没有一个确切的定义。一般认为孔深与孔径之比大于5～10,甚至到100或100以上的孔叫深孔。 一、麻花钻加工深孔的缺点 深孔钻削在很久以前以至于现在还没有使用深孔加工专用机床的厂家,都是用麻花钻进行钻削,这种加工方法存在下列缺点:     

深孔加工技术的基本资料

深孔加工与用普通麻花钻加工孔不大相同,其排屑、钻尖冷却等都很困难。一般孔长为孔径10倍以上的称作深孔。深孔加工方法大体上分为两种方法,它们彼此适应不同的孔径范围。     

AUTOREGRESSIVE MODEL AND POWER SPECTRUM CHARATERISTICS OF CURRENT SIGNAL IN HIGH FREQUENCY GROUP PULSE MICROELECTROCHEMICAL MACHINING

The identification of the inter-electrode gap size in the high frequency group pulse micro-electrochemical machining (HGPECM) is mainly discussed. The auto-regressive(AR) model of group pulse current flowing across the cathode and the anode are created under different situations with different processing parameters and inter-electrode gap size. The AR model based on the current signals indicates that the order of the AR model is obviously different relating to the different processing conditions and the inter-electrode gap size; Moreover, it is different about the stability of the dynamic system, i.e. the white noise response of the Green's function of the dynamic system is diverse. In addition, power spectrum method is used in the analysis of the dynamic time series about the current signals with different inter-electrode gap size, the results show that there exists a strongest power spectrum peak, characteristic power spectrum(CPS), to the current signals related to the different inter-electrode gap size in the range of 0-5 kHz. Therefore, the CPS of current signals can implement the identification of the inter-electrode gap.     

基于磁流变液深孔钻削颤振抑制技术的研究

在传统的深孔加工过程中,切削振动很难抑制,只能凭借加工经验来判断和处理。本文利用磁流变液减振器来抑制振动,详细分析了磁流变液减振器的三种工作模式:流动模式、剪切模式和挤压模式。通过对深孔加工系统模型的分析得到系统动力学方程,并利用MATLAB/Simulink对系统动力学模型进行仿真分析,验证其可行性。比较分析结果表明,磁流变液减振器能够有效抑制深孔加工的切削振动。     

基于DEFORM-3D的深孔枪钻切屑成形机理分析

切屑形态对枪钻深孔加工中孔成型精度影响较大,利用DEFORM-3D有限元仿真软件模拟深孔加工中切屑的形成过程、形态和断屑方式,准确复现切屑的形成过程及形态,并计算切屑的曲率与厚度。模拟分析与记录轴向力、扭矩和切削过程温度等参数,揭示出力与扭矩的全过程变化规律,分析得出切削刃温度最高区域、相邻区域的温度分布规律,为切削过程工艺参数的控制提供理论依据。试验与仿真数据对比分析表明,采用有限元分析方法可为枪钻深孔切削过程工艺参数选取和优化提供基本可信的依据,并有效缩减切削试验次数。     

深孔镗杆在推镗和拉镗时的ANSYS受力分析

深孔镗削是提高深孔加工精度的一种方法,它能校正己有孔上的缺陷,如圆度误差、直线度误差,从而获得良好的几何精度和表面粗糙度。深孔镗削的加工方式、运动形式、镗刀的轨迹方程和对镗削的受力分析是深孔镗削加工中各不稳定因素的渊源,在深孔镗削过程中,运用合适的镗削方式可以减小切削系统的振动。针对多刃均布式深孔镗刀,在推镗和拉镗方式下进行受力分析,并利用PRO/E建立镗杆几何模型并生成中性几何文件,通过ANSYS有限元法,计算出推镗和拉镗时镗杆产生的挠度以及最大应力应变曲线,将二者结果进行比较,证明在细长管时拉镗加工的优势。     

亚干式深孔加工中的低温冷风雾化技术

结合干式切削加工的特点和深孔加工的特性，提出了将干式切削技术应用于深孔加工的设想，制定了运用低温冷风冷却、排屑及切削液雾化润滑刀具的亚干式深孔加工方法，并对其工作原理及在深孔加工中的具体运用进行了系统的分析和探讨，从而使干式切削技术的应用范围更广泛。     

自定心深孔参数测量装置及测量方法

深孔内径尺寸测量是大型精密仪器零件加工、制造、装配以及测量过程中的一项重要技术。在研究现有深孔测量方法的基础上,设计了一种具有自定心功能的深孔参数测量装置,背向设置的双锥体自平衡结构来实现测量主轴在被测深孔内的径向定心,对称布置的激光测距传感器进行孔径参数的实时测量,数据记录装置完成测量数据的记录与处理。与现有测量系统比较,该设计优于光杠式行走测量装置,可用于中大型精密仪器轴孔内径的高精度自动化在线测量。     

Adaptive modelling of the milling process and application of a neural network for tool wear monitoring

An adaptive signal processing scheme that uses a low-order autoregressive time series model is introduced to model the cutting force data for tool wear monitoring during face milling. The modelling scheme is implemented using an RLS (recursive least square) method to update the model parameters adaptively at each sampling instant. Experiments indicate that AR model parameters are good features for monitoring tool wear, thus tool wear can be detected by monitoring the evolution of the AR parameters during the milling process. The capability of tool wear monitoring is demonstrated with the application of a neural network. As a result, the neural network classifier combined with the suggested adaptive signal processing scheme is shown to be quite suitable for in-process tool wear monitoring     

基于J散度的模式分类方法在故障诊断中的应用

提出了一种基于J散度的谱系聚类算法，对不同状态下信号的AR模型进行了分类，以分类结果建立正常信号的标准样本，比较待检样本与标准样本之间J散度和设定闽值的大小，实现对待检样本的分类。将该方法应用于往复式压缩机气阀的故障诊断中，比较J散度与欧氏距离和相关系数在分类中的效果，证实了基于J散度的模式分类方法的分类结果更加准确。     

Investigation on shaping machining method for deep hole keyway based on on-line symmetry detection and compensation

Machining of deep hole keyway often suffers from low processing accuracy, low processing symmetry degree between keyway and the reference plane and is difficult to control. In order to enhance the processing quality, a mathematical model of space symmetry error was established based on space projection, orthogonal combination and linear fitting methods so as to study rotatable and shift-able space objects. The space symmetry error was separated into included angle error and displacement error between the fitting straight line and the benchmark line. Through included angle rotation and location measurement along with quantitative translation, the space symmetry error compensation was realized. On the basis of the proposed methods, a Double combined manual self-centering fixture (DCMSF) was designed to realize the radial self-centering and axial location for effective clamping of deep hole keyway, and the reference plane of built-in straight slot was derived out to make it detectable and controllable. Meanwhile, an Online multi-degree of freedom symmetry detection device (OMFSDD) and corresponding Numerical control (NC) programs were also designed for automatic detection and control of symmetry error. Subsequently, mass production of high symmetric deep hole keyway were realized by means of NC gear shaper servo control of rotating shaft angle compensation and bi-directional cutter back-off amount translation compensation, and combination of NC control of fixed angle processing. Deep hole keyway processing experiments indicate that the proposed method can steadily keep the symmetry within 0.03 mm. Thus, the rationality and accuracy of the proposed method was validated which provides a novel approach to high precision deep hole keyway processing.

     

绿色干式深孔加工技术的研究

阐述现代干式深孔加工的优点与面临的问题,并就面临的问题进行分析和解决.在深孔加工方案解决中,对刀具的材料、结构及几何参数进行分析改进.通过试验得出结论,所述方案与传统方案比较不仅很少用切削液,而且刀面平均磨损量减少了十个百分点.