加工误差补偿的内车削再生颤振辨识与鲁棒控制

为解决内部车削再生颤振以及加工误差问题,提出了一种基于加工误差补偿的内车削再生颤振辨识与鲁棒控制方法。首先通过第一分量法实现了切削力模型参数辨识。然后利用上一步确定的切削力模型参数,综合考虑与颤振再生特性相关的时滞项,以及切削力和柔性镗杆模型的不确定性,设计了一个鲁棒稳定控制器用于解决内部车削过程中再生颤振控制的关键问题。进一步前馈项来消除杆端偏转,有效实现了加工误差补偿。最后通过模拟内车削过程的实验证明提出方法可以得到切削系数和重叠因子的合理估计,并且可以提升切削过程颤振抗扰度,降低了切削力直流分量引起的柔性杆挠度误差。     

切削颤振的动态切削力测试与研究

切削颤振的动态切削力测试与研究东北重型机械学院于忠海，李金良，张纪信一、前言金属切削加工中．在工件与刀具之间经常发生强烈的振动．其中颤振所占比重较大。目前．关于颤振的理论．如再生自振理论，振型关联理论．摩擦特性自振理论等、各学说都是从不同的角度来解释...     

切削颤振分析与模糊控制实验研究

切削颤振是影响金属切削加工生产率和加工质量的重要因素。建立了金属切削过程的二维颤振数学模型;对颤振的稳定性进行了线性分析和非线性分析;并以颤振位移作为反馈变量,建立了基于二维模糊控制器的颤振控制系统。实验结果表明,该分析与控制对降低加工表面粗糙度具有重要意义。     

切削加工系统再生颤振机理的研究概况

再生颤振是金属切削加工过程中的一种常见现象,也是影响零件加工质量和限制生产率提高的主要因素之一。本文分别从线性和非线性颤振理论的角度,综述了国内外对再生颤振理论的研究概况。     

一种基于振动信号处理的颤振预报方案研究

针对切削过程中产生的颤振现象,通过对机床的在线监测,将采样出的振动加速度信号进行数据处理,提出一种以方差和互相关系数作为综合判据的方法来判别颤振是否发生,并在MATLAB环境下仿真证明该方法的可行性。     

基于开放式控制器的铣削颤振在线抑制

为实现在线抑制铣削颤振,对颤振领域常用的传感器监控技术,尤其是三向切削力和振动加速度传感器的各向分量在颤振监控过程中的时域和频域敏感信号特征进行试验研究。针对监控的颤振敏感信号频域特性,研究快速傅里叶变换技术对信号有效信息的在线提取技术。对自激颤振的机理进行分析,建立颤振频率与主轴转速间的关系模型,为实现变主轴转速抑制自激颤振提供理论基础。对集成在线参数采集、反馈控制的全软件型模块化铣削控制器进行设计,将在线抑制颤振的相关变主轴转速算法嵌入开放式控制器中,并设计控制参数数据流在控制器模块间的实现流程。对连续变切削深度铝合金工件进行在线颤振抑制加工试验,试验验证开放式智能铣削控制器在线抑制颤振相关技术的正确性。     

一种通过变进给量保证切削平稳的加工方法

简要介绍了常见加工过程中引起切削颤振的现象和原因,并以飞刀加工汽车同步器齿套滑块槽为例,分析了导致此种切削颤振的原因,并建立了切削力数学模型;通过改变进给量及切削速度的方法改善了切削振动,提高了生产质量。     

变速切削抑制颤振的控制系统及实验研究

为解决切削颤振给加工过程带来的不利影响,设计了基于DSP的适用于变速切削的电动机控制系统,编制了控制程序,并应用改造后的铣床进行了变速切削抑振试验。根据检测所得的加速度信号和声音信号,分析了变速幅值和变速频率对切削振动的抑制效果,对变速铣削进行了较为深入的分析和研究。     

基于IES的切削颤振孕育期信号降噪方法

切削颤振孕育期介于稳定切削与颤振爆发之间,该阶段切削力信号中颤振特征具有典型微弱信息特性。采用基于总体经验模态分解（ensemble empirical mode decomposition, 简称EEMD）与奇异值分解（singular value decomposition, 简称SVD）相结合的方法对颤振孕育期信号进行降噪时,大多存在噪声剔除不充分或微弱目标特征信息失真等问题。首先,通过引入功率谱密度（power spectral density, 简称PSD）与常相干函数（common coherency function, 简称CCF）对EEMD降噪机制进行改进,使微弱目标特征所在本征模态函数（intrinsic mode function, 简称IMF）分量得到有效提取;其次,借助池化原理（pooling principle, 简称PP）降低IMF分量复杂度,并联合SVD对其实施分块降噪,以实现对微弱目标特征中所含噪声进行有效消减;最后,耦合上述改进并重构信号,可面向微弱目标特征信号形成基于改进EEMD?SVD（improved EEMD?SVD,简称IES）的降噪方法。分别利用IES与EEMD?SVD对Rossler混沌信号进行降噪处理,并通过比较信噪比、均方误差及平滑度等降噪评价指标,对所提方法在降噪有效性及信息保真度方面的优势进行量化验证。在此基础上,再次借助所提IES方法对变轴向切深铣削实验中颤振孕育期铣削力信号进行降噪分析。结果表明,该方法能显著抑制颤振孕育期信号噪声,并能有效避免微弱颤振特征信号失真问题。     

基于时域仿真法的断续铣削颤振预测

颤振是影响铣削加工表面质量和限制切削效率的重要原因,准确获取稳定性叶瓣图是避免颤振的有效途径.精加工铣削常使用小径向切深/刀具直径比,产生过小的实时切削厚度,刀具容易脱离工件,造成显著非线性因素;过小的径向切深/刀具直径比也导致铣削加工高度断续.因此,常用的圆弧切削厚度已不能近似实际切削厚度,进而影响断续铣削加工颤振预...     

电流变液减振器在抑制深孔切削颤振上的研究

针对深孔机床切削中的颤振问题,设计了一套基于流动模式的电流变液减振器,分析了电流变液减振器的阻尼力并得出其表达式;又通过对切削颤振产生原因的分析,推导出瞬时动态钻削力的表达式;并在研究了深孔机床切削过程的基础上,建立了切削系统动力学模型,得出安装电流变液减振器后的动力学方程。在给定动力学方程中的参数值后,通过计算机仿真,对比安装和未安装电流变液减振器后的振动时域图,时域图表明电流变液减振器能有效地抑制深孔机床的切削颤振。     

超声振动干式车削尺寸精度实验研究

采用超声振动干式车削方法对钨基合金材料进行了车削加工实验,研究了切削参数、振动参数对零件加工尺寸精度的影响。结果表明,在切削深度一定的前提下,对于加工圆度影响的主次关系为:进给量>振动振幅>切削速度;而对锥度影响的主次关系为:振动振幅>切削速度>进给量。在低速低进给加工方式下,振动车削的抑振效果不明显,但随着切削速度、进给量的增大,振动切削抑振效果显著。本实验条件下,当振动振幅为3μm时,对工艺系统具有较佳的抑振效果。     

基于电流变材料的车削切断颤振抑制研究

应用电流变材料的特殊性能——对电信号的快速响应能力和连续可变的阻尼，研制了一种智能切削颤振抑制结构(刀座刚度可变部分)，并将其附加在车床刀架上，建立了机床车副颤振实时监控系统，实现了机床车削切断过程的颤振抑制。实验结果表明，利用电流变材料智能切削颤振抑制结构可以对机床车削振动进行有效控制，刀具的振动幅值减小50％以上，且工件表面的加工质量有较大提高。     

Proposal of novel spindle speed variation profile with constant acceleration rate for improvement of chatter stability

Spindle speed variation (SSV) is one of the effective methods which suppresses regenerative chatter. However, regenerative chatter can grow even if SSV is applied. In the previous work, the chatter growth characteristics in SSV were clarified. The chatter frequency changes proportionally to the varying spindle speed, and it causes the change of the magnitude of the dynamic compliance. Hence, chatter can be suppressed through SSV since the dynamic compliance usually reduces as the chatter frequency changes. A greater compliance reduction can be obtained by a higher rate of spindle speeds in two consecutive revolutions at the same angular position, i.e., acceleration rate. From the investigations in the previous work, limitation of the conventionally utilized SSV profiles is found as follows: the acceleration rate always fluctuates with speed variation and the chatter vibration grows where the acceleration rate is insufficient for suppression, and hence suppressing chatter in all sections of SSV is difficult. In this paper, a new SSV profile with a constant acceleration rate, namely CAR-SSV, is proposed to overcome the limitation of chatter stability improvement by utilizing conventional SSV profiles. The magnitude of the acceleration rate is kept constant to realize the chatter suppression effect throughout the cutting process. Through time-domain simulation and cutting experiments, the chatter stability of CAR-SSV is investigated based on the previously introduced chatter stability evaluation indices. Influence of the parameters of CAR-SSV on the stability is investigated, and an appropriate strategy for setting SSV parameters to achieve higher stability is discussed. In addition, in order to verify the effectiveness of the proposed profile, the stabilities of conventional SSV profiles and CAR-SSV are compared through time-domain simulations and cutting experiments.     

金属切削加工的颤振及避振分析

针对规避切削颤振问题,应用相对切削速度概念,提出了速度型动态切削力表达式以及车削或镗削的振动力学模型。通过对速度型动态切削力分析,解释了切削颤振产生的机理,给出了颤振发生的必要和充分条件。同时指出,在较大的切削速度范围内,存在一个或两个相对稳定的切削速度区域。如果公称切削速度处于该稳定区域,即使背吃刀量较大,系统也不易发生颤振。这种相对稳定的切削速度区域是可以预估的,文中给出了预估公式及预估方法,并由实验分析验证。依据能量原理提出的极限背吃刀量指标是预防颤振发生的有效预估指标,极限背吃刀量的表达式也解释了变速切削技术抑制颤振的原理。     

Milling force vibration analysis in high-speed-milling titanium alloy using variable pitch angle mill

Chatter may cause fast wear of tools and poor surface quality of the workpieces at high cutting speed and it will happen on different process parameters; how do we select the suitable cutting speed to suppress the chatter? In this paper, a signal analysis method for milling force and acceleration is adopted to identify chatter, which can obtain the results not only in frequency of chatter but also in the contribution for milling force at different frequencies. Through the milling experiment, the machining vibration behaviors of milling Ti–6Al–4V with variable pitch end mill were investigated. Milling force and acceleration signals obtained from experiment were analyzed and compared at stable and unstable milling processes. The experimental results show that when the chatter occurs, milling forces were found to increase dramatically by 61.9–66.8% compared with that of at stable cutting; machining surface quality became poor and machined surface roughness increases by 34.2–40.5% compared with that of at stable cutting.     

Analysis of regenerative chatter suppression with adding the ultrasonic elliptical vibration on the cutting tool

A method is proposed to suppress regenerative chatter in turning operation, in which the ultrasonic elliptical vibration is added on the cutting tool. It results in the fact that the cutting tool is separated periodically from the chip and the workpiece, and the direction of the frictional force between the rake face of the cutting tool and the chip is reversed in each cycle of the ultrasonic elliptical vibration. The experimental investigations show that the regenerative chatter occurring in ordinary turning operation can be suppressed effectively by applying the ultrasonic elliptical vibration on the cutting tool. In order to clearify the reason of the regenerative chatter suppression, theoretical analysis and computer simulation are performed on turning with ultrasonic vibration. There is a good agreement among the experimental investigations, theoretical analysis and the computer simulation.     

振动钻削的变速减振特性分析

钻削加工中的切削颤振是十分有害的 ,它严重地影响加工精度和生产率的提高 ,降低机床和刀具的寿命。振动钻削方法具有消减切削颤振的特殊功能 ,能够取得良好的加工效果。根据振动钻削所具有的变速切削特性 ,提出了振动钻削的变速减振新概念。在深入研究了机床加工系统的振动响应规律和振动变速切削减振的能量化原理的基础上 ,揭示了振动变速切削的瞬态不充分响应的减振本质。     

REGULARITY OF VIBRATION RESPONSE OF MECHANICAL SYSTEM UNDER AFFECT OF VARI-FREQUENCY EXCITING FORCE

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Chatter and dynamic cutting force prediction in high-speed ball end milling

Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.