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热误差是精密机床最主要的误差源之一。主轴是机床的关键部件,其热误差直接影响机床的加工精度。文章以某型号精密卧式加工中心主轴为对象,对其温度场和热变形进行了仿真分析。根据仿真结果发现主轴轴向热变形更严重,并结合机床结构确定温度传感器布置位置。在此基础上,对不同转速下主轴部分位置温度和轴向热误差进行现场测试。运用最小二乘法建立热误差补偿模型,直接结合机床FANUC数控系统实施主轴轴向热误差补偿。经实验验证,补偿后主轴轴向热误差减小了85%以上。 相似文献
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数控机床热误差补偿建模综述 总被引:5,自引:4,他引:1
热误差建模技术是决定热误差补偿能否有效进行的关键,对提高数控机床的加工精度至关重要。介绍数控机床热误差建模的国内外研究状况,阐述国内外常用的几种主要的热误差建模方法,即人工智能法、统计分析法、灰色系统法等,探讨各种方法的特点,指出目前研究存在的问题,并展望未来的发展。 相似文献
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热误差是数控加工中的主要误差源之一,对零件加工精度有非常大的影响。对数控车床热误差进行补偿可以有效地提高机床的加工精度。在数控车床的加工过程中,采用铂电阻温度传感器对数控加工中关键点的温度进行实时测量,再配合线性回归理论建立数控车床的热误差模型。最后根据热误差模型对数控车床的加工误差进行实时补偿,经验证该技术是可靠有效的。 相似文献
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Simulation of thermal behavior of a CNC machine tool spindle 总被引:10,自引:0,他引:10
Zhao Haitao Yang Jianguo Shen Jinhua 《International Journal of Machine Tools and Manufacture》2007,47(6):1003-1010
The thermal deformations of a CNC machine tool spindle are the major contributor of thermal error. It is very significant both theoretically and practically to study how to accurately simulate the thermal error of the spindle. Firstly, this paper proposes a method for computing the coefficient of convection heat transfer of the spindle surface by referencing the theory on computing the coefficient of convection heat transfer of a flat plate when air flows along it. Secondly, the temperature field and thermal errors of the spindle are dynamically simulated under the actions of thermal loads using the finite element method. Thirdly, the characteristics of heat flow and thermal deformation within the spindle are analyzed according to the simulation results. Fourthly, the selection principle of thermal key points, which are indispensable for building a robust thermal error model, is provided based on the thermal error sensitivity technology. At last, a verification experiment is implemented on a CNC turning center, and the results show the simulation results are satisfying to replace the experiment results for further studies. 相似文献
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当实际工况与建模工况存在差异时,传统的热误差模型往往表现出较差的鲁棒性和预测精度,主要原因在于建模数据的局限性和模型的未建模动态。为了改善上述状况,提出了一种基于数据驱动的数控机床主轴补偿模型。此模型采用无模型自适应控制算法建模,结合机床运行中生成的数据(温度数据和误差数据)对热误差模型进行实时修正,使模型能快速适应新的加工工况,从而提高模型的鲁棒性。在一台数控车床主轴上进行了试验验证,结果表明:无模型自适应控制与多元回归模型比较,其标准差、最大残差和误差平方和分别提高了41%、62%和56%,此模型的鲁棒性和预测效果好。同时,此方法为大数据在机床主轴热误差补偿中的应用奠定了基础。 相似文献
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热关健点的选择和热误差建模技术是决定热误差补偿是否有效的关键,对提高数控机床的加工精度至关重要.为了实现对数控机床热误差的补偿控制,文章利用模糊C均值(FCM)聚类方法,对机床上布置的温度测点进行优化筛选,将温度变量从20个减少到4个,然后给出了基于RBF热误差补偿建模方法.通过建模实例表明,文章提出的建模方法,在保证补偿模型精度的同时有效减少了温度测点,降低了变量耦合影响,并提高了补偿模型的鲁棒性. 相似文献
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加工中心主轴热误差实验分析与建模 总被引:2,自引:3,他引:2
以TH6350卧式加工中心为对象,构建了一套基于虚拟仪器系统的温度场和主轴的各项热误差。运用多元回归分析方法建立了加工中心主轴的热误差模型,采用模型聚类分析方法和逐步回归方法对模型进行了分析和优化,并提出了基于PC的误差补偿策略。 相似文献
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N. A. Barakat A. D. Spence M. A. Elbestawi 《International Journal of Machine Tools and Manufacture》2000,40(15):2267-2291
An adaptive compensation strategy for quasi-static error correction in intrinsic machines is proposed and tested. The proposed methodology consists of systematic modelling of the machine forward kinematics, including quasi-static errors, as well as direct modelling of the inverse kinematics using nonlinear regression analysis. The result is a model which is a hybrid of physical modelling and regression analysis modelling. In addition, the methodology includes a compensation strategy of the machine contouring errors using the state observer technique for on-line adaptive compensation. A CMM is chosen as a test bed for validation of the proposed methodology. Systematic modelling is carried out in two stages for the forward and inverse kinematics. Regression based models are verified using two different tests. The statistical analysis of variance technique (ANOVA) is used to select the best model in addition to model testing using an independent set equal to approximately 10% of the fitting data. The obtained models are then employed in two compensation strategies; one for the measurement error correction, and another one for the contouring error correction by motion command modification in the forward control path. For contouring tests, the CMM behavior at different thermal states is estimated using experimentally obtained Effective Coefficient of Thermal Expansion (ECTE). Simulations of the machine in contouring selected trajectories are carried out over a range of thermal states. Results obtained show an improvement in the CMM performance to a level close to the machine resolution. The CMM performance is tested using the standard ASME B.89.1.12M-1990 evaluation test, as well as a novel modified version of the test accounting for a thermally varying environment. Machine errors are significantly reduced using the proposed methodology. 相似文献
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Dynamic neural network modeling for nonlinear, nonstationary machine tool thermally induced error 总被引:8,自引:0,他引:8
This paper presents a new modeling methodology for nonstationary machine tool thermal errors. The method uses the dynamic neural network model to track nonlinear time-varying machine tool errors under various thermal conditions. To accommodate the nonstationary nature of the thermo-elastic process, an Integrated Recurrent Neural Network (IRNN) is introduced to identify the nonstationarity of the thermo-elastic process with a deterministic linear trend. Experiments on spindle thermal deformation are conducted to evaluate the model performance in terms of model estimation accuracy and robustness. The comparison indicates that the IRNN performs better than other modeling methods, such as, multi-variable regression analysis (MRA), multi-layer feedforward neural network (MFN), and recurrent neural network (RNN), in terms of model robustness under a variety of working conditions. 相似文献
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R. Ramesh M. A. Mannan A. N. Poo 《International Journal of Machine Tools and Manufacture》2003,43(4):435
Thermal error in machine tools has been observed to be closely linked to the temperature of critical elements of the machine. It was found, in the experiments conducted herein, that there was a significant increase in the axis positioning error on account of an increase in the temperature of the machine elements due to continuous operation. However, it was also observed that the specific operating parameters of the test cycles carried out also significantly affected the positioning error. Different sets of operating parameters generated significantly different error values even though the temperature of the machine elements generated by those operating conditions was similar. As such, this observation forms a very important consideration in the development of a generic thermal error compensation system. It appears to indicate that such a system needs to be capable of evaluating the compensation depending upon the temperature values of the machine elements as well as account for the effect that different operating parameters induce upon the positioning error under the same thermal condition of the machine. This paper attempts to analyse the thermal behaviour of a three-axis vertical machining centre under the influence of various operating parameters and, through the experimental results obtained, point out and explain the effect of these parameters on the axis positioning error. This behaviour forms the basis of an improved modelling methodology that is presented separately in Part II of this paper. 相似文献
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在追求高精度加工的现代数控系统中,热误差的消除具有重要的意义.文章首先简述了神经网络系统的特性及训练方法,成功地将神经网络模型应用于对数控机床直线进给系统的热误差进行建模,并取得了预期的成果,使最大预测误差降低到2μm,为进一步的热误差补偿奠定了基础.详细阐述了实际建模流程,根据训练数据的具体特征提出了一种新的数据预处理方法,使这些数据能更有效地应用于模型训练,是论文的一个创新点. 相似文献
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Characterizations and models for the thermal growth of a motorized high speed spindle 总被引:5,自引:0,他引:5
Jenq-Shyong Chen Wei-Yao Hsu 《International Journal of Machine Tools and Manufacture》2003,43(11):571
In this paper, the characterizing and modeling of the thermal growth of a motorized high speed spindle is reported. A motorized high speed spindle has more complicated dynamic, non-stationary and speed-dependent thermal characteristics than conventional spindles. The centrifugal force and thermal expansion occurring on the bearings and motor rotor change the thermal characteristics of the built-in motor, bearings and assembly joints. It was found that conventional static models using regression analysis and artificial neural network failed to give satisfactory model accuracy and robustness. An auto-regression dynamic thermal error model, that considers the temperature history and spindle-speed information, has been proposed and proved to improve the model accuracy. However, it was found that temperature-based thermal error models, that correlated thermal displacement of the rotating cutting tool to the temperature measurements on the spindle housing, were not robust. Many nonlinear and time-varying thermal sources, such as coolant jacket, motor air gap, motion joints and assembly interfaces influence thermal displacement. The relationship between temperature measurements and thermal displacements is highly nonlinear, time-varying and non-stationary. A new thermal model which correlates the spindle thermal growth to thermal displacements measured at some locations of the rotating spindle shaft has been proposed. It was found that the displacement-based thermal error model has much better accuracy and robustness than the temperature-based model. 相似文献