摘要
为了改善成形磨削加工过程中的热态特性,进一步提升高性能磨床的加工精度,在分析了成形磨床移动式立柱温度场特性基础上,针对移动式立柱温度场非线性、大滞后的特点,提出了逐级递推拟合式算法以预测立柱温度场变化趋势。为了检测并分析移动式立柱温度场分布,采用LabVIEW(Laboratory VirtualInstrument Engineering Workbench)虚拟仪器开发了多通道温度场检测仪器。结合实验数据将拟合算法应用到移动式立柱温度场热误差与变形分析中,拟合曲线与实验检测数据进行对比,证明此算法具有较高的拟合精度,而且运算过程快速、方法简单实用,适用于移动式立柱温度特性分析、热误差预测建模与误差消除等方面。具体包括:
第一章,本章介绍了高性能成形磨床技术国内外发展现状,讨论了热误差引起的变形对制造精度的影响。详细阐述了国外发达工业国家在温度场分析与热误差建模方面的研究现状,以及国内重点大学对此课题的研究成果。最后论述了课题的研究意义,提出了论文的主要研究内容及结构。
第二章,本章介绍了虚拟仪器在温度检测领域的作用和意义,详细阐述了温度采集系统方案的硬件配置与性能参数。采用虚拟仪器LabVIEW开发了一套多通道温度采集系统,并且解释了温度采集仪器各个模块的用途、程序设计方案、人机交互界面的设计理念与操作方法等,为后续的温度场检测实验以及算法拟合应用奠定坚实基础。
第三章,本章首先介绍了温度场热传递基础理论,并在此基础上阐述了稳态与瞬态温度场有限元分析的数学建模方法。基于实验数据绘制温度场走势图像,并对成形磨床中腰导轨移动式立柱进行工况与热源分析,通过温度对比图像说明立柱前、后侧表面存在温度差。运用有限元理论与ANSYS软件对立柱热源所产生的温度场分布进行分析,进一步证明立柱温度场分布不均衡,也为后续温度数据拟合研究建立依据。
第四章,本章提出了逐级递推拟合算法,详细阐述了实验方法、过程及结果,并根据实验数据对移动式立柱温度场热误差、热变形、误差消除进行系列研究。针对移动式立柱温度场变化符合多阶指数函数规律的特点,为了建立准确的热误差数学模型,高精度地预测立柱温度场变化趋势,针对实时间数跨度较大的多阶指数函数,提出一种新的逐级递推拟合式算法。根据不同时间常数的指数函数具有不同平衡时间的特点,通过数学方法变化,采用一阶指数函数的拟合算法进行拟合并逐级递推,分别得到多阶指数函数的不同项的时间常数和相应的幅值。最后将所提出的算法在温度场数据拟合、热变形数据拟合以及误差消除等方面进行应用,将拟合曲线与实验检测数据进行对比,证明此算法具有较高的拟合精度,而且运算过程快速、方法简单实用,适用于移动式立柱温度特性分析和热误差预测建模。
第五章,对全文进行全面的总结,并系统回顾本文的研究思路和成果。展望下一步的研究工作和计划,并为将来的研究提出设想。
In order to improve thermal characteristic of form-grinding process and further enhance machining accuracy, a step-by-step recu(?)sive fitting algorithm has been presented to predict the variation trend of form grinder movable upright column based on the analysis of non-linear and time-lagging features. To measure temperature distribution on column, a multi-channel temperature measuring device was developed on the platform of virtual instrument LabVIEW (Laboratory Virtual Instrument Engineering Workbench), and then finite element analysis was carried out. High fitting precision has been proved by comparing the fitting curve with the test curve. The fitting algorithm is suitable for temperature characteristic analysis, thermal error prediction modeling and error elimination.
Chapter One. Developing situation of high-performance form grinder both at home and abroad was introduced. Negative influence caused by thermal error and deformation was then explained. The research progress on temperature field analysis and thermal error modeling conducted by foreign developed countries and domestic key universities was clarified. At the end, the significance, content and structure of this study were presented.
Chapter Two. Detailed design plan of temperature measurement device by virtual instrument LabVIEW was presented, including hardware configurations and software parameter settings. And then, the design process of this device was explained, including the function of each module, programming method, data acquisition and exchange, man-machine interface and operation principle, and thus laying solid foundation for the following temperature measurement test and algorithm application.
Chapter Three. Finite element theory of steady-state and transient-state temperature field based on heat transfer principle was explained. Then operating condition and thermal source analysis of movable upright column was iterated through temperature contrast between the front and back profile of column. Temperature field distribution of each thermal source was analyzed by ANSYS, which further proved that temperature distribution on upright column was unbalanced and paved the way for the subsequent study on thermal data fitting of movable upright column on high-performance form grinder.
Chapter Four. Thermal error of form grinder column possessed non-linear, time-lagging and multi-parameter characteristics based on the analysis of temperature field distribution on column. Based on the analysis of data, a step-by-step recursive fitting algorithm was presented to process multi-order exponential function with large span of time constant. In accordance with the feature that exponential function with various time constants has different equilibrium time, first-order exponential function fitting algorithm was adopted; then time constant and corresponding amplitude of multi-order exponential function through step-by-step fitting. High fitting precision has been proved by comparing the fitting curve with the test curve. The fitting algorithm is suitable for temperature characteristic analysis, thermal error prediction modeling and error elimination, which were proved by practical applications.
Chapter Five. The study ideas were reviewed and results summarized. And the prospect of this thesis was also presented for further study.
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