【作者】 张皓；

【导师】 曲兴田；

【作者基本信息】 吉林大学 ， 机械制造及其自动化， 2019， 硕士

【摘要】 现代机床的发展趋势逐渐朝向高精度、高效化、高可靠性发展,对机床的动态特性有了越来越严格的要求。机床的整体性能对工件的加工质量有着极其重要的影响,本文针对混联机床的关键结部件进行实验模态分析并对薄弱环节进行结构优化,同时对机床加工精度影响最大的并联机构几何误差进行了建模分析,为机床的后续优化及误差补偿提供参考。针对混联机床关键结构:动平台、工具板以及龙门框架进行了实验模态分析,采用东方所研制的智能数据采集和信号分析系统,以力锤激励法对关键结构进行激励,并分别通过PolyLSCF频域法和特征系统实现算法对试验结果进行分析拟合,通过综合比较确定机床关键部件的模态参数:前四阶固有频率,阻尼以及振型,确定横梁结构为混联机床的薄弱环节。针对混联机床的薄弱环节——横梁结构进行了基于ANYS Workbench中的多目标响应面优化法进行结构优化,选取对横梁整体刚度与质量影响最大的五个尺寸:横梁主体的长度、宽度和高度以及导轨座的长度和宽度作为优化的设计变量,以横梁一阶固有频率、最大变形量以及总体质量作为优化输出,建立相关数学模型,通过多目标响应面优化法进行优化,从28组样本方案中选出最优方案,并与原结构进行对比,确定横梁的一阶固有频率、最大变形量以及总体质量方面均有提升,不仅提高了横梁结构的刚度,同时达到了轻量化的效果,验证了优化方案的可靠性。以机床的串联结构与并联结构的几何误差为研究对象,分别采用基于多体系统理论的建模方法与基于D-H矩阵变换的建模方法对串联结构和并联结构进行几何误差建模,着重研究并联结构的几何误差建模,并进行仿真分析。详细概述了多体系统理论与D-H矩阵变换的基本原理,全面分析并联机构所有环节的误差源,并推导出误差模型的正解与逆解。随后采用控制变量法,将各个误差参数的变化范围锁定在七级公差值到八级公差值之间,观察分析各项误差参数对动平台中心位姿的影响情况。更多还原

【Abstract】 The development trend of modern machine tools is gradually toward high accuracy,high efficiency and high reliability.There are more and more stringent requirements for the dynamic characteristics of machine tools.The overall performance of machine tools has an extremely important impact on the quality of workpiece processing.In this paper,experimental modal analysis is carried out for the key components of hybrid machine tools and structural optimization is carried out for the weak links.At the same time,the geometric errors of parallel mechanisms,which have the greatest impact on the machining accuracy of machine tools,are modeled and analyzed to provide reference for the subsequent optimization and error compensation of machine tools.The experimental modal analysis of the key structure of hybrid machine tool: moving platform,tool board and gantry frame is carried out.The intelligent data acquisition and signal analysis system developed by Dongfang Institute is used to excite the key structure by force hammer excitation method.The experimental results are analyzed and fitted by PolyLSCF frequency domain method and feature system algorithm respectively.The key of machine tool is determined by comprehensive comparison.The modal parameters of the components: the first four natural frequencies,damp and mode shapes,determine that the beam structure is the weak link of the hybrid machine tool.Aiming at the weakness of hybrid machine tool,the cross beam structure is optimized by multi-objective response surface optimization method based on ANYS Workbench.Five sizes which have the greatest influence on the overall stiffness and quality of the cross beam are selected: the length,width and height of the main body of the cross beam and the length and width of the guide rail seat.The first natural frequency and the maximum deformation of the cross beam are taken as the design variables for optimization.As well as the overall quality as the optimal output,the relevant mathematical model is established and optimized by the multi-objective response surface optimization method.The optimal scheme is selected from 28 sample schemes,and compared with the original structure,the first natural frequency,maximum deformation and overall quality of the beam are ascertained,which not only improves the stiffness of the beam structure,but also achieves the effect of lightweight.The results verify the reliability of the optimization scheme.Taking the geometric errors of serial and parallel structures of machine tools as the research object,the geometric errors of serial and parallel structures are modeled by using the modeling methods based on multi-body system theory and matrix transformation respectively.The geometric errors of parallel structures are emphatically studied and simulated.The theory of multi-body system and the basic principle of matrix transformation are summarized in detail.The error sources of all links of parallel mechanism are analyzed comprehensively,and the forward and inverse solutions of the error model are deduced.Then,the control variable method is used to lock the variation range of each error parameter between the Seven-level tolerance and the eight-level tolerance.The influence of each error parameter on the central position and attitude of the moving platform is observed and analyzed.更多还原