基于球杆仪的五轴机床RTCP误差检测及补偿

针对五轴机床RTCP误差检测存在检测时间长、测量精度低的情况,提出用球杆仪检测RTCP误差的方法,分析可知AC双转台RTCP误差不仅有4项位置误差,而且存在4项角度误差和初始安装误差。根据机床运动链建立AC双转台RTCP误差模型,采用基于球杆仪的检测方法,并推导RTCP误差元素求解方法。通过误差补偿试验验证了误差模型和误差求解方法的准确性和有效性。     

基于RTCP功能的五轴数控机床动态误差溯源方法

RTCP(Rotation tool center point)功能作为目前高档数控机床必备的功能之一,可以大幅减小由于旋转轴运动带来的非线性误差,有效提高机床加工精度。根据刀具刀尖点相对于加工工件相对静止的特点,设定刀具刀尖点不动,规划了有利于研究机床伺服系统动态性能的RTCP轨迹,并进行伺服系统仿真研究,得到刀尖点误差轨迹与机床伺服系统动态性能影响因素的对应关系,并依据此对应关系提出动态误差溯源方法,为数控机床伺服系统参数调整提供理论支持。     

五轴联动机床联动精度检测及优化方法

提出一种五轴数控机床联动精度快速检测方法:通过特殊检测轨迹下RTCP检测机床联动精度,依据刀尖点误差轨迹分析并溯源与其他驱动轴不匹配的驱动轴,通过优化驱动轴伺服系统参数提升五轴机床联动精度。通过对比优化前后标准检验试件——S形试件的试切质量,验证了该方法的有效性。     

双转台五坐标机床RTCP功能的研究

五轴加工中由于旋转运动的影响,会产生非线性误差.RTCP(绕刀具中心点旋转)功能可使数控系统自动对旋转轴的运动进行实时线性补偿,从而保证插补点始终位于编程轨迹上.在深入分析双转台五坐标机床运动原理的基础上,介绍了一种集成RTCP功能的插补算法,并在MATLAB中做了仿真计算.计算结果表明该算法可以有效减小非线性误差.     

一种基于RTCP功能的五坐标动态精度检测工具

介绍了一种五坐标动态精度检测工具,该工具结构简单,成本低廉,结合RTCP功能准确地对机床进行动态精度检测,能有效避免由于各种原因引起的检测误差,缩短检测时间,为数控机床提供更好的动态精度支持.     

一种基于最小二乘法的RTCP自动测量循环

五轴机床的RTCP功能正常工作,需要对机床的相关几何参数进行正确的标定.标定的精度直接影响到机床的RTCP动作精度.通过测头实现机床的RTCP相关参数自动标定,可以有效提高机床的RTCP参数标定效率,并保证机床的精度稳定性.提出一种基于最小二乘拟合的方法来实现机床的RTCP参数自动高精度标定,具有标定精度高,标定速度快...     

双核架构嵌入式数控系统RTCP算法研究

分析了五轴数控机床非线性误差产生的原因,阐述了RTCP减小非线性误差的算法原理,基于C-A型双摆头机床结构建模并给出了一种RTCP补偿算法。针对嵌入式数控系统的特殊性,合理设计了在双核架构嵌入式数控系统中RTCP功能的实现方法。最后,在MATLAB中仿真验证了RTCP算法对于减小非线性误差的有效性。     

一种五轴联动机床动态精度检测及优化方法

提出一种用于机床动态精度快速检测与优化的方法。在完成机床静态精度调整基础上,通过S形试件检验机床加工精度是否达标。基于S件测量结果及机床五轴联动(RTCP)精度检测,搜寻并分析存在问题的驱动轴,通过编制特定程序并测量机床运动轨迹,在对轨迹进行频域分析、圆度分析的基础上,完成机床机械结构和动态性能参数的调整,进而提升机床动态精度。通过在20多台五轴联动数控机床上应用,大幅提高了机床的加工精度,验证了上述方法的有效性。     

基于双激光跟踪仪的五轴联动激光机床空间精度检测

五轴联动机床的空间精度是衡量五轴联动机床性能的关键指标，针对五轴联动激光机床在空间精度检测过程中，因受限于五轴联动激光机床的空间结构特点而难以测量的问题，提出基于两台激光跟踪仪对五轴联动激光机床空间精度进行识别与测量的方法。两台跟踪仪分别记录五轴联动激光机床上下两部分运动轨迹，并将轨迹坐标提取出来，再将坐标值根据相同位置进行综合汇总提取，然后通过曲线拟合得到最终合成轨迹，最后用最小二乘法比较设定轨迹与实测拟合轨迹的差值，得到机床的空间轨迹精度。试验测试表明，相较于传统的激光干涉仪或连杆仪的测量方式，通过双激光跟踪仪标定拟合的方式可以更快速有效地得到五轴联动激光机床绕B、C轴进行RTCP联动的精度和空间轨迹精度，并且该方法具有较高的可操作性与重复性。     

五轴数控机床的动态特性测定和调整方法

五轴机床对机床装备制造业意义非凡,RTCP功能是衡量五轴机床性能的重要指标。在执行RTCP过程中,由于旋转轴的加入,需要对直线轴进行非线性补偿,因此旋转轴和直线轴的伺服动态特性需要进行测定和调整,才能保证加工动态精度。文章对RTCP原理进行了简单介绍,设计了一种五轴动态精度测定算法,通过该算法对五轴机床的5个伺服轴特性进行了强弱排序,从而对伺服参数进行优化和调整。以五轴叶轮加工为例,将伺服参数调整前后所加工的叶轮的加工质量进行对比,证明该方法取得了较好的效果。     

On the workpiece setup optimization for five-axis machining with RTCP function

Nonlinear errors in five-axis machining process are caused due to the nonlinear motions of the rotational axes, which are inevitable. For the RT-type machine tool, the workpiece setup location on the working table has a direct effect on the nonlinear errors, thus there must be an optimal setup position which can reduce the nonlinear errors. Today’s five-axis machine tools are mostly equipped the with the RTCP (rotational tool center point) function, with which the NC program becomes independent from the workpiece setup. In this paper, we have focused on finding the optimal workpiece setup for the RT-type machine tool with RTCP function, more specifically, the Mikron UCP 600 five-axis machine tool in our lab. The kinematics of the machine tool is briefly analyzed. Based on that, the nonlinear error evaluation method with RTCP interpolation is derived. With this method, nonlinear errors can actually be considered as a function of the workpiece setup position. Then, the particle swarm optimization (PSO) is applied to find the optimal workpiece setup, in which a mutation operation is used since PSO traps into local optimum easily. The proposed optimal workpiece setup method is implemented and tested. Example results show that the optimal setup with least nonlinear errors can be found. Some interesting results also show that the nonlinear errors are not sensitive with the z component of the workpiece setup vector. The proposed optimization is nearly zero-cost and easy to both understand and implement, yet has a potential to reduce the nonlinear errors and thus to improve the accuracy of five-axis machining.     

Geometric characterisation and simulation of position independent geometric errors of five-axis machine tools using a double ball bar

A double ball bar (DBB) is extensively used to evaluate the geometric and dynamic performance of three-axis machine tools by means of the XY, YZ and XZ planar circular tests. Errors can be estimated by comparing them with known error profiles. However, such geometric interpretation of error plots of five-axis machine tools is limited. In this paper, a five-axis machine tool model is established with Homogeneous Transformation Matrices (HTMs), laying the foundation for characterising particular geometric shapes induced by various Position Independent Geometric Errors (PIGEs) of all five axes. A testing scheme is proposed to evaluate the target five-axis machine tool in two major steps: testing the rotary axes individually and testing the linear-rotary axes couples. In the first step, each rotary axis is tested with two substeps, with and without the extension bar on the DBB. The second step requires each linear and rotary axes combination to move simultaneously. Both approaches are performed with only one setup, thus simplifying the setup procedure and reduce the machine down time. To show the validity of the method, PIGEs for each axis are simulated with the given machine tool model. Several DBB trajectories are simulated using the machine tool model. Compared with the actual testing plots, the simulated DBB error plots are helpful to diagnose the PIGEs of linear and rotary axes based on their particular geometric shapes. The results suggest that the proposed method along with the given error characteristics can be used as a fast indication of a five-axis machine tool’s performance.     

带RTCP功能五轴机床后置处理程序的编制

针对不带RTCP功能的五轴机床,利用矩阵,计算其空间坐标系旋转后新的坐标值,得出通用公式,进而引出带RTCP功能五轴机床后处理程序编制的基本原理。     

五轴联动数控系统中RTCP技术的研究

在论述RTCP功能的基础上,推导了RTCP通用数学模型。针对B-C轴双回转工作台五轴数控机床的RTCP算法,开发了集成RTCP算法的五轴数控加工过程仿真软件,并使用该软件验证了算法的正确性。为开发具备RTCP功能的高档数控系统进行了探讨性的研究。     

转台-摆头式五轴机床几何误差测量及辨识

为降低转动轴几何误差对转台-摆头式五轴机床精度的影响,提出了基于球杆仪的位置无关几何误差测量和辨识方法。基于多体系统理论及齐次坐标变换方法建立了转台-摆头式五轴机床位置无关几何误差模型,依据旋转轴不同运动状态下的几何误差影响因素建立基于圆轨迹的四种测量模式,并实现10项位置无关几何误差的辨识。利用所建立的几何误差模型进行数值模拟,确定转动轴的10项位置无关几何误差对测量轨迹的影响。最后,采用误差补偿的形式实验验证所提出的测量及辨识方法的有效性,将位置无关几何误差补偿前后的测量轨迹进行比较。误差补偿后10项位置无关几何误差的平均补偿率为70.4%,最大补偿率达到88.4%,实验结果表明所提出的建模和辨识方法可用于转台-摆头式五轴机床转动轴精度检测,同时可为机床精度评价及几何精度提升提供依据。     

[可靠性建模及试验技术]面向数控机床可靠性试验的多维力随动加载装置

面向五轴联动数控机床的可靠性试验提出多维力随动加载方法,对五轴联动进给主轴施加多维力载荷,形成复杂进给抗力,部分模拟主轴复杂切削力环境。基于6-PUS并联机构研制多维力随动加载装置,采用模糊PID控制器建立显式力控制系统,比例和积分增益可随加载误差自适应调节。在五轴联动数控机床上开展多维力随动加载实验,结果表明,加载装置能够跟随机床主轴的单轴、三轴联动和五轴联动进给运动,根据期望值对主轴施加三维力,加载误差小于3.2%,在机床执行多种加工轨迹时形成有效进给抗力,为后续引入动态加载模拟复杂切削力提供理论和装备支撑。研究成果可为数控机床可靠性试验提供低成本、可循环的加载方式,有利于测试的规模化和标准化发展,也可为精度保持性、超载试验、跑合试验等机床性能测试提供新的负载模拟思路。     

基于综合评价体系的五轴数控机床加工性能评价和误差溯源方法

五轴数控机床的加工性能在制造行业一直是研究的热点,基于检验试件切削是常见的测评方法,然而试件和机床之间的映射关系难以确定,出现误差后如何调整精度成为难点。为了科学对其评价,通过仿真平台建立了机床控制系统参数与五轴机床检验试件——S试件加工误差之间的映射关系,引入机床各轴分类评价的隶属度,此基础上开发了误差溯源的综合评价体系,由三坐标测量机得到的S件轮廓误差数据反求出机床的加工性能等级和较差的轴类控制参数,并制订了基于S试件的机床加工精度测评规范,最后通过某五轴AB摆数控机床的切削试验,验证了方法的有效性。该成果有助于解决我国高端制造业长期缺乏机床性能测评的共性技术问题,具有重要的应用前景和经济价值。     

Quantitative evaluation method for machining accuracy retention of CNC machine tools considering degenerate trajectory fluctuation

Accuracy retention is an important performance index of CNC machine tools. At present, research on the evaluation of machining accuracy retention of CNC machine tools mainly focuses on accuracy value of a fixed time point or different time periods, but studies on the fluctuation degree of degradation trajectory related to time change are limited. Extracting simple and effective degradation characteristics of machining accuracy and then evaluating machining accuracy retention considering fluctuation of degradation trajectory are necessary. The volume error model of CNC machine tools is established on the basis of multibody system theory in this study. Three-dimensional volume error vector is transformed into one-dimensional machining accuracy degradation by calculating offset distance between spatial error and origin points. Degradation data obtained via regular measurement and calculation are used to establish the complete degradation trajectory model of the CNC machine tools machining accuracy using radial basis function interpolation method according to the fluctuation degree of degradation trajectory, and concepts of average degradation rate and average degradation amount are defined. Lastly, examples showed that these two indicators can intuitively reflect fluctuation degree of machining accuracy degradation of CNC machine tools and effectively and quantitatively evaluate accuracy retention of CNC machine tools. The quantitative evaluation method of accuracy retention of CNC machine tools defined in this study considers the fluctuation degree of accuracy degradation trajectory. The quantitative evaluation index of accuracy retention demonstrates satisfactory engineering application because it can reflect not only the accuracy change of a single machine tool but also accurately compare the accuracy retention between different machine tools.