五轴数控机床基于热-力耦合效应的空间复合误差建模技术

Regarding the dynamic, integrated, volumetric and coupling characteristic of the machine tool error, modeling of the volumetric error integrated geometry, thermal and force on five-axis NC machine tool feeding system is studied.. Through the multi-body kinematics analysis of the five-axis motion, the quasi-static error model integrated geometric error and thermal error is established at the TCP. Based on the multi-line and the circular trajectory algorithm, geometric error and thermal error of the machine tool’s movement pairs and revolute pairs are measured to recognize the error parameters in error model. The volumetric thermal error can be predicted by decomposing the model, and the rotation error can be obtained by decoupling the model for circle feeding error compensation.. Considering the heat transfer, the heat convection and the thermal dynamics theory and regarding the stress equilibrium equation of thermal elastic, the mechanism of thermal - mechanical coupling is investigated, and the integrated dynamic error model of a five-axis machine tool based on thermal - mechanical coupling is built. . In order to get the thermal and force induced error under the simulated actual operating conditions, the device that is to measure the machine tool error while loading the simulated force and thermal with the feed movement of the machine tool is developed. . Influence of the operating parameters and interface features on machine tool’s thermal and dynamic characteristics will be analysed through sensitiveness analysis method. Prediction accuracy of the integrated error will be validated by experiment and simulation.

针对机床误差动态性、综合性、空间性和耦合性的特点，研究五轴数控机床进给系统几何、热、力空间复合误差的建模技术。. 基于五轴多体运动学关系，在刀具切削点建立几何和热的准静态复合误差模型；基于多线法和圆轨迹法，测量机床移动副、转动副的几何误差和热误差，辨识误差模型中的误差参数；分解模型以获得空间热误差，解耦模型以获得用于圆周进给误差补偿的转动误差。. 结合传热学、热对流、热力学等理论，从结构内部热弹性力学应力平衡方程出发，探索热-力耦合机理，建立五轴机床基于热-力耦合效应的复合误差模型。. 研制一套力和热的负载模拟加载及误差在线检测装置，在模拟切削力和模拟热源随动加载的同时测量机床变形，以获得在模拟实际工况下的机床热-力耦合误差。. 采用灵敏度方法分析机床运行参数、接合部特性等对热特性和动特性的影响。实验和仿真相结合验证所建复合误差模型的预测精度。

对五轴机床在线性和转动轴进给及五轴联动时的几何、热、力空间复合误差建模和补偿技术进行研究，主要研究内容包括：（1）基于多体运动学理论，根据五轴机床拓扑结构和运动相邻体误差矩阵，建立了五轴机床准静态下由几何和热引起刀具相对于工件的位置和姿态误差的数学模型；（2）对传统九线法提出改进方法，辨识误差模型中线性轴误差元素；通过球杆仪的双球实际位置推导，获得能够解耦移动轴插补运动误差的转动轴误差元素的辨识模型；（3）根据弹性体在热力载荷下温度和应变率的变化、温度和热应力引起的应变公式，得到耦合效应下的变形；对主轴进给部件建立热力耦合仿真模型，得到耦合场的变形，分析力变形、热变形及耦合变形的占比关系；（4）为了验证建立的热力耦合误差模型，研发一套对主轴进给部件进行模拟热和力载荷并测量误差的装置，在运动副热源依据摩擦热加载，在刀刃上依据切削热和切削力加载，使机床免于真实切削而能够测量其误差；（5）基于建立的五轴机床准静态误差模型，提出两种误差补偿方法：基于刀尖点位姿误差的逐点比较离线补偿方法先通过修正转动轴转角来补偿刀轴姿态矢量误差，再通过修正线性轴位置来补偿刀尖点位置坐标的误差；基于西门子840D温度补偿功能的在线补偿方法利用西门子840D的温度补偿功能，开发了误差补偿系统的硬件平台、数据通信、数据采集及误差计算模块。