五轴数控机床的热力耦合机理及同步控制的理论与试验研究

At presnet, the improvement of machining accuracy by improving the machining quality of the machine tool components becomes more and more difficult, while error compensation and improving the control accuracy are effective approaches to overcome this dilemma.But timeivarying heat error and mismatch of dynamic parameters among the feed axes stemming from time-varying cutting make error compensation and inproving the control accuray inperfectible. This project takes five-axis CNC machine tools as the object of study and focuses on the problems of thermal and mechanic couplings and controlled synchronization for the multi-axis feed system. By virtue of combining theoretical investigation with numeric calculation and experimnets, the effects of machining technological parameters and meterial function on cutting forces are investigated to determine stability lobe diagrams.The effect of the technological parameters on the dynamic coupling parameters of kinematic pairs stemming from cutting forces is investigated to explore the mechanism of dynamic coupling for the five-axis feed system. The evolution of temperature and heat deformation distributions for the components with time is investigated to reveal the mechanism of thermal coupling for the five-axis feed system. Identified approaches of the dynamic coupling parameters and the heat error will be proposed by investigating the relationship among the dynamic coupling parameters, heat deformation of the components, torque currents of the servo motors. Modelling and measurement techniques of the kinematic errors are investigated to propose a method of geometric error deviation in five-axis machine tools. With errors and force compensations, cross-coupling controllers of tool tip position synchronization, tool orientation synchronization, and tool tip and orentation synchronization are proposed to minimize conturing errors and improve the machining accuracy of CNC machine tools.

目前，依靠提高机床零部件质量提高加工精度已变得越来越困难，而误差补偿及提高控制精度则成了摆脱这一困境的有效措施。但由于机床热误差和切削力的时变性导致各进给轴动态参数的不匹配，很难达理想的效果。本项目以五轴数控机床为研究对象，针对多轴进给系统的热力耦合及轮廓同步控制问题，通过理论分析、数值计算与试验相结合，探索加工工艺参数与材料性能对切削力的影响规律，确定切削稳定区域图；研究各运动副动力学耦合参数随工艺参数的变化规律，揭示五轴进给系统的动力学耦合机理；探索机床各结构部件温度分布与热变形随时间的演化规律，揭示多轴进给系统的热耦合机理；依据热力耦合机理，探索切削力与系统热误差随各驱动器力矩电流的变化规律，提出动力学耦合参数与热误差的辨识方法；探索几何误差检测分离辨识方法，建立具有力补偿与全误差补偿的刀尖位置、刀具方向、刀尖位置与刀具方向的交叉耦合同步控制器，最小化加工误差，提高数控机床的加工精。

目前，依靠提高机床零部件质量提高加工精度已变得越来越困难，而摩擦前馈补偿及热误差补偿成为提高机械零件加工精度摆脱这一困境的有效措施。但由于机床结构本身关节较多，受制造精度及装配工艺影响较大，致使进给系统摩擦力的多变性及机床热源分布的复杂性，导致补偿模型的精确度较差，很难达理想的效果。因此，本项目针对五轴数控轮廓铣削机床的铣削稳定性和直线进给系统的力热耦合特性及补偿问题展开了研究工作，完成了如下研究内容。. (1)基于再生颤振机理，建立了再生颤振状态下的动态铣削力模型，并根据李雅普诺夫稳定性理论，得到了高速铣削时的稳定性判据，采用稳定性极限图法，分析了铣削系统的动力学参数和刀具几何参数对颤振稳定域的影响规律，并通过数值仿真证明了其正确性。. (2)建立全滚珠的载荷分布模型，通过数值计算分析了轴向载荷和螺母滚珠丝杠副的结构参数对滚珠接触载荷、接触角及接触刚度的影响；开发出数控系统软件，获得了工作台位置时间及伺服电机力矩电流时间的离散数据，进而提出了估计进给系统摩擦力估计算法，分析了丝杠局部误差及磨损状态、导轨与丝杠装配不平行度、进给方向及进给速度、丝杠力矩传动段刚度对摩擦力瞬时均值和波动量频谱的影响。求取了工作台不同位置摩擦力随其进给速度关系的曲线参数，验证了摩擦力随进给速度的变化规律为非Stribeck行为，进而提出了基于工作台位置和进给速度的双重多项式摩擦力预测模型，并进行摩擦力前馈补偿控制的数值仿真进行了验证。基于伺服电机力矩电流和工作台位置数据，提出了计算出滚珠与丝杠及滚珠与螺母滚道之间的接触载荷谱的提取方法。. (3) 建立了滚珠丝杠进给系统的温度及热误差检测试验系统，提出了集成蒙特卡罗法的有限元法计算方法，实现了进给系统热源发热率的辨识，获得了进给系统的温度场和热误差分布规律，提出了热源中心温度及进给系统热误差预测模型和系统热误差自适应在线补偿方法，并进行了试验验证。