基于机电-刚柔耦合特性的进给系统动态误差影响因素分析

Analysis of influencing factors of dynamic error of feed system based on electromechanical-rigid-flexible coupling characteristics

进给系统动态误差是决定数控机床加工精度的关键因素,明确机械系统和控制系统参数以及两者之间耦合作用对进给系统动态误差的影响是当前面临的重要课题。以某五轴联动加工中心的进给系统为研究对象,充分考虑进给系统传动件结合面间刚度和滚珠丝杠柔性特征,搭建了进给传动系统动力学模型,并利用有限元软件进行了验证。利用典型三环PID(proportion integration differentiation,比例积分微分)控制结构搭建了机电-刚柔耦合进给系统动力学模型,通过仿真分析研究了机械系统参数和控制系统参数对进给系统动态误差的影响规律。结果表明,机械系统参数中,滚珠丝杠导程和螺母副轴向刚度对进给系统动态误差的影响显著,支撑轴承轴向刚度的影响不明显;控制系统参数中,位置环比例增益对进给系统动态误差的影响显著,速度环比例增益的影响不明显。研究结果为实现进给系统动态误差的可预知和可控性奠定了理论基础。

The dynamic error of feed system is a key factor in determining the machining accuracy of CNC(computer numerical control) machine tools. Clarifying the influence of mechanical system parameters and control system parameters as well as the coupling between them on the dynamic error of the feed system is an important subject currently facing. Taking the feed system of a five-axis linkage machining center as the research object, the dynamics model of the feed transmission system was established through fully considering the stiffness between the joint surface of the transmission parts of the feed system and the flexibility characteristics of the roller screw, and the model was verified by finite element software. Based on the typical three-loop PID(proportion integration differentiation) control structure, the electromechanical-rigid-flexible coupling dynamics model of the feed system was built.On this basis, the influence law of mechanical system parameters and control system parameters on the dynamic error of feed system was studied through the simulation analysis. The results showed that among the mechanical system parameters, the influence of ball screw lead and axial stiffness of nut pair on the dynamic error of feed system was significant, while the influence of axial stiffness of support bearing was not obvious. Among the control system parameters, the position loop proportional gain had a significant influence on the dynamic error of feed system, but the influence of the speed loop proportional gain was inconspicuous. The research results lay a theoretical foundation for realizing the predictability and controllability of dynamic errors of the feed system.