一种数控滚齿机工作台动态特性建模方法及实验分析

Modeling and Experimental Analysis for Worktable Dynamic Characteristics of CNC Gear Hobbing Machine

为了研究数控滚齿加工中滚刀轴转速波动引起的工件轴速度波动的动态响应特性,对数控滚齿机旋转工作台即工件轴的伺服控制问题进行了分析。首先根据电机学原理和机械动力学原理对伺服控制系统组成的各个环节进行了建模和分析,推导出旋转工作台的整体伺服控制系统模型,并考虑到伺服控制环节在动态响应过程中的摩擦因素,引入了非线性Stribeck黏性摩擦结构;然后利用Simulink建立了滚齿机旋转工作台的伺服系统仿真模型,并研究了不同的位置和速度指令频率变化对工件轴伺服动态响应影响效果;最后通过数控滚齿机工作台控制实验来验证工件轴的动态响应特性。仿真结果表明:旋转工作台伺服系统在低速运行时,位置跟踪存在"平顶"现象,速度跟踪存在"死区"现象;旋转工作台伺服系统位置和速度的跟随率随着指令频率的增大而减小,当指令频率增大到31Hz时,速度跟随率不足10%。在和仿真相同的指令频率变化条件下,进行滚齿机工件轴的转速控制实验,工件轴的响应曲线与仿真响应曲线基本吻合,验证了模型的有效性和可靠性。该模型可为数控回转工作台伺服进给系统设计、伺服控制方法研究及故障诊断等工作提供理论依据。

To reveal the dynamic characteristics of worktable axle of CNC gear hobbing machine due to interrupted cutting,the servo control system of the worktable is analyzed.According to electromechanical principle and mechanical dynamic principle,every component model of the servo control system is constructed to derive an overall servo control system model of the rotary table.Considering the nonlinear Stribeck friction factor,a simulation model of the worktable servo system is established by Simulink.The effects of different position and speed command frequency variation on the dynamic response of the workpiece axis servo system are discussed and the servo dynamic characteristics reflecting the location and speed of the worktable axle are obtained.When the servo system of the rotary table runs at low speed,the"flat top"exists inthe position tracking,and the"dead zone"exists in the speed tracking.The position and speed following rate of the servo system of the rotary worktable decrease with the increasing given command frequency,especially when the instruction frequency increases to 31 Hz,the following rate is less than 10%.The model accuracy is verified by online test of the worktable,the experimental response curves coincide with the simulated ones well at the same command frequency.