铣削过程多源扰动影响下直线电机推力电流频谱特性分析

Linear Motor Thrust Current Spectrum Characteristics Under Influence of Multi-Source Disturbance in Milling Process

针对机床实际铣削过程中进给系统受多源、多频扰动影响,特别是直驱进给系统由于“零传动”特性,运动精度受外界扰动影响更为显著的问题,研究了机床加工过程多源扰动机理、频谱特征及其影响下直线电机进给系统推力电流频谱特性,综合分析了铣削过程中刀具-主轴系统的多源扰动,建立了考虑刀具偏心跳动的铣削力模型、主轴离心力模型、主轴轴承振动模型,并分析多源扰动频谱特性。表征了多源扰动激励下直线电机进给系统输出位移波动特性,并在直线电机驱动的VMC0865机床上完成单轴进给切削实验。实验结果表明:在进给速度为1500 mm/min、主轴转速为5000 r/min、切宽为2 mm、切深为2 mm的情况下,X轴位移波动均方值从0.36μm增加到0.81μm,推力电流均方值从0.94 A增加到1.15 A;推力电流增加了主轴转频及其倍频、分频、边频的谐波成分;切削力会影响进给系统运动精度,从而影响零件加工质量和加工精度,验证了切削过程对直线电机进给系统推力电流频谱特征的影响;对比了不同切削参数对进给系统推力电流频谱特征的影响,明确了主轴转速是对推力电流频谱特征最为显著的切削参数。该研究对于直驱进给系统控制算法改进与加工参数选择具有重要指导意义。

The feed system is affected by multi-source and multi-frequency disturbances in the actual milling process of the machine tool,especially the direct-drive feed system due to the zero transmission,the motion accuracy is more significantly affected by external disturbances.The disturbance mechanism,frequency spectrum characteristics and linear motor feed system thrust current spectrum characteristics are investigated.Comprehensively considering the multi-source disturbance of tool-spindle system during the milling process,the milling force model,spindle centrifugal force model,spindle bearing vibration model are established and the corresponding multi-source disturbance spectrum characteristics are analyzed.The displacement fluctuation characteristics of linear motor feed system under multi-source disturbance excitation are characterized,and single-axis feed cutting experiment is completed on VMC0865 machine tool driven by a linear motor.The experimental results show that as the feed speed is 1500 mm/min,spindle speed is 5000 r/min,cutting width is 2 mm,and cutting depth is 2 mm,the mean square value of X-axis displacement fluctuation increases from 0.36μm to 0.81μm,and the mean square value of thrust current increases from 0.94 A to 1.15 A;the thrust current heightens the harmonic components of the spindle frequency and its multiplication,division and side frequencies;cutting force affects motion accuracy of the feed system,thereby lowers the quality and accuracy of the part processing.The influence of the process on the spectral characteristics of thrust current of linear motor feed system and the influence of different cutting parameters on the spectral characteristics of thrust current are comparatively analyzed.It is obvious that spindle speed is the most significant cutting parameter for spectral characteristics of thrust current.