Dynamic Motion Error Traceability of CNC Machine Tool Feed System under Electromechanical Rigid-flexible Coupling Analysis
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摘要: 动态运动误差是影响数控机床加工精度的关键因素,但因其具有时变性、随机性与动态性,研究难度大,其产生机理尚不明确,严重阻碍了机床加工精度的提升。本文旨在溯源进给系统的动态运动误差,提出了基于机电-刚柔耦合特性分析的数控机床进给系统动态运动误差溯源方法。通过不同进给速度下切削圆试件,基于三坐标标定与球杆仪圆测试分离出由机械结构引起的动态运动误差。同时,基于机电刚柔耦合动力学模型进行仿真分析,其仿真结果与实验分离结果吻合度达70%以上,从而验证了该方法的可行性与动力学模型的准确性。Abstract: Dynamic motion error is a crucial factor affecting the machining accuracy of CNC machine tools. However, it is challenging to study due to its time-varying, random and dynamic characteristics. Also, its generation mechanism is not clear, which seriously hinders the improvement of machine tool machining accuracy. To trace the dynamic motion error, a dynamic model of feed system based on electromechanical rigid-flexible coupling analysis and relative dynamic motion error traceability method are proposed in this study. By cutting circular specimens at different feed rates, the dynamic motion error caused by mechanical structure is separated based on the calibration results of the coordinate measuring machine (CMM) and the results of double ballbar (DBB) circular test. Meanwhile, based on the electromechanical rigid-flexible coupling dynamic model for simulation analysis, the coincidence between the simulation results and the experimental separation results is more than 70%. Hence the feasibility of the method and the accuracy of the dynamic model are verified.
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表 1 直线进给系统的机械结构参数
参数 数值 电机转动惯量Jm 4.26×10-4 kg·m2 丝杠转动惯量Js 2.58×10-4 kg·m2 反电动势系数Ke 1.42 V·s/rad 电枢电阻Ra 0.65 Ω 电枢电感La 0.011 2 H 电机扭转常数Kt 2.35 Nm/A 滚珠丝杠导程P 0.01 m 工作台质量mt 2 000 kg 联轴器扭转刚度k1 1 100 Nm/rad 丝杠螺母连接刚度k2 5×107 N/m 滚珠丝杠黏性阻尼Bs 0.235 Nm/(rad·s-1) 工作台滑动阻尼Bt 1 000 N/(m·s-1) 表 2 PID三环控制参数
参数 X轴 Y轴 位置环比例增益Kp/s-1 12 25 速度环比例增益Kv/(A·s·rad-1) 138 65 速度环积分时间常数τv/s 0.958 0.885 电流环比例增益Ki/(V·A-1) 86 78 电流环积分时间常数τi/s 0.967 0.872 表 3 不同进给速度下球杆仪圆测试的结果
进给速度/(mm·min-1) 最大值/μm 最小值/μm 极差/μm 均值/μm 800 82.6 -91.2 173.8 -6.7 1 000 84.2 -90.4 174.6 -6.8 1 200 82.6 -92.2 174.8 -6.9 1 500 83.1 -90.3 173.4 -6.5 1 800 83.4 -91.6 175.0 -7.0 -
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