Modeling and analysis of servo dynamics errors on measuring paths of five-axis machine tools
Modeling and analysis of servo dynamics errors on measuring paths of five-axis machine tools
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DOI：
10.1016/j.ijmachtools.2012.11.002
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发表时间：
2013-03
影响因子：
14
通讯作者：
Ming-Tzong Lin;Shih-Kai Wu
中科院分区：
文献类型：
--
作者：
Ming-Tzong Lin;Shih-Kai Wu
动态误差是五轴机床实现高速加工的主要误差源之一。通过伺服动力学建模和伺服控制方法可以对该误差进行估计和补偿。本文提出了一种五轴测量路径上的轮廓误差模型，该模型可以准确地估计五轴同步运动时刀具中心点（TCP）的动力学和轮廓误差。根据C型五轴机床的运动学构型，推导了其正、逆运动学方程。为了生成平滑的测量路径，S形加减速（ACC/DEC）方法被应用于规划运动轨迹。通过将测量轨迹指令代入伺服动力学模型，推导出TCP的轮廓误差模型。为了研究五轴伺服回路的动态增益对TCP轮廓图的影响，研究了不同增益下的十二种组合。结果表明，CK 2轨迹的稳态轮廓误差由一个偏移量和一个双圆弧轨迹组成，这与两轴轮廓轨迹的稳态轮廓误差有很大的不同，通过调节伺服回路的增益，可以消除五轴之间的动态失配，减小TCP（CETCP）的轮廓误差。为了验证轮廓误差方程，仿真和实验表明，所提出的方法显着提高轮廓性能的TCP进行五轴同步运动时。
Dynamic error is one of the major error sources for five-axis machine tools in achieving high-speed machining. It can be estimated and compensated by means of servo dynamics modeling and servo control method. This paper presents a contour error model on five-axis measuring paths where the dynamics and contour errors of the tool center point (TCP) can be estimated accurately during five-axis synchronized motions. The forward and inverse kinematics equations are derived according to the kinematic configuration of a C-type five-axis machine. To generate smooth measuring paths, the S-shape acceleration/deceleration (ACC/DEC) method is applied on planning the motion trajectory. The contour error model of the TCP is derived by substituting the commands of the measuring trajectory into the servo dynamics models. To investigate how the contour charts of the TCP are affected by the dynamic gains of five-axis servo loops, twelve combinations under different gains are studied. It is shown that, for the CK2 path, the steady-state contour error consists of an offset and a double-circular trajectory which is quite different from that of two-axis contour path. By tuning the gains of the servo loops, the dynamics mismatch among five axes can be eliminated and the contour error of the TCP (CETCP) can be reduced. To validate the contour error equations, simulations and experiments are performed to demonstrate that the proposed method improves the contouring performance of the TCP significantly when performing five-axis synchronized motions.