基于分段拟合的机床大尺寸工作台热误差补偿模型

Model of Thermal Error Compensation of Large Size Worktable for Machine Tools Based on Piecewise Fitting

大型机床工作台在往复运动过程中,丝杠螺母会产生大量的热,一部分热量从螺母传入工作台导致工作台两侧翘曲,使工作台不同位置产生不同热误差。为提高大尺寸机床工作台的纵向热误差补偿精度,提出分段拟合热误差建模预测方法。该方法是沿工作台横向在多个位置建立对应点的纵向热误差模型,然后由各点单模型预测值进行分段拟合建立工作台整体预测模型,利用分段拟合模型实现对工作台任意位置热误差预测。同时为了提高热误差模型预测精度和鲁棒性,采用粒子群优化算法根据实时反馈热误差数据对模型参数辨识,使热误差模型能适应机床最新的工作状态。在一台三坐标铣床工作台上进行试验,建立X轴快速运动时工作台纵向热误差模型,试验结果表明:该方法鲁棒性好预测精度高,能够实现大尺寸工作台任意位置的热误差补偿,且具有一定的通用性。

When worktable is traveling along the X,Y, orZ axis of machine tool back and forth, due to frictional interaction between moving parts, a great amount of heat is generated in ball–screw drive systems, and part of it is transferred to the worktable, by which two sides of the worktable parallel to the guide way will be warped. So the thermal deformations of various positions on the worktable are different. In order to improve the accuracy of thermal error compensation of large size worktable, a multi-location forecasting model with piecewise fitting compensation method is proposed. The corresponding thermal error model of the multi-point on the worktable is established, and piecewise fitting of multi-point prediction model is used to implement a thermal error compensation for whole worktable. Furthermore, to improve prediction accuracy and robustness of the thermal error model, particle swarm optimization algorithm is utilized to identify the model parameters based on the real-time feedback data, and thus the thermal error model could adapt to the latest working condition of the machine tools. The thermal error compensation experiment of the worktable in a three coordinate milling machine is carried out under the condition ofX-axis’s fast movement. The experimental results indicate that this method has a good robustness and a high precision, which can compensate thermal error of large size worktable at any position, and this method is of universal applicability.