Total differential methods based universal post processing algorithm considering geometric error for multi-axis NC machine tool

Multi-axis numerical control machining for free-form surfaces needs CAD/CAM system for the cutter location and orientation data. Since these data are defined with respect to the coordinate of workpiece, they need converting for machine control commands in machine coordinate system, through a processing procedure called post processing. In this work, a new universal post processing algorithm considering geometric error for multi-axis machine tool with arbitrary configuration. Firstly, ideal kinematic model and real kinematic model of the multi-axis NC machine tool are built respectively. Difference between the two kinematic models is only whether to consider the machine tool's geometric error or not. Secondly, a universal generalized post processing algorithm containing forward and inverse kinematics solution is designed to solve kinematic models of multi-axis machine tool. Specially, the inverse kinematics solution is used for the ideal kinematic model, while the forward kinematics solution is used for the real kinematic model. Then, a total differential algorithm is applied to improve the calculation speed and reduce the difficulty of inverse kinematics solution. Realization principle of the total differential algorithm is to transform the inverse kinematics solution problem into that one of solving linear equations based on spatial relationship of adjacent cutter locations. Thirdly, to reduce the complexity of geometric error calibration experiment, effect weight of geometric error components is determined by the sensitivity analysis based on orthogonal method, and then the real kinematic model considering geometric error is established. Finally, the universal post processing algorithm based on total differential methods is implemented and demonstrated experimentally in a five-axis machine tool. The results show that the maximum error value can be decreased to one-fifth using the proposed method in this paper.     

基于补偿模糊神经网络的数控机床热误差预报模型

文章提出了一种基于补偿模糊神经网络的数控机床热误差预报模型,讨论了该模型的详细结构、模糊规则、训练算法及相关技术问题,并给出了智能预报结果和精度评价.     

基于嵌入式Internet的数控机床通信控制器的研究

介绍了一种数控机床通信控制器的设计与实现方法，这种通信控制器用于生产中大量使用的普通数控机床。通信控制器由ATMEGAl28L和RTL8019AS构成，采用嵌入式Internet技术实现，可以完成数控机床RS232接口数据、开关量和模拟量信号到Internet的双向转换并能实现基于Web方式的数控机床远程控制。     

基于SVPWM的数控机床控制系统仿真与分析

鉴于空间矢量脉宽调制法(SVPWM)诸多优点,如果能对其先进行一些仿真研究必定会给它在数控机床方面的应用实践带来不少裨益.由此,首先对SVPWM技术原理进行了介绍,特别对其线性组合SVPWM波形的实现方法进行了详细的讨论.其次,在MATLAB/SIMULINK环境下,把这种SVPWM实现方法放入了一个数控电机闭环转差控制系统中进行应用仿真.通过对定子磁链,转矩等进行仿真研究,结果表明与理论分析一致,从而为SVPWM在数控电机控制系统中应用提供了一定的参考价值.     

A new method and instrument for measuring circular motion error of NC machine tools

A new method and instrument for measuring circular motion error of numerical control (NC) machine tools are described in this paper. The instrument consists of a linear displacement transducer bar with two balls at each end and a high accuracy rotary encoder. The radius variations are detected by the transducer and the rotation angle of the bar is measured by the rotary encoder while the machine is moving in a circular path. The measuring area is circular except for a small area around the center of the disc. The bar can be expanded and contracted along its axis for different application. The instrument has a compact structure and can be installed on a machine tool simply and quickly. It is shown by the experimental results that the instrument has good repeatability and high precision of measuring circular motion trajectories. The instrument can be widely used especially in the error-compensation and error-source project in the industrial application.     

基于PMAC的BKX-Ⅰ型变轴数控机床数据通讯及数控加工的实现

文章围绕北京理工大学自行研制的BKX-Ⅰ型变轴数控机床,针对机床的应用特性,在开发BKX-Ⅰ型变轴数控机床开放式数控系统的基础上,对工业PC机和运动控制卡PMAC之间的数据通讯以及不同容量大小的数控加工刀位轨迹文件在PMAC上的具体实现方式进行了分析与研究,为数控系统的建造提供了依据.     

基于内置传感器的数控机床动态加工误差测量方法

以HJ044双转台型五轴联动数控机床为例,以机床内置传感器信息和多体系统理论为基础,建立了刀具相对工件的运动学模型,提出了一种基于内置传感器信息的动态加工误差测量方法。该方法利用机床编码器或光栅尺等机床内置传感器信息获取机床各轴运动位移,并结合机床运动学模型,测量由机床的动态特性引起的加工误差。并通过实验表明该方法是一种简单有效的数控机床动态加工误差测量方法。     

A method of testing position independent geometric errors in rotary axes of a five-axis machine tool using a double ball bar

Ensuring that a five-axis machine tool is operating within tolerance is critical. However, there are few simple and fast methods to identify whether the machine is in a “usable” condition. This paper investigates the use of the double ball bar (DBB) to identify and characterise the position independent geometric errors (PIGEs) in rotary axes of a five-axis machine tool by establishing new testing paths. The proposed method consists of four tests for two rotary axes; the A-axis tests with and without an extension bar and the C-axis tests with and without an extension bar. For the tests without an extension bar, position errors embedded in the A- and C-axes are measured first. Then these position errors can be used in the tests with an extension bar, to obtain the orientation errors in the A- and C-axes based on the given geometric model. All tests are performed with only one axis moving, thus simplifying the error analysis. The proposed method is implemented on a Hermle C600U five-axis machine tool to validate the approach. The results of the DBB tests show that the new method is a good approach to obtaining the geometric errors in rotary axes, thus can be applied to practical use in assembling processes, maintenance and regular checking of multi-axis CNC machine tools.     

基于PCI总线并联机床运动控制卡设计

本文针对并联机床数控系统的工作特点和要求,通过对TI公司DSP芯片TMS320VC33和Cypress公司PCI接口芯片CY7C09449PV的功能和特点进行分析,设计了一种基于PCI总线的运动控制卡,能够较好地满足并联机床数控系统对运动控制部件的实时性和控制精度的要求.