基于模糊遗传算法的优化设计

在工程实际应用中,优化设计方法往往因为目标函数或约束函数不能用设计变量的数学显式表示或函数复杂导致计算效率下降.本文提出一种模糊遗传算法的优化设计方法,能够迅速找到全局最优解,并加快收敛速度和减少计算工作量.     

Development and implementation of a NURBS interpolator with smooth feedrate scheduling for CNC machine tools

Parametric interpolation for Non-Uniform Rational B-Spline (NURBS) curve has become more important than ever before in the control of CNC machine tools. An effective NURBS interpolator not only can obtain accurate contour trajectories, but also have smooth dynamics performance. This paper proposes a numerically efficient NURBS interpolation scheme which consists of two stages namely preprocessing and interpolating. In the stage of pre-processing, the parameter interval is split into several blocks at breakpoints and an iterative numerical quadrature method is applied for each block. By means of the iterative quadrature method, the initial parameter intervals of each block are divided into several subintervals according to the arc length approximation error. Meanwhile, the curvature of each knot and the cubic polynomial coefficients of each subinterval are obtained. Then the critical points with large curvature of each block are found from the candidate points and the tolerated speed of each critical point is calculated according to the constraints of chord error and centripetal acceleration. Hence, the feedrate scheduling based on the S-shaped acceleration profile for each block can be preplanned via the approximate arc length of each subinterval, the tolerated speed of each critical point and kinematics characteristics such as acceleration/deceleration and jerk limits of the machine tools. In the stage of interpolating, the parameter of the next interpolation point can be calculated directly using the cumulative arc length and the cubic polynomial coefficients of each subinterval. Finally, a series of numerical simulations and real machining experiments are conducted, and the simulation and experimental results have showed the good performance of the proposed NURBS interpolator both in efficiency and accuracy.     

The feedrate scheduling of parametric interpolator with geometry,process and drive constraints for multi-axis CNC machine tools

Parametric interpolator has been widely adopted in machining sculptured parts. Accordingly, the feedrate scheduling of parametric interpolator plays a role in CNC machine tools especially for multi-axis machines with linear and rotary axes, since a smooth movement is beneficial for achieving better surface geometry as well as shorter machining time. This paper presents a new feedrate scheduling method for the five-axis machining of geometrically complex part with geometry, process and drive constraints. The satisfaction conditions of constraints are first built and the proportional adjustment of feedrate sensitive regions is proved to be suitable for simultaneously reducing the magnitudes of constraints such as angular acceleration, linear acceleration, axis accelerations and jerks. The initial feedrate profile is first constructed with confined chord error, angular velocity and axis velocities owing to the independence of these constraints. Then, for each iterative adjustment a curve evolution strategy is used to deform the target feedrate profile to the adjusted positions instead of the re-interpolation of feedrate profile, until the final desired feedrate profile is achieved without violated constraints. Simulations and experiments are conducted and the results validate the performances of the proposed method.     

基于FMECA的数控机床主轴系统故障分析

数控机床主轴系统是数控机床的关键子系统,其故障较多,而每次故障现象又比较单一,因此,单纯通过故障现象往往不能作为故障诊断和排除的依据。应用 FMECA 分析方法,分析数控机床主轴系统各组成部分的故障模式及故障原因,并进一步计算各组成部分的危害程度,得到的危害程度为制定设备维修策略提供了参考。     

Design- and control-concept for compliant machine tools based on controller integrated models

The paper presents a novel design- and control-concept for machine tools aiming for lightweight design. A Kalman-filter containing a model of the mechanical structure is applied. The Kalman-filter calculates the dynamic dislocation of the machine tool body with respect to the tool-center-point and its velocity. Dislocation and velocity are used for the correction of the CNC's setpoint values. Experimental results show, that the dynamic dislocation had been reduced considerably. This allows for a compliant design contrary to the established design-concept of stiff frames. The concept is proposed for direct-drive machine tools used for micro-milling.     

基于球杆仪的数控机床误差识别与补偿

论述了数控机床几何误差的球杆仪识别及软件补偿技术。提出了从Renishaw球杆仪测量数控机床的联动误差数据中识别反向间隙、直线度、垂直度、定位误差的一种方法;建立了机床结构的每个误差元和切削刀具相对工件位置误差相联系的通用数学模型;用球杆仪在数控机床上进行补偿前后加工轨迹的测量实验表明该方法效率高、效果显著。     

A new sampled-data drive for CNC machine tools

A mathematical analysis of a sampled-data servo-drive system controlled by the step control algorithm for computer numerical control (CNC) is presented. The step control algorithm provides for rapid and precise positioning and is ready for practical implementation. Its performance, including stability, damping ratio, maximum overshooting, steady-state error for both the step and ramp input, and bandwidth for accurate circular motion, is studied and depicted in design charts. The design procedure proceeds by using the design charts to choose the weighting factor and the sampling period to satisfy the specifications of the system. The effectiveness of the proposed control algorithm is demonstrated by simulation and experiment.     

基于运动控制器的激光加工机床数控系统研究

针对现有激光加工机床数控系统的不足,提出了以多轴运动控制器为核心的激光加工机床开放式数控系统设计方案,该方案以运动控制器为CNC控制核心,PC机为支撑单元,对硬件选型和软件设计进行了说明,为激光加工机床数控系统的研究提供了新的思路。     

基于89C51/52单片机的数控机床面板智能处理单元

本文提出了基于８９Ｃ５１／５２单片机的数控机庆机板智能处理单元,介绍了基工作原理和系统软硬件,设计了一种新的软件消除键拌动算法。该处理单元通过标准串口与数控系统交换信息,已经用了三从九控铣床手动操作面板的控制,软硬件均可以可靠工作。     

NURBS-based fast geometric error compensation for CNC machine tools

In this paper, a novel method for the compensation of geometric errors of CNC machine tools is presented. The key idea is to use the basis functions of the setting NURBS path to approximate its error compensation function and to generate a new compensated NURBS path. In this way, both the setting and the compensated NURBS path have the same NURBS form. More importantly, the control points of the error compensation function can be obtained by simply calculating the positioning deviations of the control points of the setting NURBS path using the error model. A high compensation accuracy can be achieved through the systematic insertion of new knots, which creates new control points and raises the flexibility of NURBS in representing the error compensation function. The real-time interpolation of the compensated NURBS path completes the error compensation automatically. Simulations and experiments have shown that the new method delivers the same positioning accuracy as a model-based real-time geometric error compensation method does, but without additional real-time CPU loading. The proposed method can also be implemented in the post-processor of a CAM system for off-line compensation.     

Total ballbar dynamic tests for five-axis CNC machine tools

The linear and rotary axes of a five-axis machine tool are driven simultaneously to generate a specified tool position and orientation in workpiece coordinates. It is crucial that these servo-controlled axes are of balanced dynamics to achieve high tracking accuracy. In this paper, ballbar circular tests for all possible combinations of linear and rotary axes of a five-axis machine tool are investigated and total ballbar dynamic tests are proposed. Through the relational arrangement of the test sequence, the total ballbar dynamic tests can be employed to identify dynamic differences between linear and rotary axes. More importantly, the velocity gains of the position control loops of all servo-controlled linear and rotary axes can be tuned synchronously to eliminate gain mismatch errors. Experimental results have proved the effectiveness of the new methods.     

Fast real-time NURBS path interpolation for CNC machine tools

In this paper, a novel fast real-time non-uniform rational B-spline (NURBS) path interpolation method is presented. This method efficiently integrates the data processing of a NURBS path in a CNC controller, from pre-processing to real-time interpolation. In the calculation of the total length of the NURBS path, the numerical adaptive quadrature method adapts to the integrand, i.e. the first derivative of the length function, automatically, dividing the parameter interval into subintervals with fine or coarse spacing according to the varying condition of the integrand. This new method takes full advantage of the subdivision scheme. The key point is to generate inverse length functions (ILF) for each resulting subinterval. In the real-time NURBS path interpolation, the new setting path parameter can be calculated directly using the ILF without the need for any time-consuming computation of NURBS derivatives and iteration. The proposed method is extremely fast, accurate and suitable for real-time implementation, and simulations and practical tests proved its effectiveness.     

基于遗传算法的车间设备布局优化设计

文章针对某厂曲轴生产车间设备布局问题采用遗传算法进行优化设计.首次提出了搬运矩概念,很好的解决了生产多种工件的车间设备布局优化问题.优化设计结果符合生产实际要求.     

基于遗传算法的模糊神经网络控制器在GTAW中的应用

GTAW(钨极气体保护电弧焊)是一种能够很好控制线能量，进行高质量薄板焊接的方法。焊接过程是一个复杂的、多参数耦合的高度的非线性系统，在实际焊接过程中难以实现实时、有效的在线控制。模糊控制吸收了人的经验思维的特点；神经网络则对信息的处理具有自组织、自学习的特点；遗传算法是一种全局优化搜索方法，具有简单通用、普遍性强，适合并行处理和应用范围广的优点。作者将三者有机地结合起来，在模糊神经网络控制器的基础上利用了改进的遗传算法，并分析了其网络结构和离线学习的方法，协调利用三者的优势设计了一种新型的模糊控制器，并使之用于脉冲GTAW仿真中，结果证明了该新型模糊神经网络控制器比传统的模糊控制器具有一定的优越性。     

Feed optimization for five-axis CNC machine tools with drive constraints

Real time control of five-axis machine tools requires smooth generation of feed, acceleration and jerk in CNC systems without violating the physical limits of the drives. This paper presents a feed scheduling algorithm for CNC systems to minimize the machining time for five-axis contour machining of sculptured surfaces. The variation of the feed along the five-axis tool-path is expressed in a cubic B-spline form. The velocity, acceleration and jerk limits of the five axes are considered in finding the most optimal feed along the tool-path in order to ensure smooth and linear operation of the servo drives with minimal tracking error. The time optimal feed motion is obtained by iteratively modulating the feed control points of the B-spline to maximize the feed along the tool-path without violating the programmed feed and the drives’ physical limits. Long tool-paths are handled efficiently by applying a moving window technique. The improvement in the productivity and linear operation of the five drives is demonstrated with five-axis simulations and experiments on a CNC machine tool.     

Modal parameter identification for CNC machine tools using Wavelet Transform

The paper presents a new use of the Continuous Wavelet Transform for modal parameter identification applied to CNC machine tools. Firstly, the resonant frequencies and damping ratios of the CNC machine tool axis drive are estimated in the frequency domain using the transmissibility relation at resonance. The experimental Bode diagrams are determined using a novel measurement practice for the decoding of signals generated by a position encoder.This paper focuses on a novel application of the Continuous Wavelet Transform to identify the resonance frequencies and corresponding damping ratios of the CNC machine tool axis drive. The proposed method has the ability to detect variations in the amplitude levels of weak components embedded in strong noise and non-stationary processes. The superior ability of the Wavelet Transform to identify accurately modal parameters is demonstrated by comparing the results of the two different methods.     

利用PMC进行数控机床故障诊断和维修

PMC是数控机床的控制中心,机床的很多控制指令都要经过PMC处理后才能控制执行机构。通过对PMC的检查,利用PLC可以快速、准确地判断数控机床故障。     

基于ARM的嵌入式卷板机数控系统研究与设计

针对目前广泛应用的基于工控机与PLC开发的卷板机数控系统的改造和更新,设计一套基于ARM处理器和CPLD为控制核心的嵌入式卷板机数控系统,介绍该数控系统的各种硬件接口设计及数控系统软件的开发。该数控系统可灵活搭配硬件接口模块、运行嵌入式Linux操作系统、拥有良好的基于Qt设计的人机交互界面,为卷板机数控系统开发提供了一种解决方案。     

Compact design for high precision machine tools

Due to raising functional integration in micro fluidic, micro mechanic, micro electronic and micro optical systems the trend to scaling down the work piece sizes while increasing its complexity requires high precise machine accuracy. With respect to the process and geometrical parameters, most of the finishing manufacturing processes can be covered by milling and grinding operations with three or five machine axes. But whereas the available machine tools hardly achieve the required process dynamic and accuracy in all degrees of freedom, the requirements still increase. For this reason the Fraunhofer IPT has developed high precise machine tools following a compact design strategy by reducing the overall machine dimensions as far as conventional machine components such as measuring or drive systems were available. The developments of two compact machine tools exemplify the dynamic and accuracy enhancement by compact design and are described in the following.     

环形模拟传感器在数控机床上的应用

本文简要介绍了Turck环形模拟传感器的基本特性.并通过该传感器在高速卧式车削中心HTC3275zy上顶尖控制的应用实例,详细介绍了环形传感器在应用中的硬件和软件的设计方法.说明了在数控机床上应用传感器技术的必要性和重要性.