复杂曲面相贯线焊接轨迹控制算法的研究及仿真

曲面与圆管之间的焊接比较普遍,为了实现复杂曲面相贯线的自动焊接,在五自由度焊接机床的基础上,以圆锥面与圆管的焊接为研究对象,构造圆锥面与圆管的相贯线方程,利用等长直线段拟合整条相贯线,实现运动轨迹的插补运算,计算出插补各点的坐标参数及焊枪角度,以对焊枪姿态进行实时调整。利用OpenGL软件,对插补运动进行动态仿真,观察运动轨迹是否正确,仿真结果验证了在五自由度焊接机床上,该运动控制算法可以实现复杂曲面相贯线的自动焊接。     

基于软件的复杂相贯线接缝自动焊接运动控制算法

在介绍五轴联动数控焊接机床结构与工作原理的基础上,重点研究了基于软件体系结构的复杂相贯线接缝自动焊接运动控制算法。以实现椭球面封头焊接接管的相贯线接缝自动焊接为例,分别介绍了相贯线接缝空间曲线方程构建、利用直线段插补拟合接缝曲线时各插补离散点坐标参数与焊枪姿态调整参数计算以及各坐标轴插补位移量计算等算法。利用本文介绍的软件算法对复杂相贯线接缝自动焊接运动过程进行控制,具有较高的柔性和通用性,并且大幅度地降低了设备成本。     

圆管相贯线接缝优化的等间距直线逼近算法的研究

两圆柱管之间的连接形成的相贯线接缝为复杂的空间曲线。为了实现两圆管相贯线接缝的自动焊接,加工出满足焊接精度的相贯线接缝,需要对数控设备的运动轨迹进行控制。首先建立圆管斜交的空间相贯线数学模型,通过MATLAB编程验证曲线模型的正确性,在对数控设备运动学模型分析的基础上将空间曲线展开到平面曲线,利用Origin软件拟合平面展开曲线,根据优化的等间距法原理,利用VB软件开发了数控系统实现了插补过程的动态仿真。结果表明,该算法能够满足相贯线轨迹控制的精度要求,为相贯线研究设计奠定了技术基础。     

NURBS曲线实时插补算法研究

提出了一种包含插补误差和进给加速度实时监控的NURBS曲线实时插补算法,该算法有效的避免了曲线求导和曲率的复杂计算。运用参数的对分法预估下一插补点,极大限度简化了插补的实时计算,保证了算法的实时性。     

NURBS曲线实时插补方法的研究

提出了一种综合插补误差和进给加速度控制的NURBS曲线实时插补算法,该算法有效地避免了曲线求导和曲率的复杂计算.运用参数域上的黄金分割法预估下一插补点,极大地简化了插补的实时计算,保证了算法的实时性.     

一种简化计算的S型加减速NURBS插补算法

针对目前NURBS曲线插补中加减速控制方法不足的问题,实现了加工过程中进给速度的平滑过渡,提出了一种新的NURBS曲线插补方法,包括速度规划和实时插补两个方面。速度规划采用了一种基于曲率自适应的简化计算的S型加减速方法,并结合"双向插补"的思想实时预测减速点,防止产生过大的弓高误差;实时插补则利用Muller插值和Newton迭代法计算了下一周期的插补参数,进而求出了下一时刻到达的空间坐标点。最后与已有插补方法进行了仿真分析比较。研究结果表明,该方法能保证加速度连续和加加速度有界,有效减少弓高误差和进给速度波动,提高机床运行的平稳性。     

基于参数方程的数据采样圆弧插补算法

数据采样圆弧插补算法已取得了较大的进展,但大多较为复杂,编程计算量大,在插补公式的统一性、特殊圆弧的插补等方面还不够完善。探讨了一种基于圆弧参数方程的、以步进角为中间变量的新型圆弧插补算法;结合计算机数值运算的特点,改进了距离终点判别方法,利用下一插补点与插补终点的距离作为终点判别依据;在LabVIEW环境下进行了与传统算法对比的插补仿真实验。结果表明,此算法不仅能正确地进行整圆插补终点的判别,实现整圆插补,而且可将计算误差减小为原来的1/104,计算速度提高33%。此算法简单可行,易于编程,适用于任意圆弧的插补,计算速度快且无误差累积效应,精度较高。     

用于五轴联动数控机床的曲线插补控制策略

为实现复杂曲面零部件的高速高精数控加工,提出了一种用于五轴联动数控机床的曲线插补控制策略.实现该控制策略的数控机床控制器将控制任务分为非实时任务和实时任务两部分.非实时任务包括刀具路径信息中位置矢量的曲线插值计算和刀位矢量的曲线插值计算;实时任务包括位置矢量插值曲线和刀位矢量插值曲线的实时插补计算,以及插补点坐标的逆机床运动变换.加工实验表明,该插补加工方法町以用于五坐标数控机床的运动控制,具有良好的应用前景.     

基于NURBS曲线的工业机器人位置插补算法研究

针对直线圆弧插补在线计算量大,样条插补不能描绘自由曲线,提出了一种将NURbS算法应用于工业机器人控制系统的描绘自由曲线的实时高精度插补算法。该算法基于NURbS曲线矩阵表达式,利用插补前分段加减速控制的对称性反向插补预测减速点,整合了Taylor展开式和Adams方法预估曲线参数,通过加减速、弓高误差和法向加速度进行实时步长自适应控制,并由预估-校正进行精度控制。仿真与实验结果表明,该插补算法实时性好,精确度高。     

一种三次均匀B样条曲线的轨迹规划方法

针对复杂曲线的数控加工,提出一种新的插补方法。首先采用一种三次B样条曲线的重叠拼接算法实时地对复杂曲线进行拟合,进而综合弓高误差、速度和加速度等因素,给出具有自适应调整能力的插补步长确定算法,该算法在提高轮廓加工精度的同时,可减小加工过程中的冲击。最后,对插补周期内节点的轨迹进行了规划,以确保运动轨迹满足速度、加速度以及加加速度的平滑约束条件。仿真实验结果表明,该方法在实时插补过程中,可以保证复杂曲线插补加工的高速与高精度,且具有很好的速度、加速度以及加加速度平滑性。     

Development of a real-time trajectory generator for NURBS interpolation based on the two-stage interpolation method

This paper deals with the real-time NURBS interpolation method in which the interpolation error between the ideal curve and the interpolated curve is compensated within the machine basic length unit (BLU). Parametric curve interpolation methods are based on the Taylor series expansion of curve parameters and an approximation. This approach enables effective feed command generation following the target curve. However, the interpolation error caused by the curve segmentation cannot be controlled.In this research, a two-stage interpolation method that compensates for interpolation errors within machine BLU is proposed. The interpolation result was filtered by an acceleration/jerk limitation equation. Through this two-stage interpolation, both the interpolation error condition and the motion dynamics can be satisfied.Using computer simulations in which interpolation results are revaluated by a numerical iteration method, it is shown that the two-stage interpolation algorithm can interpolate target curves precisely with geometric and dynamic contentment. The proposed algorithm was implemented in the CNC simulator system and an experimental run was conducted to identify the real-time adaptation.     

实时快速NURBS直接插补技术

为了解决基于泰勒展开式的NURBS插补算法存在的速度波动问题,提高NURBS插补实时性,深入研究了NURBS曲线直接插补方法。根据插补原理,提出了一种不同于泰勒展开式的插补计算方法,并研究了一种NURBS快速计算方法。在满足插补过程精度要求的前提下,由进给速度直接计算插补点坐标,并采用递推矩阵对NURBS进行快速求值求导计算,有效地减小了速度波动,而且提高了计算速度和插补实时性。仿真结果证明了该方法的可行性和有效性。     

基于十字链叉的NURBS曲面插补算法及仿真分析

针对目前曲面插补算法存在的实时性不强,插补算法需要大量的额外空间,算法步骤繁琐以及对插补过程产生的大量数据点的数据处理问题,为了保证作为数控技术核心模块的曲面插补算法的高速、高精度性能,基于德布尔递推算法思想,重新推导出了适合于曲面插补的新的NURBS曲面表达式,在此基础上重新设计了曲面插补快速算法,并着重研究了新算法的实时性.另外,为验证新算法的正确性和有效性,提出并实现了十字链叉数据表达结构,对NURBS曲面插补点微细步长及插补质量进行了分析.建立了以VC6.0/MFC为平台的、集弓高误差、速度、加速度等功能分析于一体的算法仿真验证系统,并以汽轮机叶片为例进行了验证.研究结果表明,该算法可以满足曲面插补高速、高精度的性能要求.     

插值模糊算法在点焊控制中的应用

针对点焊过程的特点,设计了基本的模糊控制方案,并进一步使用插值算法其进行了改进。使用插值算法相当于细分了控制规则,从根本上消除了量化误差,改善了系统的稳态性能。     

An interpolation method for the open CNC system based on EPM

A typical open computer numerical control (CNC) system should own the capability of being redeveloped easily and effectively, and any improvements of interpolation algorithm or machining technique could be put into practice by users conveniently. However, this is not always available in the current open CNC systems. To solve this problem, an interpolation method based on external profile mode (EPM) is introduced to improve the universality and the performance of an open CNC system in this paper. The method is realized with a rough interpolation in the PC host and a fine interpolation in the slave motion controller. With this method, various interpolation algorithms can be easily realized in the rough interpolation when machining complex contours. Meanwhile, the machining parameters during each interpolation cycle can be wholly determined by the host, so a real-time adjustment of machining parameters can be accomplished during the interpolation. The working principal of EPM is presented in this paper, and the realization of interpolation algorithms with the proposed method is described. A look-ahead algorithm for determining the machining parameters of each segment is implemented based on the length of segments in the rough interpolation. An acceleration/deceleration strategy with confined jounce is proposed in the look-ahead algorithm. The experimental results of specific profile interpolation show that the interpolation method based on EPM can make the open CNC system more universality and high performance.     

Parameter u and arc S modeling of B-spline for NC machining with CL points preprocessing algorithm

This paper proposes a novel B-spline interpolation based on CL points preprocessing algorithm and on u-S modeling, aiming to overcome the shortages of linear and circular interpolations. A B-spline toolpath trajectory is generated by fitting a given set of CL points. CL points are preprocessed by chord distance to reduce computation load, thus using fewer feature CL points to generate a B-spline toolpath trajectory. As for disadvantages due to parameter updating for B-spline interpolation, a fifth order polynomial based on u-S modeling is constructed to map the desired curve length S to the corresponding spline parameter u, cutting the real-time computation load. Simulation results are provided to verify the feasibility and effectiveness of the proposed interpolation algorithm.     

Precision NURBS interpolator based on recursive characteristics of NURBS

In NURBS interpolation, real-time parameter update is an indispensable step which affects not only feedrate fluctuation but also contour error. Using Taylor approximation interpolation method to find the next interpolation point causes a large feedrate fluctuation due to the accumulation and truncation errors. This paper presents a new, simple, and precise NURBS interpolator for CNC systems. The proposed interpolation algorithm does not use Taylor’s expansion, but the recursive equation of the NURBS formula. A simulation study is conducted to demonstrate the advantages of this proposed interpolator compared with those using Taylor’s equation. It is readily seen that this interpolator using the new concept of interpolation for modern CNC systems is simple and precise. The proposed method can be used for interpolating a continuous NURBS curve.     

基于递归特征分析的NURBS曲线插补算法

在分析NURBS曲线公式中基函数递归特征的基础上,提出了一种新的NURBS曲线插补算法。该算法通过前一个参数增量值和前一段插补弦长来确定下一个参数增量值,进而实现对参数的密化。仿真实验结果表明,该算法在改善弦长误差和减小计算量方面优于Taylor展开插补算法。     

Optimization of weld bead geometry in GTAW of CP titanium using imperialist competitive algorithm

This paper aims to use a novel optimization algorithm called imperialist competitive algorithm (ICA) in order to optimize the weld bead geometry in the gas tungsten arc welding process. This algorithm offers some advantages such as simplicity, accuracy, and time saving. Experiments were conducted in order to collect welding data and obtain a relationship for the bead geometry as a function of welding current, arc voltage, welding speed, and arc length. Furthermore, a regression equation for depth of penetration and bead width was obtained using the least squares method, and the equations were optimized using ICA. Ultimately, the value of the input variables to obtain minimum bead width and maximum depth of penetration was calculated using ICA. Computational results indicate that the proposed algorithm is quite effective and powerful in optimizing the cost function.