一种自适应B样条插补算法研究

针对复杂轮廓零件数控加工的实际要求,设计了一种在可控弦高误差插补算法基础上加入前瞻功能的自适应非均匀B样条插补算法.该方法能够根据曲线的形状,自适应地调整进给速度,保持速度平稳,并通过前瞻模块在速度变化敏感区域对加减速进行处理,满足机床加减速要求.     

面向高速加工的样条曲线实时插补算法

数控加工追求更高的加工效率和光洁的加工表面,但大多数样条曲线插补算法是根据进给速度、最大合加/减速度和合加加速度来设计的,并没有考虑如何充分利用单轴的最大加减速能力。提出一种时间近似最优的样条曲线实时插补算法,它面向数控系统对高速加工的需求,在考虑机床动态性能的基础上,充分利用单轴的最大加减速能力,以达到理论上近似最优的加工效率。同时该算法通过预处理求速度限制曲线、速度曲线反向链接和平滑处理三个步骤求出满足加工精度以及机床单轴的最大加速度、加加速度等约束条件的加工速度曲线,能有效提高加工表面的粗糙度。仿真结果表明,该算法在有效提高加工效率的同时,能实现对减速点的精确定位,得到光滑的加工速度曲线。     

基于分数次幂多项式的NURBS曲线快速插补方法研究

为减小NURBS曲线插补过程中对机床产生的柔性冲击,针对目前常用的S型速度控制策略中加加速度不连续以及速度变化相对缓慢的问题,在满足加加速度最大值限制的前提下,提出了一种基于分数次幂多项式的速度控制方法。结合加工路径曲率变化设计了前瞻算法计算加减速位移,自适应确定减速点。仿真结果表明,该方法可以快速提高进给速度,实现加加速度的平滑过渡。     

数控加工速度前瞻及插补算法的研究

在保证数控加工的加工精度和速度稳定性的基础上,研究了数控机床连续直线段加工的速度前瞻和回溯优化方法。根据速度前瞻的结果和进给倍率的变化,采用直线加减速的方法进行插补;采用C++和Matlab对本算法进行了开发。仿真结果表明了算法的有效性。     

基于FIR滤波的NURBS插补算法研究

在考虑数控加工精度和加工效率的基础上,针对传统加减速控制中减速点预测不准的缺陷,提出了一种基于级联滤波器的NURBS插补算法。该插补算法根据速度敏感点将要加工的曲线进行分段处理,避免了插补过程中的爬行与过冲,提高了加工质量。基于弓高误差的速度自适应调整使得加工精度一直在允许的范围之内,基于滤波器的进给速度控制方案使速度过渡平稳,提高了插补的效率。最后对提出的NURBS插补算法进行了实验仿真,结果证明该算法的可行性。     

样条曲线插补速度规划算法的研究

设计了一种适合多种样条曲线（三次样条曲线,Bezier曲线和B样条曲线）插补算法,通过速度控制前瞻缓冲区设置,在保证加工精度的基础上,实现了系统在样条曲线插补过程中加减速处理,改善了插补速度曲线,并满足了机床加减速性能要求。     

基于S型加减速的自适应前瞻NURBS曲线插补算法

为实现加工过程中进给速度和加速度的平滑过渡,减小其突变时对机床的冲击,更好地保证加工精度,提出一种基于S型加减速的前瞻自适应非均匀有理B样条曲线插补算法.该算法根据弓高误差的要求,确定出各插补点的自适应进给速度及位置参数,然后找出速度改变点及其等速区间.为避免相邻速度改变点间加减速过程的互相影响,分别在插补前瞻距离和预前瞻距离内,根据设备允许的最大加速度、加加速度以及S型加减速算法对各速度改变点参数进行分析,筛选出决定加减速过程的关键点,再进行S型加减速控制,使进给速度和加速度得以平滑过渡,从而满足机床加减速能力的要求.仿真结果表明,该算法能够满足高速高精度的要求,验证了其可行性.     

NURBS曲线新S型加减速反向寻优插补算法研究

NURBS曲线的弧长与参数之间无精确的解析关系,导致基于S型加减速进行插补时,曲线长度计算和减速点的预测十分困难,为此提出了新S型反向寻优插补算法。首先建立新S型加减速模型,将分段后的曲线逐段取出,利用新S型算法进行速度规划。接着对速度敏感点进行校正,并反向插补寻找减速点。通过插补实例证明,该算法适应性、实时性较好,能够满足高速高精度数控加工的要求。     

高强钢变截面辊弯成形轮廓曲线插补算法与速度规划

针对进给步长为单位短直线逼近实际曲线会引起弓高误差,提出一种限制弓高误差和根据曲率半径变化调整插补步长的轮廓曲线插补算法。鉴于单纯考虑轮廓曲线时,可能会导致单道次的最大速度,最大加速度超出设备极限值,综合分析多道次速度分布规律,找出速度敏感点,分析最佳加减速控制点,并考虑曲线连接点和变速距离等,提出加减速前瞻控制算法。回弹是板材成形内应力的释放结果,为了保证尺寸精度提出回弹补偿算法,试验结果表明,新的算法显著提高了轮廓曲线的插补精度、速度协调性和尺寸精度。     

基于de Boor算法的NURBS曲线自适应插补研究

在现代数控加工中已普遍使用NURBS曲线插补,但大多数NURBS曲线插补都致力于取得恒定的进给速度而不是轮廓精度,对此,提出了基于de Boor算法的NURBS自适应插补算法.将de Boor算法应用于NURBS曲线插补中,并用限定弓高误差对插补的进给速度实行自适应调节,实现了数控加工中进给速度的平滑过渡,减少速度急剧变化时对机床的冲击,保证了NURBS曲线实时插补和轮廓加工的精度.通过仿真证明了这种插补算法的实时性和实际应用的可行性.     

LOOK-AHEAD ALGORITHM FOR VELOCITY CONTROL BASED ON PARAMETERIZED CURVE INTERPOLATOR

To avoid suffering gouge and transient overshooting in high speed cutting machining, a novel parametefized curve interpolator model with velocity look-ahead algorithm is proposed. Based on a prearrangement step interpolation algorithm for parameterized curves and considering high curvature points, parameterized curve tool path is divided into acceleration segments and deceleration segments by look-ahead algorithm. Under condition of characteristics of acceleration and deceleration stored in control system, deceleration before high curvature points and acceleration after high curvature points are realized in real-time in high speed cutting machining. Based on new parameterized curve interpolator model with velocity look-ahead algorithm, a real cubic spline is machined simulativly. The simulation results show that velocity look-ahead algorithm improves velocity changing more smoothly.     

基于曲率加权累加的动态速度前瞻控制

针对在高速加工、快速检测等高速进给条件下,传统速度控制方法容易导致工件过切、机床抖动等问题,提出了基于离散衔接点曲率加权累加的速度前瞻程序段数动态选择的方法。首先,分析了基于5次样条曲线拟合离散衔接点方法,然后推导了到各衔接点的曲率表达式,最后根据各点曲率加权累加值进行动态速度前瞻程序段控制,并进行了仿真验证。仿真结果表明,动态速度前瞻避免了前瞻路径过短不能完成减速要求和前瞻段数过多占用系统资源,一定程度上解决了速度和精度的冲突问题,提高了系统的性能和加工效率。     

基于过控制顶点曲线的微线段过渡插补方法

针对微线段数控加工过程中的插补问题,为减小微线段数控加工中的速度波动,实现转接点的平滑过渡,提出过控制顶点曲线的过渡插补算法。首先构建微线段曲线的过渡矢量模型,根据基于特征多边形顶点的曲线模型的几何特性,构建过控制顶点曲线的过渡矢量模型,然后采用过控制顶点曲线过渡模型对微线段进行插补计算,根据加工误差计算控制顶点,确定约束速度并实时进行前瞻处理,最后通过实例进行了验证。实验结果表明,所提出的方法有效地提高了微线段转接速度,缩短了加工时间,实现了曲线的平滑过渡。     

5轴联动数控系统速度控制方法

高速加工过程中,在刀具路径上容易产生过冲,影响加工精度,因此必须提前对加工速度进行优化处理.基于数据采样法,利用当量位移和坐标轴方向系数实现了5轴联动线性插补;利用直线加减速原理进行插补前加减速控制;对速度前瞻控制方法进行了深入探讨,实现了相邻程序段转接处速度优化、连续微小程序段速度计算、减速点提前预测及前瞻程序段数动态选择等.仿真结果表明,速度平滑连续,有效地解决了5轴联动线性插补中的速度控制问题,提高了加工精度和加工效率.     

一种高速高精的路径动态前瞻规划算法

由于路径规划过程与速度规划过程之间缺乏信息交换,加工过程会出现加工速度与加工质量降低的现象,针对这一问题,提出了种高速、高精的路径动态前瞻规划算法。根据相邻加工路径之间的关系,规划出过渡圆弧半径的初始值;根据当前过渡圆弧与相邻的前一个过渡圆弧之间的关系,调整当前过渡圆弧的半径值;利用前瞻算法,结合具体的速度规划方式,进一步调整过渡圆弧的半径值,以确保加工过程中刀具既可以加速到路径所允许的最大速度,又可以在减速点前进行有效的减速。试验表明,通过将路径规划过程与速度规划过程相结合,算法在系统允许的误差范围内实现了有效的路径规划,并且最大程度地提高了加工速度,在保证加工精度的同时,提高了加工效率。     

Generation of velocity profiles with speed limit of each axis for high-speed machining using look-ahead buffer

An efficient look-ahead algorithm to generate velocity profiles is presented in this paper. Algorithm allows for a nonzero starting point velocity and end point velocity of every line segment to increase machining productivity. The paper considers the intelligence of look-ahead to achieve faster machining speed, along with required accuracy. Speed limitation of a specific axis and the direction change of an axis are newly added to the constraints of the velocity profile problem. This paper solves graphically the problem of generating velocity profiles and derives the equations for representing the velocity profile. A method to manage the look-ahead buffer is also proposed. To generate velocity profiles using the look-ahead buffer, three phases are proposed. Phase 1 determines the velocity conditions such as the maximum velocity, starting point velocity and end point velocity. In phase 2, velocity profiles are generated independently. Phase 3 handles the change of the start or end point velocity. This phase 3 is repeated until all adjacent point velocities are the same. The proposed method was utilized in the manufacturing field to engrave aluminum tire molds. It was demonstrated that this method contributes to an increase of the machining accuracy and a reduction of the production time.     

一种适应插补离散化特性的微线段直接插补算法

由于插补的离散化特性,微线段内很难实现梯形速度控制,并存在最后一个插补点与线段终点不重合问题。提出一种新的算法,以连续微线段为研究对象,从两端向中间进行线段端点速度前瞻,然后在预定点进行速度衔接处理。速度前瞻通过正向规划和反向验证使拐点速度达到最大,从而规划出微线段端点速度。根据微线段的端点速度和长度调用基于变插补周期的线段内速度规划,完成整个速度处理。仿真结果表明:该算法能够实现离散插补过程的梯形加减速并消除了插补残余长度。     

Development of integrated acceleration/deceleration look-ahead interpolation technique for multi-blocks NURBS curves

Modern motion control adopts acceleration/deceleration before interpolation (ADBI) motion planning to eliminate path command errors. However, the individual velocity profiles might not be continuous at the junction of the blocks. Acceleration/deceleration after interpolation (ADAI) method may provide an alternative for solving the discontinuous problems, but it causes path command errors. In this paper, an integrated acceleration/deceleration interpolation (IAD) scheme which integrates the ADBI and ADAI modules is proposed. The ADBI provides a look-ahead function which plans the feedrate profiles based on chord errors, command errors, curvatures, and acceleration limits. Within the look-ahead function, the command error equation is utilized to determine the feedrate at the junction of adjacent blocks. Then the ADBI performs non-uniform rational B-spline (NURBS) interpolation using the planned feedrate profile and outputs the position points to the ADAI module. The ADAI module processes the points by a digital convolution technique such that the continuity of the block junction velocity is ensured. Finally, the IAD is applied to the multi-block NURBS interpolation to validate its effectiveness. Simulations and experiments are conducted to demonstrate the IAD scheme. It is shown that the IAD scheme can reduce the acceleration significantly at the junctions of the blocks under the given tolerance of the command error. Furthermore, the proposed algorithm can improve tracking and contour accuracies as compared to the hybrid multi-blocks look-ahead approach.     

参数曲线柔性加减速前瞻控制算法

针对参数曲线插补的特点,使用S形加减速和三角函数加减速相结合的柔性加减速方法对参数曲线的插补路径进行前瞻控制。在规划前瞻速度过程中,首先根据加工曲线的曲率变化自适应地将前瞻距离分为曲率上升段和曲率下降段。在对前瞻路径进行S形加减速规划时,遇到路径上曲率频繁变化段,为了减小计算量,采用三角函数加减速的方法对速度进行重新规划。这样,在满足机床加减速要求的同时降低了系统计算负荷。仿真结果和实例表明,该算法能够适应复杂曲线的变化,满足高速高精度插补的要求。     

A universal velocity profile generation approach for high-speed machining of small line segments with look-ahead

Usually a complex contour-machining program generated by CAD/CAM systems composes a lot of small line segments. The intelligence of look-ahead is key to meeting the demand of high speed and high accuracy in the machining of these line segments. By now most researchers just utilize the simplest trapezoidal velocity profiles to deal with the look-ahead problem. Also the number of look-ahead line segments in most commercially available CNC systems is fixed, which cannot make full use of CNC processors. Therefore, a universal velocity profiles generation approach and corresponding optimal look-ahead algorithm based on dynamic back tracking along a doubly linked list are proposed in this paper. Two novel strategies, one for reducing feed rates fluctuation and the other for reducing move errors that come from digital integration and accumulated computation, are also presented. By using the proposed look-ahead techniques, arbitrary velocity profiles having the desired acceleration and deceleration characteristics for the movement of a lot of small line segments can be generated efficiently. Thus, the machining productivity can be dramatically increased without sacrifice of accuracy. The results of simulations and experiments showed the proposed approach was feasible and effective.