任意多岛型腔数控加工路径生成算法研究

提出了一个用于计算具有任意多岛型腔环切加工刀具轨迹的算法.该算法采用干涉标志分别生成型腔轮廓和各个岛的等距偏移轮廓,然后通过二维布尔运算进行偏移轮廓的合并,再进行轮廓生成树的深度优先遍历,可以得到最终的环切加工轨迹.     

带任意多岛屿的型腔环切加工刀轨生成

对带任意多岛屿的型腔环切加工刀轨生成进行了研究 ,提出了一种等距环互交处理的快速简便算法 ,设计了多个岛屿之间、岛屿与型腔之间的干涉处理方法 ,算法在超人CAD/CAM软件中实现 ,实践表明 ,该功能模块运行速度快 ,稳定性好 ,具有工程应用价值。     

基于Voronoi图的型腔加工刀具轨迹规划算法

Voronoi图是计算几何中非常有用的工具,它将几何多边形划分为若干子域,每个子域分别对应轮廓中的某段,子域中的任一点到对应的轮廓段距离最近,在各个子域中分别构造对应轮廓段的等分线。把该算法应用到型腔加工中,生成型腔结构的Voronoi图;然后在此基础上利用等距偏置法,生成型腔加工的刀具轨迹。该算法的应用不仅能消除传统刀轨算法中产生的多余环和自交环,避免过切现象,还能提高计算效率和加工精度。     

均匀偏置型腔加工残留区域分析

模具型腔平面铣削加工过程中,第一次加工采用两倍刀具半径均匀偏置型腔轮廓得到粗加工刀轨,然后对加工后残留区域进行分析,在不换刀的情况下先对刀轨之间的残留区域进行补加工,再换半径较小的刀具对轮廓边界拐角和轮廓与岛屿之间残留区域进行加工,生成加工刀轨。该方法大大提高了加工效率。     

复杂型腔加工区域的自动识别

为了解决型腔加工中交互式定义型腔和岛屿的不足,提出了一种简单有效的加工区域自动识别方法。为了识别型腔加工区域,首先构建了环关系矩阵,通过查询环关系矩阵的方式完成了轮廓环树的构建。在获得轮廓环树后,通过评估节点的深度来达到自动识别复杂型腔的目的。该方法无需用户直接参与,减轻了用户的负担,避免了出错的可能性。实例表明,该方法能自动有效地识别型腔加工区域,从而简化了数控编程步骤,提高了编程效率。     

复杂型腔刀位轨迹规划的优化算法

针对行切法加工复杂型腔,对型腔边界与岛屿轮廓进行扫尾处理时,如何得到最短且合理的刀位轨迹,提出了一种优化算法。首先利用最小树得到环与环之间的最短连通路径。但是无序的最小树却无法映射为扫尾处理的最短刀位轨迹,因此应对同一父节点下的同层子节点进行排序,通过生成最小有序树得到最短的刀位轨迹,减少了空行程从而提高加工效率。该优化算法易于实现,已在自行研制的模具CAM软件中得到成功的应用。     

基于非接触光学的金刚石滚轮石墨型腔测量方法

为了实现对金刚石滚轮石墨型腔的高精度测量,建立了基于激光同轴位移传感器的型腔轮廓测量系统,介绍了系统组成与测量原理、系统坐标系建立及参数标定方法,并提出型腔径向圆跳动与轴向圆弧轮廓度参数的测量计算方法。试验结果表明,径向圆跳动的测量标准差为0.003 3 mm,轴向圆弧半径测量值最大偏差为1.7μm,圆弧轮廓度测量值最大偏差为0.7μm,测量精度高。     

复杂形状区域行切加工刀具轨迹生成

讨论了由任意多段直线、圆弧、自由曲线及其组合构成边界轮廓，且边界内包含多个岛屿的复杂区域加工刀具轨迹计算问题。详细介绍了岛屿分解、边界轮廓刀具干涉处理、加工路线规划及刀具轨迹生成原理与算法。     

恒切削力2D轮廓铣削刀路优化研究

针对零件轮廓曲率半径和精加工余量对切削力的影响,通过正交切削实验,获得轮廓曲率半径、精加工余量与峰值切削力之间的相互影响关系,提出了一种适用于变曲率轮廓铣削的恒切削力2D轮廓铣削刀具路径生成算法。通过生成一条新的偏置路径,即修正的半精加工刀具路径,调节精加工路径各处余量。将此算法应用于包含自由曲线轮廓的不规则型腔加工,结果表明,该算法可以使精加工中的峰值切削力维持在一个恒定的状态,从而改善了加工质量。     

基于边界矩的机械零件图像轮廓特征提取技术

为实现机械零件的有效分类,针对零件具有比较明显的轮廓特征的特点,提出了基于边界矩的零件图像轮廓特征提取方法.首先采用轮廓提取算法,提取零件二值图像的轮廓,在进行水平倾斜校正后,以零件的质心为中心,将轮廓图像划分为若干个扇形子区域.利用改进的边界矩计算方法,分别计算出各子区域的边界矩,从而得出零件轮廓图像边界矩的分布特性.最后,采用K均值聚类算法对提取的零件轮廓特征进行分类,实验结果证明了该方法的有效性.     

Contour-parallel offset machining for trimmed surfaces based on conformal mapping with free boundary

The parametric surfaces of some manufactured parts are often subjected to the Boolean operation of other objects; generating suitable NC tool paths from such trimmed surface remains a challenge. This paper presents a new planar development-based method to generate contour-parallel offset paths of trimmed surfaces. To avoid direct frequent identifications and removals of interferences of offset curves on 3D-trimmed surface possibly with multiple holes or restricted regions, the original surface is flattened in the plane domain using a two-stage approach which consists of conformal mapping with free boundary and further nonlinear accuracy improvement. Then, sequent offsets of the boundary curves of the planar region are generated, and the global interferences are detected and removed using an efficient and robust divide-and-conquer strategy. Based on a tree data structure, a tool-path linking algorithm is also given with less or no tool retractions, and subsequently, the resulting planar paths are inversely mapped to the physical space. Illustrated examples have been conducted to testify the affectivity and the applicability of the proposed contour-parallel offset machining method.     

基于粒子群的多毫米波安防机器人环境感知方法

安防机器人常工作于昏暗、烟雾等环境,毫米波有探测这类环境的能力,但其点云是稀疏的,可将多毫米波的点云融合 以提高环境感知的能力。 点云融合时需要精确的结构参数,针对测量法获取结构参数存在误差的问题,在分析多毫米波点云坐 标的基础上,利用粒子群算法对毫米波雷达结构参数进行搜索,并根据搜索结果进行点云融合以及环境地图的构建;同时提出 稀疏点云地图的评价指标,对毫米波感知效果进行定量评价。 利用安防机器人在昏暗环境下开展实验,结果表明与结构参数由 测量法获取的多毫米波感知系统对比,点云数量有所增加,地图边界空洞数量平均减少 55% ,边界噪声率平均下降 12. 9% ,物 体点云离散度平均下降约 0. 06,中心位置的偏移量均有所减小。     

New morphological methods to generate two-dimensional curve offsets

For the purpose of generating 2D curve offsets used in 2.5D machining, four new methods based on morphological operations on different mathematical entities are presented in this paper. All of the methods, which lend themselves for parallel processing, exploit the idea that the boundaries formed by a circular structuring element whose center sweeps across the points on a generator/base curve comprise the entire offsets of the progenitor. The first approach, which is a carry-over from image processing, makes good use of morphological operations on binary images to produce 2D offsets via contour tracing algorithms. The second method, which is to rectify the high memory cost associated with the former technique, utilizes morphological operations on (boundary data) sets. The implementation of this basic technique is illustrated by two Matlab functions given in the paper. Despite its simplicity, the time complexity of this paradigm is found to be high. Consequently, the third method, which is evolved from the preceding one, reduces the time complexity significantly with the utilization of a geometric range search method. This technique, which has a considerable margin for improvement, is found to be suitable to be used as a part of the real-time motion command generator for CNC applications. Unlike the previous schemes, the final approach uses polygon operations to generate such curves. The run-time of this technique is highly governed by the complexity of the polygon overlay algorithm selected. The paper analyzes the complexity of each technique. Finally, the presented methods are evaluated (in terms of run-time and geometric accuracy) via two test cases where most CAD/CAM packages fail to yield acceptable results.     

M-PSK突发通信测试中DFT内插载波盲估计算法研究

在宽带通信信号实时多域分析通用架构基础上,针对宽带M-PSK突发通信信号实时多域分析中的快速载波同步,提出了一种基于离散傅里叶变换(DFT)插值的载波频偏相偏联合估计算法.该算法根据最大似然估计理论,首先对定时同步后的被测信号进行非线性变换去除调制信息,然后利用DFT变换得到载波频偏相偏粗估计,最后通过线性内插改善估计精度,实现载波频偏和相偏的精确估计.仿真及实验结果表明:通过内插算法处理后,载波估计误差方差更加逼近克拉美-罗(Cramer-Rao bound)界.该算法可在不增加DFT变换点数情况下,提高DFr对频率和相位的分辨力.     

A new offset algorithm for closed 2D lines with Islands

In this paper, a new offset algorithm for closed 2D lines with islands is introduced and the result is illustrated. The main point of the proposed algorithm is that every point is set to be an offset using bisectors, and then invalid offset lines, which are not to be participated in offsets, are detected in advance and handled with an invalid offset edge handling algorithm in order to generate raw offset lines without local invalid loops. As a result, the proposed offset method is proved to be robust and simple, moreover, has a near O(n) time complexity, where n denotes the number of input lines. The proposed algorithm has been implemented and tested with 2D lines of various shapes.     

NC toolpath generation for arbitrary pockets with Islands

This paper presents an efficient algorithm for generating cutter paths for the NC milling of arbitrary pockets with multiple islands. In this algorithm, the pocket border and island profiles are made up of concave or convex segments comprising linear and circular arc elements. For the generation of NC tool paths, the algorithm is divided into four stages, namely, profile pre-processing stage, offset calculation, determination of the termination condition, and determination of the path sequence. Compared with the other pocketing algorithms, the main aspect of this work is that the pocket border and island profiles are pre-processed in the first stage of the algorithm. Making use of contour bridges in the profile pre-processing stage, the island profiles are connected to the pocket border profile to form a closed path. This then simplifies the calculations in cutter offsets and eliminates the problem of nesting which occurs in some other pocketing algorithms.     

TOOL PATH PLANNING USING VORONOI DIAGRAM AND THREE STACKS

0 INTRODUCTIONThe offsets generating is one of the fundamentalproblems encounterd in many fields, such as the NCmachining, mesh generation, robot motion planningand so on. Deok-scon Kim's wo.k[l] was verycreative about POlygon offsetting using a Voronoidiagram and two stacks. He presented the concepts ofthe intersection state transition (IST ). AlthoughDeoksoon Kim's linear algorithm['1 has the highestefficiency of all the offsetting algOrithms['~'] atpresent, it still needs improvin…     

一种新的分布式MIMO-OFDM系统同步算法

针对不等周期同步算法多段重复引起的同步峰值模糊的问题,提出了一种适用于多输入/多输出正交频分复用(MIMO-OFDM)系统的定时同步算法,算法在原有的不等周期同步模式(UPSP)算法的基础上对其进行结构的优化,同时利用Zadoff_Chu序列良好的互相关性来提高算法的性能。仿真结果表明,提出的算法在AWGN和多径信道下能有效地进行定时同步,特别是在多径情况下,新算法较UPSP算法能更有效地提高准确定时概率。     

Automatic detection of onset and offset of QRS complexes independent of isoelectric segments

Accurate location to onset and offset of QRS complex from ECG signal is help measuring other features and it is a important and challenge task to recognize these onsets and offsets from ECG signal without isoelectric segment. The algorithm, which is introduced in this paper, does not depend on isoelectric segment and can accurately detect these onsets and offsets. In the algorithm, for every sample within about a cardio cycle of locally normalized ECG signal, two fitting straight lines are obtained respectively, from two sets of samples before and after the sample. And then two gradients and a smaller included angle corresponding to the two fitted lines are calculated. Third, those samples whose two gradients satisfied a pre-set value are taken as candidates for the R peak, and the sample with the minimal included angle is regarded as the R peak in this cardiac cycle. Finally, respectively before and after the detected R peak, the algorithm researches the onset and the offset of the QRS complex according to the same decision strategy. All 32 sets of 12-lead ECG records from http://physionet.org/pn3/twadb/ are employed to evaluate the method. The experimental results show that compared with three traditional methods, the method can more accurately detect all onsets and offsets and has better robust on interference.     

A novelty digital algorithm for online measurement of dielectric loss factor of electronic transformers

There are many inherent performance limitations using traditional algorithms for online measurement of dielectric loss factor including synchronous sampling, no interharmonics and power system frequency must be invariable. In a non-stationary signal environment where power frequency fluctuation and interharmonic components exist, there is no guarantee of measurement accuracy by using traditional methods. The paper proposed a high-accuracy digital algorithm for online measurement of dielectric loss factor of electronic transformers. Theoretical basis of the new algorithm is based on a new data processing procedure including data truncation and data addition which compensates phase distortion as a result of the spectrum of addition data contains offsets. The algorithm can accurately extract the fundamental signal and calculate dielectric loss factor. Measured results from simulations and practical engineering projects show that the new algorithm has good application feasibility without being affected by the limitations rendered above.