文章快速检索 高级检索

Corner building method and algorithm of automatic programing for aircraft structural parts
CUI Zhiwei , ZHENG Guolei
School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Received: 2015-12-08; Accepted: 2016-01-08; Published online: 2016-02-15 16:30
Foundation item: National Science and Technology Major Project (2012ZX04010051); Aviation Joint Fund of Liaoning Province of China (2014028026)
Corresponding author. ZHENG Guolei, Tel.: 010-82339128 E-mail: zhengguolei@buaa.edu.cn
Abstract: Aimed at the problems of inefficiency, heavy work and unstable quality in corner numerical control (NC) programing for aircraft structural parts, a new auto-extended method based on rounded corner face was put forward. Combined with process knowledge, the processing model of corner is set up, which is the key issue of automatic NC programming. First, some new terms were introduced, such as corner, rounded corner face, processing model of corner and interference region of corner machining. Next, in order to set up a model of corner processing, some methods were proposed which include auto-extended technology, side surface of revolution and cutting element computation methods, and interference region building approach. Based on the above research, an automatic NC programing system of corner was developed, which had been successfully applied in a large aviation manufacturing enterprise. The preliminary application shows that the method is valid for increasing efficiency and quality of corner NC programing, which leads to programing workload reduction.
Key words: corner     aircraft structural parts     numerical control (NC) machining     processing model     automatic programing

1 转角及其加工模型定义

1.1 转角

 图 1 转角 Fig. 1 Corner

Vn为转角的正轴向，即转角轴向与z轴夹角较小的方向。根据右手螺旋定则判定左侧面和右侧面，即掌心面向转角轴线握拳，大拇指指向与Vn一致，四指指向即“frfsfbfl”方向。

Vs为侧面体外法向，α=arccos[Vs·z/(|Vs||z|)]，若π/2 < α < π，则侧面为闭角面，侧面倾角θ < 0；若0 < α < π/2，则侧面为开角面，侧面倾角θ>0；若α=π/2，则侧面为竖直面，侧面倾角θ=0。

 图 2 转角面 Fig. 2 Rounded corner face

s={fci|i=1, 2, …, m}为侧转面fs的转角面集，且m>1，若s组成的区域为连通域，则称fs为连通侧转面，如图 2(a)所示，否则，称fs为非连通侧转面，如图 2(b)所示。

1.2 加工模型

 图 3 转角加工模型 Fig. 3 Processing model of corner

 图 4 切元 Fig. 4 Cutting element

 图 5 干涉域 Fig. 5 Interference region

 图 6 左干涉域 Fig. 6 Left interference region
 图 7 右干涉域 Fig. 7 Right interference region

1)若I={Il}，则称Mc为左干涉模型。

2)若I={Ir}，则称Mc为右干涉模型。

3)若I={Il, Ir}，则称Mc为全干涉模型。

4)若I=Ø，则称Mc为无干涉模型。

2 加工模型构建算法 2.1 算法流程

 图 8 加工模型构建流程 Fig. 8 Flowchart of processing model building

1)夹角θ满足αminθαmax

2)侧转面半径R满足rminRrmax

3)包含完整的切入元或切出元。

Mc为有效加工模型。

2.2 关键技术及算法

2.2.1 侧转面计算

1)转角面自动扩展技术

 图 9 转角面自动扩展技术算法流程 Fig. 9 Algorithm flowchart of auto-extended technology for rounded corner face

lc={li|i=1, 2, …, n}为转角面fc的边集合，且n≥3，lilcli的共边面集合s={fi|i=1, 2}，不妨设f1=fc, f2fc，若f1f2满足G2以上连续性，则称lifc的有效边，f2fc的有效面。

n级和n-1级转角面集合分别为fcnfcn-1fcn所有转角面的边lc={li|i=1, 2, …, m; m≥3}，lilcli的共边面集合s={fi|i=1, 2}，不妨设f1fcn，若f1f2满足G2连续，且f2fcnf2fcn-1，则称lin级有效边，f2n级有效面。

 图 10 转角面计算 Fig. 10 Rounded corner face calculation

2)直纹处理

Zhou等[15]提出基于特征的碎面自动拟合方法，该方法不适合非连通侧转面等复杂类型侧转面的处理；通常直纹面造型需要给定2条相对的初始边界，2条边界称为基线，然后将基线上相应的等参数点用直线相连接来构造直纹面[16]。本文采用此直纹面造型方法，并结合侧转面的几何特点，给出其直纹面拟合的主要步骤如下。

①截面线生成

 图 11 截面线生成 Fig. 11 Section curves creation

②母线拟合

③基线拟合

2.2.2切元计算

1)界点计算

 图 12 转角示例 Fig. 12 Corner sample

 图 13 投影向量 Fig. 13 Projected vector

 图 14 更新顶点 Fig. 14 Update vertices

 图 15 转角夹角 Fig. 15 Corner angle

2)界边

3)切面及切边计算

 图 16 加工区域轴向外轮廓 Fig. 16 Axial-profile of machining region

 图 17 切边 Fig. 17 Cutting edge

2.2.3 干涉域构建

 图 18 干涉域构建流程 Fig. 18 Flowchart of interference region building
 图 19 右干涉域计算结果 Fig. 19 Calculation results of right interference region
3 算法实现及测试

 图 20 转角加工模型实例 Fig. 20 Case of processing model of corner
 图 21 转角加工刀轨仿真 Fig. 21 Tool path simulation of corner machining

 类型 tc 正确率/% 连通侧转面 0 98.5 1 98.2 -1 98.2 2 97.5 非连通侧转面 0 97.2 1 96.5 -1 96.5 2 95.1

 类型 tc 平均交互次数 平均耗时/s 效率/% 手工 自动 手工 自动 ηt ηw 连通侧转面 0 40 1 120 1 99.2 97.5 1 60 1 180 1 99.4 98.3 -1 60 1 180 1 99.4 98.3 2 70 1 240 1 99.6 98.6 非连通侧转面 0 40 3 120 2 98.3 92.5 1 60 3 180 2 98.9 95.0 -1 60 3 180 2 98.9 95.0 2 70 3 240 2 99.2 95.7

4 结论

1)该技术无需进行繁琐的交互操作和复杂的几何计算，只需交互选取任意一转角面，即可自动完成转角特征计算，并建立其加工模型，特征计算准确、高效，实用性强。

2)基于加工模型研究开发的转角数控加工自动编程系统已成功应用于某型号飞机的生产，转角数控加工程序编制效率提高95%以上，而且加工质量更高、更稳定。

 [1] CHEN S L, ZHENG G L, ZHOU M, et al. Process-scheme-driven automatic construction of NC machining cell for aircraft structural parts[J]. Chinese Journal of Aeronautics, 2013, 26 (5) : 1324 –1335. DOI:10.1016/j.cja.2013.07.035 [2] 施建飞, 李迎光, 刘旭, 等. 基于属性边点图的飞机结构件筋特征识别方法[J]. 计算机集成制造系统, 2014, 20 (3) : 521 –529. SHI J F, LI Y G, LIU X, et al. Rib feature recognition method for aircraft structural parts based on vertex attributed adjacency graph[J]. Computer Integrated Manufacturing Systems, 2014, 20 (3) : 521 –529. (in Chinese) [3] 高鑫, 李迎光, 张臣, 等. 飞机结构件内型转角一体加工刀轨生成方法[J]. 航空学报, 2014, 35 (9) : 2660 –2671. GAO X, LI Y G, ZHANG C, et al. An integrated machining tool path generation method for corner and profile of aircraft structural parts[J]. Acta Aeronautica et Astronautica Sinica, 2014, 35 (9) : 2660 –2671. (in Chinese) [4] TOLOUEI-RAD G M, PAYEGANEH G. A hybrid approach to automatic generation of NC programs[J]. Journal of Achievements in Materials and Manufacturing Engineering, 2005, 14 (1-2) : 83 –89. [5] HAN J H, PRATT M, REGLI W C. Manufacturing feature recognition from solid models:A status report[J]. IEEE Transactions on Robotics, 2000, 16 (6) : 782 –796. DOI:10.1109/70.897789 [6] HENDERSON M R, ANDERSON D C. Computer recognition and extraction of form features:ACAD/CAM link[J]. Computers in Industry, 1984, 5 (4) : 329 –339. DOI:10.1016/0166-3615(84)90056-3 [7] JOSHI S, CHANG T C. Graph-based heuristics for recognition of machined features from a 3D solid model[J]. Computer-Aided Design, 1988, 20 (2) : 58 –66. DOI:10.1016/0010-4485(88)90050-4 [8] 刘雪梅, 张树生, 崔卫卫, 等. 逆向工程中基于属性邻接图的加工特征识别[J]. 计算机集成制造系统, 2008, 14 (6) : 1162 –1167. LIU X M, ZHANG S S, CUI W W, et al. Machined features recognition based on attributed adjacency graph in reverse engineering[J]. Computer Integrated Manufacturing Systems, 2008, 14 (6) : 1162 –1167. (in Chinese) [9] VANDENBRANDE J H, REQUICHA A A G. Spatial reasoning for the automatic recognition of machinable features in solid models[J]. IEEE Transactions on Transacitions on Pattern Analysis & Machine Intelligence, 1993, 15 (12) : 1269 –1285. [10] TSENG Y J, JOSHI S B. Recognition of interacting rotational and prismatic machining features from 3D mill-turn parts[J]. International Journal of Production Research, 1998, 36 (11) : 3147 –3165. DOI:10.1080/002075498192346 [11] WOO T C.Feature extraction by volume decomposition[C]//Proceedings CAD/CAM Technology in Mechanical Engineering.Cambridge:MIT, 1982:76-94. [12] SAKURAI H, DAVE P. Volume decomposition and feature recognition, Part Ⅱ:Curved objects[J]. Computer-Aided Design, 1996, 28 (6-7) : 519 –537. DOI:10.1016/0010-4485(95)00067-4 [13] SHEEN B T, YOU C F. Machining feature recognition and tool-path generation for 3-axis CNC milling[J]. Computer-Aided Design, 2006, 38 (6) : 553 –562. DOI:10.1016/j.cad.2005.05.003 [14] YU F F, DU B, REN W, et al. Slicing recognition of aircraft integral panel generalized pocket[J]. Chinese Journal of Aeronautics, 2008, 21 (6) : 585 –592. DOI:10.1016/S1000-9361(08)60178-8 [15] ZHOU G, LI Y, LIU C, et al. A feature-based automatic broken surfaces fitting method for complex aircraft skin parts[J]. International Journal of Advanced Manufacturing Technology, 2015, 84 (5-8) : 1001 –1011. [16] WANG C C L, ELBER G. Multi-dimensional dynamic programming in ruled surface fitting[J]. Computer-Aided Design, 2014, 51 (6) : 39 –49. [17] 任朴林, 周来水, 安鲁陵, 等. 基于散乱数据截面线的曲面重构算法研究[J]. 机械设计与制造工程, 2003, 32 (3) : 82 –85. REN P L, ZHOU L S, AN L L, et al. A surface reconstruction algorithm based on planar contours of discrete data[J]. Machine Design and Manufacturing Engineering, 2003, 32 (3) : 82 –85. (in Chinese)

#### 文章信息

CUI Zhiwei, ZHENG Guolei

Corner building method and algorithm of automatic programing for aircraft structural parts

Journal of Beijing University of Aeronautics and Astronsutics, 2016, 42(12): 2730-2737
http://dx.doi.org/10.13700/j.bh.1001-5965.2015.0810