虚拟加工环境建造的关键技术研究
摘要
虚拟加工技术是指数控机床在虚拟环境中的映射，它集制造技术、机床数控理论、计算机辅助设计(CAD)、计算机辅助制造(CAM)和建模与仿真技术于一体。人能够凭直觉感知计算机产生的三维仿真模型的虚拟环境，虚拟加工过程能为产品设计可制造性的分析提供关键数据。在实际数控加工过程中，为了校验数控代码的正确性，需要进行反复试切直至确认数控代码能够完成预定的加工任务，同时数控加工参数也需要反复调试，这些操作不仅效率低下，占用了机器资源，而且有可能引起刀具碰撞或干涉等问题而造成经济损失。虚拟加工过程，能节省资源并避免风险。它的好处还体现在通过真实地模拟机床加工过程的行为来快速地对机床操作人员进行培训，也可帮助机床制造商向潜在的远程客户逼真演示其产品。该技术的采用可缩短产品的开发周期，降低生产成本，提高产品质量和生产效率。随着科学技术的进步，虚拟加工将在虚拟制造业中发挥其更大的作用。
本文从虚拟产品的可加工性角度出发，对虚拟加工环境的结构及其关键技术进行了研究，并开发了一个三维虚拟加工环境原型系统，其中的设备单元为一个虚拟铣削加工中心。系统在NC代码或刀位文件的驱动下运行，在加工过程中可连续不断地改变视角，以观察加工过程中加工中心的部件运动、零件和型腔的成型过程。该原型系统的仿真效果具有真实感强，实时性好的优点，可用于对设计的产品进行可加工性验证。
在国内虚拟机床技术研究的基础上，本文对数控加工过程的可视化进行了研究，包括虚拟加工环境的建造、刀具轨迹的优化模型及刀位计算、虚拟加工的NC代码翻译与实现，并着重于虚拟加工的NC代码翻译与实现的算法研究。总结出一套虚拟加工技术的实施方案。本系统以Windows98为开发平台，采用C++Builder软件及三维图形软件标准接口OpenGL为工具，初步设计了整个虚拟加工的过程。系统的结构包括：
(1)虚拟加工环境：虚拟加工环境由机床、工件、刀具和夹具构成，采用OpenGL和CAD对机床、夹具、刀具和工件进行特征造型。
(2)虚拟加工过程：包括数控程序译码、三维动画仿真。数控加工过程仿真主要指几何仿真。几何仿真将刀具与零件视为刚体，不考虑切削参数、切削力及其它因素对切削加工的影响，只是对数控程序进行翻译，产生刀具位置数据，并以此数据驱动机床运动部件和刀架运动，刀具对工件进行虚拟切削等。
The technology of virtual machining is the reflection of numerical controlling machine tool in the virtual environment, it make the manufacturing technology, the numerical controlling theory of machine tool, the Computer Aided Design (CAD), the Computer Aided Manufacture (CAM), the technology of modeling and simulation into a whole system. The people can feel the virtual environment of 3D simulative model produced by computer depending on instinct; the process of virtual manufacturing provides key data to analyze the producibility of product design. In the real process of numerical controlling machining, it is necessary to try cutting repeatedly until we can affirm that the numerical controlling code can accomplish scheduled machining task in order to verify the validity of the numerical controlling code. At the same time, numerical controlling machining parameter needs also to debug repeatedly, these operations not only have lower efficiency and occupy the machine resource, but also have the possibility to
make the tool collision and interference and other problems. The process of virtual manufacturing can save the resources and avoid risk. The benefit of the process of virtual manufacturing also shows that it can train the operators of machine tool through simulating really the machine tool's machining process, and help the machine tool's manufacturer to demonstrate realistically their products to latent long-distance clients. The using of virtual manufacturing technology can shorten period of the product's development, lower the production cost, advance product's quality and producing efficiency. With the developing of the science and technology, virtual machining will
bring into play great roles in the virtual manufacturing.
The paper studies the configuration and key technology of the virtual machining environment from the point of view of virtual product's machinability, and develops one archetypal system of three-dimensions virtual machining environment; the equipment unit among the system is a virtual milling-machining center. When the system is running driven by the NC code, it can change continuously the angle of view in the process of machining to observe the parts moving of the machining center and the molding procedure of the part and model-cavity. The effect of simulating of this archetypal system is excellence and better real time; the archetypal system can be used to verify the machinability to the designed virtual prototype of products.
Basing on studying internal virtual machine tool technology, the author researches the visibility to the numerical controlling machining process, the algorithm research of setup of the virtual machine environment, optimization module of the trace of the tool and calculation of the tool position, the translation and achievement of NC-code. And focus on the algorithm research of the translation and achievement of NC-code, and has summed up a set of actualizing scheme of virtual machining technology. Taking Windows 98 as the development platform and using C++ software and 3D Graphical software standard interface OpenGL as tools. This system designs basically the whole virtual machining process. The modules of the system including:
1. Virtual machining environment: virtual machining environment is made up of machine tool, workpiece, cutter and clamp, and uses OpenGL and CAD to carry through the feature modeling to machine tool, workpiece, cutter and clamp. II
2. Virtual machining process: this module includes the NC program coding, the 3D animation simulation. The numerical controlling machining process simulation mainly is geometry simulation. The geometry simulation looks the cutter and parts as rigid body, not considers cutting parameter, cutting force and other factors' influence to cutting machining, only translates numerical controlling program, gives birth to the cutting position's data, and uses these data to drive machine tool's moving parts, the tool cuts workpiece in virtual environment.
本文从虚拟产品的可加工性角度出发，对虚拟加工环境的结构及其关键技术进行了研究，并开发了一个三维虚拟加工环境原型系统，其中的设备单元为一个虚拟铣削加工中心。系统在NC代码或刀位文件的驱动下运行，在加工过程中可连续不断地改变视角，以观察加工过程中加工中心的部件运动、零件和型腔的成型过程。该原型系统的仿真效果具有真实感强，实时性好的优点，可用于对设计的产品进行可加工性验证。
在国内虚拟机床技术研究的基础上，本文对数控加工过程的可视化进行了研究，包括虚拟加工环境的建造、刀具轨迹的优化模型及刀位计算、虚拟加工的NC代码翻译与实现，并着重于虚拟加工的NC代码翻译与实现的算法研究。总结出一套虚拟加工技术的实施方案。本系统以Windows98为开发平台，采用C++Builder软件及三维图形软件标准接口OpenGL为工具，初步设计了整个虚拟加工的过程。系统的结构包括：
(1)虚拟加工环境：虚拟加工环境由机床、工件、刀具和夹具构成，采用OpenGL和CAD对机床、夹具、刀具和工件进行特征造型。
(2)虚拟加工过程：包括数控程序译码、三维动画仿真。数控加工过程仿真主要指几何仿真。几何仿真将刀具与零件视为刚体，不考虑切削参数、切削力及其它因素对切削加工的影响，只是对数控程序进行翻译，产生刀具位置数据，并以此数据驱动机床运动部件和刀架运动，刀具对工件进行虚拟切削等。
The technology of virtual machining is the reflection of numerical controlling machine tool in the virtual environment, it make the manufacturing technology, the numerical controlling theory of machine tool, the Computer Aided Design (CAD), the Computer Aided Manufacture (CAM), the technology of modeling and simulation into a whole system. The people can feel the virtual environment of 3D simulative model produced by computer depending on instinct; the process of virtual manufacturing provides key data to analyze the producibility of product design. In the real process of numerical controlling machining, it is necessary to try cutting repeatedly until we can affirm that the numerical controlling code can accomplish scheduled machining task in order to verify the validity of the numerical controlling code. At the same time, numerical controlling machining parameter needs also to debug repeatedly, these operations not only have lower efficiency and occupy the machine resource, but also have the possibility to
make the tool collision and interference and other problems. The process of virtual manufacturing can save the resources and avoid risk. The benefit of the process of virtual manufacturing also shows that it can train the operators of machine tool through simulating really the machine tool's machining process, and help the machine tool's manufacturer to demonstrate realistically their products to latent long-distance clients. The using of virtual manufacturing technology can shorten period of the product's development, lower the production cost, advance product's quality and producing efficiency. With the developing of the science and technology, virtual machining will
bring into play great roles in the virtual manufacturing.
The paper studies the configuration and key technology of the virtual machining environment from the point of view of virtual product's machinability, and develops one archetypal system of three-dimensions virtual machining environment; the equipment unit among the system is a virtual milling-machining center. When the system is running driven by the NC code, it can change continuously the angle of view in the process of machining to observe the parts moving of the machining center and the molding procedure of the part and model-cavity. The effect of simulating of this archetypal system is excellence and better real time; the archetypal system can be used to verify the machinability to the designed virtual prototype of products.
Basing on studying internal virtual machine tool technology, the author researches the visibility to the numerical controlling machining process, the algorithm research of setup of the virtual machine environment, optimization module of the trace of the tool and calculation of the tool position, the translation and achievement of NC-code. And focus on the algorithm research of the translation and achievement of NC-code, and has summed up a set of actualizing scheme of virtual machining technology. Taking Windows 98 as the development platform and using C++ software and 3D Graphical software standard interface OpenGL as tools. This system designs basically the whole virtual machining process. The modules of the system including:
1. Virtual machining environment: virtual machining environment is made up of machine tool, workpiece, cutter and clamp, and uses OpenGL and CAD to carry through the feature modeling to machine tool, workpiece, cutter and clamp. II
2. Virtual machining process: this module includes the NC program coding, the 3D animation simulation. The numerical controlling machining process simulation mainly is geometry simulation. The geometry simulation looks the cutter and parts as rigid body, not considers cutting parameter, cutting force and other factors' influence to cutting machining, only translates numerical controlling program, gives birth to the cutting position's data, and uses these data to drive machine tool's moving parts, the tool cuts workpiece in virtual environment.
引文
1 肖田元，郑会永，王新龙，韩向利．虚拟制造体系结构研究．计算机集成制造系统，1999，(1)：33～38
2 曹岩，刘宁，赵汝嘉．基于虚拟制造系统的企业集成研究．计算机集成制造系统，1999，(1)：25～29
3 肖田元，韩向利等．虚拟制造内涵及其应用研究．系统仿真学报，2001，13(1)：118～121
4 White J A, Pence I W. Progress in Material Handling and Logistics. USA: Spring -Vela, 1991.
5 Shah J, Mantilla M, Man D. Advances in Feature Based Manufacturing. Holland: Elsevier North, 1994.
6 Gupta K, Mau D S. A systematic Approach for analyzing the manufacturability of machined parts. Computer Aided Design, 1995, 27(5): 342～343
7 Kimura F. product and process Modeling as a Kernel for Virtual Manufacturing Environment. Annual of The CIRP, 1993, 42(1): 85～93
8 Wiens GJ. An overview of virtual manufacturing. Virtual Manufacturing-Proceeding of 2nd Agile Manufacturing conference (AMC' 95), Albuquerque, New Mexico, USA: ERI Press: 1995, 233～243
9 Kodiak A. Concurrent Engineering:Automation, Tools and Techniques. USA: Spring-John Wiley & Sons Inc. USA, 1993.
10 肖田元，韩向利．虚拟制造的定义与关键技术．清华大学学报．1998，38(10)：102～106
11 Kawabe S. et al.. Programming for Machining based on Workplace Models in Computer. Annals of CIRP. 1978, 10(4): 351～355
12 R. O. Anderson. Detecting and Eliminating Collisions in NC machining, CAD.1978, 10(4):231～238
13 Chappel I T. The Use of Vectors to Simulate Material Removal by Numerically Controlled Milling. CAD. 1983, 15(3): 156～158
14 U. A. Sungurtekin. Graphical Simulation and Automatic Verification of NC machining Programs, Proc. IEEE Robot. & Automat. (Apr. 1986);156～165
15 K. K. Wang Real-time Verification of Militarism NC Programs with Raster Graphics. Proc. IEEE Robot Automat. Apr. 1986; 166～171
16 John Woodwork. Shape Models in Computer Integrated Manufacturing: A Review. CAD. June, 1988:103～112
17 Kunwoo Lee, C. G. David. A hierarchical Data Structure for Representing Assemblies. CAD. 1985, 17(1): 15～20
18 Matthew Moore, et al. Collision. Detection and Response for Computer Animation, Computer Graphics. 1988,22(4): 289～297
19 H. Nobrio, S. L. Tanimoto. A New Interference Check Algorithm using Octree. Advanced Robotics. 1989, (3): 12～18
20 W. Sandbery, Collision Detection Using Sphere Approximation, Proc. Int. Conf. on Robotics and Factories of Future. California, 1987: 457～460
21 梁宏宝 钟诗胜 王知行．虚拟加工环境中的三维图形数据结构的研究．计算机仿真．2000，17(3)：34～38
22 梁宏宝 钟诗胜 王胜昆．虚拟加工中的毛坯数据模型．大庆石油学院学报．2000，24(2)：101～102
23 曾里，肖天元等．一个虚拟装配系统的实现．系统仿真学报．2002，14(9)：1149～1153
24 任秉银 唐余勇．数控加工中的几何建模理论及其应用．第一版．哈尔滨：哈尔滨工业大学出版社，2000．117～118
25 K Tang, Charles C Cheng and Yakove Dayan. Offsetting Surface Boundaries and 3-Axis Gouge-Free Surface Machining. Computer-Aided Design, 1995,27(12):915～926
26 梁宏宝 钟诗胜 王知行 闫继东 王庆娟．机械虚拟加工技术．大庆石油学院学报．2000，24(2)：101～102
27 陈周造，陈灿煌．精通C++ Builder程序设计高级教程．第一版．北京：北京新丰印刷厂，2001．
28 彭晓明，王坚．OpenGL深入编程与实例揭秘．第一版．北京：人民邮电出版社，1999．119～130
29 梁宏宝 钟诗胜 王胜昆．虚拟加工中的毛坯数据模型．大庆石油学院学报．2000，24(2)：101～102
30 K Tang, Charles C Cheng and Yakove Dayan. Offsetting Surface Boundaries and 3-Axis Gouge-Free Surface Machining. Computer-Aided Design, 1995,27(12):915～926
31 B K Choi and C S Jun. Ball-end Cutter Interference Avoidance in NC machining of Sculpture Surfaces. Computer-Aided Design, 1989, 21(6): 371～378
32 K Choi, C S Lee and J S Hwang et al. Compound surface modeling and machining. Computer-Aided Design, 1988, 20(3): 127～136
33 C Lone and T M Ozsoy. NC Machining of Freeform Surfaces. Computer-Aided Design, 1987, 19(2):85～90
34 Giusee Catania. A Computer-aided Prototype System for NC Rough Milling of Free-form Shaped Mechanical Part-pieces. Computer in Industry, 1992, (20):275～293
35 Marshall and J G Friffiths. A New Cutter-path Topology for Milling Machines. Computer-Aided Design, 1994,26(3): 204～214
36 Jordan J Cox and Yasuko Takezaki et al. Space-filling Curves in Tool-path alications. Computer-Aided Design, 1994, 26(3): 215～224
37 G W Vickers and C Bradley. Curved Surface Machining through Circular Arc Interpolation. Computers in Industry, 1992, (19):329～337
38 I D Faux and M K Pratt. Computational Geometry for Design ad Manufacture. Ellis Horwood. Chichester, 1980. 2752～80
39 任秉银 唐余勇．数控加工中的几何建模理论及其应用．第一版．哈尔滨：哈尔滨工业大学出版社，2000．2～40
40 苏步青，刘鼎元．计算几何，上海：上海科技出版社，1981．48～56．
41 韩向利．CIMS中的加工过程仿真技术．清华大学博士后研究报告 1997，3．
42 李文忠等 数控原理及应用控机床．机械工业出版社．2002年1月．第一版．46～48．
43 杜君文 邓广敏 数控技术．天津大学出版社 2002年2月．第一版．90～118．
2 曹岩，刘宁，赵汝嘉．基于虚拟制造系统的企业集成研究．计算机集成制造系统，1999，(1)：25～29
3 肖田元，韩向利等．虚拟制造内涵及其应用研究．系统仿真学报，2001，13(1)：118～121
4 White J A, Pence I W. Progress in Material Handling and Logistics. USA: Spring -Vela, 1991.
5 Shah J, Mantilla M, Man D. Advances in Feature Based Manufacturing. Holland: Elsevier North, 1994.
6 Gupta K, Mau D S. A systematic Approach for analyzing the manufacturability of machined parts. Computer Aided Design, 1995, 27(5): 342～343
7 Kimura F. product and process Modeling as a Kernel for Virtual Manufacturing Environment. Annual of The CIRP, 1993, 42(1): 85～93
8 Wiens GJ. An overview of virtual manufacturing. Virtual Manufacturing-Proceeding of 2nd Agile Manufacturing conference (AMC' 95), Albuquerque, New Mexico, USA: ERI Press: 1995, 233～243
9 Kodiak A. Concurrent Engineering:Automation, Tools and Techniques. USA: Spring-John Wiley & Sons Inc. USA, 1993.
10 肖田元，韩向利．虚拟制造的定义与关键技术．清华大学学报．1998，38(10)：102～106
11 Kawabe S. et al.. Programming for Machining based on Workplace Models in Computer. Annals of CIRP. 1978, 10(4): 351～355
12 R. O. Anderson. Detecting and Eliminating Collisions in NC machining, CAD.1978, 10(4):231～238
13 Chappel I T. The Use of Vectors to Simulate Material Removal by Numerically Controlled Milling. CAD. 1983, 15(3): 156～158
14 U. A. Sungurtekin. Graphical Simulation and Automatic Verification of NC machining Programs, Proc. IEEE Robot. & Automat. (Apr. 1986);156～165
15 K. K. Wang Real-time Verification of Militarism NC Programs with Raster Graphics. Proc. IEEE Robot Automat. Apr. 1986; 166～171
16 John Woodwork. Shape Models in Computer Integrated Manufacturing: A Review. CAD. June, 1988:103～112
17 Kunwoo Lee, C. G. David. A hierarchical Data Structure for Representing Assemblies. CAD. 1985, 17(1): 15～20
18 Matthew Moore, et al. Collision. Detection and Response for Computer Animation, Computer Graphics. 1988,22(4): 289～297
19 H. Nobrio, S. L. Tanimoto. A New Interference Check Algorithm using Octree. Advanced Robotics. 1989, (3): 12～18
20 W. Sandbery, Collision Detection Using Sphere Approximation, Proc. Int. Conf. on Robotics and Factories of Future. California, 1987: 457～460
21 梁宏宝 钟诗胜 王知行．虚拟加工环境中的三维图形数据结构的研究．计算机仿真．2000，17(3)：34～38
22 梁宏宝 钟诗胜 王胜昆．虚拟加工中的毛坯数据模型．大庆石油学院学报．2000，24(2)：101～102
23 曾里，肖天元等．一个虚拟装配系统的实现．系统仿真学报．2002，14(9)：1149～1153
24 任秉银 唐余勇．数控加工中的几何建模理论及其应用．第一版．哈尔滨：哈尔滨工业大学出版社，2000．117～118
25 K Tang, Charles C Cheng and Yakove Dayan. Offsetting Surface Boundaries and 3-Axis Gouge-Free Surface Machining. Computer-Aided Design, 1995,27(12):915～926
26 梁宏宝 钟诗胜 王知行 闫继东 王庆娟．机械虚拟加工技术．大庆石油学院学报．2000，24(2)：101～102
27 陈周造，陈灿煌．精通C++ Builder程序设计高级教程．第一版．北京：北京新丰印刷厂，2001．
28 彭晓明，王坚．OpenGL深入编程与实例揭秘．第一版．北京：人民邮电出版社，1999．119～130
29 梁宏宝 钟诗胜 王胜昆．虚拟加工中的毛坯数据模型．大庆石油学院学报．2000，24(2)：101～102
30 K Tang, Charles C Cheng and Yakove Dayan. Offsetting Surface Boundaries and 3-Axis Gouge-Free Surface Machining. Computer-Aided Design, 1995,27(12):915～926
31 B K Choi and C S Jun. Ball-end Cutter Interference Avoidance in NC machining of Sculpture Surfaces. Computer-Aided Design, 1989, 21(6): 371～378
32 K Choi, C S Lee and J S Hwang et al. Compound surface modeling and machining. Computer-Aided Design, 1988, 20(3): 127～136
33 C Lone and T M Ozsoy. NC Machining of Freeform Surfaces. Computer-Aided Design, 1987, 19(2):85～90
34 Giusee Catania. A Computer-aided Prototype System for NC Rough Milling of Free-form Shaped Mechanical Part-pieces. Computer in Industry, 1992, (20):275～293
35 Marshall and J G Friffiths. A New Cutter-path Topology for Milling Machines. Computer-Aided Design, 1994,26(3): 204～214
36 Jordan J Cox and Yasuko Takezaki et al. Space-filling Curves in Tool-path alications. Computer-Aided Design, 1994, 26(3): 215～224
37 G W Vickers and C Bradley. Curved Surface Machining through Circular Arc Interpolation. Computers in Industry, 1992, (19):329～337
38 I D Faux and M K Pratt. Computational Geometry for Design ad Manufacture. Ellis Horwood. Chichester, 1980. 2752～80
39 任秉银 唐余勇．数控加工中的几何建模理论及其应用．第一版．哈尔滨：哈尔滨工业大学出版社，2000．2～40
40 苏步青，刘鼎元．计算几何，上海：上海科技出版社，1981．48～56．
41 韩向利．CIMS中的加工过程仿真技术．清华大学博士后研究报告 1997，3．
42 李文忠等 数控原理及应用控机床．机械工业出版社．2002年1月．第一版．46～48．
43 杜君文 邓广敏 数控技术．天津大学出版社 2002年2月．第一版．90～118．