【作者】 陈秀生；

【导师】 张承瑞；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 数控技术诞生后的50年间，数控编程都是基于ISO6983标准，即采用G，M代码描述如何加工，其本质特征是面向加工过程。近年来的研究和实践表明，基于ISO6983的传统数据接口存在现场编程或修改非常困难、产品信息不全、系统间信息交换困难等缺点，不利于实现数控系统的智能化，已成为阻碍制造系统信息集成的瓶颈，严重制约着数控系统乃至制造业的发展。为此，欧美等发达国家提出了一种新的CAM／CNC接口规范，称为STEP-NC，即为CNC定义的一种与STEP兼容的新接口标准。STEP-NC遵从STEP(ISO 10303)中对几何信息的描述规则，同时又加入了与数控加工有关的工艺信息，并以面向对象的方式通过一系列特征的几何信息和加工要求来描述整个数控加工任务，从而将产品数据交换STEP标准(ISO 10303)延伸到数控加工领域，建立起一条贯穿产品设计与制造过程的信息高速公路。STEP-NC的出现对于数控技术的发展乃至整个制造业，将产生深远的影响。STEP-NC取代传统的G、M代码以后，数控加工阶段实际上成为制造信息最集中的阶段，数控系统能够全面了解加工对象、加工资源、条件以及本身运行状况，从而可以实现对加工过程进行智能化控制。本文的研究是基于STEP-NC的智能化数控系统开发的一部分，以车削为研究对象，重点研究了STEP-NC车削数控系统中仿真模块实现的关键技术，为STEP-NC车削数控系统智能化的实现提供了理论依据。作为STEP-NC数控车削系统智能化决策的依据，仿真模块是STEP-NC数控系统的重要组成模块之一，在对仿真模块在数控系统中所执行的功能进行分析的基础上，提出了基于STEP-NC的数控车削加工仿真系统的体系结构。整个体系结构由仿真数据准备、仿真建模和仿真运行等三大部分组成。仿真数据准备主要是指进行仿真前所必须进行的数据的处理、加工规划、刀具路径规划等工作。根据建模的目的和作用的不同，仿真建模主要由两部分组成：几何仿真建模和物理仿真建模。物理仿真建模主要包括了切削力、振动、加工质量、加工温度场、刀具磨损等模型的建立。几何仿真建模主要是指几何仿真所需要的几何模型、运动模型、仿真控制模型等的建立。仿真运行和输出是指在仿真环境中运行仿真模型，得出仿真结果。该体系结构为STEP-NC车削加工仿真的研究提供了基础。STEP-NC车削程序的解析、加工规划以及刀具路径规划是进行仿真的前提。基于STEP-NC车削标准和车削程序，对STEP-NC车削程序的解析、工艺规划和刀具路径规划进行了研究。STEP-NC车削程序解析的关键是程序语言向建模仿真语言的翻译和程序信息的检索，根据EXPRESS语言的语法特点，制定了STEP-NC标准采用的描述方式向仿真建模语言(C++)映射的规则，应用该规则可以将STEP-NC程序的不同数据结构转化为不同的C++类；提出了根据关键字和属性检索STEP-NC车削程序信息的方法，检索得到的信息赋值给C++类对象中的成员变量，从而可以完成程序的解析。根据STEP-NC车削信息中对工艺问题的描述，分析了车削加工规划所涉及的基本问题，采用在工步之间加入一些辅助工步或操作的方法实现了车削工步序列的连续化问题，从而解决了车削加工规划的基本问题。在对几何模型的建立方法进行分析的基础上，根据STEP-NC车削加工的特点，提出了STEP-NC车削仿真工件几何模型的建立方法。将制造特征按照工步进行划分，形成工步制造特征，进行工件几何造型时，将工步制造特征依照其在工件坐标系中的位置和加工后的工件的几何模型叠加在一起，形成工件的初始几何模型，进行加工时，按照工步的执行顺序，依次从初始工件模型上去除每个工步的制造特征，形成加工后的工件。采用上述方法，在仿真时可以清晰的表达每个工步制造特征的加工情况，从而解决了车削仿真工件几何建模的基本问题。切削力建模与仿真是STEP-NC车削加工过程物理仿真的基础，根据STEP-NC车削数据模型和数控程序中的信息，建立了适用于STEP-NC车削加工过程的切削力模型。STEP-NC车削程序提供了工件材料、切削用量以及刀具参数等信息，这些信息是影响STEP-NC车削加工过程切削力的主要因素，刀具和工件相对位移的变化将引起切削力的变化，进而引起加工过程中的振动，最终影响到加工质量。论文中的切削力建模过程综合考虑了切削加工过程中工件材料、切削用量、刀具几何参数以及刀具-工件的相对位移等因素，建立了包含上述因素的STEP-NC切削力的机械模型，模型可以较为全面地反映各因素对STEP-NC车削加工切削力的影响，建立了STEP-NC切削力模型仿真运行的软件环境，通过应用所建立的STEP-NC车削加工切削力模型进行仿真，得出了STEP-NC提供的各加工参数对切削力的影响规律，为STEP-NC车削加工过程中切削力的智能控制提供了决策依据。振动仿真是STEP-NC数控加工物理仿真的重要内容之一，应用基于STEP-NC标准的工艺系统参数和STEP-NC程序提供的加工参数，以切削过程中切削面积的动态变化为基础，建立了STEP-NC车削加工系统的振动模型。振动模型综合考虑了STEP-NC车削加工的切削用量、刀具几何参数和工艺系统参数的影响，编写了振动仿真程序。应用建立的模型通过仿真分析了STEP-NC车削系统的各个参数对系统中振动的影响，为STEP-NC车削数控系统对振动进行分析提供了技术上的解决方案。根据STEP-NC标准，提出了STEP-NC框架下的车削表面粗糙度的表达方式，基于本文提出的表达方式，STEP-NC车削控制器可以将加工后的以STEP-NC格式描述的表面粗糙度信息反馈给CAD／CAM系统，便于实现CAD／CAM与基于STEP-NC的CNC系统的集成。表面粗糙度和表面形貌是STEP-NC车削数控系统智能化控制的对象，本文的研究建立了STEP-NC车削表面粗糙度和表面形貌的二维、三维数学模型。建立的模型综合考虑了切削用量、刀具几何参数以及系统振动情况的影响，应用建立的模型进行了仿真。仿真结果表明仿真模型可以分析刀具几何参数、切削用量以及系统振动情况对表面粗糙度和表面形貌的影响，从而数控系统的仿真模块可以根据本文提供的模型分析和控制加工工件的表面粗糙度。以上述STEP-NC仿真关键技术的研究为基础，应用本文提出的STEP-NC几何建模技术和物理仿真模型，对典型工件的车削加工过程进行了研究。根据典型工件的STEP-NC车削程序，建立了工件和刀具的几何模型，仿真了加工过程刀具的运动轨迹，应用典型工件的基于STEP-NC的加工信息以及加工系统的STEP-NC描述信息，根据论文中的物理仿真模型，分析了工件加工过程的稳定性以及切削力、表面粗糙度、表面形貌的情况。通过应用论文中建立的模型和提出的关键技术对典型零件的车削过程进行仿真分析，证明了论文中建立的模型适用STEP-NC车削加工系统。本文提出的STEP-NC的关键技术，可以较好的完成STEP-NC控制器仿真模块的部分仿真功能，有助于STEP-NC车削智能化数控系统根据程序中的信息分析加工过程，本文的研究为STEP-NC车削智能化数控系统的智能化的实现提供了基本的技术支持，对基于STEP-NC的智能化数控的系统的开发将会起到积极的促进作用。更多还原

【Abstract】 During the past fifty years, digital controlled machines are mostly programmed based on ISO 6983, also known as G, M code. ISO 6983 specifies the path of the center of cutter in machine coordinate, instead of the coordinate of parts. With little knowledge of machining system, machining processes are difficult to implement intelligent control. According to ISO 6983, data from CAD/CAM must be pre-processed by the post-processor before they can be used in the CNC system. Therefore, it is difficult for the CNC system to be integrated with CAD/CAM system. In the recent research and development of CNC system, a number of problems have been found with the interface based on ISO 6983. All these problems indicate that the interface has caused the bottleneck for the further development of CNC technology and the manufacturing industry. To remedy the problems existed in the interface based on ISO 6983, a new data interface named STEP-NC was presented by EU and USA. STEP-NC is strictly harmonized with ISO 10303 (STEP) and hence the data from the CAD/CAM system is ready to be used in the CNC system directly. Through the fluent data exchange based on STEP-NC, CAD/CAM and CNC can be integrated seamlessly. The basic machining unit used in the STEP-NC program is workingstep. Workingsteps are effectively machining tasks that correspond to high-level machining features and associated process parameters. With the detailed and objected-oriented description of the machining process based on STEP-NC, the forthcoming controllers for the STEP-NC system can get a comprehensive understanding of machining object, resource, condition, and thus make intelligent control of the machining process.Aiming at turning, this dissertation presents a partial development work for the intelligent STEP-NC controller. Key technologies to the simulation module in the STEP-NC controller were studied. The research will provide a theory foundation for the STEP-NC controller in controlling the cutting process intelligently.To aid the controllers in making intelligent control, simulation module is designed to be one of the key parts in the STEP-NC controllers. According to the analysis of simulation module’s function, the architecture for intelligent STEP-NC turning simulation system is presented. The whole simulation system can be divided into three parts: simulation preparing part, simulation modeling part and simulation running part. In the Simulation part, tasks such as data processing, workplan making and tool path generation are executed. Simulation modeling in the simulation system can be divided into geometrical modeling and physical modeling. Physical modeling are named for the modeling of the physical factors such as cutting force, vibration, surface finish, cutting temperature and tools worn in the cutting process. Geometrical modeling is the construction of geometrical model, movement model and simulation control model. The models are simulated and then simulation results are obtained in the simulation running part. The architecture presented in this thesis provides a foundation for the STEP-NC turning simulation research.Program interpretation, process plan and tool path generation are the vital tasks for the STEP-NC simulation. In this thesis, researches are carried on for the STEP-NC program interpretation, process plan and tool path generation based on the STEP-NC standard and program. The key to the interpretation of STEP-NC program are the program translation and program information searching. A STEP-NC program file is a schema which is comprised of a set of entity instances linked by references from one to another. Entity is defined with EXPRESS language. Programming language used in geometric simulation is C++. To execute the translation task, several rules are made out for the STEP-NC description language and simulation modeling language. Using these rules, entities defined in the EXPRESS format can be translated into C++ classes. A new method for the information search based on the key words and attributes is brought forward. After the searched information is evaluated to the member of C++ class, the interpretation of the program will be completed. According to the technology description among the STEP-NC turning information, essence problems for the process plan are analyzed. A number of assistant workingsteps and operations are added to the machining process to make the workingstep running fluently. Therefore, the basic problems for the process plan are solved.A geometrical modeling method for STEP-NC turning workpiece is brought forward in this dissertation. To model the workpiece, manufacturing feature is divided into workingstep manufacturing features. Workingstep features are placed on the finished workpiece according to their position in the workpiece coordinate, through this way, the rawpiece is modeled. When the simulation is running, workingstep manufacturing features will be removed from the rawpiece conform to the sequence described in the process plan. After all the workingstep manufacturing features are removed, the simulation will be finished. Through this way, key technology for workpiece modeling is solved.Simulation and modeling of cutting force is the foundation of the STEP-NC turning process physical simulation. Using the parameters provided in the STEP-NC turning program, a mechanistic model of cutting force for the STEP-NC turning system is presented. Main impact factors of the cutting force such as workpiece materials, cutting tools material, cutting parameters and cutting parameters are described in the STEP-NC program. Relative deflections between the workpiece and the cutting tool caused by the vibration will lead to the variety of the cutting force. The variety of the cutting force results in the vibration of the cutting process and affects the surface quality. Modeling of the cutting force in the dissertation have taken the impact of the workpiece materials, cutting tools material, cutting parameters, cutting parameters and cutting process vibration into account. Using the cutting force model, impacts of the main factors to the cutting force can be assessed. Simulation environment was set using simulation software MATLAB. Simulations with the cutting force model, laws for the impact of the cutting parameters in the STEP-NC program to the cutting force are acquired. Based on the cutting force simulation function of the simulation module, the STEP-NC controller can control the cutting process intelligently.Vibration simulation is an important part of STEP-NC turning physical simulation. According to ISO 14649, expressions of the technology system parameters are brought forward. With the technology parameters and cutting parameters based on STEP-NC, the vibration simulation model is developed. In the STEP-NC vibration model, cutting parameters, tools parameters and technology system parameters are taken into account. The impacts of these factors are analyzed through the running of the vibration simulation model. With the vibration model developed in the dissertation, the STEP-NC controller can analyze and control the vibrations in the STEP-NC turning system intelligently.According to STEP-NC standard, surface roughness description for the STEP-NC turning system is put forward. Using the description, surface roughness information can be fed back to the CAD/CAM system. The description of surface roughness of STEP-NC is of great help for the integration of CAD/CAM and CNC.Surface roughness and appearance are the objects for the STEP-NC controller to control the cutting process intelligently. Two dimensional and three dimensional mathematical models for surface roughness and appearance are established. In the mathematical model, cutting parameters, tools geometry parameters and system vibrations are taken into account. Using the models to simulate the surface roughness and surface appearance, the results shows that the model can be used to analyze the impact of tool geometry parameters, cutting parameters and vibration to the surface roughness and surface appearance. Therefore, the surface roughness model and surface appearance model developed in the thesis can be used in the simulation module of the controllers to analyze the surface roughness and appearance in STEP-NC turning.A case study is used to verify the developed geometrical simulation technology and physical simulation model. A typical workpiece is used for the case study. According to the STEP-NC program of the workpiece, workpiece geometrical model and tool geometric model is constructed. With the geometrical models and the movement information in the STEP-NC program, tool path is simulated. According to the parameters presented in the STEP-NC program, physical simulation models developed in the thesis are applied to analyze the cutting force, vibration and surface finish in the machining of the workpiece. Simulation results have shown that the developed model and the presented technology are of great useful for the intelligent STEP-NC control system to analyze and control the turning process intelligently. As a result, this dissertation provides a foundation technical support for the realization of STEP-NC controller’s intelligence. Simulation research will be of great helpful for the development of STEP-NC controller.更多还原