【作者】 李鹏；

【导师】 张承瑞；

【作者基本信息】 山东大学 ， 机械电子工程， 2011， 博士

【摘要】 目前在数控系统开放性研究已经日臻成熟的情况下,人们为了突破CNC与制造系统上层CAx之间的信息交流瓶颈,增强制造系统的集成性,提出了一种新的加工数据模型—STEP-NC (STEP for numerical controller)。使用STEP-NC取代传统G&M代码作为数控系统的加工数据模型,为数控系统带来了丰富的加工设计和规划信息,为数控系统智能化的发展提供了新的契机。与此同时STEP-NC的使用还引起了数控系统体系结构的巨大变化。为此本文开展了关于STEP-NC型数控系统架构及其关键支撑技术的研究,尤其侧重于STEP-NC型数控系统智能化实现的研究。本文分析了传统数控系统的基本结构,针对智能数控系统的需求进行了软硬件实施平台的选取。分析了STEP-NC数据模型的结构和特点,探讨了STEP-NC型数控系统的新特征,进而提出了一种STEP-NC型开放式智能数控系统的架构模型。该数控系统架构模型包含了五个主体部分：本地工艺规划模块、智能决策模块、开放式软NC核、加工专家库系统和工业实时以太网现场总线平台。该体系架构为将来STEP-NC型数控系统的进一步研究奠定了基础。同时,本文还对STEP-NC在数控系统中几个基本功能的实现进行了研究。利用ST-Developer提供的Java开发环境进行STEP-NC信息的提取和解释,以Java3D引擎为基础开发了STEP-NC三维显示和加工仿真模块,将STEP-NC的本地工艺规划功能划分为三个层次,提出了一种STEP-NC工艺规划层与数控内核层对接的方法。开发了验证程序对上述三个STEP-NC功能模块进行了实验验证。引入本体论的思想构建了一个三层数控加工本体专家库模型,实现了对数控加工领域内的相关加工知识的建模。分析了数控加工本体构建的意义和定位,明确了数控加工本体建模的开发语言和工具,对数控加工领域内的主要概念进行了划分和定义,采用SWRL进行数控加工语义规则设计。研究了Express数据模型到OWL本体模型的映射规则和机制,探讨了数控加工本体专家库与智能数控系统集成的方法。实验表明,该数控加工本体专家库可以有效的表达数控加工领域内的知识,同时具有一定的智能推理能力,能够为STEP-NC型开放式智能数控系统提供智力支持。采用工业实时以太网作为数控系统的底层硬件平台,既能满足开放性要求,又能保证与制造系统上游设计管理单元之间具有良好的集成能力。本文采用本课题组所研发的EtherMAC实时以太网总线作为STEP-NC型开放式智能数控系统的底层硬件平台,分析了EtherMAC的拓扑结构、工作原理以及从站实施方案。在Linux RTAI平台下为EtherMAC总线开发了主站协议栈,经试验测试,在该主站协议栈下EtherMAC在不需要专有硬件和高性能的RTOS或者控制器的情况下,其定时同步性能以及周期通讯的实时性能与现在流行的几种实时以太网总线水平相当,完全满足同步实时运动控制的要求,同时还为其它应用程序提供了灵活的应用集成接口。分析了Linux RTAI平台下开放式软数控内核EMC2的结构,提出了以EMC2为核心,上层对接STEP-NC工艺规划模块,下层对接EtherMAC实时以太网总线平台的STEP-NC型开放式智能数控系统的集成方案。采用EMC2的HAL模块设计思想,实现了EtherMAC总线协议的集成,采用ECM2的Canon命令作为STEP-NC加工的数控中间语言,实现了STEP-NC工艺规划模块的集成。在集成后的STEP-NC型开放式智能数控系统架构内,验证了STEP-NC加工数据模型驱动加工的能力以及EtherMAC总线平台的运动控制能力。表明本文所提出的STEP-NC型开放式智能数控系统具有切实的可行性,在该数控系统架构内可以方便灵活的进行功能模块尤其是智能模块的扩展,为将来STEP-NC型数控系统的开发和研究奠定了基础。更多还原

【Abstract】 At present, a lot of researches have been done to improve the openness of the CNC and the CNC openness theories are getting mature gradually. However, there is still a bottle neck between CNC and the high level manufacturing system CAx in aspect of sharing information. Therefore, to achieve the integration of the whole manufacturing system, a new machining data model, STEP-NC (STEP for numerical controller) was proposed. The utilization of STEP-NC as the machining data model, instead of traditional G&M codes, brings abundant information for designing, process planning and machining. Besides, STEP-NC provides a new opportunity for the intelligent CNC. Meanwhile, the use of STEP-NC causes some greate changes in the architecture of CNC system. For this reason, this paper promotes the research on the architecture of STEP-NC compliant CNC systems and the related key technologies, especially on the realization of intelligence of STEP-NC compliant CNC system.The basic structure of traditional CNC systems is reviewed and the software and hardware platforms are selected based on the requirements of intelligent CNC systems. The detailed structure and properties of STEP-NC data model are analyzed and the new characteristics of STEP-NC compliant CNC are studied. Then an architecture of open and intelligent STEP-NC compliant CNC system is presented. This CNC framework contains 5 main parts:a local process planning module, an intelligent decision making module, an open soft NC core, an expert knowledge base system and a real-time Ethernet fieldbus platform. This architecture is the basis for the following researches.The realization of some basic functions is also studied. The Java libraries provided by ST-Developer are used to develop the interpreter that is used to extract and explain STEP-NC data. The Java3D engine is used for display and simulation in 3D. The local process planning module is divided into three levels. An interlinkage method between the process planning and the NC kernel is given. The above three STEP-NC function modules are tested by developing the validation programes. The ontology conception is introduced to construct a three layered ontology expert model. The related knowledge of machining in CNC area is modeled. The importance of constructing the CNC machining ontology is analyzed. The developing language and tools are specified. The main concepts in CNC domain are classified and defined, and the SWRL is used to design the semantic rules. Meanwhile, the mapping mechanism between Express data model and OWL ontology model is studied. The integration method between CNC machining expert knowledge base and intelligent CNC system is also presented. The experiment indicates that the CNC ontology expert knowledge base can describe the knowledge in CNC area and possess the reasoning capability to support the intelligent behavior of STEP-NC compliant CNC system.The adoption of real-time industrial Ethernet as low level hardware platform can satisfy the requirement of openness, and thus can guarantee the integration with upper level units of designing and management. A real-time Ethernet which is called as EtherMAC is developed by our research group and adopted by this paper. The topology structure, working mechanism and slave scheme are detailed in this paper. The protocol stack for the master node under Linux RTAI is developed. The real-time and synchronization performance is almost equal to the prevailing real-time Ethernet even without proprietary hardware and high performance RTOS, so it totally satisfies the requirement of isochronous real-time motion control. In addition, the master protocol stack also provides a flexible integrating interface for other application programs.The soft NC kernel of EMC2 under Linux RTAI is studied. An integrating scheme for STEP-NC compliant open and intelligent CNC is proposed. The EMC2 is regarded as the core, the STEP-NC process planning module is integrated on upper level and the EtherMAC platform is integrated on lower level. The HAL conception of EMC2 is used here, where the EtherMAC protocol stack is integrated. The canon language is adopted as the middle language for CNC machining, where the STEP-NC process planning module is integrated. In this integrated architecture, the capability of driving machining with the data model of STEP-NC and the capability of motion controlling with EtherMAC platform are validated. With this architecture, the intelligent modules and function modules are easy to extend. These indicate that the system proposed in this thesis is feasible, and can provide a basic platform for future researches on intelligent STEP-NC compliant CNC systems.更多还原