通用型CAPP专家系统中知识表示和推理机制的研究

ＣＡＰＰ作为ＣＡＤ与ＣＡＭ的中间桥梁，是ＣＩＭＳ必不可少的重要环节．本文针对开发通用性ＣＡＰＰ专家系统过程中，产品零件表示和工艺规程设计这两个关键问题，根据事物之间的相似性原理，提出了面向对象的产品零件和工艺规程的知识表示方法，以满足ＣＡＰＰ系统对产品零件信息表示的完整性、通用性、逻辑可分解性、动态性和相容性等要求，并在此基础上提出了ＣＡＰＰ专家系统的混合推理机制，包括单继承、多继承、非单调继承、类比推理等．     

An intelligent modeling and analysis method of manufacturing process using the first-order predicate logic

Manufacturing process refers to machining sequence from raw materials to final products. Process plan has important effects on manufacturing process. In general, process designer relies on his experience and knowledge to arrange the process plan. For a complex part, it takes long time and effort to determine process plan. In this paper, an intelligent modeling and analysis method using the first-order predicate logic is proposed to evaluate the manufacturing performance. First, the logic predicates used to represent the process plan are defined according to the machining methods, and the predicate variables are discussed in detail. Consequently, the process plan can be represented in the form of the first-order predicate logic. Second, a type of element model composed of four nodes and four links is put forward in order to construct the process model. All components in this element model are respectively explained, and the mapping relationship between element model and predicate logic is described in detail. According to engineering practices, logic inference rules are suggested and the inference process is illustrated. Hence, the manufacturing process model can be constructed. Third, the process simulation is carried out to evaluate the performance of manufacturing system by using measures such as efficiency, the machine utilization, etc. Finally, a case study is given to explain this intelligent modeling method using the first-order predicate logic.     

Integration of product design,process planning,scheduling, and FMS control using XML data representation

An efficient model for communications between CAD, CAPP, and CAM applications in distributed manufacturing planning environment has been seen as key ingredient for CIM. Integration of design model with process and scheduling information in real-time is necessary in order to increase product quality, reduce the cost, and shorten the product manufacturing cycle. This paper describes an approach to integrate key product realization activities using neutral data representation. The representation is based on established standards for product data exchange and serves as a prototype implementation of these standards. The product and process models are based on object-oriented representation of geometry, features, and resulting manufacturing processes. Relationships between objects are explicitly represented in the model (for example, feature precedence relations, process sequences, etc.). The product model is developed using XML-based representation for product data required for process planning and the process model also uses XML representation of data required for scheduling and FMS control. The procedures for writing and parsing XML representations have been developed in object-oriented approach, in such a way that each object from object-oriented model is responsible for storing its own data into XML format. Similar approach is adopted for reading and parsing of the XML model. Parsing is performed by a stack of XML handlers, each corresponding to a particular object in XML hierarchical model. This approach allows for very flexible representation, in such a way that only a portion of the model (for example, only feature data, or only the part of process plan for a single machine) may be stored and successfully parsed into another application. This is very useful approach for direct distributed applications, in which data are passed in the form of XML streams to allow real-time on-line communication. The feasibility of the proposed model is verified in a couple of scenarios for distributed manufacturing planning that involves feature mapping from CAD file, process selection for several part designs integrated with scheduling and simulation of the FMS model using alternative routings.     

Automated inspection process planning: Algorithmic inspection feature recognition, and inspection case representation for CBR

General metrological inspection planning is among the least explored computer-aided process planning (CAPP) domains. This paper explores certain basic issues involved in inspection planning using case-based reasoning in an environment of a Generic CAPP Support System. Firstly, algorithmic methods for characterizing and extracting inspection features are proposed and discussed. A sequential knowledge based filtering method is developed to reduce the number of inspection features typically encountered in metrological inspection planning. Finally, a formalized approach for case representation of relevant inspection domain knowledge using a newly developed parametric-list technological feature graph (PLTFG) is presented.     

A layered architecture for manufacturing operation planning

Machining operation planning involves the selection and sequencing of machining operations for fabricating a workpiece. It is the first step in the process of generating a detailed process plan for a workpiece. In the past five years, several knowledge-based systems have been developed. Two knowledge representation schemes are employed: production rules and frames. Each of these exhibits some general properties of human information processing but neglects the other. None of the existing systems is able to solve real-world problems. The main focus of this paper is on a layered architecture for manufacturing knowledge representation and automated reasoning for operation planning. This can be addressed through a discussion of both the knowledge representation structure and the inference mechanism. The proposed layered architecture has been implemented on a microcomputer using PROLOG. The results are satisfactory.     

工艺规划数据模型的构造

本文阐明计算机辅助工艺规划中一种新的数据模型，构造和表达一般性工艺规划进程，工艺规划数据模型包括产品模型和方法模型两个部分。产品模型表达产品在机械加工过程中各个状态；方法模型描述对产品进行加工的工艺方法和操作顺序。     

Systematic modeling and reusing of process knowledge for rapid process configuration

Rapid product development relies heavily on quick and reliable process planning and knowledge reuse. Process configuration borrows the principles of product configuration and applies them to process planning. It allows the reuse of hierarchical, historical and case-based manufacturing process knowledge to generate process plans efficiently and effectively. This paper presents a systematic knowledge model for manufacturing process cases. The model represents process knowledge at different levels of granularity and to facilitate process configuration. With this knowledge model the process knowledge is categorized into 6 levels: (i) core process skeletons, (ii) process networks, (iii) process routes, (iv) process segments, (v) processes/workplan, and (vi) operations/working step. Based on the systematic knowledge model, this paper also proposes an approach to achieve rapid process configuration by reusing the process knowledge and by performing the involved configuration rules so as to create an appropriate, reliable and effective process plan. The prototype for a graphical process planner based on this knowledge model is developed and an aerospace example is used to validate the proposed process knowledge model and process configuration.     

基于资源约束的CAPP系统

在分析目前的专用型 ＣＡＰＰ和通用型 ＣＡＰＰ的优缺点的基础上，建立了基于资源约束的 ＣＡＰＰ模型，该模型可在用户所建的资源子系统约束下，进行工艺评价，同时在车间环境下动态生成工艺规划和加工参数，能适应目前制造业的柔性化趋势。     

A new process knowledge representation approach using parameter flow chart

Knowledge in various stages of the product development process has become increasingly important for manufacturing companies to improve their performance, especially for those One-of-a-Kind Production (OKP) companies producing highly customized products. Process knowledge is a very special type of knowledge that controls how products are best manufactured. This knowledge can help OKP companies produce high value-added products with better quality at shorter times and at a competitive cost. Process knowledge is normally hard to capture and manage and is even more difficult to represent. This paper proposes a Parameter Flow Chart (PFC) based new knowledge representation method which efficiently combines parameter information, flow chart technology, and visualization technology. The goal of this research is to provide a user-friendly and effective way of representing process knowledge for OKP companies so they can develop and accumulate their own process knowledge repository. The basic definition and principle of the approach will be introduced first and the software system model then proposed. Two related key issues, the modeling of various chart units used in the PFC approach and dealing with expressions containing various parameters, are discussed in detail. The prototype version of the system has been developed and demonstrated with case studies, which has proven the feasibility of the proposed approach.     

Hybrid knowledge model of process planning and its green extension

The green process planning model was a necessary research field of the green manufacturing, which has drawn increasing attention from many scholars. This study proposes a multi-method [Backus–Naur Form (BNF) frame, binary tree,production rules, and objective-oriented methodology] hybrid frame model of process planning and reasoning mechanism. In this model, the hierarchical BNF frame was applied to modeling the structure of parts, the stages of process decisions and the existing green process indicators set. Then, two “procedure” programs were designed for the information exchange among the above models. This green-process planning model was proposed based on the traditional intelligent process planning model and was intended to introduce an overall (compared with the traditional partial green-process planning model) green-process decision mode. In the last section of this paper, a case study of the green-process planning for a stepped shaft is provided along with a number of essential knowledge models to illustrate the feasibility of this hybrid knowledge model.     

A grammatical optimization approach for integrated process planning and scheduling

Rapid developments in computerized manufacturing environments and increasing overlapping in the capability of manufacturing resources provoked integration of many manufacturing functions including process planning scheduling. Several approaches have been developed in the literature in order to integrate process planning and scheduling. In this paper a novel approach which makes use of grammatical representation of generic process plans is used within a multiple objective tabu search framework in order to integrate process planning and scheduling effectively. Detailed explanations along with an example problem are presented in the paper. Proposed approach is tested on literature problems and also hypothetically generated flexible job shop scheduling problems with alternative process plans to analyze its performance and efficiency.     

e-CAPP: A distributed collaborative system for internet-based process planning

Advances in distributed technologies have enabled engineers to communicate more effectively, collaborate, obtain, and exchange a wide range of design resources during product development. Shared internet-based virtual environments allow experts in remote locations to analyze a virtual prototype, together and simultaneously in centers in which the product is being developed.This paper presents a system for distributed and collaborative environment which could assist manufacturing enterprises and experts in discussing, suggesting, evaluating and selecting best process plans for family of manufacturing parts. The represented e-CAPP system enables the implementation of expert knowledge in an appropriate knowledge repository. The knowledge from this repository is integrated into intra-company CAPP systems and used while generating process plans for new products. The proposed internet-based collaborative environment, dedicated to distributed process planning, is yet another step in the direction advancing of distributed manufacturing.     

A feasible approach to the integration of CAD and CAPP

Although current CAD systems are declared to be feature-based, in fact, the so-called feature is just a modeling macro or menu name such as Protrusion, Revolution, Cutout, Block, etc., instead of a design feature or manufacturing feature in accordance with engineering practice. Consequently, product model data insufficiency and incompatibility between varieties of application systems are still the major barriers to system integration, especially the integration of design and process planning. This paper proposes a practical solution for a bi-directional integration of CAD and CAPP on the platform of commercial CAD systems. The key techniques such as feature recognition and conversion, feature parameter and constraint extraction, feature tree reconstruction, technical information processing, process planning, automatic process drawing marking and 3D material stock CAD model generating are discussed. And the extracted features and their related technical information and knowledge are encapsulated together with the geometry-oriented CAD model to form an integrated product information model to facilitate effective integration with the downstream activities. The integrated CAD/CAPP system is implemented on a commercial CAD package, UGS/SolidEdge. A case study and industry implementation illustrate the feasibility of the approach proposed.     

Modeling and optimization of manufacturing process performance using Modelica graphical representation and process analytics formalism

This paper concerns the development of a design methodology and its demonstration through a prototype system for performance modeling and optimization of manufacturing processes. The design methodology uses a Modelica simulation tool serving as the graphical user interface for manufacturing domain users such as process engineers to formulate their problems. The Process Analytics Formalism, developed at the National Institute of Standards and Technology, serves as a bridge between the Modelica classes and a commercial optimization solver. The prototype system includes (1) manufacturing model components’ libraries created by using Modelica and the Process Analytics Formalism, and (2) a translator of the Modelica classes to Process Analytics Formalism, which are then compiled to mathematical programming models and solved using an optimization solver. This paper provides an experiment toward the goal of enabling manufacturing users to intuitively formulate process performance models, solve problems using optimization-based methods, and automatically get actionable recommendations.     

A knowledge-based process planning framework for wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) provides a rapid and cost-effective solution for fabricating low-to-medium complexity and medium-to-large size metal parts. In WAAM, process settings are well-recognized as fundamental factors that determine the performance of the fabricated parts such as geometry accuracy and microstructure. However, decision-making on process variables for WAAM still heavily relies on knowledge from domain experts. For achieving reliable and automated production, process planning systems that can capture, store, and reuse knowledge are needed. This study proposes a process planning framework by integrating a WAAM knowledge base together with our in-house developed computer-aided tools. The knowledge base is construed with a data-knowledge-service structure to incorporate various data and knowledge including metamodels and planning rules. Process configurations are generated from the knowledge base and then used as inputs to computer-aided tools. Moreover, the process planning system also supports the early-stage design of products in the context of design for additive manufacturing. The proposed framework is demonstrated in a digital workflow of fabricating industrial-grade components with overhang features.     

用于柔性生产线方案设计的分层工艺规划方法

在建立面向对象工艺模型的基础上，提出用于柔性生产线方案设计的分层工艺规划方法，即特征工艺设计、零件装夹定位规划、特征排序规划、工步排序规划、工序聚合规划等5个层次．采用基于黑板的递阶式层次推理结构，实现了综合排序策略，完成了用于柔性生产线方案设计的CAPP系统开发。     

基于CAPPFramework的CAPP专家系统研究与实践

论文基于863目标产品CAPPFramework(CAPP应用框架与开发平台),采用面向对象的信息分析与建模,介绍了面向对象的CAPP专家系统平台构建技术,包括面向对象的知识获取、知识表示、工艺决策推理,并介绍了该CAPP专家系统平台在2-5坐标平面结构件CAD/CAPP/CAM数控编程系统中的应用。     

A case-based system for process planning

Process planning is the phase of manufacturing that is concerned with the selection, and sequencing of manufacturing operations necessary to transform an initial stock material into a finished part. It is a tedious operation that requires highly skilled and experienced personnel of which there is currently great shortage. To disseminate the costly expertise and to reduce process planning times, which tend to add high costs to small batch production, many automated computer systems have been introduced and applied. All these systems, though, require the supervision of an experienced human being and fail to capture the knowledge and reasoning behind process planning decisions. The causes of the lack of an efficient automatic system for process planning are the unique characteristics of the domain. In contrast to other areas where knowledge-based and expert systems have been applied, process planning demands the solution of several different planning problems before a final solution is achieved. Every change introduced to the previous world model creates a completely new world model with its own, new constraints and preconditions that nedd to be satisfied. This, in turn, affects the applicability of the knowledge to the new model.

To provide solutions to the above problems we have designed a prototypical knowledge-based system that uses the high level, dynamic memory structures of MOPs (Memory Organization Packages), meta-MOPs and TOPs (Thematic Organization Packets) to rearrange its knowledge according to its experiences and to predict and avoid errors. To model the dynamic, sharable knowledge and the constantly changing world model a knowledge-representation language named TOLTEC has been designed and used in the system. Furthermore, we propose a novel planning method based on abstract plans and constraints that can solve planning problems in uncertain domains given incomplete information.     

基于Web和XML的CAPP系统

介绍了一种基于Web和XML的CAPP系统,主要包括系统的体系结构、系统的信息流程、基于XML工艺文档表示、工艺规则对XML文档的操作、XML文档的客户端处理。在网络环境中,客户端与服务器端利用XML进行信息交互,提高了Web环境下CAPP系统的性能,满足了企业工艺设计的需求,也使B/S模式下的应用系统面临的诸多问题得到很好的解决。     

基于实例的回转类零件工艺路线决策方法研究

以回转类零件为例,利用基于实例的推理（ＣＢＲ）方法、专家系统方法和特征技术,构造了一套完整实用的基于实例的工艺路线决策方法。构造了一种相似性参数计算公式,论述了新零件与实例进行比较和匹配的策略和算法,以及实例工艺信息筛选和实例工艺线修正方法,在实例抽取过程中,新零件与实例的匹配信息被详细记录下来,使得以实例抽取为基础的实例工艺信息筛选和工艺线路修正算法变得相对简单并易于实现。