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大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 1 knowledge based blackboard framework for stamping process planning in progressive die design S B Tor G A Britton W Y Zhang Springer Verlag London Limited 2004 Abstract It is widely accepted that stamping process planning for the strip layout is a key task in progressive die design How ever stamping process planning is more of an art rather than a science This is in spite of recent advances in the field of artificial intelligence which have achieved a lot of success in incorporating built in intelligence and applying diverse know ledge to solving this kind of problem The main difficulty is that existing knowledge based expert systems for stamping process planning lack a proper architecture for organizing heterogeneous knowledge sources KSs in a cooperative decision making en vironment This paper presents a knowledge based blackboard framework for stamping process planning The proposed ap proach speeds up the progressive die design process by automat ing the strip layout design An example is included to show the effectiveness of the proposed approach Keywords Knowledge based Object oriented Progressive die design Stamping process planning 1 Introduction Progressive dies for producing sheet metal parts in mass pro duction have been widely applied in various industries such as aerospace electronics machine tools automobiles and re frigeration These dies can perform piercing notching cut off blanking lancing bending shaving drawing embossing coin ing trimming and other miscellaneous forming operations at a single setup Hence a progressive die is generally very com plex Stamping process planning and die structure design are difficult and demanding tasks Stamping process planning starts with an unfolding of a model of stamped metal part to produce a flat pattern followed by nesting the pattern to produce a blank layout Next stamping operations are planned and operations are assigned to die sta tions The resulting plan is typically represented as a strip layout which guides the subsequent die structure design The produc tivity accuracy cost and quality of a progressive die mainly depends on the strip layout and hence a stamping process How ever stamping process planning still remains more of an art rather than a science Historically this activity is mainly car ried out manually based on designers trial and error experience skill and knowledge Recent advances in the field of artificial intelligence AI have given rise to the possibility to construct AI based systems that incorporate built in intelligence and apply diverse knowledge to 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 2 solving progressive die design problems including strip layout design automation The diverse knowledge sources KSs re lated to stamping process planning include unfolding knowledge to produce a flat pattern nesting knowledge to produce a blank layout mapping knowledge to transform stamping features into stamping operations and staging knowledge to sequence the stamping operations A discussion of some knowledge based pro gressive die design work related to our study can be found in Sect 2 However the existing work is based on the conventional architecture of knowledge based expert systems which are in capable of managing heterogeneous KSs effectively This limits both their practicability and scalability To address the above issue it is necessary to provide a coop erative problem solving strategy that can foster communication between diverse KSs and accommodate different knowledge representation schemes within an integrated framework Hence a knowledge based blackboard framework consisting of a black board control system and a few independently executing KSs have been developed This framework provides a cooperative de cision making environment and facilitates a hybrid knowledge representation scheme including procedures production rules and object oriented representations A prototype system has been implemented using the object oriented expert system shell CLIPS C Language Integrated Pro duction System 1 which is interfaced with a parametric and feature based CAD system Solid Edge through C An ex ample is provided to demonstrate our approach and to show its effectiveness in stamping process planning 2 Related work Research in the computer aided stamping process planning has been widely reported since the 1970s The advantages of auto mated process planning are productivity improvements cost re ductions and design automation From the mid 1970s to mid 1980s the first generation of CAD CAM systems for progressive die design were de veloped 2 5 though few of them are based on AI techniques These early systems are characterized by basic computer graph ics facilities standardization of die components and standard ization of design procedures They reduced design and drafting lead time However as these systems represent design know how in the form of conventional procedural programming languages only generation of the die part list and drafting of the assembly and part drawings are executed using computers The designer still needs to decide most of the important decisions interactively including strip and die layouts Since the late 1980s significant efforts have been made by worldwide researchers to integrate a wide variety of AI and traditional CAD approaches to develop dedicated progressive die design automation systems including strip layout design automation Knowledge based approach is a popular AI technique that has been used in intelligent stamping process planning and die design system For example researchers at the University of Massachusetts USA have described a knowledge based sys tem for design of progressive 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 3 stamping dies for a simple hinge part 6 The system generates the flat pattern geometry and de velops a strip layout automatically Researchers at the National University of Singapore have been developing an intelligent pro gressive die IPD design system since the late 1980s They used feature modeling and rule based approach to realize automatic punch shape selection strip layout development and 3 D die configuration 7 8 Based on a feature relationship tree that de scribes the stamped metal part and its topological information model based reasoning and spatial reasoning techniques have been employed to reason out certain stamping processes and guide the overall planning process to develop the strip layout automatically Researchers at the Indian Institute of Technology have developed a computer aided die design system CADDS for sheet metal blanks 9 based on heuristic rule based reason ing and parametric programming techniques The greatest advan tage achieved by the system is the rapid generation of the most efficient strip layouts Researchers at the University of Liverpool have worked on design automation for progressive piercing and blanking dies 10 11 Their work is based on applying a coding technique to characterize the stamped part geometric features which is subsequently used to generate the type and layout of the die punches and then develop the strip layout automatically Researchers at Huazhong University of Science and Technol ogy China have developed an intelligent progressive die design system HPRODIE 12 With feature mapping rule based rea soning and case based reasoning techniques most of the design processes including strip layout design can be carried out auto matically Researchers at Pusan National University Korea have developed a compact computer aided process planning CAPP system for progressive die design 13 Based on production rules the work is capable of carrying out an intelligent stamp ing process planning work with automatic development of blank layout strip layout and die layout Though knowledge based systems have achieved a lot of suc cess in stamping process planning most of the intelligent pro gressive die design automation prototypes reviewed above are rather restricted to specific application domains or still need considerable interactive input from experienced designers to de velop strip layouts This is because they still inherit the disadvan tages of the conventional architecture of knowledge based expert systems which are incapable of managing heterogeneous KSs effectively Researchers at the National Taiwan Institute of Technology have adopted various AI techniques including fuzzy reasoning pattern recognition rule based reasoning back propagation neu ral network genetic algorithms and Petri nets for the stamping process planning and design of progressive shearing cut and bending dies 14 16 However their work lacks an explicit and consistent model to integrate these AI techniques into a compre hensive design environment In this paper another popular AI technique blackboard ar chitecture is adopted to develop a blackboard based stamping process planning system In the last two decades blackboard ar chitecture has been successfully used in a wide variety of areas such as speech recognition 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 4 signal processing engineering de sign and process planning Thompson and Lu 17 used a black board architecture to provide a cooperative decision making en vironment that is suitable for concurrent product and process design Srihari et al 18 developed a real time CAPP system for printed circuit board PCB assembly by integrating multiple KSs including planning expert and dynamic information pro cessing modules in the blackboard architecture Chen et al 19 developed a concurrent product design evaluation system using a blackboard architecture to classify knowledge into diverse KSs suitable for qualitative and quantitative evaluation respectively In the past few years blackboard architecture has proven to be suitable for tooling design such as fixture design 20 and in jection moulding design 21 though this kind of application is still in its infancy stage Roy and Liao 20 report the preliminary work that investigates the suitability of using a blackboard archi tecture as a K1 problem solving model for fixture design It de scribes the creation of various functional KSs for fixture design and their organization in a cooperative problem solving environ ment Kwong et al 21 proposes a blackboard based system for concurrent process design of injection moulding which facili tates the simultaneous considerations of moulding part design tool design machine selection production scheduling and cost as early as possible in the conceptual design stage However we have not found in the literature any attempt to apply the blackboard architecture to stamping process planning for sheet metal parts It has been mentioned in our earlier work 22 that a blackboard architecture is well suited for constructive prob lem solving like process planning of stamping operations where the problem space is large and knowledge from many different sources must be integrated to achieve a solution This topic is now to be extensively elaborated in the present paper 3 Blackboard framework for stamping process planning Cooperative decision making for knowledge based stamping process planning involves a variety of KSs such as unfolding knowledge to produce flat pattern nesting knowledge to produce blank layout mapping knowledge to transform stamping features into stamping operations and staging knowledge to sequence the stamping operations These KSs may be expressed in different representation schemes such as procedures rules and objects This justifies the use of a blackboard framework that can man age heterogeneous KSs effectively The KSs interact through the blackboard to develop a solution incrementally The proposed blackboard framework consists of three major components the blackboard data structure KSs and a control module Fig 1 and was developed using object oriented expert system shell CLIPS The different components of the blackboard framework are described as follows 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 5 3 1 Object oriented blackboard data structure The blackboard is a globally accessible database which con tains the data and partial solutions and is shared by a number of independent KSs The KSs contribute their partial solutions to the blackboard which lead to a final solution incrementally The blackboard is structured as a hierarchy of solution parti tion levels which represent different aspects or stages of the solution process Partial solutions are associated with each level and may be linked to information on other levels using algorith mic procedures or heuristic rules Each level contains planning objects that are used to represent the solution space in an object oriented manner This leads to the added advantage in knowledge system development because object oriented approach supports software modularity reusability and scalability Referring to Fig 1 the planning solution is partitioned into four different object levels stamping part stamping features stamping operations and stamping process plan each represent ing initial input or different partial solutions posted on the black board by the specialist KSs They are described as follows 3 1 1 Input data to the blackboard Input data to the blackboard mainly includes the part and press ob jects The generic declaration of a part object includes the basic attributes such as part type part dimensions weight surface treat ments blank thickness blank material annual production blank dimensions etc and points to its constituent stamping feature ob jects that will be elaborated later on The press object contains the attributes such as press type press tonnage bolster dimensions bed open dimensions shut height number of strokes etc 3 1 2 Object oriented feature modeling to stamped metal parts Since traditional geometric modeling techniques do not capture design intent e g design for manufacturing they are in gen eral unable to support sophisticated and intelligent reasoning 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 6 capabilities e g knowledge based process planning Recently the concept of machining features has been introduced to cre ate a direct link between design and manufacturing 23 Feature modeling is a relatively new way of storing design and manu facturing information in CAD CAM CAPP systems Similarly stamping features of a stamped metal part can enable stamping process planning tasks to be performed directly from the geo metric model Stamping features are information carriers that are used to model a stamped part with a set of design and manu facturing information including geometric and non geometric at tributes Each of these stamping features can be manufactured with a specific stamping operation or a combination of stamping operations Using the hierarchical classification structure of general de sign features by Chen et al 24 a stamped metal part can be modeled with four categories of stamping features Primary features flat drawing etc Positive secondary features tab curl emboss hem bead flange etc Negative secondary features hole extrusion hole profile de form slot step etc andConnective secondary features bend blend etc In this work the object oriented feature representation is em ployed to encapsulate design and manufacturing information in a stamping feature object For example a hole feature object contains the basic attributes such as feature type feature ID pri mary feature ID position orientation depth diameter precision roughness etc and methods to calculate perimeter Besides representation of individual stamping features a comprehensive representation of feature relations guarantees that all the stamping features associated with stamping process planning are considered In addition the data on feature relations are useful for determining the sequence of stamping operations and sometimes the stamping operations themselves Four criti cal types of relations among stamping features is in is on adjacent to and precision associated are identified which have been elaborated in our previous work 25 and won t be repeated in this paper for conciseness For example a precision associated relation represents design constraints that arise when a stamping feature does not directly connect to but is associ ated with another stamping feature by a toleranced dimension The feature relation data is also included in the feature object for more complete feature modeling 3 1 3 Stamping operation objects mapped from stamping feature objects On the blackboard the stamping operation objects are in a lower level than the stamping feature objects and are used to define the manufacturing process from metal strip to the formed metal part Stamping features constitute a stamped part while stamp ing operations are selected as elements of a stamping process plan Essentially the stamping process planning task is to trans form a set of stamping features into a set of stamping opera tions and to describe the relations between these The generic declaration of a stamping operation object includes stamping op eration type geometric shapes geometric constraints precision roughness relationships with stamping features control param eters etc Typical stamping operation objects include piercing 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 7 notching cut off blanking lancing shaving drawing emboss ing coining trimming and other miscellaneous forming opera tions A stamping feature may be manufactured with a specific stamping operation one to one mapping or a combination of stamping operations one to many mapping Several stamping features may also be manufactured with a single stamping oper ation many to one mapping 3 1 4 Graph based stamping process plan After the mapping from stamping features to a set of stamping operations the remaining process planning task is to assign each stamping operation to the relevant die station according to an op timal sequence of stamping operations Stamping operations are sequenced in a progressive manner by creating stamping opera tion relations and using them to form a stamping process plan This formal description of operation relations forms the founda tion of automatic strip layout design A graph based approach is used to arrange the stamping op eration objects in a stamping process plan The graph consists of a set of nodes that store information about the stamping opera tions and a set of arcs that store information about the operation relations Stamping operations are related to one another through two kinds of relationship cluster or precedence relations Cluster stamping operations are executed simultaneously and can be staged at the same die station Stamping operations in prece dence must be performed in sequence and so they are staged in adjacent die stations Cluster relation and precedence rela tion are represented by dashed ellipses and directed solid line respectively as shown in Fig 2 Note that stamping operations B and C work simultaneously and are staged at the same die station while stamping operation A precedes operation B and is staged in a die station immediately prior to the one for the operation B The strip layout can be generated by a computer automat ically using the graph based stamping process plan which is suited for computer implementation and leads to efficient formu lation and solution procedures 以沖壓工藝規(guī)劃知識進行的級進模設(shè)計 大連交通大學(xué) 2017 屆本科生畢業(yè)設(shè)計外文翻譯 8 摘 要 人們普遍認為沖壓工藝規(guī)劃的布局是級進模設(shè)計中的關(guān)鍵任務(wù) 有史以來 沖壓工藝 規(guī)劃是一門藝術(shù) 而不是一門科學(xué) 雖然人工智能在將內(nèi)置的智能和應(yīng)用多樣化的知識窗 臺解決這類問題已經(jīng)取得了很多最新進展 而現(xiàn)在主要的困難是 現(xiàn)有的基于知識的專家 系統(tǒng) 沖壓工藝規(guī)劃缺乏適當(dāng)?shù)募軜?gòu)組織異構(gòu)知識源 KSS 的合作決策 EN vironment 本文提出了沖壓工藝規(guī)劃知識型面板框架 建議 AP proach 通過自動售貨機 荷蘭國際 集團的帶狀布局設(shè)計 加快了級進模設(shè)計過程 關(guān)鍵詞 基于知識 面向?qū)ο?級進模具設(shè)計 沖壓工藝規(guī)劃 1 引言 級進模在大眾中生產(chǎn)鈑金件已被廣泛應(yīng)用于各種行業(yè) 如航空航天 電子 機床 汽 車 這些模具可在一次裝夾完成穿孔 開槽 切斷 落料 彎曲 刮 拉絲 浮雕 修剪 和其他雜項成形操作 因此 級進模通常是非常復(fù)雜的 因此沖壓工藝規(guī)劃和模具結(jié)構(gòu)設(shè) 計是困難的 苛刻的任務(wù) 沖壓工藝規(guī)劃開始 沖壓金屬部件的模型的展開 以產(chǎn)生一個平面的圖案 隨后通過 嵌套圖案 以產(chǎn)生一個空白的布局 下一步 計劃沖壓操作和操作分配到工步 由此產(chǎn)生 的計劃通常表示為一個帶狀布局 指導(dǎo)后續(xù)的模具結(jié)構(gòu)設(shè)計 在全局模具生產(chǎn)過程中 模 具的精度 成本 和一個級進模的質(zhì)量主要取決于帶布局 這使得有史以來 沖壓工藝設(shè) 計是一門藝術(shù) 而不是一門科學(xué) 從歷史上看 這項活動主要是汽車生產(chǎn)里衍生出來的 根據(jù)設(shè)計師的試錯經(jīng)驗 技能和知識來進行模具的設(shè)計 在人工智能 AI 領(lǐng)域的最新進展引起的可能性 以構(gòu)建包含內(nèi)置的智能 AI 為基礎(chǔ) 的系統(tǒng)和多樣化的知識應(yīng)用于解決級進模的設(shè)計問題 其中包括條帶布局設(shè)計自動化 多 樣化的知識源 KSS 到?jīng)_壓工藝規(guī)劃 包括展開知識 以產(chǎn)生一個平面的圖案 排料的 知識 以產(chǎn)生一個空白