【正文】 mercial distinct logic controllers can reduce programming leadtime and labor cost. In particular, the thesis is relevant with respect to the following aspects. In modern manufacturing, systems are characterized by product and process innovation, bee customerdriven and thus have to respond quickly to changing system requirements. A major challenge is therefore to provide enabling technologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in realtime, therefore, giving a significant petitive edge in industrial practice. Studies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of puting resources. For instance, the programming of PLCs still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in programming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards [IEC 60848, 1999。用戶可通過編程來編制通訊協(xié)議、交換數(shù)據(jù)（例如： ASCII碼字符），具有 RS232接口的設(shè)備也可用 PC/PPI電纜連接起來進(jìn)行自由通訊方式通訊。在局部功能塊設(shè)計(jì)階段，單個(gè)功能將被設(shè)計(jì)出來，并予以驗(yàn)證。 軟件工業(yè)被認(rèn)為是系統(tǒng)性能的破壞者和系統(tǒng)復(fù)雜性的產(chǎn)生者?？梢酝ㄟ^分析估計(jì)看狀態(tài)模型是否達(dá)到想要的目標(biāo)。注釋和標(biāo)記甚至還可以準(zhǔn)確地引用零件號(hào)，如果需要更換零件的話。一部分存儲(chǔ)器用來存儲(chǔ)輸入和輸出狀態(tài)。但工作節(jié)奏由震蕩信號(hào)控制。例如，在實(shí)踐中， VISI設(shè)計(jì)是一種有效的計(jì)算機(jī)輔助設(shè)計(jì)。它采用了可編程序的存儲(chǔ)器，用來在其內(nèi)部存儲(chǔ)執(zhí)行 邏輯運(yùn)算，順序控制、定時(shí)、計(jì)數(shù)和算術(shù)運(yùn)算等操作的指令，并通過數(shù)字式和模擬式的輸入和輸出，控制各種類型的機(jī)械或生產(chǎn)過程。可編程控制器及其有關(guān)外圍設(shè)備，易于與工業(yè)控制系統(tǒng)聯(lián)成一個(gè)整體，易于擴(kuò)充其功能的設(shè)計(jì)。 PLC不需要使用目前的以軟件設(shè)計(jì)為基礎(chǔ)軟件工程方法論，因?yàn)?PLC程序要求對(duì)軟件和硬件搜都要考慮到。 運(yùn)算器用于進(jìn)行數(shù)字或邏輯運(yùn)算，在控制器指揮下工作。一個(gè)輸入的實(shí)際狀態(tài)存儲(chǔ)狀態(tài)存儲(chǔ)在專用存儲(chǔ)器位上，為 “1” 或者 “0” 。這將加快由于損壞零件而引起的任何問題的修理速度。第二，為狀態(tài)模型的描述提供結(jié)構(gòu)描述，這個(gè)結(jié)構(gòu)描述可以說明邏輯要求和如細(xì)節(jié)安全規(guī)則的限制。逐漸下降的硬件價(jià)格，破壞了對(duì)通過優(yōu)化程序獲得的軟件性能的需要。在系統(tǒng)設(shè)計(jì)階段，所有功能塊都將被整合起來，整個(gè)系統(tǒng)行為特性和功能將會(huì)通過仿真形式加以測(cè)試。 當(dāng)上位機(jī)脫機(jī)時(shí)，在下位機(jī)控制下，整個(gè)系統(tǒng)能正常運(yùn)行。 IEC611313, 1993。 Fourth functional improvements, strong functional interface. TWO、 History of PLC Programmable Logic Controllers (PLC), a puting device invented by Richard E. Morley in 1968, have been widely used in industry including manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with softwired logic or socalled relay ladder logic (RLL), a programming language visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, 1999]. Although PC based control has started to e into place, PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLCs per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices of puting hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5billion industry at the present time. Though PLCs are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trialanderror. Alike software engineering, PLC software design is facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating `If houses were built like software projects, a single woodpecker could destroy civilization.” Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic programs. Though the hardware costs of PLCs are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that lowcost PLCs can be used. In general, the productivity in generating PLC is far behind pared to other domains, for instance, VLSI design, where efficient puter aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLCprogramming requires a simultaneous consideration of hardware and software. The software design bees, thereby, more and more the major cost driver. In many industrial design projects, more than of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC programs. In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and reconfigurability of manufacturing systems. A further problem, impelling the need for a systematic design methodology, is the increasing software plexity in largescale projects. The objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves highlevel description based on state transition models that treat automation control systems as discrete event systems, a stepwise design process, and set of design rules providing guidance and measurements to achieve a successful design. The tangible oute of this research is to find a way to reduce the uncertainty in managing the control software development process, that is, reducing programming and debugging time and their variation, increasing flexibility of the automation systems, and enabling software reusability through modularity. The goal is to overe shortings of current programming strategies that are based on the experience of the individual software developer. Three、 now of PLC From the structure is divided into fixed PLC and Module PLC, the two kinds of PLC including CPU board, I/O board, display panel, memory block, power, these elements into a do not remove overall. Module type PLC including CPU module, I/O modules, memory, the po