plc英文資料和中文翻譯

1、MotivationProgrammable Logic Controllers (PLC), a computing 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 s

2、oft-wired logic or so-called 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.Although PC based control has started to come into place, PLC based control will remain the technique to whic

3、h 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 h

4、ardware value of more than 8 billion US dollars has been predicted, though the prices of computing hardware is steadily dropping. The inventor of the PLC, Richard E Morley, fairly considers the PLC market as a 5-billion industry at the present time.Though PLCs are widely used in industrial practice,

5、 the programming of PLC based control systems is still very much relying on trial-and-error. 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 Particularly, practical problems

6、 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 low-cost PLCs can be used.In general, the

7、 productivity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily applicable to the PLC based software design because PLC-programming require

8、s a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial design projects, more than SO0/a of the manpower allocated for the control system design and installation is scheduled for testing and debugging PLC

9、programs Rockwell, 1999.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 complex

10、ity in large-scale projects.Objective and Significance of the ThesisThe objective of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automation c

11、ontrol 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 outcome of this research is to find a way to reduce the uncertainty in managing the control software development process, that

12、 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 overcome shortcomings of current programming strategies that are based on the experience of the individual software

13、 developer.A systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, b

14、y state machines. Formal representations provide a high-level description of the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired goals. Secondly, a state machine description provides a structured representation to conve

15、y the logical requirements and constraints such as detailed safety rules. Thirdly, well-defined control systems design outcomes are conducive to automatic code generation- An ability to produce control software executable on commercial distinct logic controllers can reduce programming lead-time and

16、labor cost. In particular, the thesis is relevant with respect to the following aspects.Customer-Driven ManufacturingIn modern manufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements. A major

17、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 real-time, therefore, giving a significant competitive edge in industrial practi

18、ce.Higher Degree of Design Automation and Software QualityStudies have shown that programming methodologies in automation systems have not been able to match rapid increase in use of computing resources. For instance, the programming of PLCs still relies on a conventional programming style with ladd

19、er 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; IEC-61131-3, 1993; IEC 61499, 19

20、98; ISO 15745-1, 1999 have been formed to fix and disseminate state-of-the-art design methods, but they normally cannot participate in advancing the knowledge of efficient program and system design.A systematic approach will increase the level of design automation through reusing existing software c

21、omponents, and will provide methods to make large-scale system design manageable. Likewise, it will improve software quality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railro

22、ads.System ComplexityThe software industry is regarded as a performance destructor and complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimization and efficiency. The result is that massive and less efficient software code on one ha

23、nd outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into complexity of unmanageable dimensions; software redesign and maintenance-essential in modern automation systems-becomes nearly impossible. Particularly, PLC programs have evolved from a couple lines

24、 of code 25 years ago to thousands of lines of code with a similar number of 1/O points. Increased safety, for instance new policies on fire protection, and the flexibility of modern automation systems add complexity to the program design process. Consequently, the life-cycle cost of software is a p

25、ermanently growing fraction of the total cost. 80-90% of these costs are going into software maintenance, debugging, adaptation and expansion to meet changing needs Simmons et al., 1998.Design Theory DevelopmentToday, the primary focus of most design research is based on mechanical or electrical pro

26、ducts. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design. A system design theory for large-scale and complex system is not yet fully developed. Particularly, the que

27、stion of how to simplify a complicated or complex design task has not been tackled in a scientific way. Furthermore, building a bridge between design theory and the latest epistemological outcomes of formal representations in computer sciences and operations research, such as discrete event system m

28、odeling, can advance future development in engineering design.Application in Logical Hardware DesignFrom a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extremely complex with several million parts and a product development

29、 time of 3 years Whitney, 1996. The design process is normally separated into a component design and a system design stage. At component design stage, single functions are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is test

30、ed through simulation. In general, a complete verification is impossible. Hence, a systematic approach as exemplified for the PLC program design may impact the logical hardware design.Programming languagesHigher level PLC programming languages have been around for some time, but lately their popular

31、ity has been mushrooming. As Raymond Lavelle, vice president and general manager, Siemens Energy and Automation. Inc, Programmable Controls Division, points out :As programmable controls are being used for more and more sophisticated operations, languages other than ladder logic become more practica

32、l, efficient, and powerful. For example, it's very difficult to write a trigonometric function using ladder logic. Languages gaining acceptance include Boolean, control system flowcharting, and such function chart languages as Graphtec and its variations. And theses increasing interest in langua

33、ges like C and BASIC.PLCs in process controlThus far, PLCs have not been used extensively for continuous process control. Will this continue? The feeling that Ive gotten, says Ken Jeannette, manager, product planning, Series One and Series Six products, at GE Frame North America, "is that PLCs

34、will be used in the process industry but not necessarily for process control.Several vendors-obviously betting that the opposite will happen-have introduced PLCs optimized for process applications. Rich Ryan ,manager, commercial marketing, Allen-Bradley Programmable Controls Div, cites PLCs increasi

35、ng use in such industries as food, chemicals, and petroleum. Ryan feel there are two types of applications in which theyre appropriate.One, "he says, "is where the size of the process control system that's being automated doesnt justify DCSdistributed control systems.With the starting

36、price tags of those products being relatively high, a programmable controller makes sense for small, low loop count applications. The seconds where you have to integrate the loop closely with the sequential logic. Batch controller sere prime examples, where the sequence and maintaining the process v

37、ariable are intertwined so closely that the benefits of having a programmable controller to do the sequential logic outweighs some of the disadvantages of not having a distributed control system.Bill Barkovtz, president of Triconex, predicts that "all future controllers that come out in the pro

38、cess control system business will embrace a lot more PLC technology and a lot more PLC functionality than they ever did before.Communications and MAPCommunications are vital to an individual automation cell and to the automated factory as a whole. We've heard a lot about MAP in the last few year

39、s, and a lot of companies have jumped on the band wagon. Many, however were disappointed when a fully-defined and completed MAP specification didnt appear immediately. Says Larry Kumara:Right now , MAP is still a moving target for the manufacturers specification that is not final. Presently, for exa

40、mple, people are introducing products to meet the MAP 2.1standard.Yet 2.1-based products will be obsolete when the new standard for MAP,3.0is introduced.Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example , has an ongoing MAP-compatibility program, but F

41、rank Newborn, vice president of Omrons Industrial Division, reports that because of the lack of a firm definition, Omron's PLCs don't yet talk to MAP.Since its unlikely that an individual PLC would talk to broadband MAP anyway, makers are concentrating n proprietary networks. According to Sa

42、l Provanzano, users fear that if they do get on board and vendors withdraw from MAP, they ll pulse width modulation control system be the ones left holding a communications structure thats not supported.PLC IntroductionProgrammable controller is the first in the late 1960s in the United States, then

43、 called Plc programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other control functions. The concept is presented Plc General Motors Corporation. Plc and the basic design is the computer

44、 functional improvements, flexible, generic and other advantages and relay control system simple and easy to operate, such as the advantages of cheap prices combined controller hardware is standard and overall. According to the practical application of target software in order to control the content

45、 of the user procedures memory controller, the controller and connecting the accused convenient target.譯文動力1968年，Richard E. Morley創(chuàng)造出了新一代工業(yè)控制裝置可編程邏輯控制器(PLC),現(xiàn)在，PLC已經(jīng)被廣泛應(yīng)用于工業(yè)領(lǐng)域，包括機械制造也、運輸系統(tǒng)、化學(xué)過程設(shè)備、等許多其他領(lǐng)域。初期可編程控制器只是用一種類似于語言的軟件邏輯于代替繼電器硬件邏輯，并且使開發(fā)時間由6個月縮短到6天。雖然計算機控制技術(shù)已經(jīng)產(chǎn)生，但是PLC控制因為它的高性能、本錢低、并且對惡劣的環(huán)境有很強的

46、適應(yīng)能力而在工業(yè)控制的廣泛應(yīng)用中保持優(yōu)勢。而且，盡管硬件的價格在逐漸下跌，據(jù)估計，根據(jù)Frost和Sullivan對PLC市場的調(diào)查研究說明，每年銷售硬件的價格要比銷售PLC的價格一千五百萬至少多出八十億美元。PLC的創(chuàng)造者Richard E. Morley十分肯定的認(rèn)為目前PLC市場是一個價值五十億的工業(yè)雖然PLC廣泛應(yīng)用于工業(yè)控制中，PLC控制系統(tǒng)的程序依然和語法有關(guān)。和軟件過程一樣，PLC的軟件設(shè)計也以同樣的方式會遇到軟件錯誤或危機。Morley在演講中著重強調(diào)了這個方面。PLC程序要解決的實際問題是消除軟件錯誤和減少老式梯形邏輯語言的花費。盡管PLC的硬件本錢在繼續(xù)下降，但是在工業(yè)控制

47、上減少梯形邏輯的掃描時間仍然是一個問題，以至于可以用到低耗時的PLC。一般來說，和其他領(lǐng)域相比生產(chǎn)PLC的周期要短很多。例如，在實踐中，VISI設(shè)計是一種有效的計算機輔助設(shè)計。PLC不需要使用目前的以軟件設(shè)計為根底軟件工程方法論，因為PLC程序要求對軟件和硬件搜都要考慮到。因此，軟件設(shè)計越來越成為花費動力。在許多的工業(yè)設(shè)計工程中，超過    的人力分配給了控制系統(tǒng)設(shè)計和安裝，并且他們要對。PLC程序測試和排除錯誤，再者，PLC控制系統(tǒng)不適合設(shè)計對適應(yīng)性和重構(gòu)有越來越多要求的生產(chǎn)系統(tǒng)。一個更深入的問題是在大規(guī)模的工程中軟件越來越復(fù)雜，促使要有一個系統(tǒng)化的設(shè)計方法論。

48、主題的客觀性和重要性主題的客觀性是為PLC自動控制系統(tǒng)建立一個系統(tǒng)化的軟件設(shè)計方法論。這個設(shè)計方法論包括以狀態(tài)轉(zhuǎn)換模型為根底的精確的描述，這個轉(zhuǎn)臺轉(zhuǎn)換模型是自動控制系統(tǒng)的抽象系統(tǒng)。方法論還包括一個逐步的設(shè)計過程，并且要設(shè)置一個設(shè)計規(guī)那么，這樣才能為一個成功的設(shè)計提供導(dǎo)向和方法。這項研究的真正目的是找到一個減少控制軟件開展過程的不穩(wěn)定性的方法，也就是說，減少程序和調(diào)試時間以及它們的變化，以增強自動控制系統(tǒng)的適應(yīng)性，并且通過調(diào)整軟件使得軟件可以再度使用。這樣的目的是為了克服目前程序策略的缺乏之處，而目以前的程序策略是以個人軟件開發(fā)者的經(jīng)驗為根底的。 一個系統(tǒng)化的設(shè)計PLC程序的方法可以克

49、服傳統(tǒng)程序生產(chǎn)控制系統(tǒng)的缺點，并且在一些工業(yè)應(yīng)用總有很大的不同。自動控制系統(tǒng)是狀態(tài)模型用公式語言或等價的語言描述的。公式描述對被控制的系統(tǒng)的行為提供一個精確的描述。第一，可以通過分析估計看出狀態(tài)模型是否到達想要的目標(biāo)。第二，狀態(tài)模型的描述提供結(jié)構(gòu)描述，這個結(jié)構(gòu)描述可以說明邏輯要求和細(xì)節(jié)平安規(guī)那么的限制。第三，好的控制系統(tǒng)設(shè)計是對自動控制代碼生成有益的一種能夠產(chǎn)生可執(zhí)行的控制軟件的能力，不同的邏輯控制器可以減少程序掃描時間和執(zhí)行那個時間。特別的值得在注意的是這個主題與隨后的局部的是有一定關(guān)系的。訂制生產(chǎn)在現(xiàn)代制造業(yè)中，系統(tǒng)是用過程和結(jié)果的革新來描述的，變得Customer-Driven，并且因此

50、不得不改變系統(tǒng)性能以快速做出反響。因此，一個大的挑戰(zhàn)是提供技術(shù)以限制自動控制系統(tǒng)對變化需要和新時機的反響，所以，設(shè)計和操作知識可以實時的被再次利用，在工業(yè)實踐中提供了一個重要的競爭面。高水平的自動化設(shè)計和軟件質(zhì)量研究說明，在自動化系統(tǒng)中，程序?qū)崿F(xiàn)的方法已經(jīng)與計算機資源應(yīng)用的急速增長不能匹配。例如，可編程邏輯控制器程序仍然依靠一種方便的有邏輯梯形圖的程序?qū)崿F(xiàn)模式。結(jié)果，程序上的延遲和資源成了生產(chǎn)工業(yè)過程的主要絆腳石。在可編程邏輯控制器程序設(shè)計過程中，測試和調(diào)試可能會占用超過百分之五十的人力。在開展和傳播“已經(jīng)形成標(biāo)準(zhǔn)IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999，但是，根本上這些標(biāo)準(zhǔn)都不能參與有效的程序和系統(tǒng)設(shè)計方面知識的革新。系統(tǒng)的方法通過使用原有的軟件模塊，有助于增加設(shè)計自動化的水平，同時也將提供一種可管理的大規(guī)模系統(tǒng)設(shè)計的方法。同樣的，它也將改善軟件的質(zhì)量的可靠性，以及關(guān)系到系統(tǒng)的較高平安標(biāo)準(zhǔn)，尤其是這些對環(huán)境有危害影響的，比方：機場控制、公共鐵路運輸。 系統(tǒng)復(fù)雜性軟件工業(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。逐漸下降的硬件價格，破壞了對通過優(yōu)化程序獲得的軟件性能的需要。其結(jié)果是，一方面造成了大量而低效率的程序代碼，另一方面并沒有獲得高的硬件性能。其次