【正文】 ed all decision making logic in simple ladder logic which appeared similar to electrical schematic diagrams. The electricians were quite able to trace out circuit problems with schematic diagrams using ladder logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLC used a form of instruction list programming, based on a stackbased logic solver. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and working. The data handling, storage, processing power and munication capabilities of some modern PLC are approximately equivalent to desktop puters. PLClike programming bined with remote I/O hardware, allow a generalpurpose desktop puter to overlap some PLC in certain applications. Under the IEC 611313 standard, PLC can be programmed using standardsbased programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. 6039。 Need the kit not standard exterior connects and conditionally once requested to the environment and the spot。s person － machine to the words means(if keyboard, CRT and speech have a conversation), in recent years because of the spot emergence and related standard establishment of total line principle, and the quick development of product, the PLC bee the spot total line of an importance constitute part, extended PLC applied realm further. Because the PLC raised function with gentle degree in the meantime, make its application quickly increase, and make widely available many other longlost spare parts manufacture industry realm. Later on again expand to and criticize quantity to produce with continuous production line relevant of industrial realm. Along with the CIMS (calculator integration manufacturing system) development, the PLC is still used for factory by people to correspond by letter a work at present in, bee a calculator with other intelligence controllers and calculator system together prehensive control system in of importance constitute part, especially unit class and work station class. From 1969 the first set P L C publish up to now and the programmable controller about experienced three stages: First stage: The PLC capacity of the development is smaller, I/O the point be small at 120: customer saves area capacity or so scan the speed as 20~50 ms K B in the 2 KB s, the instruction is more simple and only have logic an operation and account, count etc., weave distance language to adopt a simple language sentence a predicative speech. Mainly use to make amount of switch a control on the usage. Second stage: The PLC capacity has to expand, the I/O point is from 5121024:00, customer39。 這些把 PLC 連結(jié)到感應(yīng)器和主動(dòng)器。表達(dá)的大部份最早的 PLCs 所有的在簡單的梯邏輯中的決策邏輯出現(xiàn)相似的對(duì)電概要的圖表。 一個(gè)圖解式的規(guī)畫記號(hào)法呼叫繼續(xù)的功能圖解從特定的可設(shè)計(jì)的控制器可得。通過 PLC與各種單元自動(dòng)化裝置（如智能儀表、數(shù)字化傳單裝置、智能的液壓和氣動(dòng)閥組等）以及現(xiàn)場總線、計(jì)算機(jī)網(wǎng)絡(luò)系統(tǒng)，構(gòu)成了車間和工廠自動(dòng)化的完整體系。當(dāng)今 PLC具有采集與處理大量數(shù)據(jù)、完成數(shù)學(xué)運(yùn)算、與其它智能器件通信的能力，以及具有先進(jìn)的人－機(jī)對(duì) 話手段（如鍵盤、 CRT和語音對(duì)話），近年來由于現(xiàn)場總線理念的出現(xiàn)和相關(guān)標(biāo)準(zhǔn)的建立，以及產(chǎn)品的迅速發(fā)展， PLC成為 現(xiàn)場總線的一個(gè)重要組成部分，進(jìn)一步擴(kuò)大了 PLC的應(yīng)用領(lǐng)域。編程語言除了使用語句表外，還可以使用梯形圖編程語言。小型 PLC使用的手握式編程器使用大面積液晶顯示器，也可以用梯形圖和 GRAFCET語言進(jìn)行編程。為了提高 系統(tǒng)的可靠性，設(shè)計(jì)上考慮了容錯(cuò)技術(shù)和冗余技術(shù)等。使用上，主要用來作開關(guān)量控制。這時(shí)的 PLC系統(tǒng)已開始具有如下一些特點(diǎn)：環(huán)境適應(yīng)性較強(qiáng)，可以使用于車間現(xiàn)場；有較高的可靠性和診斷 能力，維修容易；基本能適應(yīng)不同的制造過程所需，柔性度有 了較大提高，只要改變系統(tǒng)中的程序即可改變控制“邏輯”，而 無需改造或更換控制硬件等。 由于 PLC吸取微電子技術(shù)和計(jì)算機(jī)技術(shù)的最新成果，因此發(fā)展十分迅速，從單機(jī)自動(dòng)化到整條生產(chǎn)線的自動(dòng)化，乃至整個(gè)工廠的生產(chǎn)自動(dòng)化，從柔性制造系統(tǒng)