Bailey DCS卡件 INFI 90 IMMFC04 MULTIFUNCTION CONTROLLER
Bailey DCS卡件 INFI 90 IMMFC04 MULTIFUNCTION CONTROLLER
Bailey DCS卡件 INFI 90 IMMFC04 MULTIFUNCTION CONTROLLER
DCS控制系統(tǒng)與PLC控制系統(tǒng)之間的差別:
1.DCS是一種“分散式控制系統(tǒng)”,而PLC只是一種(可編程控制器)控制“裝置”,兩者是“系統(tǒng)”與“裝置”的區(qū)別。系統(tǒng)可以實(shí)現(xiàn)任何裝置的功能與協(xié)調(diào),PLC裝置只實(shí)現(xiàn)本單元所具備的功能.
2.在網(wǎng)絡(luò)方面,DCS網(wǎng)絡(luò)是整個(gè)系統(tǒng)的中樞神經(jīng),和利時(shí)公司的MACS系統(tǒng)中的系統(tǒng)網(wǎng)采用的是雙冗余的100Mbps的工業(yè)以太網(wǎng),采用的標(biāo)準(zhǔn)協(xié)議TCP/IP。它是安全可靠雙冗余的高速通訊網(wǎng)絡(luò),系統(tǒng)的拓展性與開(kāi)放性更好.而PLC因?yàn)榛旧隙紴閭€(gè)體工作,其在與別的PLC或上位機(jī)進(jìn)行通訊時(shí),所采用的網(wǎng)絡(luò)形式基本都是單網(wǎng)結(jié)構(gòu),網(wǎng)絡(luò)協(xié)議也經(jīng)常與標(biāo)準(zhǔn)不符。在網(wǎng)絡(luò)安全上,PLC沒(méi)有很好的保護(hù)措施。我們采用電源,CPU,網(wǎng)絡(luò)雙冗余.
3.DCS整體考慮方案,操作員站都具備工程師站功能,站與站之間在運(yùn)行方案程序下裝后是一種緊密聯(lián)合的關(guān)系,任何站、任何功能、任何被控裝置間都是相互連鎖控制,協(xié)調(diào)控制;而單用PLC互相連接構(gòu)成的系統(tǒng),其站與站(PLC與PLC)之間的則是一種松散連接方式,是做不出協(xié)調(diào)控制的功能。
4.DCS在整個(gè)設(shè)計(jì)上就留有大量的可擴(kuò)展性接口,外接系統(tǒng)或擴(kuò)展系統(tǒng)都十分方便,PLC所搭接的整個(gè)系統(tǒng)完成后,想隨意的增加或減少操作員站都是很難實(shí)現(xiàn)的。
5.DCS安全性:為保證DCS控制的設(shè)備的安全可靠,DCS采用了雙冗余的控制單元,當(dāng)重要控制單元出現(xiàn)故障時(shí),都會(huì)有相關(guān)的冗余單元實(shí)時(shí)無(wú)擾的切換為工作單元,保證整個(gè)系統(tǒng)的安全可靠。PLC所搭接的系統(tǒng)基本沒(méi)有冗余的概念,就更談不上冗余控制策略。特別是當(dāng)其某個(gè)PLC單元發(fā)生故障時(shí),不得不將整個(gè)系統(tǒng)停下來(lái),才能進(jìn)行更換維護(hù)并需重新編程。所以DCS系統(tǒng)要比其安全可靠性上高一個(gè)等級(jí)。(www.dqjsw。。com.cn)
6.系統(tǒng)軟件,對(duì)各種工藝控制方案更新是DCS的一項(xiàng)zui基本的功能,當(dāng)某個(gè)方案發(fā)生變化后,工程師只需要在工程師站上將更改過(guò)的方案編譯后,執(zhí)行下裝命令就可以了,下裝過(guò)程是由系統(tǒng)自動(dòng)完成的,不影響原控制方案運(yùn)行。系統(tǒng)各種控制軟件與算法可以將工藝要求控制對(duì)象控制精度提高。而對(duì)于PLC構(gòu)成的系統(tǒng)來(lái)說(shuō),工作量極其龐大,首先需要確定所要編輯更新的是哪個(gè)PLC,然后要用與之對(duì)應(yīng)的編譯器進(jìn)行程序編譯,zui后再用的機(jī)器(讀寫(xiě)器)專門一對(duì)一的將程序傳送給這個(gè)PLC,在系統(tǒng)調(diào)試期間,大量增加調(diào)試時(shí)間和調(diào)試成本,而且極其不利于日后的維護(hù)。在控制精度上相差甚遠(yuǎn)。這就決定了為什么在大中型控制項(xiàng)目中(500點(diǎn)以上),基本不采用全部由PLC所連接而成的系統(tǒng)的原因。
7.模塊:DCS系統(tǒng)所有I/O模塊都帶有CPU,可以實(shí)現(xiàn)對(duì)采集及輸出信號(hào)品質(zhì)判斷與標(biāo)量變換,故障帶電插拔,隨機(jī)更換。而PLC模塊只是簡(jiǎn)單電氣轉(zhuǎn)換單元,沒(méi)有智能芯片,故障后相應(yīng)單元全部癱瘓。
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