1756-OF8，1756-OF8

1756-OF8

 

1756-OF8

用于汽車(chē)內(nèi)部測(cè)量與執(zhí)行部件之間的數(shù)據(jù)通信。CAN結(jié)構(gòu)模型取ISO/OSI模型的第1、2、7層協(xié)議，即物理層、數(shù)據(jù)鏈路層和應(yīng)用層。
 
此外還值得一提的是，可尋址遠(yuǎn)程傳感器數(shù)據(jù)公路（Highway Addressable Remote Transducer，HART）協(xié)議，早推出的一種兼容4~20mA模擬信號(hào)和調(diào)制數(shù)字信號(hào)的現(xiàn)場(chǎng)總線(xiàn)協(xié)議。其數(shù)字通信由于采用調(diào)制/解調(diào)方式，屬于模擬系統(tǒng)向數(shù)字系統(tǒng)轉(zhuǎn)變過(guò)程中的過(guò)渡產(chǎn)品，因而在當(dāng)前的過(guò)渡時(shí)期具有較強(qiáng)的競(jìng)爭(zhēng)力，得到了較快的發(fā)展。
 
3、現(xiàn)場(chǎng)總線(xiàn)的未來(lái)
 
現(xiàn)場(chǎng)總路線(xiàn)將成為工業(yè)控制發(fā)展的革命性飛躍，有關(guān)現(xiàn)場(chǎng)總線(xiàn)的報(bào)道層出不窮，其中令人關(guān)注的焦點(diǎn)集中在能否出現(xiàn)全統(tǒng)一的現(xiàn)場(chǎng)總線(xiàn)標(biāo)準(zhǔn)。
 
不同的現(xiàn)場(chǎng)總線(xiàn)有不同的功能，各有其適用的場(chǎng)合，靠一種現(xiàn)場(chǎng)總線(xiàn)打天下的想法看來(lái)不太現(xiàn)實(shí)。當(dāng)然，從另一方面來(lái)講，相當(dāng)一部分現(xiàn)場(chǎng)總線(xiàn)是大同小異的，技術(shù)上非常接近，在優(yōu)勝劣汰的環(huán)境下同類(lèi)總線(xiàn)終將趨于統(tǒng)一。但商業(yè)利益上的激烈競(jìng)爭(zhēng)是這個(gè)問(wèn)題的主要原因，對(duì)于現(xiàn)場(chǎng)總線(xiàn)形成巨大影響的自動(dòng)化廠(chǎng)商，因?yàn)橐M可能維護(hù)自身的地位和利益而不愿放棄其已擁有的現(xiàn)場(chǎng)總線(xiàn);因此，在未來(lái)較長(zhǎng)的一段時(shí)間內(nèi)，現(xiàn)場(chǎng)總線(xiàn)標(biāo)準(zhǔn)之爭(zhēng)會(huì)越演越烈。
開(kāi)放式控制系統(tǒng)

控制系統(tǒng)
 
1、開(kāi)放性控制系統(tǒng)的概念
 
長(zhǎng)期以來(lái)，制造與生產(chǎn)企業(yè)所采用控制系統(tǒng)大多是專(zhuān)用的、封閉的體系結(jié)構(gòu)，其構(gòu)成系統(tǒng)的硬件是按照各自的標(biāo)準(zhǔn)度身定制的。無(wú)論是DCS，PLC還是FCS，雖然它們具有結(jié)構(gòu)簡(jiǎn)單、技術(shù)成熟、產(chǎn)品批量大等優(yōu)點(diǎn)，但相對(duì)日新月異的生產(chǎn)要求，也越來(lái)越暴露出其固有的缺點(diǎn)。在許多情況下,當(dāng)用戶(hù)要想進(jìn)行功能上的擴(kuò)展或變化時(shí)，都必須求助于系統(tǒng)的提供商，如想把特殊要求融入到控制系統(tǒng)中去時(shí)，都是比較困難的。這無(wú)形中不僅提高了制造企業(yè)的成本，也成為控制系統(tǒng)升級(jí)換代的“瓶頸”。
 
由于市場(chǎng)競(jìng)爭(zhēng)越來(lái)越劇烈，從而要求制造商具有較強(qiáng)的市場(chǎng)適應(yīng)能力，這一趨勢(shì)促成了一個(gè)新概念的產(chǎn)生，即模塊化、可重構(gòu)、可擴(kuò)充的軟硬件系統(tǒng)，這就是開(kāi)放式控制系統(tǒng)。這一系統(tǒng)為制造廠(chǎng)提供了將其技術(shù)與任何第三方的技術(shù)或產(chǎn)品進(jìn)行集成的可能性。
 
2、國(guó)際控制系統(tǒng)制造商的開(kāi)放路線(xiàn)
 
據(jù)國(guó)際機(jī)構(gòu)美國(guó)自動(dòng)化市場(chǎng)研究公司ARC（Automation Research Corp.）調(diào)查預(yù)計(jì)，在亞洲，基于PC的控制系統(tǒng)、以太網(wǎng)的I/O模件等開(kāi)放式系統(tǒng)的銷(xiāo)售額預(yù)計(jì)近兩年的增幅達(dá)到145%，所以，可見(jiàn)在控制系統(tǒng)市場(chǎng)中，開(kāi)放系統(tǒng)的增長(zhǎng)率遠(yuǎn)遠(yuǎn)高于傳統(tǒng)的控制系統(tǒng)。
 
幾乎所有的制造商都已認(rèn)識(shí)到了開(kāi)放系統(tǒng)必將是自動(dòng)化系統(tǒng)的未來(lái)。在任何一家控制系統(tǒng)制造商的新產(chǎn)品樣本中，都可以看到“開(kāi)放性”的字樣。但是，他們的開(kāi)放性通常都是在原有的系統(tǒng)上層加上一些接口實(shí)現(xiàn)局部的互連和通信，并非真正意義上的開(kāi)放。不要說(shuō)控制器的底層，就是在操作站這一層，他們?cè)趯?shí)現(xiàn)與外界通信方面存在著重重困難。這種狀況的產(chǎn)生并不是由于他們無(wú)法開(kāi)發(fā)出全開(kāi)放的系統(tǒng)，而是出于其產(chǎn)品戰(zhàn)略考慮不愿也不能這樣做。盡管開(kāi)放式控制系統(tǒng)的市場(chǎng)增長(zhǎng)率較高，但由于值還不大，制造商不愿放棄已經(jīng)現(xiàn)成的數(shù)十倍的市場(chǎng)。
 
但這些公司對(duì)于開(kāi)放式系統(tǒng)市場(chǎng)并非采取坐視不理、惟我獨(dú)尊的態(tài)度。各個(gè)公司均在考慮用現(xiàn)有的產(chǎn)品組合出形式上的“開(kāi)放式”系統(tǒng)。如西門(mén)子的PCS7和 WinAC，實(shí)際上就是用工控機(jī)下掛S7的PLC而組成的概念性的系統(tǒng)，典型地表示了其一方面不想在開(kāi)放式系統(tǒng)領(lǐng)域落后于他人，同時(shí)又不想失去老用戶(hù)的復(fù)雜情結(jié)。類(lèi)似的還有Rockwell-AB的ControlLogic，F(xiàn)isher-rosemount的Delta-V等等，都是將原有的專(zhuān)用系統(tǒng)加上“開(kāi)放”的標(biāo)簽。他們的目的都是相同的，那就是既不錯(cuò)過(guò)開(kāi)放式系統(tǒng)這班航船，又可以將原有的系統(tǒng)盡量多地銷(xiāo)售出去。全力致力于真正開(kāi)放式系統(tǒng)開(kāi)發(fā)的反而是一些新興的相對(duì)較小的公司如美國(guó)的Opto22，SoftPLC，Controlsoft以及英國(guó)的Transmitton等等。這些公司沒(méi)有過(guò)去的包袱，所開(kāi)發(fā)的產(chǎn)品的市場(chǎng)目標(biāo)也不存在搶自己飯碗的問(wèn)題，所以他們可以沒(méi)有后顧之憂(yōu)地宣傳。由于他們的產(chǎn)品是充分考慮了開(kāi)放性的，今后將成為開(kāi)放性控制系統(tǒng)的新的生力軍。
 
3、國(guó)際開(kāi)放式系統(tǒng)研究存在的問(wèn)題
 
首先，開(kāi)放式控制系統(tǒng)的概念不清晰，沒(méi)有解決開(kāi)放控制系統(tǒng)的平臺(tái)問(wèn)題。各系統(tǒng)所采用的體系結(jié)構(gòu)并不一致，相互之間缺乏兼容性和互換性，因而各系統(tǒng)軟硬件不具備可移植性和互操作性。
 
其次，沒(méi)有充分利用像Windows、UNIX、OS/2等新型操作系統(tǒng)。軟件開(kāi)發(fā)思想與技術(shù)落后，始終處于甚至低于結(jié)構(gòu)化程序設(shè)計(jì)的水平。沒(méi)有充分利用面向?qū)ο蟆④浖赜玫溶浖こ讨械男吕碚?、新技術(shù)，而這些正是實(shí)現(xiàn)開(kāi)放性控制系統(tǒng)的關(guān)鍵所在。

 

【誠(chéng)信經(jīng)營(yíng)】【質(zhì)量可靠】【進(jìn)口原裝】【拆包防偽】
 
 
【超大庫(kù)存】【當(dāng)天付款】【順豐速運(yùn)】【歡迎搶購(gòu)】
本公司主要優(yōu)勢(shì)產(chǎn)品：
 
【..美國(guó)..英維思 Invensys FOXBORO I\A系統(tǒng), Triconex ESD系統(tǒng)】
 
【..美國(guó).. .AB ..1756系列,1785系列,1746系列,1747系列,1771系列】
 
【..瑞士.. .ABB.. 機(jī)器人 DSQC系列,ABB Advant OCS,ABB Procontic PLC CPU
 
】
 
【..法國(guó)....施耐德.. 140莫迪康昆騰系列處理器,內(nèi)存卡,電源模塊等。】
 
 
【..美國(guó)...通用電氣..GE..IC693/IC697系列】
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