1756-OF8，1756-OF8

1756-OF8

 

1756-OF8

用于汽車內(nèi)部測量與執(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模擬信號和調(diào)制數(shù)字信號的現(xiàn)場總線協(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)變過程中的過渡產(chǎn)品，因而在當前的過渡時期具有較強的競爭力，得到了較快的發(fā)展。
 
3、現(xiàn)場總線的未來
 
現(xiàn)場總路線將成為工業(yè)控制發(fā)展的革命性飛躍，有關(guān)現(xiàn)場總線的報道層出不窮，其中令人關(guān)注的焦點集中在能否出現(xiàn)全統(tǒng)一的現(xiàn)場總線標準。
 
不同的現(xiàn)場總線有不同的功能，各有其適用的場合，靠一種現(xiàn)場總線打天下的想法看來不太現(xiàn)實。當然，從另一方面來講，相當一部分現(xiàn)場總線是大同小異的，技術(shù)上非常接近，在優(yōu)勝劣汰的環(huán)境下同類總線終將趨于統(tǒng)一。但商業(yè)利益上的激烈競爭是這個問題的主要原因，對于現(xiàn)場總線形成巨大影響的自動化廠商，因為要盡可能維護自身的地位和利益而不愿放棄其已擁有的現(xiàn)場總線;因此，在未來較長的一段時間內(nèi)，現(xiàn)場總線標準之爭會越演越烈。
開放式控制系統(tǒng)

控制系統(tǒng)
 
1、開放性控制系統(tǒng)的概念
 
長期以來，制造與生產(chǎn)企業(yè)所采用控制系統(tǒng)大多是專用的、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準度身定制的。無論是DCS，PLC還是FCS，雖然它們具有結(jié)構(gòu)簡單、技術(shù)成熟、產(chǎn)品批量大等優(yōu)點，但相對日新月異的生產(chǎn)要求，也越來越暴露出其固有的缺點。在許多情況下,當用戶要想進行功能上的擴展或變化時，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，都是比較困難的。這無形中不僅提高了制造企業(yè)的成本，也成為控制系統(tǒng)升級換代的“瓶頸”。
 
由于市場競爭越來越劇烈，從而要求制造商具有較強的市場適應(yīng)能力，這一趨勢促成了一個新概念的產(chǎn)生，即模塊化、可重構(gòu)、可擴充的軟硬件系統(tǒng)，這就是開放式控制系統(tǒng)。這一系統(tǒng)為制造廠提供了將其技術(shù)與任何第三方的技術(shù)或產(chǎn)品進行集成的可能性。
 
2、國際控制系統(tǒng)制造商的開放路線
 
據(jù)國際機構(gòu)美國自動化市場研究公司ARC（Automation Research Corp.）調(diào)查預(yù)計，在亞洲，基于PC的控制系統(tǒng)、以太網(wǎng)的I/O模件等開放式系統(tǒng)的銷售額預(yù)計近兩年的增幅達到145%，所以，可見在控制系統(tǒng)市場中，開放系統(tǒng)的增長率遠遠高于傳統(tǒng)的控制系統(tǒng)。
 
幾乎所有的制造商都已認識到了開放系統(tǒng)必將是自動化系統(tǒng)的未來。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“開放性”的字樣。但是，他們的開放性通常都是在原有的系統(tǒng)上層加上一些接口實現(xiàn)局部的互連和通信，并非真正意義上的開放。不要說控制器的底層，就是在操作站這一層，他們在實現(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法開發(fā)出全開放的系統(tǒng)，而是出于其產(chǎn)品戰(zhàn)略考慮不愿也不能這樣做。盡管開放式控制系統(tǒng)的市場增長率較高，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。
 
但這些公司對于開放式系統(tǒng)市場并非采取坐視不理、惟我獨尊的態(tài)度。各個公司均在考慮用現(xiàn)有的產(chǎn)品組合出形式上的“開放式”系統(tǒng)。如西門子的PCS7和 WinAC，實際上就是用工控機下掛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放式系統(tǒng)領(lǐng)域落后于他人，同時又不想失去老用戶的復(fù)雜情結(jié)。類似的還有Rockwell-AB的ControlLogic，F(xiàn)isher-rosemount的Delta-V等等，都是將原有的專用系統(tǒng)加上“開放”的標簽。他們的目的都是相同的，那就是既不錯過開放式系統(tǒng)這班航船，又可以將原有的系統(tǒng)盡量多地銷售出去。全力致力于真正開放式系統(tǒng)開發(fā)的反而是一些新興的相對較小的公司如美國的Opto22，SoftPLC，Controlsoft以及英國的Transmitton等等。這些公司沒有過去的包袱，所開發(fā)的產(chǎn)品的市場目標也不存在搶自己飯碗的問題，所以他們可以沒有后顧之憂地宣傳。由于他們的產(chǎn)品是充分考慮了開放性的，今后將成為開放性控制系統(tǒng)的新的生力軍。
 
3、國際開放式系統(tǒng)研究存在的問題
 
首先，開放式控制系統(tǒng)的概念不清晰，沒有解決開放控制系統(tǒng)的平臺問題。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，沒有充分利用像Windows、UNIX、OS/2等新型操作系統(tǒng)。軟件開發(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)計的水平。沒有充分利用面向?qū)ο?、軟件重用等軟件工程中的新理論、新技術(shù)，而這些正是實現(xiàn)開放性控制系統(tǒng)的關(guān)鍵所在。

 

【誠信經(jīng)營】【質(zhì)量可靠】【進口原裝】【拆包防偽】
 
 
【超大庫存】【當天付款】【順豐速運】【歡迎搶購】
本公司主要優(yōu)勢產(chǎn)品：
 
【..美國..英維思 Invensys FOXBORO I\A系統(tǒng), Triconex ESD系統(tǒng)】
 
【..美國.. .AB ..1756系列,1785系列,1746系列,1747系列,1771系列】
 
【..瑞士.. .ABB.. 機器人 DSQC系列,ABB Advant OCS,ABB Procontic PLC CPU
 
】
 
【..法國....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...通用電氣..GE..IC693/IC697系列】
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