【導讀】當今的控制系統(tǒng)被廣泛運用于許多領域。從單純的工業(yè)控制系統(tǒng)到協(xié)同控制。則是這兩者的變種。被應用的控制系統(tǒng)的種類取決于技術要求。而且，實踐表明，經濟和社會因素也對此很重要。完整的文獻記載和技術支持。經濟因素使決定趨向于協(xié)同工具。碼并可以更快速地解決問題是家庭控制系統(tǒng)的要求。多年的操作經驗表明哪個解。決方法是最主要的不重要，重要的是哪個可行。由于異類系統(tǒng)的存在，針對不同。協(xié)議的支持也是至關重要的。系統(tǒng)，和CCS工具，以及它們之間的操作?？刂葡到y(tǒng)，德國電子同步加速器研究所普遍開始研究過程控制。此外，在實現(xiàn)對復雜的低溫冷藏系統(tǒng)的開閉過程中，頻率項目顯得尤為重要。有必要增加接口解決總線問題并增加運算能力，以便于低溫控制。HERA試驗控制的要求。而通信網絡的暢通與否取決于不存檔的數(shù)據總量，不取決于報警系統(tǒng)。問題也迫使計劃提前。最后，與Orsi公司的合同被取消了。該PVSS腳本庫允許執(zhí)行復雜的序列以及復雜的圖形。

　　

【正文】 o the clients. In any case a lot of overhead for ?just? checking alarm limits. DCS system again have the advantage that clients can either register themselves for alarm states und thus get the information forwarded or are configured to send alarmchanges to certain destinations spread around the control system. The latter case is only possible for systems which in total are configured with all the nodes taking part in the controls work. 3 Trending and Archiving Trending has bee an important business in control systems architectures. Trends are necessary to trace error conditions or for post mortem and performance analysis of the controlled plant. Besides some custom implementations which are capable to store the data of plete control objects, most of the trending tools archive scalar data. Additional features like conditional trending or correlation plots make up the difference between individual implementations. 4 Programming Interfaces With respect to open programming interfaces PLC?s and DCS systems have a mon strategy. They are running reliably because there?s no way to integrate custom code which could interfere with the internal processing. As a consequence the customer has to order ?specials? which are extremely expensive – or fet about it and use the system as a black box. Since SCADA systems by definition must be able to municate with a variety of I/O subsystems they already have some built in API?s which allow to integrate custom functionality. Specially collaborative systems need a certain openness to fulfill all the requirements from various development groups. Programming interfaces on all levels like fontend I/O, frontend processing, working etc. are mandatory. A clear advantage for this type of system. 5 Redundancy If redundancy means the seamless switch which takes over all the states and all the values of the I/O and all states of all programs currently running, it is a domain of only a few DCS systems. Custom or CCS implementation do not provide this kind of functionality. Maybe because of the immense effort and the fact that it is only required in rare cases. Besides processor redundancy, redundant works or I/O subsystems are available for certain mercial DCS systems. Again – a domain which is not covered by SCADA or CCS implementations. Advanced safety requirements may be covered by redundant PLC subsystems. These are for instance installed in (nuclear) power plants. Requirements for Personal Protection Systems (PPS) can sometimes only be fulfilled by redundant PLC?s. In process controls redundant PLC?s are only used in rare cases. 6 Namespace The flat namespace of SCADA systems has already been described in the alarm section. Some SCADA systems (like PVSSII) provide the notion of control objects or structured data which is a rare case. In all other cases so called field objects must be specified. These are objects which consist of a list of properties (implemented as I/O points) and a set of methods ( implemented asmacros or function calls). One of these approaches is the UniNified Industrial COntrol System (UNICOS) at CERN [5]. DCS systems and most of the custom/ collaborative systems are record – or device oriented. The difference being that typically one record is connected to a single I/O point and provides this way all sub features of a record implementation like individual engineering units, display and alarm limits. The device oriented approach allows to connect several I/O points. The major difference being the fact that an object oriented device implementation provides methods and states for a device while (EPICS) records only serve a certain set of built in functions. Naming hierarchies are not specific to a type of implementation. They are available for some systems of any kind. For sure hierarchical naming schemes are desirable. IMPLEMENTATION STRATEGIES After having shown all the possible controls approaches it is time to have a look at the implementation of control systems. Starting from the I/O level one has to decide whether mercial solution are required, feasible or wanted. Special I/O does not always require custom solution for the fontend controller. Signals can be converted into standard signals but this does not apply for all kinds of signals. Resolution, repetition rates and signal levels might require custom developments which must be integrated into the overall control architecture. Even if the signals can not be connected to standard I/O interfaces it might be possible to develop I/O controllers which implement a field bus interface which allow the integration with mercial control systems. Once this level of integration is not possible custom frontend controllers like VME crates e into play. Besides the decision whether special I/O requires dedicated custom solutions one has to decide who will do which part of the work? Does for instance the necessity of VME crates prohibit the delivery of a ?turn key? system built by industry? Or does a PLC based frontend system require a mercial SCADA system for high level controls? Turn Key Systems It is a clear trend in industry to deliver turn key systems. It allows a modular design of the whole system. Individual ponents can be subcontracted to several panies and tested locally. Once delivered to the construction site the primary acceptance tests have already been passed and the second phase, to integrate the subsystem into the global control system begins. While the detailed specification of control loops etc. is now part of the subsystems contract, the customer has to specify clearly how much information of the subsystem must be made available, what the data structures will look like and which connection (field bus/ Ether) will be used. Most turn key systems are delivered with PLC?s. The constru