Analysis on the development status of the strategy

  • Detail

With the rapid development of networking technology, the vigorous rise of fieldbus technology and its wide application in the field of industrial control, domestic and foreign control system manufacturers have launched their own new distributed control products, which has promoted the closer integration of 4C (computer, control, communication, CRT) technology in the field of industrial control, The new control system is more powerful and reliable. The birth of each new control system is usually accompanied by the design and implementation of an upper strategy configuration software. The system control strategy configuration software is the upper software part of the distributed control system, which is the interface between the user and the system. It is an indispensable part of the system to complete the logical configuration of the field equipment operation in the control system, so as to realize the control of the system. In the face of such a situation in which a wide variety of distributed control systems and strategic configuration software with different characteristics compete, it is worth discussing and carefully studying the direction of the strategic configuration software, which plays an important role in the system

second, Historical Review

the development of system control strategy configuration software is closely related to the emergence and development of distributed control system

the early distributed control system was closed. Each system manufacturer independently produced its own product components, such as i/o modules, control stations, operator stations and engineer stations, and completely independently designed and developed the system network and control configuration software. Every link in the use of users should be restricted by the manufacturer. The hardware products of various manufacturers cannot be replaced each other, and the systems and protocols used in the communication network are also different

in recent years, with the continuous development of computer technology and the continuous strengthening of system software and hardware functions, this situation has improved. Most operator stations and engineer stations use general-purpose computers, and the software and hardware of the computer system are interchangeable; At the same time, in terms of communication networks, major manufacturers have also begun to adopt general-purpose computer networks with strong compatibility, such as Ethernet, rs-232/484 and so on. The birth of fieldbus technology has injected new vitality into the distributed control system of Jung industrial media Co., Ltd. as a leading B2B industrial information provider, making the distributed control system have a truly fully distributed system. The formulation of Fieldbus international standard further improves the interoperability and interchangeability of the control system

compared with the rapid development of distributed system hardware and underlying software, the development of upper strategy configuration software is relatively backward in versatility and interchangeability. Each system manufacturer develops the upper strategy configuration software independently, and the configuration software is also very different in design style and specification, especially in interface friendliness, ease of use and configuration efficiency. The direct consequence is that every time users (such as field engineers) come into contact with a new control system, they must re learn the architecture, programming language and use method of their strategic configuration software, which forms a bottleneck to improve production efficiency; For manufacturers, they need to constantly improve software products according to various needs put forward by users, and will invest a lot of human and material resources in the development, maintenance and upgrading of configuration software

PLC control system based on microprocessor has made rapid development since its birth in 1968, and has become a widely used control equipment in the field of industrial control. When all kinds of PLC products poured into the market, the International Electrotechnical Commission (IEC) timely and correctly guided the healthy development of PLC system. In 1993, the international standard IEC61131 for PLC was officially issued, in which part 3 standardized five programming languages and their basic elements of PLC, of which three were graphical languages (function block diagram, ladder diagram and sequential function diagram), and two were textual languages (instruction table and structured text). This standard has played a decisive role in promoting the development of PLC software technology and even the whole industrial control software. The programming language of IEC standard is convenient and practical, with a high degree of standardization, so that users can soon be familiar with the configuration work, and can quickly apply the original knowledge to the new system, eliminating users' repeated learning of different configuration software languages, and greatly improving work efficiency; For manufacturers, human and material resources can be invested in the hardware network or other aspects of the control system. After the birth of IEC standard, PLC control system manufacturers at home and abroad have successively adopted their programming language to standardize their software products. In this step, PLC is in the forefront of all kinds of distributed control systems

III. analysis of the current situation at home and abroad

at present, the system control strategy configuration software is mainly for FCS system, DCS system and PLC system. According to the realization of the system and its scale, the realization forms of configuration software are different, but the function can be divided into two parts: physical configuration and logical configuration for the control system. Physical configuration mainly refers to the software configuration of system composition, including the selection of field equipment and its function blocks, and some configuration processes involving system composition; Logic configuration is mainly the planning and design of the control strategy used for the operation of the control system, including the selection, connection, parameter setting and communication configuration of each function block in the field equipment, system variable setting, reading and writing, etc. Logic configuration is a process of programming system control strategy

with the gradual promotion of IEC standard in the application of PLC system configuration software, some domestic and foreign distributed control system (DCS) manufacturers also began to pay attention to the significance of this international standard for the standardization of DCS system configuration software, and successively applied IEC standard to their DCS system configuration software

On the other hand, with the rise and development of fieldbus technology, some domestic fieldbus control system manufacturers also began to apply IEC standards to their FCS configuration software products

at present, the development of upper strategy configuration software in distributed control system has the following characteristics

(I) the degree of implementation of IEC standard compatibility is different

the degree of implementation of IEC standard compatibility, the difference mainly focuses on two points: (1) the depth of standard implementation; (2) In terms of the number of programming languages specified in the standard. IEC standard not only regulates the syntax, semantics, expression and display rules of programming language elements, but also specifies the overall organization mode and construction form of control program and the communication rules to be followed between program modules. The partial and full implementation of these specifications forms the depth problem of standard compatibility. At present, the configuration software products of some major PLC system manufacturers have achieved full compatibility with IEC standards, that is, almost all the contents specified in IEC standards. DCS system is far less compatible with IEC standard than PLC system, and some products are only 1 Magnetic ring: 13.5 (inner) x32.8 (outer) x7.9 (thick), model: 201542 is compatible with IEC standards in some aspects of programming language elements, such as the rules of expression and display; Other products are compatible with IEC standards in terms of syntax, semantics, expression and display rules of language elements, but they still have not achieved the organization of the overall control program. Scientists are preparing to enable the world's first machine for clearing the largest marine plastic waste dump on the earth, which is compatible with specifications such as mode and construction form, communication rules to be followed between program modules, and the degree of realization is also very different. On the other hand, there are also great differences in the number of programming languages regulated by the standard. Although the IEC standard does not stipulate that all the five programming languages must be realized, after all, the realization of more programming languages means that users can be provided with more choices, which makes the configuration method more flexible and efficient, and is more conducive to engineers to express their logical thinking of face-to-face control

it should be pointed out that the system functions of PLC and DCS are different. PLC system is usually used for discrete logic control and sequential control. Measurement and control are mainly digital signals. The control strategy programming language usually adopts LD (ladder diagram), IL (instruction table) and SFC (sequential function diagram); DCS system is mainly used for continuous control, and its object signal is mainly analog quantity. The control strategy programming language usually adopts FBD (function block diagram) and st (structured text). Of course, there are historical reasons for the differences in the compatibility of PLC system and DCS system with IEC standards. IEC standard was initially formulated based on PLC system, and many places are aimed at the characteristics of PLC, which is not completely applicable to some early DCS systems. But at the same time, it should be noted that the obvious boundary between PLC and DCS in system structure and function is rapidly disappearing, and the two systems can usually replace each other. Therefore, it is only a matter of time before DCS finally achieves full compatibility with IEC standards

(II) PLC and DCS systems are the mainstream, and FCS has great potential to be tapped

at present, the design and development of system control strategy configuration software by domestic and foreign manufacturers are still mainly focused on PLC system and DCS system, and FCS system only accounts for a relatively small part. The main reason is that the current process control system still takes PLC and DCs as the main body, FCS only exists as a field level digital fully distributed control system, and DCS and MIS systems are still needed to complete the high-level coordination, scheduling and management above the process level. At the same time, the upper strategy configuration software developed for FCS system mainly adopts foundation fieldbus technology. The control system based on FCS completely distributes the control functions to the field equipment at the bottom, realizing the distributed control in a complete sense, which is qualitatively different from the traditional DCS in architecture. The function blocks in the logical configuration are distributed to the physically dispersed field devices for execution, and the connection and communication between different function blocks in each device should be realized at the same time, which is quite different from the traditional single processor for all control behaviors, and it is also more difficult to realize. At present, the standardization of function block diagram programming still needs to be officially promulgated and popularized by IEC61499 and iec61804. At present, there is little development of upper strategy configuration software corresponding to FCS system. For example, there is no control strategy configuration software for FCS based on WorldFIP protocol. It can be seen that while PLC and DCS system control strategy configuration software occupy the mainstream position, the research and development of FCS system control strategy configuration software has great potential, which has very practical and positive significance in theory and practice

(III) software design styles are different, and the function realization has its own advantages and disadvantages.

the coexistence of multiple software development platforms determines that the design styles of configuration software are very different, and the differences in the thinking mode, programming habits and even aesthetic concepts of software developers and designers further aggravate the degree of this difference. At the same time, because there is no specification for the design of configuration software, the implementation methods of the same function also have their own emphasis, and the implementation of configuration function has its own advantages and disadvantages. For example, syscon software of SMAR system302 system can realize the dual functions of physical configuration and logical configuration of FCS System at the same time, but it is provided to the user's group

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