Comparison of several Fieldbus models with influence in China at present

comparison of several Fieldbus models affecting China at present (reproduced)

Http://blog.163.com/[email protected]/blog/static/1936511220098135240135/

First, the origin of Fieldbus technology

Traditional field-level and workshop-level automation monitoring and information Integration System (including: Based on PC, PLC, DCS product Distributed control System), one of the main features is that the field layer equipment and controller connection is a one-to-one) an I/O point to the device of a measurement and control point) so-called the I/O wiring, signal transmission 4~ 20mA (transmit analog information) or VDC (transmit switching volume information) signal.

The disadvantages of such a system are:

1. The information integration ability is not strong: The Controller and the field equipment by the I/O connection, transmits the 4~20ma analog signal or the 24VDC and so on the switch quantity signal, and monitors the field equipment. In this way, the controller obtains the limited information, the massive data such as the equipment parameter, the fault and the fault record and so on data is difficult to obtain. The low level data, the information integration ability is not strong, can not fully meet the requirements of the CIMS system to the underlying data.

2. System is not open, the integration of poor, professional is not strong: In addition to the field equipment are connected by standard 4~20MA/24VDC, the system other software and hardware can only use a product. The lack of interoperability and interchangeability between different manufacturers ' products makes integration poor. This system rarely leaves an interface, allowing other vendors to integrate their own expertise in control techniques, such as control algorithms, processes, recipes, etc. into a common system, so there are few industry-oriented monitoring systems.

3. Reliability is not easy to guarantee: For a wide range of distributed systems, a large number of I/O cables and laying construction, not only increases costs, but also increases the system's unreliability.

4. Maintainability is not high: because the field-level equipment information is not complete, on-site equipment on-line fault diagnosis, alarm, recording function is not strong. On the other hand, it is very difficult to complete the parameters of remote parameter setting and modification of field equipment, which affects the maintainability of the system. Fieldbus technology can be summed up in several ways:

A. Develop bus communication protocols and technical standards

B. Automation manufacturers according to the standard production of a variety of automation products, including controllers, sensors, actuators, drives and control software

C. Practical application in, the use of a communication cable, all the field equipment connected to the controller, the formation of equipment and workshop-level digital communication network.

Second, the field bus technical characteristics

1. Because of the openness of the network protocol, the information exchange between the devices of different manufacturers can be realized. Users can, according to their own needs and considerations, from different suppliers of products to form a system of arbitrary size. Establish an open interconnection system in automation field via Fieldbus.

2. Interoperability and interoperability are information transmission and communication between interconnected devices and systems, and interoperability refers to the ability to replace each other with similar performance devices produced by different manufacturers.

3. Intelligent and functional autonomy of the field equipment it will be the sensor measurement, compensation meter, engineering volume processing and control functions scattered to the field equipment, only by the field equipment can complete the basic functions of automatic control, and can at any time to diagnose the operation of the equipment state.

4. The highly dispersed fieldbus of the system structure has constituted a new system structure of the full dispersion control system. It has fundamentally changed the distributed control system of DCS concentration and dispersed phase, simplifies the system structure and improves the reliability.

5. On-site environment adaptability work in the production site front-end, as the factory network at the bottom of the field bus, is designed for the field environment and design, can support twisted-pair, coaxial cable, optical cable, radio frequency, infrared, power line, etc., with strong anti-jamming ability, can use two-wire system to achieve electricity and communication, and can meet the

Third, the advantages of Fieldbus

Because of the above characteristics of fieldbus, especially the simplification of the FIELDBUS system structure, the control system from the design, installation, transportation to the normal production operation and maintenance, has demonstrated the superiority.

1. Save hardware quantity and investment because the field bus system scattered in the field of intelligent equipment can directly perform a variety of sensor control alarm and calculation functions, thus reducing the number of transmitters, no longer need a separate regulator, calculation unit, and no longer need the DCS system signal conditioning, conversion, isolation and other functional units and complex wiring, You can also use industrial PC as the operating station, which saves a lot of hardware investment, and can reduce the floor area of the control room.

2. Save installation costs The wiring of the Fieldbus system is very simple, a pair of twisted pair or a cable can usually be attached to a plurality of devices, so the cable, terminal, slot box, bridge the amount of use is greatly reduced, wiring design and the work of the joint proofreading also greatly reduced. When the need to increase the field control equipment, no need to add new cables, can be connected to the original cable in the vicinity, saving investment, but also reduce the design, installation of the workload. According to the calculation data of typical test project, it is shown that the installation cost can be saved more than 60%.

3. Save maintenance cost because the field control equipment has the ability of self-diagnosis and simple fault handling, and the relevant diagnostic maintenance information is sent to the control room through digital communication, the user can inquire the operation of neon equipment, diagnose and maintain information, so as to analyze the cause of failure and quickly eliminate it, shorten the maintenance downtime, and the system structure is simplified. Wiring is simple and reduces maintenance effort.

4. Users have a high degree of System Integration Initiative users can freely choose the equipment provided by different vendors to integrate the system. Avoid being "framed dead" by selecting a product of a certain brand. Using the device's selection range will not be a helpless for incompatible protocols and interfaces in system integration. Make the system integration process of the initiative firmly in the hands of the user.

5. Improve the accuracy and reliability of the system as the intelligent and digitized fieldbus equipment, compared with the analog signal, it fundamentally improves the accuracy of measurement and control, reducing the transmission error. At the same time, because the structure of the system is simplified, the equipment and wiring are reduced, the internal function of the field instrument is strengthened, and the transmission of the signal is reduced, which improves the reliability of the system.

6. In addition, because of its equipment standardization, functional modularity, it also has the advantages of simple design, easy to reconstruct. Four, several influential field bus technology

Since the late 80, there have been several fieldbus technologies that have gradually formed their impact and have shown their own advantages in a number of specific application areas. They have their own characteristics, but also show a strong vitality. The development of Fieldbus technology has played and will continue to play a larger role.

1. Foundation Fieldbus (FF)

Its predecessor is the United States Fisher-rosemount Company-led, United Foxboro, Yokogawa, ABB, Siemens and other more than 80 companies developed by the ISP agreement and France Alstom, Germany and other French companies, led by several WORLDFIP agreement with 150 companies in Europe and North America. The foundation Fieldbus is supported by major suppliers of automatic control equipment in the field of Process control. These companies have a thorough understanding of the functional needs of the industry's underlying network, as well as the ability to develop the field-controlled equipment in this area. Therefore, the bus has considerable authority. At present, it has only low-speed fieldbus protocols and products. Low-speed Fieldbus speed of 31.25kbps, communication distance of up to 1900 meters (can be extended repeater), can support bus power supply, support intrinsically safe explosion-proof environment. The upper layer is connected directly to the industrial Ethernet. The physical transmission media can support twisted pair, optical cable and wireless transmission, and the protocol complies with the IEC61158-2 standard. The transmission signal of its physical medium is based on Manchester code. This is a very promising fieldbus. At present, its application areas mainly in the process automation mainly, such as petrochemical, chemical and other fields, mainly used in the production process of continuous control.

2. WorldFIP

WORLDFIP Fieldbus is mainly developed by several multinational companies in France and is a French standard and European standard. The WORLDFIP organization currently has more than 100 membership lists. In June 1994, the European part of the WORLDFIP remained independent after the merger of WORLDFIP's North American part with the ISP became FF. The French-based WORLDFIP organization has adopted a flexible strategy: actively promote mature WORLDFIP technology and products, seize the market, on the other hand, also actively support the establishment of the world's only fieldbus standard work, support IEC fieldbus standards, and is ready to Once the IEC standard is passed, a product connected to the IEC standard is immediately available to keep itself in an invincible position. It is also a member of the FF. The WORLDFIP uses a three-layer structure: Physical layer, Data link layer and application layer.

A. Physical layer: The WORLDFIP physical layer adopts the international standard IEC 61158-2, which ensures that information is transferred from one device to other devices connected to the bus, and the transmission medium is shielded twisted pair or optical fiber. The transfer rates are 31.25kb/s, 1mb/s, and 2.5mb/s, and the standard rate is 1mb/s.

B. Data link layer: The Data Link layer is responsible for transmission, error, and access control. There are two kinds of address spaces, which are periodic and non-periodic data exchange, variable addressing and message addressing, and the communication mode of the producer-user, broadcast Id-dat inquiry Frame-response Rp-dat reply frame, and the centralized media access control by the bus arbiter. The bus arbitrator and producer have space-time uniqueness respectively.

C. Application layer: The WORLDFIP application layer provides two kinds of access to the variable and the message.

WORLDFIP a variety of hard and soft products from communication chips to development tools, there are more than 350 kinds. With these products, field equipment such as transmitters, actuators, I/O or processing units (PC, PLC, etc.) can be conveniently attached to the WORLDFIP fieldbus.

WORLDFIP has many features and advantages in technology.

A. Practicality. WORLDFIP uses the IEC physical layer standard, supports the cable redundancy, most of the protocols are cured on the hardware, the stability is strong; its producer/user mode and bus arbiter scheduling method ensures that a large amount of information is transmitted on a bus without interfering with the communication of time-bound variables.

B. It has very strong anti-jamming ability and real-time performance, can fully meet the IEC EMC standards for electromagnetic compatibility, its communication mode supports background transmission of messages, cycles and event variables to ensure that the diagnostic information transmission does not affect real-time control.

C.WORLDFIP Fieldbus regardless of low or high speed, only a set of communication protocols, so do not need any bridge or gateway, low speed and high-speed network interface only with software to complete.

D. Its producer/user (Producer/consumer) mode and bus arbiter are especially suitable for industrial process control. Both IEC standards and FF specifications Use this mode of communication, except for the names. The terms for FF are publisher/receiver (Publisher/subscriber) and Link Activity Scheduler (LAS). This also explains why WORLDFIP supports IEC standards because it is relatively easy to convert to IEC technology.

E.WORLDFIP is an open fieldbus, WORLDFIP product designers, users or integrators can get help from the WORLDFIP organization. These help include: technical training, technical support, and technical testing. It can be based on users, integrators and developers to provide a variety of training services to help you in the product development and application and installation process, the correct use of the WORLDFIP protocol and a variety of devices, to provide customers with product planning, hardware design, software design and testing support , but also for the manufacturers to develop and sell products to provide technical identification. This identification is a test of the interoperability capabilities of the devices in a system using the WORLDFIP network.

The WORLDFIP organization currently has more than 100 members, and they have also extended this technology to a wide range of applications while jointly researching and developing the technology. After more than more than 10 years of application and improvement, WORLDFIP is a fully fledged technology with a full range of communication products and development tools. WORLDFIP Fieldbus has been widely used in power generation and distribution, building automation, mechanical processes, locomotives, railway transportation, shipping and shipbuilding, Metro, food and beverage industry, nuclear industry, chemical industry, aviation and aerospace, automotive manufacturing and other automation control areas.

3. PROFIBUS

Profibus is the Fieldbus standard for German national standards DIN19245 and European standard EN50170. The PROFIBUS series is made up of PROFIBUS-DP,PROFIBUS-FMS,PROFIBUS-PA. The technology was launched by more than 10 German companies and research institutes based in Siemens Corporation. It uses the physical layer, data link layer of the OSI model. The FMS also uses the application layer. The transmission medium can be twisted-pair, or it can be an optical cable. Up to 127 sites can be hooked up. DP is a high-speed low-cost communication for device-level control systems and decentralized I/O communication, using DP can replace 24VDC or 4~20ma signal transmission, the data transmission type is RS485. Suitable for applications in the field of machining automation. FMS means the field information specification, for the workshop-level monitoring network, is a token structure, real-time multi-master network, the data transmission type is RS485, the transmission rate is 9.6kbps~12mbps, the maximum transmission distance at 12Mbps 100m, 500Kbps 400m. PROFIBUS-FMS is suitable for textile, building automation, programmable controller, low voltage switch and so on. PA is designed for process automation, data transmission using digital, bit synchronization, Manchester code. Transmission rate: 31.25kbit/s, voltage type. The sensor and actuator can be linked on a bus, and has intrinsically safe explosion-proof function, bus power supply. The physical layer complies with the IEC61158-2 standard. Since Profibus has three different buses for different applications, it has a wide application field. The DP and FMS systems use the same transmission technology and a unified bus access protocol, so the two systems can operate simultaneously on the same cable. The PA and DP need to be connected through a coupler.   3. P-net

P-net is a Danish national and European standard. Its user organization currently has nearly 100 companies, members of the Institute. is a multi-master slave-master bus (can accommodate up to 32 master stations per segment), using shielded twisted-pair cable RS485, each segment of the bus up to 1200 meters, each segment can connect up to 125 devices, bus segments using repeaters. The data is transmitted asynchronously with NRZ encoding, and the transfer rate is 76.8kbit/s. Its main applications are in the agricultural and food processing industries, such as: dairy plants, breweries, agro-environmental control, animal husbandry systems, in other areas such as asphalt and cement production, textile industry, quality control systems, power plants, solar power plants and other fields are also used.

4. LonWorks

LON (local operating networks) bus is a local operation network introduced by American Echelon Company in 1991, which provides a strong means of realizing distributed monitoring system. With its support, a new generation of intelligent low-cost on-site measurement and control products was born. In order to support Lon bus, Echelon company developed LonWorks Technology, which provides a complete development platform for Lon bus design and finished products. Currently using LonWorks technology products widely used in industrial, building, home, energy and other automation fields, Lon Bus has become one of the most popular fieldbus. The LonWorks protocol supports the OSI seven-layer protocol, which is implemented using the form of network variables. Network variables The data transfer between nodes is done only through the interconnection of individual network variables. And because of the support of hardware chip, it realizes the real-time and interface of the intuitive, concise fieldbus application requirements. The neuron chip (neuron chip) is the core of LonWorks technology, it is not only the Lon bus communication processor, but also as a general-purpose processor for acquisition and control, all the operation of the network in LonWorks technology is actually done through it. Its main application areas are in building automation control. Due to its excellent performance/price ratio, it has been applied in other fields.

5. CAN

Can is the abbreviation for Control area Network, which was first introduced by the German Bosch company for data communication between the internal measurement and execution components of the vehicle. Its bus specification has been developed as an international standard by ISO International standards Organization. Thanks to the support of Motorola, Intel, Ohilip, Siemence, NEC and other companies, it has been widely used in discrete control fields. The can protocol is also based on the open system Interconnection model of the international Standard Organization, but its model structure is only three layers, that is, only the physical layer, data link layer and the application layer of the top layer are taken from the OSI underlying. Its signal transmission medium is twisted-pair wire. The communication rate is up to 1mbps/40m and the direct transmission distance is up to 10km/5kbps. The number of hooks can be up to 110 units. Can signal transmission uses the short frame structure, the effective byte number of each frame is 8, thus the transmission time is short, the probability of being disturbed is low. When the node is seriously wrong, it has the function of automatic shutdown to cut off the connection between the point and the bus, so that the other nodes on the bus and its communication are not affected, and have strong anti-jamming ability.

6. HART

Hart is an abbreviation for the Highway addressable remote transducer (open communication protocol for addressable remote sensor high-speed channels). Originally developed by Rosemount Company and supported by more than 80 well-known instrument companies, the Hart Communications Foundation was established in 1993. Strictly speaking, it is not a fieldbus. It is the realization of digital signal communication on the existing analog signal transmission line, which belongs to the transitional product in the process of transforming the analog system into the digital system, so it has a strong market competition ability in the current transitional period, and has got a relatively fast development. Hart uses a unified device description Language DDL. Field device developers use this standard language to describe device features, and the Hart Foundation is responsible for registering and managing these device descriptions and compiling them into a device description dictionary, which uses DDL technology to understand the characteristics of these devices without having to develop a dedicated interface for those devices. But because of this kind of analog digital mixed signal system, it is difficult to develop a kind of communication interface chip which can meet the requirements of each company. Hart can use bus power, can meet the intrinsic safety explosion-proof requirements, and can be composed of hand-held programmer and management system host as the main equipment of the dual-master System.

Four, several field bus application field

Bus type	Manufacturing	Transmission and distribution	Public Building automation	Instrument Process Control
WorldFIP	***	***	**	***
Profibus	***	**	**	***
Ff				***
LonWorks	*	*	***
CAN	***
DeviceNet	***	*

V. International STANDARDS of IEC

Buses that are striving to become a subset of the Fieldbus International standards are:

Type 1 Control Net

Type 2 Profibus

Type 3 p-net

Type 4 FF HSE

Type 5 SwiftNet

Type 6 WorldFIP

Type 7 Interbus

The current Fieldbus closest to the IEC standard is FF and WORLDFIP only.

Comparison of several Fieldbus models with influence in China at present