Detailed exploration of fieldbus technology, all aspects of PROFIBUS fieldbus technology

“Fieldbus technology is a general term, and for practical applications, fieldbus technology can be divided into various categories. In order to improve everyone’s understanding of fieldbus technology, this article will introduce the relevant content of PROFIBUS fieldbus technology. If you are interested in fieldbus technology, keep reading.

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Fieldbus technology is a general term, and for practical applications, fieldbus technology can be divided into various categories. In order to improve everyone’s understanding of fieldbus technology, this article will introduce the relevant content of PROFIBUS fieldbus technology. If you are interested in fieldbus technology, keep reading.

1. Overview of PROFIBUS

PROFIBUS is an international, open, field bus standard that does not depend on equipment manufacturers. PROFIBUS transmission speed can be selected in the range of 9.6kbaud~12Mbaud and when the bus system is started, all devices connected to the bus should be set to the same speed. It is widely used in manufacturing automation, process industry automation and automation in other fields such as building, transportation and power. PROFIBUS is a field bus technology used for factory automation workshop level monitoring and field device level data communication and control. The distributed digital control and field communication network can realize the monitoring from the field equipment level to the workshop level, thus providing a feasible solution for the realization of the comprehensive automation of the factory and the intelligentization of the field equipment.

2. Features of PROFIBUS

As a widely used field bus technology in the industry, Profibus has its own characteristics in addition to the advantages of a general bus. The specific performance is as follows:

(1) The transmission information length is 255B, the data length is 244B, and the typical length is 120B.

(2) The network topology is linear, tree or bus, with active bus termination resistors at both ends.

(3) The transmission rate depends on the network topology and bus length, ranging from 9.6Kb/s to 12Mb/s.

(4) The number of stations depends on the signal characteristics, such as the shielded twisted pair, each segment is 32 stations (without repeaters), and there are 127 stations with repeaters.

(5) The transmission medium is shielded/unshielded twisted pair or optical fiber.

(6) When using twisted pair, the transmission distance can reach 9.6km, and when using optical fiber, the transmission length is 90km.

(7) The transmission technology is RS-485 transmission of DP and FMS, IEC1158-2 transmission of PA and optical fiber transmission.

(8) Adopt a single bus orientation protocol, including token passing between master stations and master-slave mode between slave stations.

(9) Data transmission services include two types: cyclic and acyclic.

Three, the composition of PROFIBUS field bus

PROFIBUS consists of three compatible parts, namely PROFIBUS-DP (Decentralized Periphery). PROFIBUS-PA (Process Automation). PROFIBUS-FMS (Fieldbus Message SpecificaTIon).

PROFIBUS CDP: A high-speed, low-cost communication for device-level control systems and distributed I/O communication. Using PROFIBUS-DP can replace 24VDC or 4-20mA signal transmission.

PORFIBUS-PA: Designed for process automation, it enables sensors and actuators to be connected on a single bus with intrinsic safety specifications.

PROFIBUS-FMS: For workshop-level monitoring network, it is a token structure. Real-time multi-master network.

Four, PROFIBUS transmission technology

PROFIBUS provides 3 kinds of data transmission technologies: RS-transmission technology for DP/FMS, IEC1158-2 transmission technology for PA, and optical fiber transmission technology.

1. RS-485 transmission technology for DP/FMS (H2)

Since the DP and FMS systems use the same transmission technology and unified bus access protocol, the two systems can operate simultaneously on the same cable. RS-485 transmission is a commonly used transmission technology for PROFIBUS, and the cable is a shielded twisted pair copper wire.

2. IEC1158-2 transmission technology for PA (H1)

IEC1158-2 is a bit synchronization protocol that can carry out continuous transmission without current. It is used in PROFIBUS-PA and can meet the requirements of chemical and petrochemical industries. It maintains its intrinsic safety and powers field devices via the bus.

3. Optical fiber transmission technology

When the PROFIBUS system is applied in a large environment, fiber optic conductors can be used to increase the high-speed transmission distance. The characteristics of the optical fiber vary with the type of material used, and inexpensive plastic fiber conductors can be used for distances less than 50m, and glass fiber conductors can be used for distances less than 1km.

Five, PROFIBUS application

A typical factory automation system should be a three-level network structure, and the Profibus-DP/PA control system based on the fieldbus is located in the lower layers of the factory automation system, namely the field level and the workshop level. Fieldbus Profibus is a digital communication network for field level and workshop level.

1. Field device layer

The main function is to connect field devices such as distributed I/O, sensors, drives, actuators, switches,[3]Lighting equipment, complete on-site equipment control and inter-equipment chain control. The master station is responsible for bus communication management and communication of all slave stations. All equipment production process control programs on the bus are stored in the master station and executed by the master station.

2. Workshop monitoring layer

Workshop-level monitoring is used to complete the connection between production equipment in the workshop, such as the connection between the main controllers of three production lines in a workshop, to complete workshop-level equipment monitoring. Workshop-level monitoring includes online monitoring of production equipment status, equipment failure alarm and maintenance, etc. It usually also has workshop-level production management functions such as production statistics and production scheduling. Workshop-level monitoring usually requires a workshop monitoring room on the operator workstation and printing equipment. Workshop-level monitoring network can use Profibus-FMS, it is a multi-master network, in this, the data transmission speed is not important, but to be able to transmit large-capacity information.

3. Factory management

The workshop operator workstation can be connected to the workshop office management network through the hub, and the workshop production data can be sent to the workshop management. As a sub-network of the main network, the workshop management network is connected to the factory backbone network through switches, bridges or routers, and integrates the workshop data into the factory management.

The Ethernet in the workshop management layer is the communication protocol standard of IEEE802.3 and IETFTCP/IP. The backbone network of the factory can adopt networks such as FDDI or ATM according to the actual situation of the factory.

Six, the development status of PROFIBUS

(1) Multiple buses coexist, among which the application of PROFIBUS bus runs through major fields: according to the market survey of ARC Company in the United States, the demand for various field buses in the world market is: process automation 15% (FF, PROFIBUS-PA, WorldFIP) , 18% in the field of medicine (FF, PROFIBUS-PA, WorldFIP), 15% in manufacturing (PROFIBUS-DP, DeviceNet), 15% in transportation (PROFIBUS-DP, DeviceNet), 34% in aviation and defense (PROFIBUS-FMS, LonWorks , ControlNet, DeviceNet), agriculture is not counted (P-NET, CAN, PROFIBUS-PA/DP, DeviceNet, ControlNet), buildings are not counted (LonWorks, PROFIBUS-FMS, DeviceNet). It can be seen that, with the passage of time, there will be only six or seven types of buses that occupy about 80% of the market, and their application fields are relatively clear. For example, FF and PROFIBUS-PA are suitable for processes in process industries such as metallurgy, petroleum, chemical industry, and medicine. Control, PROFIBUS-DP, DeviceNet are suitable for processing and manufacturing, LonWorks, PROFIBUS-FMS, DeviceNet are suitable for buildings, transportation, agriculture. But this division is not absolute, and they penetrate each other.

(2) The application field of Profibus bus continues to expand: The bus that has achieved good performance in certain application fields will often further develop to other fields according to needs. For example, Profibus has developed PA on the basis of DP, which is suitable for the process industry.

(3) Strong background of Profibus bus: Profibus bus has a unique international user organization, which has now become a German standard and is mainly supported by Siemens. In addition, Profibus co-exists with other kinds of buses in competition.

Seven, the development prospect of PROFIBUS

Compared with other field bus systems, the advantage of PROFIBUS is that it is guaranteed by the stable international standard EN50170, and has been verified by practical application to be universal. And a large number of mature, open and general technologies are used to apply to various fields. Currently, the fields that have been applied include processing and manufacturing, process control and automation. The open and vendor-independent communication vision of PROFIBUS has been implemented in more than 100,000 successful applications. Market research confirms that PROFIBUS accounts for more than 40% of the market of open industrial fieldbus systems in the German and European markets. PROFIBUS is supported by international manufacturers of automation technology and equipment, all of which have their own technical advantages and can provide a wide range of high-quality new products and technical services, and will develop towards a simplified network structure.