PROFIBUS is an international, open, fieldbus standard that does not depend on equipment manufacturers. The PROFIBUS transmission speed can be selected from 9.6 kbaud to 12 Mbaud and all devices connected to the bus should be set to the same speed when the bus system is started. It is widely used in manufacturing automation, process industry automation, and automation in other areas such as buildings and transportation power. PROFIBUS is a fieldbus technology for factory automation shop floor monitoring and field device layer data communication and control. Decentralized digital control and field communication network for field-to-floor monitoring at the plant level provides a viable solution for comprehensive plant automation and field device intelligence.
PROFIBUS featuresAs the most widely used fieldbus technology in the industry, Profibus has its own characteristics in addition to the advantages of the general bus. The specific performance is as follows:
(1) The maximum transmission information length is 255B, the maximum data length is 244B, and the typical length is 120B.
(2) The network topology is linear, tree or bus type 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 for shielded twisted pair, 32 stations per segment (no repeater), and up to 127 stations with transponders.
(5) The transmission medium is a shielded/unshielded twisted pair or fiber.
(6) When using twisted pair, the transmission distance can be up to 9.6km, and when using fiber, the maximum transmission length is 90km.
(7) Transmission technology is RS-485 transmission of DP and FMS, IEC1158-2 transmission of PA and optical transmission.
(8) Adopt a single bus orientation protocol, including the master-slave mode between the token transfer and the slave between the master stations.
(9) Data transmission services include both cyclic and acyclic.
PROFIBUS consists of three compatible parts, namely PROFIBUS-DP (Decentralized Periphery). PROFIBUS-PA (Process AutomaTIon). PROFIBUS-FMS (Fieldbus Message SpecificaTIon).
PROFIBUS–DP: A high-speed, low-cost communication for communication between device-level control systems and distributed I/O. Use PROFIBUS-DP to replace 24VDC or 4-20mA signal transmission.
PORFIBUS-PA: Designed for process automation, the sensor and actuator are connected to a single bus with intrinsic safety regulations.
PROFIBUS-FMS: used for workshop level monitoring network, is a token structure. Real-time multi-master network.
PROFIBUS provides three 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 a uniform bus access protocol, the two systems can operate simultaneously on the same cable. RS-485 transmission is one of the most commonly used transmission technologies for PROFIBUS. The cable is shielded twisted pair copper wire.
2. IEC1158-2 transmission technology for PA (H1)IEC1158-2 is a bit-synchronous protocol for continuous currentless transmission for PROFIBUS-PA to meet the requirements of the chemical and petrochemical industries. It maintains its intrinsic safety and powers field devices over the bus.
3. Optical fiber transmission technologyWhen the PROFIBUS system is used in a large environment, fiber optic conductors can be used to increase the high-speed transmission distance. The characteristics of the fiber vary with the type of material used. For distances less than 50 m, inexpensive plastic fiber conductors can be used, and glass fiber conductors can be used at distances less than 1 km.
A typical factory automation system should be a three-level network structure based on the fieldbus Profibus-DP/PA control system located at the lower level of the plant automation system, ie at the field level and at the shop floor level. Fieldbus Profibus is a digital communication network for field and shop floor.
Field device layerThe main function is to connect field devices, such as distributed I/O, sensors, drives, actuators, switches, [3] lamp equipment, complete field device control and interlock control between devices. The master station is responsible for bus communication management and communication for all slave stations. All equipment production process control procedures on the bus are stored in the master station and executed by the master station.
2. Workshop monitoring layerWorkshop-level monitoring is used to complete the connection between the production equipment in the workshop, such as the connection between the main controllers of three production lines in a workshop, and complete the workshop-level equipment monitoring. Workshop-level monitoring includes online monitoring of production equipment status, equipment failure alarms and maintenance. There are also shop-level production management functions such as production statistics and production scheduling. Shop floor monitoring usually requires a workshop monitoring room on the operator workstation and printing equipment. The shop-level monitoring network can use Profibus-FMS, which is a multi-master network. At this level, the data transmission speed is not the most important, but it can transmit large-capacity information.
3. Factory managementThe shop operator workstation can be connected to the shop floor management network through a hub to send shop floor production data to the shop floor management. As a subnet of the main network, the workshop management network is connected to the backbone network of the plant through switches, bridges or routers, and integrates the workshop data into the factory management.
The workshop management usually refers to Ethernet, which is the communication protocol standard of IEEE802.3 and IETFTCP/IP. The factory backbone network can use networks such as FDDI or ATM depending on the actual situation of the factory.
(1) A variety of buses coexist, of which the application of PROFIBUS bus runs through all major fields: According to the market research of ARC in the United States, the demand for various fieldbuses in the world market is: process automation 15% (FF, PROFIBUS-PA, WorldFIP) 18% of pharmaceuticals (FF, PROFIBUS-PA, WorldFIP), processing and manufacturing 15% (PROFIBUS-DP, DeviceNet), transportation 15% (PROFIBUS-DP, DeviceNet), aviation, defense 34% (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 buses occupying about 80% of the market, and its application fields are relatively clear. For example, FF and PROFIBUS-PA are suitable for processes in metallurgical, petroleum, chemical, pharmaceutical and other process industries. Control, PROFIBUS-DP, DeviceNet are suitable for processing and manufacturing, LonWorks, PROFIBUS-FMS, DeviceNet are suitable for building, transportation, agriculture. But this division is not the right thing, and they are mutually infiltrated.
(2) Profibus bus application field continues to expand: Bus that has achieved good performance in certain application fields will often further develop into other fields according to needs. For example, Profibus developed PA on the basis of DP to apply to the process industry.
(3) The powerful background of the Profibus bus: The Profibus bus has a unique international user organization and is now a German standard with the main support of Siemens. In addition, Profibus coexists with other various buses in competition.
The development prospect of PROFIBUSCompared with other fieldbus systems, the biggest advantage of PROFIBUS is that it has a stable international standard EN50170 as a guarantee, and it has been universally verified by practical application. A large number of mature, open and versatile technologies are used in various fields, and the fields that have been applied include manufacturing, process control and automation. PROFIBUS openness and vendor-independent communication scenarios have been implemented in more than 100,000 successful applications. Market research confirms that PROFIBUS accounts for more than 40% of the open industrial fieldbus system market in Germany and Europe. PROFIBUS is supported by manufacturers of internationally renowned automation technology equipment. They all have their own technological advantages and can provide a wide range of high quality new products. Product and technical services will be simplistic towards the development of the network structure.
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