Fieldbus
Encyclopedia
Fieldbus is the name of a family of industrial computer network
protocols used for real-time distributed control, now standardized as IEC 61158.
A complex automated
industrial system — such as manufacturing assembly line — usually needs an organized hierarchy of controller systems to function. In this hierarchy there is usually a Human Machine Interface
(HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controller
s (PLC) via a non-time-critical communications system (e.g. Ethernet
). At the bottom of the control chain is the fieldbus that links the PLCs to the components that actually do the work, such as sensor
s, actuator
s, electric motors, console lights, switch
es, valve
s and contactor
s.
, star, ring, branch, and tree network topologies
. Previously computers were connected using RS-232
(serial connections
) by which only two devices could communicate. This would be the equivalent of the currently used 4-20 mA communication scheme
which requires that each device has its own communication point at the controller level, while the fieldbus is the equivalent of the current LAN-type connections
, which require only one communication point at the controller level and allow multiple (hundreds) of analog
and digital
points to be connected at the same time. This reduces both the length of the cable required and the number of cables required. Furthermore, since devices that communicate through fieldbus require a microprocessor
, multiple points are typically provided by the same device. Some fieldbus devices now support control schemes such as PID control
on the device side instead of forcing the controller to do the processing.
This form of "standard" was first developed for the European Common Market, concentrates less on commonality, and achieves its primary purpose — elimination of restraint of trade between nations. Issues of commonality are now left to the international consortia that support each of the fieldbus standard types. Almost as soon as this "8-headed monster" was approved, the IEC standards development work ceased and the committee was dissolved. A new IEC committee SC65C/MT-9 was formed to resolve the conflicts in form and substance within the more than 4000 pages of IEC 61158. The work on the above protocol types is substantially complete. New protocols, such as for safety fieldbuses or realtime ethernet-based fieldbuses are being accepted into the definition of the international fieldbus standard during a typical 5-year maintenance cycle.
Both Foundation Fieldbus and Profibus technologies are now commonly implemented within the process control field, both for new developments and major refits. In 2006, China saw the largest FF (Foundation Fieldbus) systems installations at NanHai and SECCO, each with around 15000 fieldbus devices connected.
IEC 61158 consists of the following parts, under the general title Digital data communications for measurement and control – Fieldbus for use in industrial control systems:
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See List of automation protocols for more examples.
, which was conceived as early as 1975 for office connectivity and later found uses in industry, the majority of fieldbus standards were developed in the 1980s and became fully established in the marketplace during the mid-1990s. In the United States, Allen-Bradley
developed standards that eventually grew into DeviceNet
and ControlNet
; in Europe, Siemens
and other manufacturers developed a protocol which evolved into PROFIBUS
.
During the 1980s, to solve communication problems between different control systems in cars, the German company Robert Bosch GmbH
first developed the Controller Area Network
(CAN). The concept of CAN was that every device can be connected by a single set of wires, and every device that is connected can freely exchange data with any other device. CAN soon migrated into the factory automation marketplace (with many others).
Despite each technology sharing the generic name of fieldbus the various fieldbus are not readily interchangeable. The differences between them are so profound that they cannot be easily connected to each other. To understand the differences among fieldbus standards, it is necessary to understand how fieldbus networks are designed. With reference to the OSI model
, fieldbus standards are determined by the physical media of the cabling, and layers one, two and seven of the reference model.
For each technology the physical medium and the physical layer standards fully describe, in detail, the implementation of bit timing, synchronization, encoding/decoding, band rate, bus length and the physical connection of the transceiver to the communication wires. The data link layer standard is responsible for fully specifying how messages are assembled ready for transmission by the physical layer, error handling, message-filtering and bus arbitration and how these standards are to be implemented in hardware. The application layer standard, in general defines how the data communication layers are interfaced to the application that wishes to communicate. It describes message specifications, network management implementations and response to the request from the application of services. Layers three to six are not described in fieldbus standards.
Technical committees, with representatives of many different companies, have been responsible for turning the original specifications into international ISO standards. Bury, among others, reports that work is underway to implement a common fieldbus protocol. This will entail a common set of application-layer services that can be provided regardless of the lower-layer implementation details. Although very much in its infancy, it is expected that this protocol may become reality by 2010. Whether designed for low-level sensor communications or high-level machine connectivity (or both), a Fieldbus is an important enabling technology for an open architecture controller.
It is difficult to make a general comparison of fieldbus performance because of fundamental differences in data transfer methodology. In the comparison table below it is simply noted if the fieldbus in question typically supports data update cycles of 1 millisecond or faster.
):
-based industrial communication systems have been established, most of them with extensions for real-time communication. These have the potential to replace the traditional fieldbuses in the long term.
Here is a partial list of the new Ethernet-based industrial communication systems:
For details, see the article on Industrial Ethernet
or EN 954-1. Depending on the actual protocol, fieldbus can provide measures like counters, CRC's, echo, timeout, unique sender and receiver ID's or cross check. Ethernet/IP
and SERCOS III
both use the CIP Safety protocol, Ethernet Powerlink
uses openSAFETY
, while FOUNDATION Fieldbus and Profibus
(PROFIsafe
) have varieties of their communications protocol which are compatible with safety systems.
and PROFIBUS PA. Both technologies use the same physical layer (2-wire manchester-encoded current modulation at 31.25 kHz) but are not interchangeable. As a general guide, applications which are controlled and monitored by PLCs (programmable logic controllers) tend towards PROFIBUS, and applications which are controlled and monitored by a DCS (digital/distributed control system) tend towards FOUNDATION Fieldbus. PROFIBUS technology is made available through Profibus International with headquarters in Karlsruhe, Germany. FOUNDATION Fieldbus technology is owned and distributed by the Fieldbus Foundation of Austin, Texas.
Foundation Fieldbus End User Councils:
Independent organizations:
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
protocols used for real-time distributed control, now standardized as IEC 61158.
A complex automated
Automation
Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization...
industrial system — such as manufacturing assembly line — usually needs an organized hierarchy of controller systems to function. In this hierarchy there is usually a Human Machine Interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
(HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controller
Programmable logic controller
A programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...
s (PLC) via a non-time-critical communications system (e.g. Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
). At the bottom of the control chain is the fieldbus that links the PLCs to the components that actually do the work, such as sensor
Sensor
A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...
s, actuator
Actuator
An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current, hydraulic fluid pressure or pneumatic pressure, and converts that energy into some kind of motion. An actuator is the mechanism by which...
s, electric motors, console lights, switch
Switch
In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....
es, valve
Valve
A valve is a device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category...
s and contactor
Contactor
A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings. A contactor is controlled by a circuit which has a much lower power level than the switched circuit....
s.
Description
Fieldbus is an industrial network system for real-time distributed control. It is a way to connect instruments in a manufacturing plant. Fieldbus works on a network structure which typically allows daisy-chainDaisy chain (electrical engineering)
In electrical and electronic engineering a daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring...
, star, ring, branch, and tree network topologies
Network topology
Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....
. Previously computers were connected using RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
(serial connections
Serial communications
In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels...
) by which only two devices could communicate. This would be the equivalent of the currently used 4-20 mA communication scheme
Current loop
A current loop describes two different electrical signalling schemes.- Digital :For digital serial communications, a current loop is a communication interface that uses current instead of voltage for signaling...
which requires that each device has its own communication point at the controller level, while the fieldbus is the equivalent of the current LAN-type connections
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
, which require only one communication point at the controller level and allow multiple (hundreds) of analog
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
and digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
points to be connected at the same time. This reduces both the length of the cable required and the number of cables required. Furthermore, since devices that communicate through fieldbus require a microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
, multiple points are typically provided by the same device. Some fieldbus devices now support control schemes such as PID control
PID controller
A proportional–integral–derivative controller is a generic control loop feedback mechanism widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a...
on the device side instead of forcing the controller to do the processing.
History
Although fieldbus technology has been around since 1988, with the completion of the ISA S50.02 standard, the development of the international standard took many years. In 1999, the IEC SC65C/WG6 standards committee met to resolve difference in the draft IEC fieldbus standard. The result of this meeting was the initial form of the IEC 61158 standard with eight different protocol sets called "Types" as follows:- Type 1 Foundation Fieldbus H1Foundation Fieldbus H1Foundation Fieldbus H1 is one of the Foundation Fieldbus protocol versions. It utilises either twisted pair, or fiber media to communicate between multiple nodes and the controller...
- Type 2 ControlNetControlNet-Introduction:ControlNet is an open industrial network protocol for industrial automation applications, also known as a fieldbus. ControlNet was earlier supported by ControlNet International, but in 2008 support and management of ControlNet was transferred to ODVA, which now manages all protocols...
- Type 3 PROFIBUSProfibusPROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF...
- Type 4 P-Net
- Type 5 FOUNDATION fieldbusFOUNDATION fieldbusFoundation Fieldbus is an all-digital, serial, two-way communications system that serves as the base-level network in a plant or factory automation environment. It is an open architecture, developed and administered by the Fieldbus Foundation....
HSE (High Speed Ethernet) - Type 6 SwiftNet (a protocol developed for Boeing, since withdrawn)
- Type 7 WorldFIP
- Type 8 InterbusInterbusINTERBUS is a serial bus system which transmits data between control systems and spatially distributed I/O modules that are connected to sensors and actuators .The INTERBUS system was developed by Phoenix Contact and has been available since 1987...
This form of "standard" was first developed for the European Common Market, concentrates less on commonality, and achieves its primary purpose — elimination of restraint of trade between nations. Issues of commonality are now left to the international consortia that support each of the fieldbus standard types. Almost as soon as this "8-headed monster" was approved, the IEC standards development work ceased and the committee was dissolved. A new IEC committee SC65C/MT-9 was formed to resolve the conflicts in form and substance within the more than 4000 pages of IEC 61158. The work on the above protocol types is substantially complete. New protocols, such as for safety fieldbuses or realtime ethernet-based fieldbuses are being accepted into the definition of the international fieldbus standard during a typical 5-year maintenance cycle.
Both Foundation Fieldbus and Profibus technologies are now commonly implemented within the process control field, both for new developments and major refits. In 2006, China saw the largest FF (Foundation Fieldbus) systems installations at NanHai and SECCO, each with around 15000 fieldbus devices connected.
IEC 61158 specification
There were many competing technologies for fieldbus and the original hope for one single unified communications mechanism has not been realised. This should not be unexpected since fieldbus technology needs to be implemented differently in different applications; automotive fieldbus is functionally different from process plant control. The final edition of IEC standard IEC 61158 allows 8 technologies.This are the some hierarchic layer of the automation protocols.IEC 61158 consists of the following parts, under the general title Digital data communications for measurement and control – Fieldbus for use in industrial control systems:
- Part 1: Overview and guidance for the IEC 61158 series
- Part 2: Physical Layer specification and service definition
- Part 3: Data Link Service definition
- Part 4: Data Link Protocol specification
- Part 5: Application Layer Service definition
- Part 6: Application Layer Protocol specification
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Standards
There are a wide variety of concurring fieldbus standards. Some of the most widely used ones include:- AS-InterfaceAS-InterfaceAS-Interface is an industrial networking solution used in PLC, DCS and PC-based automation systems. It is designed for connecting simple field I/O devices AS-Interface (Actuator Sensor Interface, AS-i) is an industrial networking solution (physical layer, data access method and protocol) used in...
- CANController Area NetworkController–area network is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer....
- InterbusInterbusINTERBUS is a serial bus system which transmits data between control systems and spatially distributed I/O modules that are connected to sensors and actuators .The INTERBUS system was developed by Phoenix Contact and has been available since 1987...
- LonWorksLonWorksLonWorks is a networking platform specifically created to address the needs of control applications. The platform is built on a protocol created by Echelon Corporation for networking devices over media such as twisted pair, powerlines, fiber optics, and RF...
- ModbusModbusModbus is a serial communications protocol published by Modicon in 1979 for use with its programmable logic controllers . Simple and robust, it has since become one of the de facto standard communications protocols in the industry, and it is now amongst the most commonly available means of...
- PROFIBUSProfibusPROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF...
- BITBUS
- CompoNet
- SafetyBUS pSafetyBUS pSafetyBUS p is a standard for safe field bus communication within factory automation. It meets SIL level SIL 3 according to IEC 61508 and safety category Cat. 4 of EN 954-1- Origins :...
- SERCOS interfaceSERCOS interface- Introduction :In the field of Industrial Control Systems, the interfacing of various control components must provide a means to coordinate the signals and commands sent between control modules...
See List of automation protocols for more examples.
Cost advantage
The amount of cabling required is much lower in Fieldbus than in 4-20mA installations. This is because many devices share the same set of cables in a multi-dropped fashion rather than requiring a dedicated set of cables per device as in the case of 4-20mA devices. Moreover, several parameters can be communicated per device in a Fieldbus network whereas only one parameter can be transmitted on a 4-20mA connection.Networking
With the exception of ARCNETARCNET
ARCNET is a local area network protocol, similar in purpose to Ethernet or Token Ring. ARCNET was the first widely available networking system for microcomputers and became popular in the 1980s for office automation tasks...
, which was conceived as early as 1975 for office connectivity and later found uses in industry, the majority of fieldbus standards were developed in the 1980s and became fully established in the marketplace during the mid-1990s. In the United States, Allen-Bradley
Allen-Bradley
Allen-Bradley is the brand-name of a line of Factory Automation Equipment manufactured by Rockwell Automation . The company, with revenues of approximately US$4.5 billion in 2006, manufactures programmable automation controllers , human-machine interfaces, sensors, safety components and systems,...
developed standards that eventually grew into DeviceNet
DeviceNet
DeviceNet is a network system used in the automation industry to interconnect control devices for data exchange. It uses Controller Area Network as the backbone technology and defines an application layer to cover a range of device profiles...
and ControlNet
ControlNet
-Introduction:ControlNet is an open industrial network protocol for industrial automation applications, also known as a fieldbus. ControlNet was earlier supported by ControlNet International, but in 2008 support and management of ControlNet was transferred to ODVA, which now manages all protocols...
; in Europe, Siemens
Siemens
Siemens may refer toSiemens, a German family name carried by generations of telecommunications industrialists, including:* Werner von Siemens , inventor, founder of Siemens AG...
and other manufacturers developed a protocol which evolved into PROFIBUS
Profibus
PROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF...
.
During the 1980s, to solve communication problems between different control systems in cars, the German company Robert Bosch GmbH
Robert Bosch GmbH
Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...
first developed the Controller Area Network
Controller Area Network
Controller–area network is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer....
(CAN). The concept of CAN was that every device can be connected by a single set of wires, and every device that is connected can freely exchange data with any other device. CAN soon migrated into the factory automation marketplace (with many others).
Despite each technology sharing the generic name of fieldbus the various fieldbus are not readily interchangeable. The differences between them are so profound that they cannot be easily connected to each other. To understand the differences among fieldbus standards, it is necessary to understand how fieldbus networks are designed. With reference to the OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
, fieldbus standards are determined by the physical media of the cabling, and layers one, two and seven of the reference model.
For each technology the physical medium and the physical layer standards fully describe, in detail, the implementation of bit timing, synchronization, encoding/decoding, band rate, bus length and the physical connection of the transceiver to the communication wires. The data link layer standard is responsible for fully specifying how messages are assembled ready for transmission by the physical layer, error handling, message-filtering and bus arbitration and how these standards are to be implemented in hardware. The application layer standard, in general defines how the data communication layers are interfaced to the application that wishes to communicate. It describes message specifications, network management implementations and response to the request from the application of services. Layers three to six are not described in fieldbus standards.
Technical committees, with representatives of many different companies, have been responsible for turning the original specifications into international ISO standards. Bury, among others, reports that work is underway to implement a common fieldbus protocol. This will entail a common set of application-layer services that can be provided regardless of the lower-layer implementation details. Although very much in its infancy, it is expected that this protocol may become reality by 2010. Whether designed for low-level sensor communications or high-level machine connectivity (or both), a Fieldbus is an important enabling technology for an open architecture controller.
Features
Different fieldbuses offer different sets of features and performance.It is difficult to make a general comparison of fieldbus performance because of fundamental differences in data transfer methodology. In the comparison table below it is simply noted if the fieldbus in question typically supports data update cycles of 1 millisecond or faster.
| Fieldbus | Bus power | Cabling redundancy | Max devices | Synchronisation | Sub millisecond cycle |
|---|---|---|---|---|---|
| AS-Interface AS-Interface AS-Interface is an industrial networking solution used in PLC, DCS and PC-based automation systems. It is designed for connecting simple field I/O devices AS-Interface (Actuator Sensor Interface, AS-i) is an industrial networking solution (physical layer, data access method and protocol) used in... |
62 | ||||
| CANOpen CANopen CANopen is a communication protocol and device profile specification for embedded systems used in automation. In terms of the OSI model, CANopen implements the layers above and including the network layer. The CANopen standard consists of an addressing scheme, several small communication protocols... |
127 | ||||
| CompoNet | 384 | ||||
| ControlNet ControlNet -Introduction:ControlNet is an open industrial network protocol for industrial automation applications, also known as a fieldbus. ControlNet was earlier supported by ControlNet International, but in 2008 support and management of ControlNet was transferred to ODVA, which now manages all protocols... |
99 | ||||
| CC-Link CC-Link Industrial Networks CC-Link is an open industrial network that enables devices from numerous manufacturers to communicate. It is predominantly used in machine, cell or process control applications in manufacturing and production industries, but can also be used in facilities management, process control and building... |
64 | ||||
| DeviceNet DeviceNet DeviceNet is a network system used in the automation industry to interconnect control devices for data exchange. It uses Controller Area Network as the backbone technology and defines an application layer to cover a range of device profiles... |
64 | ||||
| EtherCAT EtherCAT EtherCAT - Ethernet for Control Automation Technology - is an open high performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times with low communication jitter and low hardware costs.-... |
65536 | ||||
| Ethernet Powerlink Ethernet Powerlink Ethernet Powerlink is a deterministic real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group... |
Optional | 240 | |||
| EtherNet/IP EtherNet/IP EtherNet/IP is a communications protocol developed by Rockwell Automation, managed by the Open DeviceNet Vendors Association and designed for use in process control and other industrial automation applications.... |
Optional | Almost unlimited | Under development | ||
| Interbus Interbus INTERBUS is a serial bus system which transmits data between control systems and spatially distributed I/O modules that are connected to sensors and actuators .The INTERBUS system was developed by Phoenix Contact and has been available since 1987... |
511 | ||||
| LonWorks LonWorks LonWorks is a networking platform specifically created to address the needs of control applications. The platform is built on a protocol created by Echelon Corporation for networking devices over media such as twisted pair, powerlines, fiber optics, and RF... |
32000 | ||||
| Modbus Modbus Modbus is a serial communications protocol published by Modicon in 1979 for use with its programmable logic controllers . Simple and robust, it has since become one of the de facto standard communications protocols in the industry, and it is now amongst the most commonly available means of... |
246 | ||||
| PROFIBUS Profibus PROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF... DP |
Optional | 126 | |||
| PROFIBUS Profibus PROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF... PA |
126 | ||||
| PROFINET IO PROFINET IO PROFINET is the open industrial Ethernet standard of PROFIBUS & PROFINET International for automation. PROFINET uses TCP/IP and IT standards, and is, in effect, real-time Ethernet.... |
Optional | Almost unlimited | |||
| PROFINET IRT | Optional | Almost unlimited | |||
| SERCOS III SERCOS III sercos III is the third generation of the sercos interface, a globally standardized open digital interface for the communication between industrial controls, motion devices, and input/output devices . sercos III merges the hard real-time aspects of the sercos interface with Ethernet. It is based... |
511 | ||||
| SERCOS interface SERCOS interface - Introduction :In the field of Industrial Control Systems, the interfacing of various control components must provide a means to coordinate the signals and commands sent between control modules... |
254 | ||||
| Foundation Fieldbus H1 Foundation Fieldbus H1 Foundation Fieldbus H1 is one of the Foundation Fieldbus protocol versions. It utilises either twisted pair, or fiber media to communicate between multiple nodes and the controller... |
240 | ||||
| Fieldbus | Bus power | Cabling redundancy | Max devices | Synchronisation | Sub millisecond cycle |
Disadvantages
There are disadvantages to using fieldbus compared to the 4-20 mA analog signal standard (or to 4-20 mA with HARTHART Protocol
The HART Communications Protocol is an early implementation of Fieldbus, a digital industrial automation protocol. Its most notable advantage is that it can communicate over legacy 4-20 mA analog instrumentation wiring, sharing the pair of wires used by the older system...
):
- Fieldbus systems are more complex, so users need to be more extensively trained or more highly qualified
- The price of fieldbus components is higher
- Fieldbus test devices are more complex compared to a (high-spec) multimeter that can be used to read and simulate analog 4-20 mA signals
- Slightly longer reaction times with fieldbus, depending on the system
- Device manufacturers have to offer different versions of their devices (e.g. sensors, actuators) due to the number of different (incompatible) fieldbus standards. This can add to the cost of the devices and to the difficulty of device selection and availability.
- One or more fieldbus standards may predominate in future and others may become obsolete. This increases the investment risk when implementing fieldbus.
Current developments
Recently a number of EthernetEthernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
-based industrial communication systems have been established, most of them with extensions for real-time communication. These have the potential to replace the traditional fieldbuses in the long term.
Here is a partial list of the new Ethernet-based industrial communication systems:
- EtherCATEtherCATEtherCAT - Ethernet for Control Automation Technology - is an open high performance Ethernet-based fieldbus system. The development goal of EtherCAT was to apply Ethernet to automation applications which require short data update times with low communication jitter and low hardware costs.-...
- EtherNet/IPEtherNet/IPEtherNet/IP is a communications protocol developed by Rockwell Automation, managed by the Open DeviceNet Vendors Association and designed for use in process control and other industrial automation applications....
- Ethernet PowerlinkEthernet PowerlinkEthernet Powerlink is a deterministic real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group...
- BACnetBACnetBACnet is a communications protocol for building automation and control networks. It is an ASHRAE, ANSI, and ISO standard protocol....
- PROFINET IOPROFINET IOPROFINET is the open industrial Ethernet standard of PROFIBUS & PROFINET International for automation. PROFINET uses TCP/IP and IT standards, and is, in effect, real-time Ethernet....
- PROFINET IRT
- SafetyNET p
- SERCOS IIISERCOS IIIsercos III is the third generation of the sercos interface, a globally standardized open digital interface for the communication between industrial controls, motion devices, and input/output devices . sercos III merges the hard real-time aspects of the sercos interface with Ethernet. It is based...
- TTEthernetTTEthernetTTEthernet is a computer network technology marketed by TTTech Computertechnik AG for use in airplanes and other real-time applications.-Description:...
- VARANVaranis a kaiju that first appeared in Varan the Unbelievable . Physically, Varan resembles a giant reptile with skin membranes between his arms and legs, allowing him to glide much like a flying dragon or flying squirrel; he also has a horned head....
For details, see the article on Industrial Ethernet
Industrial Ethernet
Industrial Ethernet refers to the use of the Ethernet family of computer network technologies in an industrial environment, for automation and process control. A number of techniques are used to adapt Ethernet for the needs of industrial processes, which require real time behavior...
Safety
Fieldbus can be used for systems which must meet safety-relevant standards like IEC 61508IEC 61508
IEC 61508 is an international standard of rules applied in industry. It is titled "Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems"....
or EN 954-1. Depending on the actual protocol, fieldbus can provide measures like counters, CRC's, echo, timeout, unique sender and receiver ID's or cross check. Ethernet/IP
EtherNet/IP
EtherNet/IP is a communications protocol developed by Rockwell Automation, managed by the Open DeviceNet Vendors Association and designed for use in process control and other industrial automation applications....
and SERCOS III
SERCOS III
sercos III is the third generation of the sercos interface, a globally standardized open digital interface for the communication between industrial controls, motion devices, and input/output devices . sercos III merges the hard real-time aspects of the sercos interface with Ethernet. It is based...
both use the CIP Safety protocol, Ethernet Powerlink
Ethernet Powerlink
Ethernet Powerlink is a deterministic real-time protocol for standard Ethernet. It is an open protocol managed by the Ethernet POWERLINK Standardization Group...
uses openSAFETY
OpenSAFETY
openSAFETY is a communications protocol used to transmit information that is crucial for the safe operation of machinery in manufacturing lines, process plants, or similar industrial environments. Such information may be e.g. an alert signal triggered when someone or something has breached a light...
, while FOUNDATION Fieldbus and Profibus
Profibus
PROFIBUS is a standard for field bus communication in automation technology and was first promoted in 1989 by BMBF...
(PROFIsafe
PROFIsafe
PROFIsafe is the first open functional safety communication technology for distributed automation systems worldwide. Its specification for PROFIBUS DP and PROFIBUS PA was published first back in spring 1999. It incorporates the knowledge of more than 25 renowned safety companies...
) have varieties of their communications protocol which are compatible with safety systems.
Market
In process control systems, the market is dominated by FOUNDATION fieldbusFOUNDATION fieldbus
Foundation Fieldbus is an all-digital, serial, two-way communications system that serves as the base-level network in a plant or factory automation environment. It is an open architecture, developed and administered by the Fieldbus Foundation....
and PROFIBUS PA. Both technologies use the same physical layer (2-wire manchester-encoded current modulation at 31.25 kHz) but are not interchangeable. As a general guide, applications which are controlled and monitored by PLCs (programmable logic controllers) tend towards PROFIBUS, and applications which are controlled and monitored by a DCS (digital/distributed control system) tend towards FOUNDATION Fieldbus. PROFIBUS technology is made available through Profibus International with headquarters in Karlsruhe, Germany. FOUNDATION Fieldbus technology is owned and distributed by the Fieldbus Foundation of Austin, Texas.
External links
- USA: Fieldbus Foundation
Foundation Fieldbus End User Councils:
- Middle East: Foundation Fieldbus End User Council - Middle East
- Australia: Foundation Fieldbus End User Council Australia Inc
Independent organizations: