FOUNDATION FIELDBUS

FOUNDATION FIELDBUS

Here, the abbreviation FB stands for the term “fieldbus”, so that Foundation FB relates to a fieldbus. This can be used flexibly and is found frequently, especially in the process automation sector. Since the development of this technology, fieldbuses have been needed to reduce the costs of installing a network. In addition to saving costs, they save time as well on account of the simplicity of the planning process as well as through improvements and securing of company operations.

Historical Background to Foundation Fieldbus

The project to development of a uniform fieldbus and create an international standard was initiated in 1992 on the part of Forma ISP. At the same time, the members of the French Flux Information Processus founded an international Organization known as WorldFIP. Initially, this federation represented a counterweight to the ISP, however two years after the foundation, a joint formation, the Fieldbus Foundation was founded for reasons of technology and economic policy. The aim of this foundation is still to find a fieldbus standard in which an IEC uniform fieldbus is created, i.e. one which can be especially used in explosive applications. Because of this, the Foundation FB shall include the FIP specification as well as the ISP specification.

The Layer Model of the Foundation Fieldbus

This fieldbus follows a model which is composed of several layers. Here, the main elements are provided by

  • the physical layer
  • the communication stack, and
  • the application

Within the layer model of the Foundation FB, the application is the lowest level, and it is composed of the function block model and the device description. The next-highest layer is the communication stack, on which the application sets itself directly. At this point, the user can access a different range of services, depending on which blocks are implemented in a device. Furthermore, the services and functions brought by the application and the application layer can be used by the system management for processing of its tasks. This communication behavior makes it possible to guarantee correct cooperation between the individual components of the bus. This also includes time synchronization of all of the measurement and control tasks of the respective field devices. The effect of the communication stack is based on distributed communication. This guarantees several points:

  • Each controlling field device can exchange data with other devices. This includes the reading of measuring values and the derivation of set values.
  • All field devices are serviced in time. The definition as a timely process provides that there are no negative effects during the processing of the control circuits.
  • Two or more devices can never access one and the same bus simultaneously.

All of this is made possible by the use of a centrally located communication control.
In this representation, the physical layer forms the highest level. This assumes a relevance within the Foundation FB. In addition to these classical layers, the Foundation FB is also characterised by its dependence on the layer model of the ISO/OSI standard. With this, the layers 3 to 6 are not realized, even if they exist in most fieldbus systems. However, the tasks still occurring within these unused layers are covered by the communication stack. The seventh layer, i.e. the highest level within such a layer model, is composed of two components, the fieldbus access sublayer and the fieldbus message specification.

Communication Control with the Foundation Fieldbus

According to the specification developed by the “Fieldbus Foundation”, control of the communication processes within the fieldbus is performed by two types of transmission:

  • Clocked data transmission: This mainly controls tasks which are evaluated as time-critical. A fixed processing schedule is set up to perform execution of the resulting tasks in due time and without access problems. This schedule is created by a system administrator during configuration of the bus system in accordance the the FF specification. During the clocked data transmission, all devices run synchronized in time, whereby the point in time and the sequence are specified in advance. This is also known as a deterministic system.
  • Non-clocked data transmission: Here, parametrization and diagnosis especially takes place within the communication control. After all, transmission of this information and data must be possible when it is required. However, the transmission of the device parameters and the diagnosis information is not time-critical, i.e. acyclic, so that with Foundation FB the non-clocked data transmission takes place exclusively in the time gaps of the clocked transmissions.

Tasks that are still to be performed with Foundation Fieldbus

No standard so far has been decided with regard to the topology and the definition of the associated subnets, as in many items the execution of the FF system still cannot be equated with the specifications of the IEC file model. The IEC fieldbus thus solves the communication tasks with the intrinsically safe H1 bus and the H2 bus above it. As such, this is a bus system with two components. In regard to the H1 bus, the fieldbus of the FF system already operates in the same way as the IEC model, but the classification of the H2 bus has not yet been completed. The only item specified is the use of the fast or high-speed Ethernet for solving problems with regard to the Foundation FB.

FOUNDATION FIELDBUS HSE

A fieldbus is used to connect field equipment (such as sensors and actuators) in an area for the purpose of communication with a control unit. If several communication members send their messages over a line, it is then necessary to establish the identification, the measured value and when (initiative) something was said. There are standardized protocols for this.

The Fieldbus Foundation is a non-profit organization consisting of the leading process and manufacturing automation companies. The first generation of the fieldbus technology was developed in the 1980s to replace the parallel wiring of binary signals that were usual at that time as well as analog signal transmission using digital transmission technology. Today, many different fieldbus systems with different characteristics have been established on the market. Since 1999, the fieldbus technology is standardized in the entire world using the IEC 61158 standard. The second generation of fieldbuses is based on real-time Ethernet.

History of the Fieldbus Foundation

The Fieldbus Foundation was founded in 1994 through the merger of ISP and WorldFIP. The first FF specification was H1, published in 1995. In 1999, the Fieldbus Foundation added an Ethernet data connection version of the protocol in a specification. The Fieldbus Foundation claims that so far, over 250 products conforming to FF and over 700,000 FF devices have been delivered.

The fieldbuses are characterised by advantages. One particular feature of note is the fact that not much work is involved in the wiring. This is something that saves a lot of time during planning and installation. With this, jumper boards, the dimensions of the switchgear cabinet and the cables are reduced. In addition, self-diagnosis by the system becomes possible. This is a feature which can break down errors. There is also higher reliability and better availability through shorter signal paths. Even in the case of analog values, the protection before F is increased. Open fieldbuses unify data transmission and device connection, regardless of the manufacturer. Another advantage is the fact that the components of different manufacturers can be exchanged more easily – at least with regard to the basic communication. As a result of this simplified exchangeability, expansions / changes are easy to perform and they guarantee flexibility and security for the future. Specification of measuring ranges is not required for transducers. This is something which again, saves time. In addition, the visual indication scale in the control system can be changed at any time.

The FF is composed of an FF linking device gateway and an FF HSE communication. This makes it possible to integrate standard FDT frame applications (e.g. SMART VISION, Field Device Manager, FieldMate, or PACTware) with the fieldbus interface module of the linking devices / Softing without problems. This solution creates the ability for transparent access to FDT-suitable field devices connected to the corresponding FF H1 networks. FDT functionalities such as simple parameterization and diagnosis are supported extensively. The FF HSE has extensive FDT-based software, so that it is possible to operate FF installations simply. Among other things, the modern user interface offers tips and online help. When the device DTMs of the individual FF H1 field devices (which are connected with the linking devices or the fieldbus interface module) are available on the computer together with the FDT frame application, the corresponding devices are recognized automatically and are entered with all the corresponding device and manufacturer information into the live list and subsequently stored. In addition to storing of error messages, the FF HSE also offers functionalities for FDT uploads and downloads, as well as connection monitoring. The FF HSE can also be used without having to activate a license key, and it is included in the scope of deliveries of the gateway and linking device products of Softing. In this way, the license for the FF HSE can be provided via the licenses of these products.

It is only in this way, that it is possible to use the many advantages of the FF HSE without additional licensing. The FF HSE kit represents an extensive package that makes it possible for the user to ensure that the communication components for the device of a manufacturer correspond to the HSE test procedures and directives. In order to successfully pass the interoperability test, a device must contain a communication component registered with the Fieldbus Foundation which has successfully passed the conformity tests. With the kit, developers can have the correct communication behavior of an HSE component entered in accordance with the FF HSE specifications of the FOUNDATION. The scope of the new FF HSE also contains expansions and several improvements.

Further functions of the FF HSE include the registration of all installed devices, the automatic searching of networks, the importing of DD and CFF files as well as the assignment of the device tags, addresses and function block tags. In addition, function block links and schedules can be configured. The downloading and uploading of configurations and schedules are also included. Function block applications in devices can be monitored online with the FF HSE. The scope of the fieldbus package includes a data access server for convenient access to data in Foundation fieldbus devices with each conforming OPC client.

Use of the high-speed Ethernet fieldbus requires a Windows-capable PC with Ethernet access. Use is possible with an operating system dating from Windows 2000, right up to the current computer version.

FOUNDATION FIELDBUS – A PROTOCOL ON A FIELDBUS BASIS

With Foundation FB, the abbreviation FB stands for fieldbus.This is a LAN standard, i.e. a standard developed for local data networks. This enables the connection of control units to devices found in process applications. After all, in the production sector, be it in the automobile industry, agriculture or other branches of the economy that work with complex installations, it is necessary to create communication between the subscribers in a network, so that these carry out automation of the work process through data exchange. The technology of the fieldbuses has shown itself to be most effective for reaching this goal. In an installation, this technology provides the connection between the sensors representing the detecting elements and the actuators as the final control elements. As mentioned, this serves the task of communication with the respective device, which assumes the task of control. The use of fieldbuses also becomes necessary as a result of the frequent need to run multiple communication subscribers over the same line. At this point, it is necessary to specify what is transmitted, when and to whom:

  • The identification,
  • the measurement values and the command,
  • and the initiative

are thus connected inseparably with each other. Protocols are used to realize such a system, one of them being Foundation FB.

What is Foundation FB?

Foundation FB is an open protocol that permits bidirectional data transmission to the field devices. This means that data packets are sent in both directions. It is therefore a point-to-point communication. The application of this technology offers four different basic services:

  1. Asset management
  2. Additional information which helps the diagnosis of a problem or condition
  3. Preventive maintenance
  4. Distributed data transfer, abbreviated as DDT.

In addition to predictive maintenance, asset management is an especially important theme for decision processes which decisively influence the installation planning. Asset management is basically system software and as such, it often is known as an installation quality management system or AGVS. Asset management is assigned to the data information area which serves the management of assets from the IT sector. This software also handles physical assets, namely machines and complex installations. Predictive maintenance has a similar meaning. Here, maintenance ‘looks ahead’ so that the assets are monitored permanently and the user can take proactive measures when faults occur. As such, these components analyze huge quantities of data that are made available from internal sources and it also can predict external influence factors and the possible risks of failure. This prevents down-time of the system, as well as the existing resources for maintenance and the installations. In general, the components are used with greater efficiency. Overall, the use of predictive management offers

  • continuous evaluation of data from different source,
  • an extensive collection of historical data for valid statements,
  • definitions of the permitted nonconformities, and
  • prognoses concerning the relevant faults.

In the meantime, these technologies are now being used by over 20 % of users, and many more plan their introduction. This also makes the use of Foundation FB relevant. This open protocol supports the applications that have just been described without problems and as such, it influences the work process positively.

Gains that are made from the use of Foundation FB

Through the use of Foundation FB, integrated components within the control and operation level emerge out of conventional device data. Through this, the protocol is characterised as an optimal interface for maintenance and installation planning. This is made clear by a list of the advantages:

  • More economic efficiency, as access is made possible to all device data and diagnoses and it can be done easily
  • Full interoperability, i.e. cooperation of all devices which have Foundation FB certification
  • Higher flexibility for manufacturing as a result of the optimized productivity of installations
  • Increased safety and reliability, which especially relates to the quality of the signals
  • Higher availability of the installation and the resulting reduction of the down-time
  • Access to the data required for transparency within process automation is always possible
  • Predictive maintenance through reliable and secure diagnosis data
  • Capacity for the exchangeability of devices
  • The ability of Foundation FB to be used in areas at risk of explosions
  • An improved information flow
  • Rapid data exchange
  • More openness through manufacturer independence

Conclusion concerning Foundation FB

Over time, this open protocol has become an indispensable technology within process automation. This is because the free use and the independence from manufacturers enables this fieldbus system to connect many installations with each other without influencing the data flow negatively. Foundation FB provides optimization of apparently any sections within a process which requires internal communication, so that this protocol is also the basis and the future of automation technology.