Fit for the future

The first step has already been completed with the definition of extended Profibus-DP functions (DPV1), enabling Profibus to meet the requirements of intelligent field devices such as modern drive controllers, visualization systems and configurable signal converters, and making it possible to transfer acyclic parameter data and alarm signals in parallel to the cyclic I/O data. One of the most important of the recent developments summarized below is open integration. In future, users will be able to choose between conventional PLC and PC-based automation technology.

PC-based automation systems ideally combine visualization, data processing, communication and control functions on a PC and are often functionally compatible with conventional PLC systems. However, the integration of hardware and software components inside a PC only works correctly if the appropriate drivers are available. Open integration consistently sets open standards: OPC (OLE for process control) that allows PC-based application programs to access process data and Profibus for data communication with local I/O devices. Open integration is not a new standard but a commitment on the part of the leading PNO manufacturers to provide open, standardized solutions both for conventional PLC systems and for PC-based automation solutions.

Redundant data transfer is required for applications in high availability processes in the power and offshore industries as well as in oil refineries. The basic principles of redundant RS-485 transmission lines have been specified for Profibus in cooperation with major control system suppliers from the power industry. Special coupling modules are used to interconnect the standard device interface with the redundant transmission line. The particular advantage of this solu-tion is that the Profibus protocol remains unchanged, so that any existing devices can be connected to the redundant transmission line without changing the interface. Coupling modules will be available shortly.

Increasing costs are forcing manufacturers to provide more economical solutions for applications that need special environmental protection. Since conventional multi-way D-type connectors and two-wire cables are not ideal for IP65/IP67 applications, good working relationships have been established with leading machine tool manufacturers, in order to specify standardized electromechanical components that will reduce installation outlay and improve transmis-sion in this important market sector. The primary aim is to achieve easier assembly and handling of cables and connectors as well as a reduction in installation times. The secondary aim is improved EMI protection in noisy environments. Once the requirements had been analyzed it be-came obvious that a hybrid solution was called for. A hybrid cable – containing optical media for transmitting data and copper conductors for supplying power – has been specified. A Harting concept has been chosen for interconnection, which combines flexible connection, a high degree of protection, T-functionality, and – for the optical media – Hewlett Packard ’snap-in‘ technology. All electrical, mechanical and optical parameters of the connectors and the transmission media will be defined by Profibus International in a Profibus Guideline to ensure a wide range of suppliers and full specification openness.

By mapping the Profibus functions to Ethernet and TCP/IP, the range of Profibus applications will be extended up to cell level. With this new initiative, PI is not aiming to replace proven RS-485 transmission technology but to extend transparent communication from the field level into the cell level of industrial communication.

An increasing demand made in connection with automation systems is that safety-level equipment (for protecting people and machinery) and standard-level equipment should no longer be separated. Users favour the integration of safety-level equipment into general-purpose systems and the combination of both safety and standard-level equipment into one transparent communication system. This new field of applications is to be opened up by defining a special safety profile. This means that plant designers will be able to work more economically both on standard technology and on safety technology using the same engineering tools and methods. With its excellent func-tionality Profibus offers an ideal basis for incorporating this ’safety factor‘. The definition of the safety profile will not result in any changes to the Profibus protocol, because the requirements will be covered by defining a profile on the application level.

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Profibus-PA is meanwhile internationally established as a standard field bus system for process automation plants. During the first quarter of 1998, system and field device manufacturers set up 23 processing plants in 14 countries. Almost 3000 PA devices were put into operation during this first quarter.

The installations include 17 different control systems from 11 manufacturers and many different PA field devices such as field instrumentation, final control devices and data acquisition and SCADA equipment from a wide range of manufactures. The new sites are located in the mining industry, chemicals and fine chemicals, food, water and waste water, breweries as well as in paint manufacturing and glue production. The installations are evidence of the wide range of applications of Profibus-PA. If account is also taken of the Profibus-FMS and DP installa-tions, in June 98 Profibus reached an installed base of 2 million devices in 200 000 industrial applications throughout the world.