Method for transferring data via a field bus of the process automation technology

p0001The invention relates to a method for transmitting data via a field bus of the process automation technology according to the preamble of claim 1.

p0002In process automation technology, field devices are often used to control an industrial process.

p0003For this purpose, the process variables are detected by means of sensors and the controlled variable is controlled by means of actuators.

p0004Field devices for flow, level, differential pressure, temperature determination etc. are generally known. They are used to detect the corresponding process variables flow, filling level, pressure, temperature etc. and are usually arranged in the immediate vicinity of the relevant process component.

p0005Examples of actuators are controllable valves, which regulate the flow of a liquid or a gas in a pipeline section.

p0006The field devices are frequently connected via a field bus to a control unit which controls the entire process sequence. The measured values ​​of the individual sensors are evaluated in the control units and the corresponding actuators are controlled.

p0007In many cases, fieldbuses are still connected to higher-level communication networks, which serve for data communication with control systems and company or office devices. This allows for continuous communication within a company from the field level to the various company levels. In addition to restricted communication in the local LAN networks, a worldwide connection via the Internet WAN is possible with a corresponding connection.

p0008The process flow is monitored and visualized in the control systems. Error messages are registered there. Direct access to the individual field devices is also possible from the control system. This allows parameter values ​​and configuration data to be queried and changed. Furthermore, diagnostic functions can also be called from the control system.

p0009A system architecture has become known, including a Profibus DP master (class 1) and a Profibus, from the article: Profibus Profile HART, Version 1.0, July 2001, order number 3.102, pages 1-17, Copyright 2001 Profibus Nutzerorganisation eV, Karlsruhe (DE) DP master (class 2). Furthermore, a HART master device is provided which consists of a Profibus DP slave and a HART master. The HART Master Device device consists of a Profibus DP slave, one or more HART masters and the Profibus DP profile for HART as an interface.

p0010Recently, in the process automation technology, systems are also known in which the field bus is dispensed with and the field devices are directly connected to a superordinate communication network. The most common network is Ethernet with TCP / IP. This allows for compatibility within different company levels and also with the Internet.

p0011The company network is used to transmit emails and process data simultaneously.

p0012The higher-level enterprise networks based on Ethernet work according to the client / server principle. Fieldbuses, on the other hand, according to the publisher / subscriber principle. The protocols are designed accordingly.

p0013The strengths of Ethernet with TCP / IP lie in the monitoring / parameterization of plants or plant parts. In contrast, fieldbuses are better suited for distributed intelligence control.

p0014Nowadays, no method is known for data transmission in fieldbuses, which meets both requirements. The object of the invention is therefore to specify a method for data transmission via a field bus of the process automation technology, which is suitable both for control tasks and also for monitoring tasks.

p0015This object is achieved by the method specified in claim 1. The essential idea of ​​the invention is that the protocol data of a second transmission protocol, the internet protocol, are mapped onto the fieldbus protocol and can thus be transmitted via the fieldbus.

p0016In a simple manner, the data field in the frame of the fieldbus telegram contains a frame of a second transmission protocol.

p0017In order to be able to distribute the data in the field device in a manner specific to the application, a distribution module is provided in the field device which analyzes the incoming fieldbus telegrams and forwards them to the respective application in accordance with their contents.

p0018The field bus system is, for example, a Profibus® or a Foundation Fieldbus®.

p0019In a simple manner, a web server can thus be implemented in the field device.

p0020In order to enable communication with the world-wide telecommunications networks, a packaging gateway is provided which maps the protocol data of the second transmission protocol into the fieldbus protocol or unpacked it in the reverse direction.

p0021A significant advantage of the invention is that no special tools are required for the query and configuration of field devices. Access is possible using standard browsers (Netscape Navigator®, Internet Explorer®). At the same time, the advantages of conventional fieldbuses can also be used for the method according to the invention.

p0022Various tools are available for parameterizing and configuring field devices. One such tool is, for example, the configuration and parameterization program CommunWin 2 by Endress + Hauser. The functionality of the field devices to be operated is made known in these operating tools by means of so-called device descriptions.

p0023Advantageous further developments of the invention are given in the subclaims.

p0024The invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing.

p0025Show it:<dl id="dl0001"><dt>FIG</dt><dd>Hardware software structure of a field device according to the invention;</dd><dt>FIG</dt><dd>Network with control unit and several field devices in schematic representation;</dd><dt>FIG</dt><dd>Structure of a fieldbus frame.</dd></dl>

p0026<figref idrefs="f0002">FIG</figref> Shows an operating device B, which is connected to various field devices F1, F2, F3 and F4 via a plurality of networks. A conventional communication link T. is used as the first network connection between the operating device B and a conversion unit U. This communication link T can be a WAN wide area network (LAN), LAN local area network (Intranet) or a direct Internet protocol connection . This connection is provided via the known services GSM, UMTS, PSTN, ISDN, Ethernet, etc.

p0027From the conversion unit U, two field buses A and B lead to the field plane with three field devices F1, F2, F3 and a field device F4. A control unit S (for example, a programmable logic controller PLC) is connected to the fieldbus A. The field devices F1, F2, F3 communicate with the control unit S via fieldbus A, which evaluates the measured values ​​of the individual field devices and actuates actuators (not shown) accordingly.

p0028<figref idrefs="f0001">FIG</figref> Shows the hardware software structure of a field device (F1, F2, F4) according to the invention on the basis of the field device F1 selected by way of example. (The field device F3 is a conventional field device.) The field device F1 is connected to the field bus A via a field bus interface FS. A distribution module VM, which is connected downstream of the fieldbus interface FS, distributes protocol data P1 and P2 either to the communication stack ST1 or ST2. The respective applications A1 and A2 are respectively connected downstream of the two stacks ST1 and ST2. The application A2 is connected to a measuring transducer interface MS (not shown). A data exchange is possible between applications A1 and A2. Conventional field devices, such as the field device F3, have only the fieldbus interface FS, the communication stack ST1 and the fieldbus application A1 as well as the measurement pickup interface MS.

p0029<figref idrefs="f0002">FIG</figref> Shows a field bus frame FR1 with a normal data field or with a frame of a further transmission protocol. For example, a Profibusframe containing a TCP / IP frame is shown. The Profibusframe FR1 consists of several data fields; SD3 Start Limiter, DA Destination Address, SA Sender Address, FC Function Code, Data, FCS Frame Checksum, and the final limit ED. The data field data can, for example, contain normal measured values ​​or also a TCP / IP frame with the corresponding data.

p0030The mode of operation of the invention is explained in more detail below.

p0031The fieldbus application A1 can communicate with the control unit S via the fieldbus A in the customary manner. The data provided by the fieldbus application A1 are packaged with the aid of the field bus stack ST1 and are transferred to the fieldbus A via the distribution module VM and the fieldbus interface FS. The distribution module VM extends the field bus frame FR1, which contains normal fieldbus data, without further modification to the fieldbus interface FS. Incoming telegrams are analyzed in the distribution module VM to determine whether fieldbus data P1 or protocol data P2 of another second transmission protocol are contained in the data field. In one case, the protocol data are forwarded to the fieldbus stack ST1, in the other case to the communication stack ST2. The data is then transferred either to the fieldbus application A1 or to the application A2. The application A2 may, for example, comprise a web server or an OPC server. Of course, field device data may be exchanged according to the first or second protocol. Thus, corresponding applications in the respective field devices can communicate with each other very simply.

p0032The mode of operation of the conversion unit U is described in more detail below. The conversion unit U, which serves as a packaging gateway, packs the TCP / IP protocol data into the fieldbus protocol and passes it on to the corresponding fieldbuses A and B, respectively. Correspondingly, fieldbus telegrams are unpacked by the field bus and passed on as TCP / IP telegrams to the corresponding communication link T. The conversion unit U can be connected to one or more field buses, which in particular also operate according to different protocols. Likewise, one or more different networks operating according to the second transmission protocol can be connected to the conversion unit U.

p0033With the operating device B, an easy access to the corresponding field devices is thus possible. The field devices F1, F2 and F4 can be configured, configured and parameterized from the operator panel B via a web browser. A significant advantage of the invention is that the operating device B can directly access the HTML pages stored in the field device F1, F2 or F4. The control device B does not need a special device description of the field device which is to be operated.

p0034With the aid of the present invention, it is possible to install TCP / IP applications in field devices without having to make changes to the existing fieldbus. Field devices without TCP / IP applications and field devices with TCP / IP applications work independently. A substantial advantage of the invention is still to be seen in the fact that TCP / IP applications can communicate with a remote operating device via a second-wire connection. Field devices of this type can also be used easily in explosion-hazardous areas (EX regions).

p0035The conversion unit U can also serve as a firewall and provide various services based on the second transmission protocol for the field devices F1, F2, F4.

p0036Furthermore, the conversion unit can also serve as a router between the various connected networks.