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In today's automation technology, Ethernet and information technology (IT) is increasingly calling the shots with established standards like TCP/IP and XML. Integrating information technology into automation allows significantly better communication options between automation systems, extensive configuration and diagnostic possibilities, and network-wide service functionality. These functions have been an integral part of PROFINET from day one.
PROFINET is the innovative open standard for Industrial Ethernet. PROFINET satisfies all requirements for automation technology. With PROFINET, solutions can be implemented for factory and process automation, for safety applications, and for the entire range of drive technology right up to clock-synchronized motion control.
Besides the use of IT technology, protection of investment also plays an important role in PROFINET. PROFINET enables the integration of existing fieldbus systems like PROFIBUS, DeviceNet, and INTERBUS, without changes to existing devices. That means that the investments of plant operators, machine and system builders, and device manufacturers, are all protected.
The use of open standards, simple operation, and the integration of existing system segments have driven the definition of PROFINET from the beginning. PROFINET is standardized in IEC 61158 and IEC 61784.
The continual further development of PROFINET offers users a long-term perspective for the implementation of their automation tasks.
For the plant or machine builders, the use of PROFINET minimizes the cost of installation, engineering, and commissioning. For the plant operators, PROFINET enables simple system extensibility and high system availability due to autonomously running system segments.
The establishment of certification now ensures a higher standard of quality for PROFINET products.
PROFINET uses Ethernet as well as TCP, UDP, and IP as the basis for communications. TCP/IP is the de-facto standard for communication protocols in the IT arena. But for interoperability, it is not enough just to establish a common communications channel between field devices based on TCP, UDP, and IP, because these standards merely represent the basis for data exchange. Additional protocols and determinations are thus needed on top of TCP or UDP, the so-called application protocols, which ensure the interoperability of applications. The interoperability of applications between field devices is only ensured when the same application protocol is being used. Typical application protocols are, for instance, SMTP (email), FTP (file transfer), and HTTP (Web).
The different application areas in industrial automation depend on a wide range of services for communications. These range from non-time-critical through real time capable to clock-synchronized. PROFINET offers therefore scalable data communications.
For non-time-critical processes, PROFINET uses Non Real Time communication (NRT) with the standard Ethernet mechanisms over TCP/IP or UDP/IP. This NRT communication follows the international standard IEEE 802.3. This is enough for most applications of process automation.
In industrial applications of factory automation, however, significantly stronger requirements for data bandwidth and for clock synchronization exist. Data exchange optimized for performance is called Real Time communication (RT), and the deterministic and clock-synchronized communications is called Isochronous Real Time (IRT), which enables clock rates of under 1 ms and a jitter precision of <1 µs.
Distributed I/O (Remote I/O) is connected through PROFINET IO. Here, the familiar I/O view of PROFIBUS is retained, in which the user data from the field devices are periodically transmitted into the process model of the control system.
PROFINET IO describes a device model, consisting of places of insertion (slots) and groups of I/O channels (subslots). The technical characteristics of the field devices are described by the GSD (General Station Description) on an XML basis.
PROFINET IO distinguishes between three following device types:
The engineering of PROFINET IO is done in the way familiar to system integrators from years with PROFIBUS. The decentralized field buses are assigned to one or more control systems during configuration. During engineering the IO-Device is to be configured to the actual system expansion based on the content in the GSD file. The IO-Device is simultaneously integrated, appropriately parameterized and configured into the PROFINET topology (1).
After completion of the engineering process, the installer loads the data for the expansion into the IO-Controller (2). The IO-Controller independently takes over data exchange with the IO-Device (3).
PROFINET CBA is a groundbreaking concept for industrial automation which fulfills the requirements of plant builders and operators for an system-wide and manufacturer-spanning engineering process. The PROFINET component model sees its real use in distributed automation systems. It is ideally suited for intelligent field devices with programmable functionality as well as controllers.
PROFINET CBA is based on the object-oriented modelling of technological modules. Based on the object model, machines and installations are structured in PROFINET in the form of technological modules. The functionality of the technological modules is encapsulated in uniform PROFINET components. From the outside, PROFINET components are accessed through uniformly defined interfaces. They can be arbitrarily connected in this way.
A distributed automation system designed in this way allows the modularization of plants and machines and therefore the reuse of segments of plants and machines. This significantly reduces engineering costs.
PROFINET based on a component model is described using a PCD (PROFINET Component Description). It is XML-based and can be generated either by the Component Generator of a manufacturer-specific configuration tool.
A vendor-independent engineering concept was created for the user-friendly configuration of PROFINET CBA systems. The engineering differentiates between the programming of the control logic of the individual technological modules (component generation using manufacturer-specific configuring tools) and the plant configuration which determines the communication relationships between the technological modules (using a PROFINET Connection Editor). As last engineering step, the connection information and configuration data are downloaded to the PROFINET components with a simple mouse-click.
PROFINET specifies a model for the integration of existing PROFIBUS and other fieldbus systems like INTERBUS and DeviceNet. This allows the construction of arbitrarily mixed systems consisting of fieldbus- and Ethernet-based segments. Thus a smooth technology transition is possible from fieldbus-based systems to PROFINET.
The large number of existing fieldbus systems makes it necessary to support their simple integration into PROFINET for reasons of investment protection. The following cases are distinguished:
Fieldbus solutions can easily and seamlessly be connected into a PROFINET system using proxies. The proxy functions as a representative of the fieldbus device on the Ethernet. It integrates the nodes connected to the underlying fieldbus system into the overlying PROFINET system. This allows the advantages of fieldbuses like high dynamics, locally exact diagnostics, and automatic system configuration to be used in the PROFINET world without settings in the devices. The transfer of system advantages simplifies planning due to well-understood workflows and the commissioning and operation using the complete diagnostic capabilities of the fieldbus system. Device and software tools are also supported in the usual manner and integrated into the management of the PROFINET system.
The proxy concept allows the device manufacturer to provide a high degree of investment protection to the plant and machine builder and end user.
PROFINET network installations are oriented towards the specific requirements of Ethernet networks in the industrial environment, like:
These give device manufacturers clear specifications of device interfaces and their cabling. The docukent "Installation Guideline PROFINET" gives system builders and operators well-proven rules for the installation of Ethernet networks.
Network management includes all functions for the administration of the network, like configuration (assignment of IP addresses), error monitoring (diagnostics), and performance optimization.
The use of TCP, UCP, and IP in PROFINET results in the requirement of assigning node participants, e.g. the PROFINET devices, their own IP parameters (IP addresses, subnet masks, etc.):
The reliability of network operations has a very high priority in network management. In existing networks, the Simple Network Management Protocol (SNMP) has established itself as the de facto standard for maintenance and monitoring of network components and their functions. In order to be able to monitor PROFINET devices with established management systems, it makes sense to implement SNMP. SNMP provides for both read access (monitoring, diagnostics) and write access (administration) to a device.
In PROFINET, only read access to device parameters are currently specified. When implementing SNMP in components, most access is to the standard information for SNMP (Management Information Base 2 (MIB 2).
The specific diagnosis of PROFINET components is possible using the mechanisms described in the correspondent PROFINET specification. SNMP should not open any other diagnostic channels in this context. It should only enable integration into network management systems which do not ordinarily process PROFINET-specific information.
A PROFINET station can also be accessed by an application using Web clients based on standard technologies from the Internet sector, like HTTP, XML, HTML, and scripting.
The data is transmitted in a standardized format (HTML or XML) and displayed using standard front ends (browsers like Netscape, MS Internet Explorer, Opera, etc.) This enables the integration of information from PROFINET components into modern multimedia-supported information systems.
Possible usage scenarios for Web integration in the areas of commissioning and maintenance are, among others, testing and commissioning, an overview of device master data, device diagnostics, and installation and device documentation.
The representation of the information available should be in both a format readable by humans (e.g. using a browser) and in a machine-readable form (e.g. an XML file). Using PROFINET Web integration, both variants are consistently available. For certain information, PROFINET Web integration also provides standardized XML schemas.
The basic component of Web integration is the Web server. It forms the interface between PROFINET and the basic technologies for Web integration.
Web integration in PROFINET can scale up with the performance and characteristics of the Web server. This means that even simple PROFINET devices, equipped only with an "embedded Web server", have equal rights with a PROFINET device with an "MS Internet Information Server" or the "Apache Web server" when participating in Web integration.
Web integration in PROFINET is designed in such a way that it can optionally be available for each device. Certain functions are optional and can be added according to the capabilities of the device. This makes scalable solutions realizable which are configured as perfectly as possible for the current application case. The PROFINET-specific elements can be integrated seamlessly into the existing Web implementation of a component.
The current trends of automation technology and the increasing usage of Ethernet in the automation industry, the options for remote maintenance through the Internet, and the networking of installation networks with offices networks or company-internal Intranets, all increase the potential risk considerably (hacker attacks, data manipulation and espionage, viruses, worms, and Trojans).
The particular focus of security in automation technology is to ensure the availability, reliable operation, and protection of industrial installations and production processes. Potential threats in automation systems can come from outside just as well as from inside.
Since security concepts from the office area really do not suffice for the particular requirements in the automation arena, security concepts for data security in automation technology have to be developed.
The PROFINET security concept can handle the great need for network security in Ethernet-based automation systems. This concept fulfills the requirements for access control, data encryption, authentication, and logging of security-relevant events.
The core of the security concept is in the security-motivated segmentation of the automation network. Secure automation cells are built. The network nodes within a cell are protected by special security network components (e.g. switches or security appliances) which control the data traffic from and to the cell and check access privileges. Only authorized data traffic is permitted. Access from client PCs to secure automation devices can be performed with a special security client software. The terminal devices thus require no security functionality of their own.
Data traffic between secure cells or between clients and the cell nodes can also be encrypted, thus secure against data espionage and data manipulation. This is especially interesting in the case of communications over insecure networks, such as is the case with remote access over the Internet for maintenance intervention.
Distributed I/O for factory and process automation had to live for a long time with the restriction that security tasks could only be triggered with conventional technology on a second level or decentrally over special buses. PROFIBUS with PROFIsafe for security-relevant applications was the first system to create a complete, open solution able to handle the known user scenarios. PROFIsafe for PROFINET follows the same principles.
PROFIsafe defines how safety-oriented devices (emergency shutoff switches, light grids, overfill protection systems, etc.) can communicate safety control information over a network securely enough that they can be used in safety-oriented automation tasks up to EN954's KAT4, AK6, or SIL3 (Safety Integrity Level). It implements secure communication with a profile, that is, using a particular format for user data and a special protocol.
The specification was collaborated upon by manufacturers, users, standards organizations, and testing institutes (TÜV, BGIA). It is based on uniform standards, particularly on IEC 61508, which specially addresses requirements for software development.
PROFIsafe takes all error possibilities into consideration (except for sabotage – Security has to be used for this) which can arise in serial bus communications, like delay, loss or repetition of data, incorrect order, incorrect addressing, or data falsification.
There are a series of protective measures from which the following were selected for PROFIsafe:
The skillful combination of these protective measures, along with a patented 'SIL monitor' (to monitor the frequency of defective messages) allows PROFIsafe to reach security classes up to SIL 3 and higher.
The PROFIsafe profile V2 is suitable for use with PROFIBUS as well as with PROFINET. The possibilities of Ethernet-based communications, such as significantly higher resources (address space, telegram size, etc.) and the use of active network components (switches, routers) are taken into account in the new version.
The drive profile PROFIdrive describes the drive interface from the point of view of the control application, along with its mapping to the communication systems PROFIBUS and PROFINET.
The PROFIdrive profile covers application scenarios from simple frequency converters to highly dynamic servo drivers. The functionality was broken down into six application classes.
Application class 1 targets applications with simple drives, like frequency converter, in which the drive is controlled through an RPM or frequency target by the overlying automation system.
In application class 2, the automation processes overlying the drive are subdivided into many subprocesses and distributed over the drives. The interface between control and drive corresponds to a high-level technology interface. All drive-related regulation processes run in the appropriate drive.
In application class 3, the drive functions as an autonomous one-axis positioning drive, while the control coordinates the overlying technological processes.
In application class 4, RPM regulation is done on the drive, and position regulation in the control; this is typical for motion control and robotics applications. The strong requirements for movements assume clock-synchronized operation.
In application class 5, a position target interface is used. Positional regulation in this case is done in the drive.
Application class 6 covers applications with distributed automation and angle synchronization between drives. In these applications, clock-synchronized operation and multicast communications between drives are necessary.
The drive model defined in PROFIdrive is built on the device model for PROFIBUS and PROFINET. The data exchange between control and rive is based on corresponding services of the communications system used (see Figure).
The configuration of a drive is done by setting parameters. PROFIdrive defines a protocol for the transmission of parameters between the control or engineering system and the drive. The protocol is transmitted over the standardized services of PROFIBUS or PROFINET. In a profile-specific area, PROFIdrive defines parameters for the configuration of the PROFIdrive interface. This enables the interoperability between drives from different manufacturers.
The functionality of PROFIdrive is suitable for use with PROFIBUS as well as with PROFINET. This makes a problem-free migration from PROFIBUS to PROFINET possible. The functionality is independent of the communication system used.
Requirements from the process engineering sector of the physical transmission technology implemented especially with PROFIBUS PA, such as intrinsic safety and bus power from devices, will also be available for systems based on PROFINET via gateway between PROFINET and PROFIBUS PA. PROFINET protects the investment in existing PROFIBUS PA systems and otherwise provides migration options from PROFIBUS PA to PROFINET. These gateway solutions are based on the PROFIBUS integration in PROFINET IO.
Since physical transmission via Ethernet with today's current state of technology does not meet the requirements of the process industry, conventional PROFIBUS PA devises will also be used in future process automation systems for process automation in addition to PROFINET devices that are connected to PROFINET through gateway solutions.
The integration of automation systems, Manufacturing Execution Systems (MES) and Enterprise Resource Planning (ERP) is gaining importance in company-wide, integrated information systems. While the interfaces between MES and ERP are defined in the context of the IEC 62264 specifications, until now there has been no specification for interfaces between MES and automation systems.
IEC 62264 divides MES into the following four operations: Maintenance Operations, Production Operations, Quality Operations, and Inventory Operations.
Since the topic of maintenance has great significance in both factory and process automation, Maintenance Operations should be supported first by PROFINET. The result is a corresponding document in which, among other things, the information content important for an MES interface is defined.
In maintenance, the procedure of state-based maintenance is currently gaining significance. It is based on the capability of devices and components to determine their states and to communicate them over agreed mechanisms.
PROFINET devices send their status to higher-level devices in a standardized format. A state model is available for this purpose, which besides the states 'good' and 'defective' also defines the two pre-warning levels 'maintenance needed' and 'maintenance required.'
Besides the Maintenance State, the capability of devices and components to provide up-to-date 'type plate information' and the information needed for functional and local assignment is an important prerequisite of MES Maintenance Operations.
The advantages of wireless data transmission are increasingly being applied in the industrial arena. This is not just for the savings in cabling costs and installation expenditure. The flexibility and mobility of wireless network infrastructure also enables completely new solutions in areas where electrical lines cannot be used, or can only be used with limitations, due to mechanical limitations, security requirements, or other environmental considerations. Application fields, for instance, are the integration of moving system parts into the communications infrastructure, or the connection of difficult to reach sensor, and also mobile operation and observation, driverless transport systems, and the like.
PROFINET communications is also possible on these wireless communications networks. PROFINET has to be ready to operate with different radio technologies for different application areas, with specific parameters regarding transfer rates, range, number of nodes, and similar. Thus profiles are specified for each technology which specify how integration into PROFINET is done, which topologies and performance values can be achieved with the technology, and what sorts of conditions apply, for instance regarding security requirements.
The specification of these profiles is an ongoing task and must keep pace with the availability of radio technologies and the requirements in the field. As a first step, a profile for WLAN is being prepared corresponding to the standards from 802.11
