Profinet

PROFINET (Process Field Network) is the open Industrial Ethernet standard of PROFIBUS & PROFINET International ( PI) for automation. Profinet uses TCP / IP and IT standards, real-time Ethernet -enabled and allows the integration of fieldbus systems.

The concept of Profinet is modular, so that the user can choose the functionality itself. This differs mainly by the type of data exchange to meet the speed requirements.

Profinet, there are two ways of Profinet IO and PROFINET CBA:

  • Profinet IO ( Input - Output ) has been created for the connection of remote peripheral to a controller (controller). The available functions and real-time characteristics in the three conformance classes CC -A, CC -B and CC -C are divided for different applications.
  • Profinet CBA ( Component Based Automation) is intended for component- based communication via TCP / IP and the real -time communication for real-time requirements in modular plant. Both channels of communication can be used in parallel.

Profinet IO and PROFINET CBA can communicate at the same time on the same bus system. They can be operated both separately and combined, so that a unit with Profinet IO in the Plant view attachment appears as a Profinet CBA.

  • 2.1 PROFINET protocols
  • 2.2 functionalities Class A (CC -A)
  • 2.3 functionalities Class B (CC -B)
  • 2.4 functionalities of the class C (CC -C)

Distributed IO ( PROFINET IO)

Overview

Profinet IO allows the connection of decentralized peripherals to a controller and thus can be seen as a direct successor of Profibus DP. Profinet IO describes the entire data exchange between devices with control or control functionality as IO controller and the field devices as IO device for cyclic data exchange as well as the parameterization and diagnostics. Used Profinet IO Ethernet -based protocols, follows the Producer-/Consumer-Modell and is depending on the conformity class for bus cycle times of several ms to 31.25 microseconds.

Field devices in a lower-level fieldbus line can be integrated via an IO proxy ( proxy for an underlying bus system ) in the Profinet IO system. This can be integrated into a Profinet IO system and used existing Profibus or Interbus systems simple.

Conformance classes

The applications with Profinet IO can be divided into three classes:

  • In the class A ( CC-A ), only the devices used are certified. For the network infrastructure, a manufacturer's certificate is sufficient. Therefore, a structured cabling or for mobile subscribers a Wireless Local Area Network can be used. Typical applications can be found in infrastructure projects (eg highway or railway tunnels) or in building automation.
  • The Class B ( CC -B) requires that the network infrastructure includes certified products and is structured according to the guidelines of Profinet IO. Shielded cables increase the robustness and Switches with management functions simplify network diagnostics and allow the detection of the network topology as desired for the control of a production line or machine. The process automation requires increased availability that can be achieved by a media and system redundancy.
  • With the C class (CC -C) can be realized with an additional positioning bandwidth reservation and synchronization of applications.
  • RT communication
  • Cyclic I / O
  • Parameter
  • Alarms
  • RT communication
  • Cyclic I / O
  • Parameter
  • Alarms
  • Network Diagnostics
  • Topology information
  • System redundancy
  • RT communication
  • Cyclic I / O
  • Parameter
  • Alarms
  • Network Diagnostics
  • Topology information
  • Reserved bandwidth (IRT )
  • Synchronization
  • Controller
  • Devices
  • Network components only with manufacturer's certificate
  • Controller
  • Devices
  • Network components
  • Controller
  • Devices
  • Network components

According to IEC 61784-5-3 and IEC 24702

  • Copper
  • Light guide
  • Wireless

According to IEC 61784-5-3

  • Copper
  • Light guide

According to IEC 61784-5-3

  • Copper
  • Light guide
  • Infrastructure
  • Building Automation
  • Manufacturing Automation
  • Process Automation
  • Motion Control

Device types

A Profinet IO system is composed of the following devices:

  • IO controller is a controller that controls the automation task.
  • IO device is a field device that is monitored and controlled by an IO controller. An IO device consists of several modules and sub-modules. The sub-modules contain the individual input and output signals to the process.
  • IO supervisor is a development tool, typically on a PC in order to parameterize the individual based IO devices and diagnostics.

System Design

A minimal Profinet IO system consists of at least one IO controller controls one or more IO devices. In addition, one or more IO supervisors for the engineering of IO devices can be switched temporarily if required optional.

If two IO systems on the same IP network, the IO controller can also share an input signal as a shared -input, in which they have read access to an IO device on the same submodule. This simplifies the combination of a PLC with a separate safety controller or a motion control. Likewise, an entire IO device to be shared as shared -device that maps the individual submodules of an IO device different IO controllers.

Each automation device with an Ethernet interface can be the same time fulfill the functionality of an IO controller and an IO device. If now occurs a controller for a partner controller as IO device and simultaneously monitored as an IO controller its periphery, a task coordination between controllers without any additional devices can be realized. In order for this controller to controller (C2C) may be exchanging data even across manufacturers simply made ​​, the engineering of a C2C communication in a profile is defined in more detail.

To increase the availability can be realized with Profinet system redundancy. In this case, two IO controllers can be configured to control the same IO device. The active IO Controller will mark its output data as primary. Unmarked output data will be ignored in a redundant IO system of an IO device. Thus, in case of failure of the second IO controller by highlighting its output data as primary uninterrupted control over all IO devices take over. How to synchronize their task, the two IO controller is not set for Profinet and will offer from the various manufacturers, the redundant control systems implemented in different ways.

Relations

Between an IO controller and IO device an application relation (AR) is established. About this AR Communication Relations (CR ) can be defined with different characteristics:

  • Record Data CR for the acyclic parameter transfer
  • IO Data CR for the cyclic process data exchange
  • CR alarm for signaling alarms in real time

Cyclic data ( IO Data CR): The content of the cyclic data traffic are the data that sends the CPU to the peripherals so that they can be output at the outputs as well as the data that reads a peripheral device at its inputs and processing to the central unit sends. Ie generally, in each cycle is such a " cyclic " data packet from the central unit to the peripheral device and vice versa.

The basis for this is a cascadable Real - Time concept, ie for each cyclic CR may have a different cycle time may be specified. The cyclic data traffic can be divided into two classes depending on the requirements: data exchange with or without clock synchronization. In popular parlance, data exchange is called without isochrone as " RT" (Real Time ), data exchange with isochronous mode as " IRT " (Isochronous Real Time).

For cyclic data transfer as efficient as possible in terms of the bandwidth is sought Profinet. Therefore, the cyclic traffic is directly based on the level of the MAC addresses and IP addresses in order ( and hence also the total length) to keep the header length of the data packet small. Since the automation tasks for Profinet IO are local rule ( a machine / system ) can get over the loss of routing capability, which one takes by waiving IP header information in purchasing.

Acyclic parameter data ( Record Data CR): In addition, there are in the data exchange between the CPU and peripheral device and acyclic data traffic, which is used for events that are just not constantly repeat themselves. Examples of acyclic data traffic are sending parameterization and configuration data at start-up of a peripheral device to the device or sending a diagnostic message from the peripheral device to the main unit during operation.

Acyclic data using the UDP / IP protocol.

Acyclic data alarm (alarm CR): Alarms are specific acyclic messages are transmitted from the peripheral device when necessary to the controller. These are time critical and as the cyclical data are therefore transferred directly via Ethernet. In contrast to the cyclic data but they must be confirmed by the recipient.

Engineering

To configure an IO system is kept almost the same as for Profibus from the " look and feel":

  • The properties of an IO device are described by the device manufacturer in a GSD file (General Station Description). When this language is the GSDML (GSD Markup Language ) - an XML-based language - is used. The GSD file is a development environment as a basis for planning the configuration of a PROFINET IO system.
  • All Profinet field devices to identify their neighbors. Thus, field devices can be replaced without additional aids and prior knowledge on failure. By reading this information, the plant topology can be represented graphically for clarity.
  • With support for the Tool Calling Interface ( TCI), each field device manufacturer can engage in any TCI -enabled development environment and configure "his" field devices and diagnostics without having to leave the development environment. Individually adjusted data can be loaded across manufacturers (eg via TCI ) and a server parameters are automatically archived. Reloading is also performed automatically during device replacement.

Technology

The functionalities of the Profinet IO can be realized with different technologies and protocols:

PROFINET protocols

Profinet uses the following protocols:

Ethernet: Only full-duplex 100 Mbit / s electric ( 100BASE -TX) or optical ( 100BASE -FX) according to IEEE 802.3 are allowed as an equipment connection. Auto Crossover is to be mandatory so waived for all ports on the use of crossed cables. From IEEE 802.1Q VLAN is used with priority tagging. All real-time data obtained allow the greatest possible priority 6 and are therefore passed with a minimum delay of a switch.

The Profinet protocol can be recorded with any Ethernet analysis tool and displayed. Wireshark decoded in the current version of the Profinet telegrams.

The Media Redundancy Protocol ( MRP) allows the creation of a redundant, protocol-independent ring topology with a switching time of less than 50 ms. For redundant ring circuits without any delay in case of error the Media Redundancy Real - Time Protocol ( MRRT ) must be used.

The Link Layer Discovery Protocol ( LLDP) has been extended with additional parameters, so that besides the recognition of neighbors and the running time of the signals on the connecting lines may be communicated.

Internet: For the connection and the acyclic services the IP protocol is used. The Address Resolution Protocol (ARP) is to extend the detection of duplicate IP addresses. For the assignment of IP addresses, the Discovery and basic Configuration Protocol (DCP ) is used mandatory. Optionally, to be used DHCP.

For the construction and management of the compounds known Remote Procedure Call ( RPC) protocol is used. In CBA while the Distributed Component Object Model ( DCOM) objects are used.

Profinet protocols and services: these functions are different log levels to achieve defined:

  • The TCP / IP protocols for Profinet CBA with reaction times ranging from 100 ms
  • The RT (Real -Time) protocol for PROFINET CBA and PROFINET IO Classes A & B, with applications typically 10 ms cycle time
  • The IRT (Isochronous Real -Time) protocol for PROFINET IO Class C applications in drive technology with cycle times less than 1 ms

Functionalities of the Class A (CC -A)

The basic function of the Profinet IO is the cyclic data exchange between the IO controller as a producer and several IO devices as consumers of the output data ( engl. Output Data) and the IO devices as producers and the IO controller as a consumer of the input data (engl. input data). Each communication relationship IO data CR between the IO controller and IO device defines the number of data and the cycle times.

All Profinet IO devices must support the device diagnosis and the safe transmission of alarms via the communication relationship for alarms alarm CR.

In addition, can be read and written to the device via the acyclic communication relationship Record Data CR device parameters with each Profinet. The record for the unique identification of an IO device, the Identification and Maintenance record 0 (I & M0) must be installed absolutely all Profinet IO devices. Optionally, further information can be stored in a standardized format as I & M 1-4.

For real-time data ( Cyclic data and alarms) the Profinet RT frames are transmitted directly via Ethernet. For the transmission of acyclic data UDP / IP is used.

Functionalities of the Class B ( CC -B)

In addition to the basic functions of the Class A units of the class B need to support additional functionality. These functions primarily support the commissioning, operation and maintenance of a Profinet IO system and to increase the availability of the Profinet IO system.

Imperative is to support the Network Diagnostics with the Simple Network Management Protocol (SNMP). Likewise, the Link Layer Discovery Protocol (LLDP ) must be supported by all devices of class B to neighbor discovery, including the extensions for Profinet. This includes collecting and providing related Ethernet port statistics for network maintenance. With these mechanisms, the topology of a Profinet IO network may at any time read out, and the condition of the individual connections can be monitored. In a known network topology, an automatic addressing the participants are enabled by their position in the topology. This simplifies the maintenance device replacement significantly, since no more adjustments must be made.

Especially for applications in process automation and process technology high availability of the IO system is important. Therefore, special procedures have been defined for Class B equipment with the existing relations and protocols. Thus, a system redundancy are realized simultaneously access the same IO devices with two IO controller. In addition, there is a prescribed sequence Configuration in Run (CiR ), how to change the configuration of an IO device with the help of these redundant relations, without losing control of the IO device.

The optional Media Redundancy Protocol ( MRP) allows the creation of a redundant ring topology with a switching time of less than 50 ms.

Functions of class C (CC -C)

For the functions of Conformance Class C (CC -C), especially the Isochronous Real-Time (IRT ) is used protocol.

With the bandwidth reservation part of the available transmission bandwidth of 100 Mbit / s is exclusively reserved for the real-time tasks. In this case a method is used similar to a time division process. The bandwidth is divided into fixed cycle times, which in turn are divided into phases. The red phase is reserved exclusively for real-time data of class C, in the orange phase, the time-critical messages are transmitted and in the green phase, the additional Ethernet messages are passed transparently. This maximum Ethernet telegrams can still be passed through transparently, the green phase must be at least 125 microseconds long. Thus, cycle times are less than 250 microseconds not possible in combination with unchanged Ethernet.

In order to achieve shorter cycle times of up to 31.25 microseconds, are decomposed into fragments as an option the Ethernet frames the green phase. These short fragments are then transmitted over the green phase. This mechanism of fragmentation is transparent to other participants in the Ethernet and thus not visible.

For the realization of these bus cycles for bandwidth reservation we need an accurate clock synchronization of all devices involved, including the switch with a maximum deviation of 1 microseconds. This clock synchronization is realized with the Precision Time Protocol ( PTP) according to the standard IEC 61588. All devices involved in the bandwidth reservation must therefore be in the same time domain.

For applications of position control for several axes or for positioning after PROFIdrive profile not only communication must be timely, but also the actions of the various drives in a Profinet must be coordinated and synchronized. The Clock synchronization of the application program on the bus cycle is allowed to realize the control functions which are performed synchronously on distributed devices.

If multiple Profinet units in a line (daisy chain) are connected, it is possible the cyclic data exchange with the Dynamic frame packing (DFP ) to further optimize. To this end, the controller sets all output data for all devices in a single IRT frame. Each device takes the passing IRT frame extract the relevant data for the device, the IRT - frame is therefore becoming shorter. For the data from the various devices to the controller, the IRT frame is assembled dynamically. The great efficiency of the DFP is that the IRT - frame is only as extensive as necessary, and the data can be transferred from the controller to the devices simultaneously with the data from the devices to the controller in full duplex.

Realization

For the realization of a Profinet interface as a controller or device be for Profinet IO ( CC-A and CC -B) and provided no additional hardware requirements for Profinet CBA that do not use a standard Ethernet interface ( 100BASE -TX or 100BASE -FX ) can be met. In order to enable a simpler line topology is recommended in a device to install a 2-port switch.

For the realization of a Class C (CC -C) an extension of hardware at a time synchronization with the Precision Time Protocol ( PTP) and the functionalities of the bandwidth reservation is required.

The methodology of the implementation is dependent on the type and the scope of the device and the expected numbers. The alternatives are

  • Development in their own home or at a service provider
  • Using Pre- modules or custom design
  • Execution in a fixed design (ASIC ERTEC 200, ERTEC 400, TPS -1) or in reconfigurable FPGA technology

Profinet components model ( Profinet CBA)

A Profinet CBA ( CBA = Component Based Automation ) system consists of various automation components. A component includes all mechanical, electrical and IT variables. The component can be created with standard programming tools.

To describe a component, a Profinet Component Description ( PCD) file is created in XML. A planning tool loads these descriptions and allows the creation of logical connections between the individual components for the realization of an investment.

This model is influenced by the current standard IEC 61499.

The basic idea of Profinet CBA is that you a full automation system in working autonomously in many cases - a divided sub-systems - and thus manageable. The structure and functionality can again be found in identical or slightly modified form well in several plants. Such so-called Profinet components are normally controlled by a limited number of input signals. Within the component performs a control program written by the user from the required functionality, and outputs the respective output signals of other control. The development process involved is independent of the manufacturer. The communication of a component-based system is configured instead of programmed. The communication with Profinet CBA ( without real-time) is suitable for bus cycle times of about 50 ms .100. In parallel arranged RT channel are data cycles as possible for Profinet IO ( a few ms).

Organization

Profinet is Profibus & Profinet defined by International ( PI), supported by the Interbus Club and since 2003 has been part of the standards IEC 61158 and IEC 61784-2.

Electromagnetic shielding Manufacturing engineering Functional Safety Network packet PROFIenergy
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