Mittuniversitetet PROFIBUS PA

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1 PROFIBUS PA

Profibus PA is the same protocol as Profibus DP. The physical medium is different with reduced voltage and current levels to meet the requirements of intrinsically safe areas.

2 Profibus PA is the same protocol as Profibus DP. The physical medium is different with reduced voltage and current levels to meet the requirements of intrinsically safe areas. Profibus PA is designed to operate in hazardous areas. Devices that operate in this environments have to follow European directive ATEX An equipment (Europe) is marked with Ex if its approved under ATEX directive Profibus PA transmission techniques are described in IEC

3 The physical layer MBP-IS Twisted cable Fixed Baudrate of kbit/s Maximum distance 1900 m Between 10 and 32 devices per segments Power Supply directly from the bus Each device has a current consumption of minimum 10 ma The maximum device number depends on the current consumption per device. (typ ) 3

4 The role of a coupler in Profibus-PA 4

5 A coupler adapts a Profibus-PA network as a DP device: electrical isolation power supply of the bus and adaptation between RS485 and IEC baud-rate adaptation (DP to 31.25kbit/s voltage mode) conversion between UART telegram and 8-bit synchronous telegram. 5

6 The couplers are relative simple devices. To work correctly the maximum speed of the Profibus DP segment must be decreased to kbit/s. A DP/PA Link acts as a slave DP and a master PA. It is not required to decrease the DP segment datarate. 6

7 Reference Official Website PROFIBUS System Description Practical Industrial Data Communications - Ch. 14a Industrial Communication Systems - Ch. 32 7

8 Profisafe

9 Profisafe is an application profile that can operate within any Profibus-DP or Pronifet network. Profisafe is based around the concept of black channel. The safety services of Profisafe are independent of the characteristics of the transmission system. Safety data are encapsulated inside Profinet and Profibus frames. 9

These safety measures include: The consecutive numbering of the PROFIsafe messages ("sign-oflife") A time expectation with acknowledgement ("watch-dog") A codename between sender and receiver

10 These safety measures include: The consecutive numbering of the PROFIsafe messages ("sign-oflife") A time expectation with acknowledgement ("watch-dog") A codename between sender and receiver ("F-Address") Data integrity checks (CRC = cyclic redundancy check) Profisafe message format: To keep track of the Consecutive Number, both sender and receiver use a counter that is synchronized via the Control Byte and Status Byte. 10

11 PROFIsafe compliant devices must have a set of parameters for the safety layer defined in the GSD file. The GSD files are protected from data corruption with a special CRC signature on storage media. Example of parameters: F_WD_Time specifies a number of milliseconds for a watchdog timer. This timer monitors the reception of the next valid PROFIsafe message. F_SIL indicates the SIL expected by the user form the particular F_Device. It is compared with the locally stored manufacturer information. F_iPar_CRC is a signature across all the iparameters within the technology of the F-Device. F_Par_CRC is a signature across all the F-Parameters which is used to ensure correct delivery of the F-Parameters. 11

12 Reference Official Website PROFIsafe System Description 12

13 Real Time Ethernet (RTE)

14 Advantages of Ethernet Simple interfacing with higher levels (supporting of TCP/IP traffic) Standard technology that is widespread, updated and supported by PC 10Base5 10BaseT 100BaseT GigaEthernet Hardware costs are decreasing Availability of IT communication instruments PC-based analyzers (Es. Wireshark -Ethereal-); Simulators Network analyzers with high performance. Emerging nodes and controllers use web and java technologies Soft-PLC, web-sensor,... Support of related technologies (optical fiber, wireless WiFi) couplers, bridges vs. subnetworks 14

15 Ethernet is just a transportation medium, what matters are the higher layers. 15

Different approaches are possible for Ethernet in industry: Tunneling of Fieldbus protocol over UDP/TCP/IP Definition of a new real-time protocol Modification of the

16 Different approaches are possible for Ethernet in industry: Tunneling of Fieldbus protocol over UDP/TCP/IP Definition of a new real-time protocol Modification of the standard MAC layer Tunneling of TCP/IP over an existing fieldbus Tunneling TCP/IP stack over same physical layers Example: TCP/IP over Interbus Segmentation of IP packets 16

17 Example: Modbus over TCP Physical layer: Ethernet 10/100 Mbit/s Characteristics: One master, 247 slaves (like Modbus) Overhead of 54 Bytes 17

18 REAL TIME ETHERNET Ethernet for real time applications Characteristics: Determinism Synchronization of communication, I/O and applications (e.g. IEEE1588) Simple protocol stack (TCP/IP is too complicated for a sensor) Compatibility with TCP/IP traffic (same infrastructure) - a part of the bandwidth is reserved for TCP/IP - router or gateway (proxy, firewall) for TCP/IP traffic Difficult coexistence among different RTEs Approaches: Full-software Hardware/software 18

19 Full Ethernet (Modbus/TCP, Ethernet/IP, Profinet IO RT, FFHSE) Standard Ethernet IEEE802.3, switched and full-duplex, with priority and VLAN + coexistence, COTS network devices (cost, technology) - No guarantee of deterministic services Ethernet compatible, but using specific devices (Profinet IO IRT) Special switches with time slicing (mandatory, no other switches allowed) + coexistence, deterministic guaranties, priorization of flow - Uses specific network devices New fieldbus and Ethernet Links (EtherCAT, Sercos III) Different MAC layer to provide real-time, use of specific devices, gateway + deterministic, short cycle time, QoS guaranteed (all data in a single frame) - Specific network devices 19

20 ETHERCAT

21 Ethernet for Control Automation Technology (EtherCAT) Introduced by Beckoff in 2002, sponsored by the open source organization Ethercat in 2003 A single Ethernet Frame is sent by the unique controller (master) and read or modified by the slaves on-the-fly Not-EtherCAT frames are passed through (coexistence) Software-based Master, Hardware-based Slaves Many topologies supported (linear, ring, tree, ) Support CAN application protocol CANopen. 21

EtherCAT: the stack Layer ISO/OSI Model ETHERCAT 7 Application Cyclic Data Exchange Acyclic Data Exchange 6-3 2 Data link Fast frame forwarding Mailbox handling IEEE 802.

22 EtherCAT: the stack Layer ISO/OSI Model ETHERCAT 7 Application Cyclic Data Exchange Acyclic Data Exchange Data link Fast frame forwarding Mailbox handling IEEE MAC 1 Physical 100Base-TX 100Base-FX The EtherCAT commands are transported in the data area of an Ethernet telegram and can either be coded via a special Ether type or via UDP/IP. Industriell Datakommunikation 22

23 EtherCAT: characteristics Hard Real-Time Fast Cycle Times within µs Precise Synchronization Protocol is processed in hardware Flexible Topology Line, Tree, Star, Daisy Chain Standard Ethernet Cabling, Cost Effective Components Master-Slave & Slave-Slave Communication Industriell Datakommunikation 23

24 EtherCAT: the Hardware Master EtherCAT master can be implemented on any equipment controller that provides an Ethernet interface. Slave All the time critical functions (communication) are implemented on FPGA or ASIC Up to devices Transmission medium No switches or Hub Ethernet 100BASE-TX (up to 100m between two nodes) 100BASE-FX (Fiber - up to 20km between two nodes) E-bus (LVSD Low Voltage Differential Signaling) Short range communication (10 m) 100 Mbps 24

25 EtherCAT operating principle The slaves manipulate the Ethernet frame on the fly Typically only one Ethernet Frame per Cycle Allows for asynchronous event triggered communication Switches are not necessary (decreased delay) 25

26 EtherCAT Frame Ethernet Header Frame Payload FCS EtherCAT Header Datagram 1 Datagram n Datagram Header Data WKC Ethernet Frame Ethernet Header (14 bytes) Payload FCS (4 bytes) Frame Check Sequence EtherCAT Frame EtherCAT Header (2 bytes) Datagram Datagram Header (10 bytes) Data (0 to 1486 bytes) WKC (2 bytes) Working Counter Datagram Header Data WKC 26

27 Addressing Datagram headers contain a 32 bit address which can be used either for logical or physical addressing. Physical Addressing Position address (incremental addressing) Used during start-up to assign a fixed address Every telegram is addressed to a single slave Position 32 bit Address 16 bit 16 bit Offset Configuration Address Offset Logical Address Logical Addressing 32-bit field address (4GByte address space with bit-wise capability) A table in the slave devices is used to convert logical address into physical address Improve the utilization ratio of the Datagram 27

28 Redundancy The ring structure In case of a Node/Cable failure, the slaves can close the loop The master requires only an addition Ethernet port 28

29 Reference Official Website Introduction Introduction 2 Industrial Communication Systems - Ch

30 PROFINET IO

31 PROFINET requirements for the Phy Layer At least 100 Mbps (100 Base-TX, 100 Base-FX); Switches (Hub cannot be used) Switches have to be designed to operate with fast Ethernet (100 Mb) Switches should support prioritized telegrams according to IEEE 802.1Q Link distance < 100 m PROFINET allows the use of proxy to integrate existing fieldbus systems 31

32 The PROFINET IO-System PROFINET IO-Controller: Exhange Data to and from the IO-Device associated; Runs the user control program PROFINET IO-Device: Field device connected to the IO-Controller PROFINET IO-Supervisor: HMI and Diagnostic 32

33 3 TYPES OF TRAFFIC 1 TCP/IP TRAFFIC Configuration and Diagnostic Data Initialization Procedures 2 REAL TIME TRAFFIC Event Triggered Data Cyclic Data 3 ISOCHRONOUS REAL TIME TRAFFIC High performance (jitter < 1μs) Isochronous Data 33

34 Profinet IO: Data exchange Every data exchange is embedded into an AR (Application Relation) Within the AR, CRs (Communication Relations) specify the data explicitly. Industriell Datakommunikation 34

35 Isochronous real time data use the channel in different time from standard TCP/IP communications. 35

36 Similarly to Profibus, every device is described by a xml-based GSD file. This contains all the information useful for the configuration of the device in to the network. Profinet similarly to Profibus PA/DP supports application specific profiles. (e.g. Profisafe) 36

37 Reference Official Website PROFINET System Description Industrial Communication Systems - Ch

38 Wireless Industrial Networks

39 Wired vs Wireless Wired Wireless Cost Steady Decreasing Security Internet Open medium Determinism Good Medium is unreliable Maintenance Cable replacement Batteries (Energy Harvesting) Mobility Limited Extensive Compactness Good Reduced by batteries Industriell Datakommunikation 39

40 Different Wireless technologies compared IR UWB NFC Frequency nm 2.4/5 GHz 2.4 Ghz MHz, 2.4 GHz Data Rate 20 kbps - 16Mbps Transmission Distance Power Consumption Application GHz Mbps 1 Mbps kbps Mbps MHz kbps 1-9 m (LOS) m 10 m 10 m <10m 20 cm Typ. 10 mw 1 W 300 mw 100 mw 100 mw Low Remote control, Short range transmission WLAN Cable Replacing Control and Automation Localization Short range transmission ZigBee WirelessHART ISA a WIA-PA Industriell Datakommunikation 40

41 Wireless Sensor Network (WSN) WSN Is a wireless network consisting of autonomous devices that communicate monitoring information from the environment What is important? Reliability Security Self-healing and Self-organizing capabilities Low Energy Consumption WSN with mesh topology Industriell Datakommunikation 41

42 Reliability and use in industrial environment The reliability of a data transmission is defined in Bit Error Rate (BER). BER is calculated as the number of bits that are not transmitted correctly over the total number of transmitted bits. The better the BER, the better the reliability of the data transmission. Six classes of applications have been defined. Industriell Datakommunikation 42

43 WirelessHART

44 Extension of HART that uses wireless communication. First release in 2007 Developed for the Process Automation Layer ISO/OSI Model HART WirelessHART 7 Application Command Oriented 6 Presentation 5 Session 4 Transport Auto-Segmented transfer of Large Data Set 3 Network Redundant Path, Self Healing Wireless Mesh Network 2 Data link Mechanical/electrical connection, TDMA/CSMA, Transmits raw bit stream Frequency Agile 1 Physical 4-20 ma copper wiring 2.4 GHz wireless, Phy 44

45 Analog Wiring vs WirelessHART Industriell Datakommunikation 45

WirelessHART: Physical Layer Based around the IEEE 802.15.4-2006 Phy layer Communication in the ISM band (2.

46 WirelessHART: Physical Layer Based around the IEEE Phy layer Communication in the ISM band (2.4GHz) with DSSS modulation; Co-existence problem with other technologies; Channel hop to avoid busy channels (15 channels) Assess channels before use; Blacklist bad channels; Transmit for a short period of time (good neighbor); Vary transmit power (security benefit too); 46

47 WirelessHART: Topologies 47

48 WirelessHART: Time Division Multiple Access Dedicated time slots Allocated based upon data transfer needs Data is time stamped Shared time slots Acyclic data transfer for Asset Management Process (valve) signatures Alarm reporting 48

49 Reference Official Website Industrial Communication Systems - Ch

50 Labs Lab1 May 17 L109- Lab2 May 18 L109- Lab3 May 28 L109- MatlabR2012a or later and Simulink are required. Industriell Datakommunikation 50

PROFIBUS and Integrated Safety architectures in Ex areas

PROFIBUS and Integrated Safety architectures in Ex areas Since 1989, PROFIBUS has developed into a worldwide leading fieldbus system used in machine and process plant automation. The main reason why PROFIBUS