Industrial Ethernet. Ke Jukka Kortela (Jerri Kämpe)

Transcription

1 Industrial Ethernet Ke Jukka Kortela (Jerri Kämpe)

2 Contents Introduction Real-time? Commercial solutions Comparison 2

3 Introduction Ethernet is de facto standard in office networks today cheap technology Willingness to utilize in fieldbuses Problem? How to assure my message gets certainly through in specified timeframe? 3

4 Contents Introduction Real-time? Commercial solutions Comparison 4

5 Defining real-time Hard real-time is hard, soft real-time is harder - E. Douglas Jensen

6 Real time What is real time? A system is real-time if it is able to react Under all operating conditions To all events correctly within the expected time constraints 6

7 Real time Determinism The exact predictability of a systems timing Jitter The tolerable deviation from a deadline when executing a command 7

8 Definitions Hard Real-Time A single timing problem is a critical error Soft Real-Time A single timing problem is tolerable. However, the average must meet the requirement Non Real-Time Timing problems may be inconvient but are not critical 8

9 Some Approaches Non Real-time Profinet V1 (PNO) Soft Real-Time Ethernet/IP (ODVA) Modbus/TCP (IDA) Profinet V2 (PNO) Hard Real-Time EtherCat (Beckhoff) Ethernet/IP with CIPsync (ODVA) Profinet V3 (PNO) 9

10 Categories of Real-Time Timeliness An action has to be executed within a maximum time Standard Ethernet? Synchronism An action has to be executed within a specified time frame. Standard Ethernet? 10

11 Utility 1 Message occurrence Utility function of the application Utility 0 Deadline t d Time 11

12 Timeliness 1 Message occurrence Utility function of the application Utility 0 Deadline t d Time 12

13 Synchronism 1 - Jitter { + Jitter { Message occurrence Utility function of the application Utility 0 Deadline t d Time 13

14 Is this possible with Ethernet? 1 Message occurrence Utility function of the application Utility 0 Deadline t d Time 14

15 Solution Separate the transmission and execution functions 1 PROBLEM? Utility Requires distributed synchronized clocks 0 Transmission Deadline t d Execution Deadline t d 15

16 Control over Ethernet - other known problems & solutions Problem Solution Shared medium Collisions Buffering Transmission speed Protocol Protocol stack Switching Full duplex Prioritization 10Mb/s 1Gb/s UDP Hardware 16

17 Real time architectures Standard Ethernet TCP/IP Ethernet/IP Modbus TCP Bypass layer 3&4 Profinet v2 Real-time in hardware Ethercat Profinet v3 TCP Standard IP Application UDP Real-time Media Access Real-time Control Ethernet 17

18 Time control IEEE 1588 Precision Time Protocol Sub-microsecond synchronization of real-time clocks in components of a networked distributed measurement and control system Intended for localized systems Simple, administration-free installation Supports heterogeneous systems of clocks with varying precision, resolution and stability. 18

19 Time distribution 19

20 Time stamping 20

21 Real-time conclusion Hard real-time Ethernet exists Coming Hard real-time applications can run over commercial off-the-shelf Ethernet network devices 21

22 Contents Introduction Real-time? Commercial solutions Comparison 22

23 Commercial solutions Many commercial solutions exist EtherCAT Modbus TCP/IP FF HSE PROFINET 23

24 EtherCAT Open real-time Ethernet network. Originally developed by Beckhoff. 24

25 EtherCAT Problem: One device has to send and receive 4 bytes of data. Conventional Ethernet frame min 84 bytes Even at 100% bus load only 4,8% utility load achieved. 25

26 EtherCAT Solution The Ethernet packet is no longer received, then interpreted and process data then copied at every device. The EtherCAT slave devices read the data addressed to them while the frame passes through the node. Similarly, input data is inserted while the telegram passes through. => One frame has info from/to several devices. 26

27 EtherCAT Usable data rate increases to over 90% 27

28 EtherCAT UDP Packages the EtherCAT protocol into UDP/IP datagrams 28

29 EtherCAT Clocks Synchronized according to IEEE 1588 Jitter << 1ms Performance 1000 distributed digital I/O 200 analog I/O (16 bit) Full frame (1486 bytes dig I/O]) 0,03 ms 0,05 ms 0,3 ms 29

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31 PROFINET Originally developed by Siemens 31

32 PROFINET PROFINET is based on Industrial Ethernet and uses the standard TCP/IP (Transport Control Protocol/Internet Protocol) for parameterization, configuration and diagnosis. Real-time communication for the transmission of useful/process data is performed on the same line 32

33 PROFINET PROFINET IO similarities with PROFIBUS DP Distributed I/O connection PROFINET CBA modular, component-based approach 33

34 PROFINET PROFINET CBA Communication Component 1 Component 3 PROFINET Controller Component 2 Intelligent Ethernet Device PROFIBUS PROFINET Device PROFIBUS Device PN PROFINET CBA: CBA: Component Connection, Communication between Components via Ethernet 34

35 PROFINET Process Automation Factory Automation Motion Control Application IT Services, TCP/IP Real-Time: 100ms 10ms <1ms IRT 35

36 PROFINET IT applications e.g. HTTP SNMP DHCP... 1 TCP/ UDP IP Standard data PROFINET applications Real-time data Real-time 2 RT 1 Open TCP/IP channel Device parameterization Reading of diagnostics data Loading of interconnections Negotiation of the communication channel for user data Real-time channel RT High-performance transfer Cyclic data Event-controlled signals 2 Ethernet Real-time switch ASIC 2 RT 3 IRT Real-time 3 Real-time channel IRT High-performance transfer Data in isochronous mode Jitter <1 sec 36

37 PROFINET IO Real-time channel RT Using standard components Performance characteristics like fieldbuses today (e.g. PROFIBUS) Typical application area: Factory Automation Cycle times can be realized in the range of 5 to 10 ms PROFINET Real-Time is fully compatible to TCP/IP standard without any restriction 37

38 PROFINET IO What are the pre-conditions for IRT? Segmentation of the communication use of time based communication Clock-Synchronization PROFINET is compatible to IEEE 1588 Extensions to IEEE 1588 better accuracy The Precision Time Protocol has been implemented < 1µs Jitter 38

39 PROFINET Real-Time Ethernet in Isochronous mode Motion Control applications use separate time domains in one cycle for real-time and non-real-time data IRT channel Open channel (TCP/IP) IRT channel Open channel (TCP/IP) Cycle 1 Cycle 2 Cycle n E.g. 1 ms position control cycle Synchronization Deterministic communication IRT data Open communication TCP/IP data 39

40 PROFINET Backbone HMI HMI HMI HMI HMI HMI HMI HMI MC MC MC MC MC MC MC MC MC Motion controller with ERTEC 400 Drive with ERTEC200 Machine module 40

41 Contents Introduction Real-time? Commercial solutions Comparison 41

42 Performance (EtherCAT marketing example) 40 Axis (each 20 Byte Input- and Output-Data) 50 I/O Station with altogether 560 EtherCAT Bus Terminals 2000 Digital Analog I/O, Bus Length 500 m Performance EtherCAT: Cycle Time 276 s at 44% Bus Load, Telegram Length 122 s for comparison: Profinet IRT 763 s, Powerlink V s*, Profinet RT 6355 s 42

43 Performance (EtherCAT marketing example) 43