WirelessHART, Technology and Deployment ( ETSI Nov. 09 ) Jean-Luc Griessmann, HART Communication Foundation Europe

Transcription

1 WirelessHART, Technology and Deployment ( ETSI Nov. 09 ) Jean-Luc Griessmann, HART Communication Foundation Europe

2 Introduction Wireless devices are everywhere! We use wireless devices in everyday life. Devices are simple and often work out of the box We sometimes accept poor service (battery life signal loss) Industry has special requirements Reliable, Secure, Simple Based upon standards We can not just send process data over a radio link 315/915MHz 433/868MHz 2.4 GHz 433MHz 315/413 MHz 315/426 MHz 433/915MHz

3 WirelessHART, Designed for Process Applications Reduce installation costs Cable connections cable trays Process monitoring / Control Hard to reach / expensive to install locations Full access to multivariable devices Control where appropriate Asset Management Condition monitoring Configuration database Plug in upgrade adapter

4 What is HART? Communication over wire 4 cyclical variables 3.5psi Device set up Calibration Diagnostic and maintenance status 4-20mA Process

5 Building on HART for evolving to WirelessHART HART is the industry standard Instrument communications protocol Main use is for commissioning Less than 10% of instruments have Time/Cond. Reporting PV Trending Security Mesh & Star All PV With Status Long Tags Process Monitoring HART 5 remote access HART is evolving Adding features Wireless is the next step Simple Secure Reliable For wireless power is important Standardization now IEC/PAS Ed. 1 Diagnostics Configuration Remote Access HART mA Loop HART 7 Wireless

6 The wireless resource Find a Frequency band which Does not need a license Is available world wide 3MHz 300MHz 30MHz 3GHz 30GHz 300GHz

7 Wireless Spectrum Use an open wireless band Industrial Scientific Medical (ISM) No site license required Need to work alongside other users (ZigBee Bluetooth, WiFi ) Choose an ISM band with global coverage 2.4GHz IEE kbps Channel hopping on per packet basis 315/915MHz 433/868MHz 2.4 GHz 433MHz 315/413 MHz 315/426 MHz 433/915MHz

8 Coexisting with other networks Need to coexist with other users of the ISM band Good worker gets the message through Good neighbour works with alongside networks Asses a channel before you use it Hop to other channels Reduce power to limit signal range Radio WirelessHART Radio Other Network WiFi CH GHz CH GHz CH GHz

9 Co-Existence Channel hop to avoid busy channels (15 channels) Asses channels before you use them Black list channels which have heavy use Transmit for a short period of time (good neighbour) Vary transmit power (security benefit too) Built into WirelessHART

10 Co-Existence Testing with other ISM users Wifi b/g Video Phone Others WirelessHART Maintained % data reliability in a 20 Instrument mesh Video, Phone & WiFi

11 Main requirements (User Input) Make it Reliable Manage power Process plants change Need redundant paths Make it Secure Secure the data Authenticate data and devices Make it Simple As simple as 4-20mA

12 WirelessHART Reliable MESH network Multiple pathways Adapts to plant conditions Gateway Multiple access points Security and Network manager Co existence Work within the ISM band Channel assessment Black listing Gateway Host Connection (High Speed fieldbus) % end to end reliability

13 WirelessHART Secure Always enabled ( keys, encryption AES 128 ) Data level Instrument authentication Message authentication Data Encryption Network level Monitor join attempts Rotate encryption keys Defeat replay attacks Short time synchronized messages (<4 msec) Can you break the code in real time?

14 Power is everything High data rate = reduced battery life Battery development will help Can use energy scavenging Build features into the specification to extend battery life WirelessHART Gateway Note: Radio time can depend upon location in the mesh

15 Location in the Mesh and Power Power: Power options include Battery External power Energy scavenging The radio burns significant battery power Parents have to route data from children Children can have routing feature switched off. Radio is on for Routing Synchronising Advertising ~10 years WirelessHART Gateway Parents routing 50% life Parents & Children some routing 70% life Children No routing 100% life

16 When to transmit in WirelessHART WirelessHART instruments are time synchronised Time distribution Time slots Allows different reporting rates within one mesh Synchronise for channel hopping Access and timing is handled automatically

17 TDMA Time Division Multiple Access Time Slot 1 Slot/Channel = 1 Transaction (10msec) Dedicated slot (PV update) Shared slot (alarm/events) Time Synchronization When a Slot Begins Common time What Frequency To use Time synchronisation and time slots are handled automatically Transaction Transmission Starts Destination Listens for Start of Message STX Source Now Listening Slots Cycle n-1 Cycle n Cycle n+1 Superframe ACK Destination ACK Starts TDMA Slot-based Communication Slot - A fixed time interval that may be used for communication between neighbors. Superframe - A collection of slots repeating at a constant rate. Each slot may have several links associated with it. Link - The full communication specification between adjacent nodes in the network. i.e., the communication parameters necessary to move a packet one hop.

18 Slot Timing Transmitting Start Slot Assessment Switch to Transmit Wait for ack Receive ack Listen CCA Message 3 to 4 msec Switch to receive 10 msec - 1 time slot - 1 channel 1 slot can transmit up to 8 PV s plus status Packet = 133 bytes 250kbit/s

19 Using WirelessHART Applications Process monitoring/control Hard to reach locations Better insight into process Ad-hoc measurements multivariable devices Equipment Monitoring Bearing temperatures Vibration Corrosion Oil pressure Air flow Asset Management Maintenance Calibration Record valve signatures Radar echo Diagnostics Valve position feedback Device health (status)

20 Planning Site Assessment Detailed site survey not required Line of Site Clear line of sight to the device with no obstructions Low Density Open areas where you can see from one device to multiple other devices Medium Density Can drive a truck through the process area High Density Can not see from one device to the next Significant metal and structural material Clear Line of Site 225m Unobstructed 150m Moderate Density 75m Highly Dense 30m

21 Planning, Deployment Best Practice Each field device has at least 3 neighbors The 3 rd neighbor will act as a backup if one of the two primary paths is obstructed or unavailable Devices (antenna) mounted >0.5m from any solid surface and off the ground Gateway Should have 5 neighbors 20% of field devices connect directly to the gateway

22 Planning, Deployment Device location Locate instruments Use repeater for devices out of range ½ power beam 45deg about horizontal Locate gateway plant segmentation Network capacity Area classification

23 Conclusion Hart is the ideal basis for a wireless instrument network Industry standard 30,000,000 installed devices WirelessHART ticks the boxes Reliable Secure - Simple Backing of major vendors Int. Standard IEC/PAS 62591