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Reti wireless per il controllo critico di processo - tecnologie e architetture emergenti

La disponibilità di nuove tecnologie per l'approvvigionamento energetico
renderà possibile l'implementazione di protocolli avanzati di comunicazione
wireless a supporto di applicazioni critiche a circuito chiuso.

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Atti di convegni o presentazioni contenenti case history
Intervento al convegno mcT Petrolchimico 2011 Milano

Pubblicato
da Alessia De Giosa




Settori: 

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Estratto del testo
Reti wireless per il controllo critico di processo: tecnologie e architetture emergenti S. Savazzi, S. Guardiano Tecnologie per il Petrolchimico 24 Novembre 2011 24 Novembre 2011 Wireless in the Oil&Gas industry ' Exploration
12 cable-free land equipment manufacturers worldwide (2011) ' Transportation/Extraction Pipeline monitoring, RFID identification, leakage monitoring, emergency alert systems ' Refining Strategic interest:
APC, Predictive mainteniance and
diagnostic, Asset Management syst. 24 Novembre 2011 - Lower Installation cost Eliminating wires means significant cost savings (wiring cost alone 40-
200 '/meter). - Lower Maintenance costs (no junction boxes, no wires or terminals that corrode, no water in
conduits, ') - Flexibility & Mobility Wireless Technology
1. Technically advancing (low-power HW manufacturing)
2. Becoming cost-effective (chip costs <2$)
3. Standardizing (IEEE 802.15.4, IEEE 802.11, ISA SP100, WirelessHART) Why wireless' 24 Novembre 2011 WiBRO 2001 2004 2007 2010 1998 WiMAX (fixed) GSM/GPRS ZigBee LTE/WiMAX (mobile) UMTS/EDGE (advanced) 2010 MB-OFDM (UWB) UWB Bluetooth WLAN (WiFi) Hotspots (802.11n) mmWave (60GHz) Wireless in Oil&Gas industry, is it time ' 24 Novembre 2011 Wireless systems 1. preserve the existing application protocols and security standards for Fieldbus
2. modify PHY/MAC design (link layer management) Wireless at Fieldbus level Application Layer PHY Layer IEEE 802.11 (WiFi), IEEE 802.15.4 (ZigBee) PROFIBUS, WorldFIP, DeviceNet,
Foundation Fieldbus (H1/HSE) ISA SP100 Fieldbus Wireless Fieldbus MAC Layer (link manag.) Wireless HART, ISA SP100 24 Novembre 2011 Closed-loop Process Control Centralized Controller Sensor Plant External Input/
disturbance k e Actuator k u I/O Sensor (Fieldbus) Cable-based closed-loop control Centralized Controller Se t p o in t Manipulated Variables (MVs) k e Disturbance Variables (DVs) Controlled/observable Variables (CVs)  k u k x C o n tr o l m es sa ge Se n so r d at a k u k x k x Reaction time T 24 Novembre 2011 Process Control and Monitoring services Low-speed closed-loop control 1. Typ. Reaction time T below 1 sec.
2. Human involved in system observation Medium/High-speed closed-loop control 1. Reaction time T below 100 msec.
2. Tooling machines and control systems (PLCs) Wireless ' Open-loop monitoring Commercial wireless systems 24 Novembre 2011 Wireless Fieldbus: challenges and problems ' Electromagnetic compatibility (EMC) and self-interference ' Enclosure and ATEX certification 1. Typ. Enclosure IP66/67, NEMA4X.
2. Explosion protection, batteries replaceable in hazardous area. ' Real-time critical control 1. Safety critical messages must be transmitted reliably within fixed deadlines 2. Reservation-based medium access ' Reliable wireless networking 1. Radio propagation assessment & design 2. Advanced network architectures (cooperative communication) 3. Enhanced controller designs (PID-enhanced) ' Battery life 1 . ISM frequency bands (433MHz, 868MHz, 902-928 MHz, 2.4GHz and 5.7GHz) 2. highest EM interference is measured at sub-GHz frequencies. 24 Novembre 2011 k x Wireless closed-loop control Reaction time T  k u C o n tr o l m es sa ge Se n so r d at a k x Stable system Real-time critical control Plant External Input/
disturbance k e I/O Wireless Sensor Sensor Actuator Wireless Centralized Controller k u k x k u 24 Novembre 2011 Real-time critical control k u C o n tr o l m es sa ge Se n so r d at a k x Unstable systemLatency! Critical condition for HW instrumentation Wireless closed-loop control Plant External Input/
disturbance k e I/O Wireless Sensor Sensor Actuator Wireless Centralized Controller k u k x k x k u 24 Novembre 2011 Reaction time  k u C o n tr o l m es sa ge Se n so r d at a k x  k u C o n tr o l m es sa ge Se n so r d at a k x Packet loss U n st a b ilit y Reliable wireless networking: packet loss (MTBF '' critical mean
time between failure)
24 Novembre 2011 Plant External Input/
disturbance k e I/O Wireless Sensor Sensor Actuator Wireless closed-loop control Wireless Centralized Controller Se t p o in t Centralized Controller Data loss compensation Reliable wireless networking 1. Wireless Radio Propagation Assessment & Design (channel modeling and classification for link quality prediction) 2. Advanced architectures to reduce packet Loss (cooperative communication and virtual-MIMO) 3. Controller designs for wireless (techniques for data-loss compensation, enhanced PID) k u k x k x k u 24 Novembre 2011 Wireless Radio Propagation Assessment d h Low/No signal d Fresnel zone Obstructed
Line-of-Sight
(O-LOS)
Non Line- of-Sight (NLOS) Evaluate the site for wireless implementation: - classify the radio propagation environment
- conduct a professional site survey (RF Spectrum Analysis) 24 Novembre 2011 h d Network planning I/O sensors
Controller Line-of-Sight (LOS) LOS
NLOS
OLOS
Network Planning and Design 24 Novembre 2011 Reliability through cooperative networking Wireless (Star topology) Wired Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h time time Out of service (Packet loss) Controller 24 Novembre 2011 Wireless (V-MIMO x2 redundancy) Wired Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h time time Out of service (Packet loss) Reliability through cooperative networking 24 Novembre 2011 Wired Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h Good (connected) Bad (disconnected) R ec ei ve d s ig n al s tr en gt h time time Wireless (V-MIMO x3 redundancy) Reliability through cooperative networking 24 Novembre 2011 Virtual MIMO: an analogy with neural networks Dendride Axon Neuron
(nerve cell) Virtual MIMO networks Virtual
antenna
k u Neural networks k x 24 Novembre 2011 Multi-hop vs Virtual MIMO architecture Time Ch. slot C A super-frame C'B B'A D'A Reaction time B D A'D B'A B'C A'B Multi-hop
architecture
Repeat TX 24 Novembre 2011 Multi-hop vs Virtual MIMO architecture Time Ch. slot C A super-frame C'B B'A D'A Reaction time B D C'D A'D D'C Cooperative repeaters Virtual-MIMO
Architecture
(x2 redundancy)
C'B C'D 24 Novembre 2011 Virtual-MIMO architecture for control-loops Virtual Controllers k u k u k u k u Wireless Fieldbus Fieldbus k u 24 Novembre 2011 Virtual-MIMO architecture for control loops Virtual Controllers k x Controlled variable k x k x k x k x Wireless Fieldbus Fieldbus 24 Novembre 2011 Plant I/O Wireless Sensor Sensor Actuator Se t p o in t Prediction filter k x' - M ea su re m en t d at a Prediction k x Lost Measurements D K M ea su re m en t d at a k x Controller design for wireless: enhanced PID I K d/dt dt ' P K PID controller Wireless Controller k x k x k x k u k u 24 Novembre 2011 High duty cycle 1 sample/s (per sensor)
Medium duty cycle 1 sample/10s (per sensor)
Low duty cycle 1 sample/min (per sensor) Battery lifetime critical! Battery lifetime Low battery B at te ry c ap ac it y (y r) 10 5 3 2 1 NiMH Lithium Supercapacitor, Energy harvesting 2010 - '' 200 Wh/kg Energy density 24 Novembre 2011 Conclusions 1. Current wireless solutions are suitable for process monitoring applications but not for control/safety applications 2. The availability of new energy harvesting technologies (based on process
temperature step changes, solar radiation, vibrations) will make it possible
to implement advanced wireless communication protocols to support
critical closed-loop wireless applications 3. Preliminary test-beds developed at Politecnico di Milano show that the
cooperative network architecture (V-MIMO) seems to satisfy the stringent
requirements of closed-loop critical control. 4. Further info can be found in upcoming IEEE publications: - S. Savazzi, S. Guardiano, U. Spagnolini, ''Wireless Critical Process Control in oil and gas refinery plants,' IEEE International Conference on Industrial Technology, March 2012 - S. Savazzi, ''Wireless Virtual-MIMO systems for closed-loop process control: protocols and experiments,' IEEE Transactions on Industrial Informatics (to appear 2012) 24 Novembre 2011 Security 1. Confidentiality. Prevents unauthorized disclosure of sensory data and ensures that only authorized entities can read the data 2. Integrity. Detect illegal alteration of data. Illegal alteration may result in serious consequences especially in critical control applications 3. Authentication. Centralized controller should corroborate the sensory data of each wireless node. Only authorized wireless nodes can gain access to the centralized controller 4. Non-repudiation. Guarantees that wireless nodes cannot deny transmission if requested Existing solutions
- Advanced Encryption Standard AES128/256
- Centralized security management
- Integrity. Use of Frequency Hopping, mitigation of sophisticated passive and active WLAN attacks
- Authentication. Support for Protected Access (WPA) and WPA2 security standards 24 Novembre 2011 Fieldbus systems, overview Fieldbuses systems define the communication architecture to deliver quality of service in industrial process control networks Application Layer PHY+Data Link Layer Some examples (Fieldbus types):
PROFIBUS, WorldFIP, DeviceNet,
Foundation Fieldbus (H1/HSE), P-Net ' ISA S50.02, IEC 61158, IEC 61784
Industrial Ethernet, IEEE 802.3u 24 Novembre 2011 Advanced architectures to reduce packet Loss Virtual MIMO networks Virtual
antenna
k u Multi-hop (mesh) networks Multi-path
(or cooperative)
routing Single-path
routing k x k x k u 24 Novembre 2011 Self-interference Radio coverage and spectrum management 24 Novembre 2011 Reservation-based medium access Time Ch. slot C A Benefits 1. predictable energy consumption (predictable network lifetime)
2. predictable latency/delay (real-time applications)
super-frame C'B A'B B'A B'A B'C E'A Reaction
time #1
B'C B'A Reaction time #2 Reservation-based MAC is supported by most advanced standards:
IEEE 802.15.4, WirelessHART, ISA SP 100.11a
I/O Wireless Sensor #2 #1 B A'B


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