wirelessprocessm&c 19 20 september apc9[brr]

8/10/2019 WirelessProcessM&C 19 20 September APC9[BRR]

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WIRELESS PROCESS MONITORING AND CONTROL:

A Brief Overview

Authors: Waqas Ikram and Nina F Thornhill

Department of Chemical Engineering

Imperial College London


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Contents

Motivation

Why use Wireless?

Opportunities for Wireless

Communication Technologies and Process Automation

Automation Pyramid

Control Systems Advancements Key Wireless Technologies

Competing Industrial Wireless Standards

Wireless Monitoring & Control:A New Regime!

Application Classification

Wireless Control: Next step up the ladder! Ongoing Activities

Conclusion

Contents

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Aims and Objectives

Understand the wireless applications in Process Industry

Examine the suitability of commercial wireless networking solutions for Process Automation

Identify the challenges of moving from open-loop to closed-loop control

Motivate the use of wireless for control

Setup a HIL test-bed for studying wireless networked control systems Develop strategies suitable for control over a resource-constraint wireless network

Motivation

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Advent of Wireless Technology in Process Automation

The pursuit to improve :

Process Operations,

Compliance with Regulations,

Operability,

Resource Management &

Safetyat reduced investment costhas paved the way for wireless technology *

The bottom-line is:

To increase the process transparencyand to utilise up-to-date knowledgeof a process/plant

Significant part of the solution is:

Wireless technology which can helpenhance this knowledgeby offering access to regions

considered inaccessible in pastdue to economical orphysical barriers

Motivation

Made possible by advancements in performance of wireless networking

and a reduction in price of networking

APC 9, York, UK , Sept 19-20 2011* DoE4


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Why use Wireless?

Motivation

Wired Technology Wireless Technology

Wear-and-tear free data transfer NO YES

Pre-planning Requirement VERY IMPORTANT LESS IMPORTANT

Installation & maintenance cost * HIGH LOW

Problem trouble-shooting connectors ** HIGH _

Infrastructure flexibility and mobility NO YES

Spare capacity requirement ***

[e.g. cards, marshalling cabinets]

VERY IMPORTANT LESS IMPORTANT

Suitability for deployment in:mobile & rotating equipments

hostile & remote locations

LESS SUITABLE SUITABLE

LESS SUITABLE SUITABLE

and less mechanical design limitations

APC 9, York, UK , Sept 19-20 2011

* ARC Avisory, 2008

** Hartebrodt et al., 2004*** Ferris, 20105


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Opportunities for Wireless:

Motivation

Industrial Measurements

Management

Environmental Monitoring

Emissions

Monitoring

Fire/Gas

DetectionClimate/Air

Monitoring

Stranded

Field Data

Stranded

Assets

Remote &

Aging Assets

Machine Condition

Monitoring

Structural Health

Monitoring

Process

Monitoring

MONITO

RING

Open-Loop

Control

Closed-Loop

Control

Supervisory

Control

CO

NTROL

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Contents

Motivation

Why use Wireless?


Communication Technologies and Process Automation (PA)

Automation Pyramid

Control Systems Evolution Key Wireless Technologies

Industrial Strength Wireless Networks



Wireless Control: Next step up the ladder!

Ongoing Activities

Conclusion

Progress so far

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IndustrialAutomat

ion

IndustrialIT

The cost-effective operation of a plant is highly dependent on automation systems,

of which communication networks are a life-lineto the process operations

Automation Pyramid:

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Control Systems Advancements [Architecture and Communication Technologies]:

3-15 psi

Pneumatic

4-20 mA

Analog

4-20 mA

SmartFieldbuses

Wireless

Technology

after (Georgiev, B [2003]) & Binsai

?

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Key Wireless Communication Technologies:

EDGE

EDGE

License-exempt, Low-power and Globally Available *

* Restriction on channels and emission levels apply

Communication Technologies and PA

IEEE802.11x (Issues) according to Irwin et al.,

-- Channel Contention linked to Scalability

-- Retransmission of data leading to delays

-- Insufficient bandwidth can lead to longer delays

-- FIFO etc.

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Wireless Standards:

Limitations of commercial solutions


Bluetooth Wi-Fi [IEEE802.11b] ZigBee

Typical Applications Cable replacement

e.g. hands-free &

mouse

Computer

networking

Monitoring and

control

Battery Life Low (days) Very Low (hours) Long (years)

Scalability Low Medium Very High

Real-time support

and Reliability

No No No

Channel Access Contention-free Contention-based Contention-based

Topology (flexibility) No No Yes

Data Rate Good Very Good Low

Hence are not suitable for Process Automation

Battery Life

Scalability

Real-time support

and Reliability

Channel Access

Topology (flexibility)

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Industrial Requirement:

Network which is:

- Secure

- Safe

- Reliable

- Energy-efficient

- Supports Real-time

- Operates in licence-exempt band

- Ensures Co-existence

- and offers QoS

Resulted in: Four standards

- ZigBee PRO

- WirelessHART

- ISA100.11a

- WIA-PA


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Key features which makes them Industrial Strength:


Reliability:- Mesh Networking- Channel Hopping- Time-Synchronized Communications

Security:- Encryption, Verification, Authentication and Session Keys

Power Efficiency:- Smart Publishing (publish data when it changes)- Time Synchronized Communication

Topology:- Flexible (e.g. star, mesh), hence spatial diversity

Determinism:- Time Division Multiple Access (TDMA)

Channel Management:- Channel Assessment and blacklisting features

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Comparison:


STANDARDS

ZigBee PRO WirelessHART ISA100.11a WIA-PA

Transceiver IEEE802.15.4 IEEE802.15.4 IEEE802.15.4 IEEE802.15.4

Topology

(Mesh Support)

Star, Tree, Mesh

(Yes)

Mesh

(Yes)

Star, Tree, Mesh

(Yes)

Hybrid Star and Mesh

(Yes)

Channel Hopping Agility Time slot Hopping Time slot Hopping &

Slow Hopping

AFD &

Time Slot Hopping

Superframe Slot Size N/A 10ms Configurable ConfigurableChannel Access CSMA/CA TDMA TDMA TDMA

Device Type FFD, RFD FFD FFD, RFD FFD, RFD

Expansion/New Extension of ZigBee Extension of HART

protocol

New protocol New protocol

Determinism No Yes Yes Yes

Channel Management

Features

Preferred Channel Blacklist Whitelist & Blacklist Adaptive

Battery Life* Best Good Good Good

Reliability and

Robustness against

Jamming

Low Good Good Depends on Hopping

mechanism

Time slot Hopping Time slot Hopping &

Slow Hopping

AFD &

Time Slot Hopping

10ms Configurable Configurable

Extension of HART

protocol

New protocol New protocol

Blacklist Whitelist & Blacklist Adaptive

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Contents

Motivation

Why use Wireless?


Communication Technologies and Process Automation (PA)

Automation Pyramid

Control Systems Evolution Key Wireless Technologies

Industrial Strength Wireless Networks




Ongoing Activities

Conclusion

Progress so far

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Classification of PA applications:

Wireless Monitoring and Control

Fu

ture

CurrentAdoption

from ISA100.11a

Mesh technologyis useful to increase reliability and range, however, it can lead to

increase in latencytimes (concern for control)

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Control applications over a wired NetworkInherent Challenges:

NCS design challenges:

Time-delay

Packet loss

Limited communications (network capacity)

Sampling-rate constraints

Disturbances in communication network


Plant SensorActuator

Wired Network

Controller

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Control applications over a wireless NetworkAdditional Challenges:

How is it different to Wired NCS?

Packet delaysand dropoutsare to be expected (more profound)

Co-existenceissue due to operation in 2.45 GHz ISM band

Power consumptionconstraint due to limited onboard battery

Connection loss(Outages)BERand Quantization error

Network congestion (shared utilization)


Plant SensorActuator

Wireless Network

Controller

Different from traditional wired systems

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Approach *:


WNCS

Network-Aware Control

Communication imperfections are to be

modelled.

System with time delays.

Compensation for delays/data loss.

Control-Aware Communication

Protocol selection or modification for

real-time performance.

Reduce delays.

Packet dropouts.

Co-Design Solution

Integrated design of application and

communication layers.

Adaptive Techniques.

- Controller Designneeds to

be robustand adaptiveto

communications constraints

AND

- Networkneeds to be optimised

for end-to-end control

performance

APC 9, York, UK , Sept 19-20 2011* Liu, X & Goldsmith, A.19


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NCS Performance (Depends on):

- Network traffic

- Network devices and application requirements

- Distributed control architecture

- Communication protocol

- Controller and its implementation


Time delaysandpacket-dropoutsdegrade control system performance, and can

even lead to instability.

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Contents

Motivation

Why use Wireless?


Communication Technologies and Process Automation

Automation Pyramid

Control Systems Advancements

Key Wireless Technologies

Competing Industrial Wireless Standards




Ongoing Activities

Conclusion

Contents

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Ongoing Activities: Time Synchronization in WSNs using Radio-Clocks

Importance: Accurate time stamping of data, data fusion, coordination etc...

Application: Process Monitoringof a spatially distributed Pipeline Network


Mote Integrated with Radio Clock

Conference Paper [ETFA 2010]:

Towards a Radio-Controlled Time Synchronized Wireless Sensor Network: A. Work in-Progress Paper.

Ikram, W.; Stoianov, I.; Thornhill, N.F.; Centre for Process Syst. Eng., Imperial Coll. London, London, UK

Deployment sites

MSF Transmitter

Imperial

College

London

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Ongoing Activities: Closed-Loop Control over a LR-Wireless Network


Conference Paper [UKACC 2010]:

Wireless Communication in Process Automation: A Survey of Opportunities, Requirements, Concerns

and Challenges . Ikram, W.; Thornhill, N.F.; Centre for Process Syst. Eng., Imperial Coll. London, UK

Wireless Network Sensor(s)

Actuator(s)

PROCESSCONTROLLER

Wireless Network

HiL setup enables to quantify and examine the issues in WNCSs

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Conclusion

The use of wireless technology in PA systems offer a cost-effective, modular andflexible system design.

The use of Wireless in Industry is currently focusing on monitoring applications.

However, closed-loop control is its natural extension.

NCS introduces latency in packet delivery and even packet drop-outs. In WNCS

these problems become more prevalent.

Conventionally control and communication systems are designed based on often

different and competing tradeoffs.

Conclusion

Using wireless communication for closing the loop requires robustness, guaranteed

real-time data delivery, integrity,securityand availabilityunder all conditions.

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WNCSs (multi-disciplinary):

Control Engineering

Communications Engineering

Real-time Computation and Embedded Programming

Systems Engineering

Closed-loop control over a constraint wireless network requires a co-design

approach for satisfactory results.

Conclusion

Thank you for listening

APC 9, York, UK , Sept 19-20 201125

wirelessprocessm&c 19 20 september apc9[brr]

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