An Introduction to
Cyber-Physical Systems
INF5910/INF9910
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Outline
• What is Cyber‐Physical Systems (CPS)?
• Applications
• Research Challenges
Cyber
Physical
CPS
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Cyber Systems
• Cyber is…
– More than just software
– More than just networking
– More than just embedded computing
Computation
• “Cyber” implies the integration of…
– Computation,
– Communication
– Control
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Physical Systems
• Physical – natural and
human-made systems
governed by the laws of
physics and operating in
continuous time
Airline
Power
Highway
Factory
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What are Cyber-Physical Systems?
• Cyber-Physical Systems –
systems in which the cyber
and physical systems are
tightly integrated at all
scales and levels
• CPS
– Integrates computation and
physical processes
– uses embedded computers
and networks to compute,
communicate, and control the
physical processes
– receives feedbacks on how
physical processes affect
computations and vice versa.
Computation
Information
Systems
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A CPS Architecture
Vincenzo Liberatore, Networked Cyber‐Physical Systems: An Introduction, 2007
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Start from an example:
Cooling Data Center
• In 2006, data centers in the US
– Use 59 billion kilowatt-hours of electricity
– Cost US$4.1 billion
•
– 2% of total USA energy budget
In 2010, expected 3% of total USA energy budget
• Cooling equipment uses at least 50% total energy cost.
• A key challenge is to minimize the cooling requirement
and improve the overall energy efficiency, toward
optimizing the operations of data center
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Cooling data center:
Cyber-physical approach
• Observation: different
workloads generate different
power consumption
– Some locations in data center
are easier to cool than others
B
A
• Solution: moving tasks from
Zone A to Zone B
– lower overall power
consumption
Temperature distribution in data center
R.K.Sharma etal. “Balance of Power: Dynamic Thermal Management of Internet
Data Centers”. Jan.2005
CPS Approach: distribute tasks among the servers to minimize the temperature
cyber
coupled
physical
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Two definitions for CPS
• ʺA cyber‐physical system (CPS) integrates computing ,
communication and storage capabilities with
monitoring and / or control of entities in the physical
world, and must do so dependably, safely, securely,
efficiently and in real‐time.“
– S. Shankar Sastry, UC Berkeley
• Cyber‐physical systems will transform how we interact
with the physical world just like the Internet
transformed how we interact with one another.
– NSF CPS Workshop, Austin, TX, Oct. 16‐17, 2006
CPS characteristics
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Cyber capability in every physical component
Networked
Sensing technology
Pervasive networking
Predictable behavior
Real‐time operation & close loop control
High confidence software & systems
Cyber and physical components are integrated
for: learning and adaptation, higher performance,
self‐organization, self assembly
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Outline
• What is cyber‐physical systems?
• Applications
• Research Challenges
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CPS applications
CPS interact with the physical world, they must operate
dependably, safely, securely, efficiently and in real-time.
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Car-to-Car Communications
• Safety: vehicles broadcast their physical state
information over a wireless network to allow their
neighbors to track them and predict possible collisions,
trigger speed-limit reminder, accident warning
• Traffic information: share information on the traffic onroad for traffic congestion alarm, get map updates
• Entertainment: search for places of interest via the
Internet
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Healthcare
• Electronic Patient Record
– Medical records at any point of service
• Home care: monitoring and control
– Heart rate, blood pressure
– wearable networks
• Operating Room
– Closed loop monitoring and control; multiple
treatment stations
– System coordination
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Power Grid/Smart Grid
• Current picture:
– Reactive equipment protection
– Power outage over the world
• 25 July 2010, Washington D.C.,
250000 people lost power
• 22 March 2010, Malta, nationwide blackout
• Better future?
– Real-time cooperative control
of protection devices
– Homes and offices are more
energy efficient to operate
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Outline
• What is cyber‐physical systems?
• Applications
• Research Challenges
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A New Research Area
• Artificial intelligence
– Can machines think?
– By A. Turing in “Computing Machinery and Intelligence”, 1950
• Ubiquitous Computing
– Computers everywhere
– By Mark Weiser, XEROX PARC, 1990
• Pervasive Computing
– 6As Model, The “authorized access to anytime‐anywhere‐any
device‐any network‐any data”
– Industry vision (1999, IBM, etc.)
• Cyber‐Physical Systems
– Computation and networking integrated with physical processes
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Research Challenges
• Build the interface between the cyber world
and the physical world?
• Why this is hard:
– No clear boundaries between cyber and physical
worlds.
– Boundaries are always changing.
– No perfect digitization of the continuous world
– Inpredicable complex systems
– Essentially multi-disciplinary
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Multi-disciplinary
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Sensing technologies
Distribute computing and networking
Real-time computing
Control theory
Signal processing
Embedded systems
This seminar will cover some basic material from
these areas, but focus on advanced research papers
related to CPS and its sub-areas.
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Introduction to
Wireless Sensor Networks
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Outline
• What is Wireless Sensor Networks (WSN)?
• Applications
• Research challenges
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Sensor nodes
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Sensor node model
Real
World
• Low-power processor
– Limited processing.
• Memory
Sensor Unit
– Limited storage
• Mobility
– No or limited movement
• Communication
Storage
– Low-power.
– Low data rate.
– Limited range.
CPU
P
O
W
E
R
Communication
• Sensors
– Scalar sensors: temperature, light, etc.
– Cameras, microphones.
• Power
– Powered by battery with long-time operation in unattended areas
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What are Wireless Sensor Networks (WSNs)?
• Networks of typically small, battery-powered,
wireless devices.
– On-board processing,
– Communication
– Sensing
• R: transmission range
• V: the set of sensor nodes
1-hop neighborhood
R
B
A
Sensor node
Wireless Sensor Network
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Outline
• What is Wireless Sensor Networks (WSN)?
• Applications
• Research challenges
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Engineering, civilian, enterprise applications
will eventually dominate
WSN in building environment
Golden Gate Bridge – San Francisco
http://www.cs.berkeley.edu/~binetude/ggb/
• WSN is deployed at the
Golden Gate Bridge to
monitor structural health
• Structural vibrations are
measured and collected by
sensors
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Forest observation, fire detection
• WSN is deployed in a forest to collect data including temperature,
humidity, illumination, and CO2 etc.
• Applications, e.g. forest surveillance, forestry observation, fire risk
http://greenorbs.org/
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Volcano monitoring
• Use WSN to monitor active and hazardous volcanoes
• Challenge: how to maximize the data collecttion,
subject to resource constraints.
http://fiji.eecs.harvard.edu/Volcano
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Military Operation:
Shooter localization
• WSN determines the shooter
location and the bullet trajectory
• Red circle: the estimated shooter
position
• Red line: the shot direction
• Green dots: sensor locations.
• Basic idea: using the arrival times
of the acoustic events at different
sensor locations, the shooter
position can be accurately
calculated using the speed of
sound and the location of the
sensors.
http://w3.isis.vanderbilt.edu/projects/nest/applications.html
Urban Sensing
• Use WSN to measure
city pollutants
Carbon monoxide (CO)
http://www.escience.cam.ac.uk/mobiledata/
• Put sensors on taxi
• When the taxi are
moving around in a city,
the sensors on the taxi
can sense and transmit
the air quality to a data
processing center
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Oceanic Environment
• British Petroleum oil spill at
the Gulf of Mexico and its
huge environment damage
in 2010
• monitor the environmental
conditions/pollution of the
ocean surface
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Wildlife behavior analysis and
interaction modeling
• Put a camera (i.e. video
sensor) on each deer.
• The captured video will be
transmitted to a remote
monitoring center for realtime viewing, control; and
wildlife behavior analysis
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Body Sensor Networks
• WSN can be on/beside/in body
• Medical monitoring, e.g. heart rate, blood pressure
• Remote monitoring and localization for aged people at
home; patient at hospital
http://www.iet.ntnu.no/nb/taxonomy/term/10?page=1
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Outline
• What is Wireless Sensor Networks (WSN)?
• Applications
• Research challenges
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Challenges
• Generally, severely energy constrained.
– Limited energy sources (e.g., batteries).
– Trade-off between performance and lifetime.
• Resource-constrained systems
– Power
– Computation
– Bandwidth
• Unstable wireless link quality
• Scalable.
– potentially large number of nodes
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Lifetime in WSN
• Objective: how to maximize the lifetime of whole network?
• Different lifetime definition based on the number of alive
nodes, coverage, connectivity, QoS
• Based on Number of alive nodes
– the time until the first sensor is drained of its energy
Tnn=minv 2 V Tv
Tnn: network lifetime; Tv: the lifetime of node v
– the time until all nodes have been drained of their energy
Tnn=maxv 2 V Tv
– the time until the fraction of alive nodes falls below a
predefined threshold β
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Research Topics
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Energy models, energy efficiency
Routing/packet forwarding
Medium access control
Localization
Data fusion
Clustering
Topology control
Security
Novel applications
QoS
– Delay, throughput, packet delivery ratio, packet error rate
– Real-time transmission in body sensor networks, wireless video sensor
networks
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Routing in Wireless Sensor Networks
Sensor node
Source node A
B
C
• Objective: choose
multi-hop routing path
from source node A to
the sink
• Constraints:
– Energy efficiency
– QoS (delay, packet
delivery ratio)
D
Sink node
Wireless Sensor Network
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Medium Access Control in WSN
• Role: coordinate access to and transmission over
a medium common to all nodes.
• Challenge:
– Interference, Limited energy, Limited bandwidth,
Fading channel, Decentralized
• Causes for energy consumption
– Packet collision, overhead, idle listening
• Performance metrics
– Throughput
– Energy consumption
– Access delay
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Localization in WSN
• Objective: determine a node’s
position
• Challenges:
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Limited communication range
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All the measurements are inaccurate
because of multi-path fading.
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Interferences
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Node mobility
• Applications
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Tracking patient, old people, children
who need help in case
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Clustering in WSN
• Role: nodes are partitioned into a
number of small groups (clusters)
to facilitate communications,
management and data
aggregation
• A cluster has
– A cluster head: the coordinator in a
cluster
– Members: nodes within a cluster
• Clustering results in two-tier
hierarchy
Intracluster communication
– Intercluster: cluster heads form the
higher tier
– Intracluster: member nodes form
the lower tier
Intercluster communication
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Cluster head
Member node
Mobile Social Networks (MSN)
Not just using mobile phone to access Facebook!
MSN
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Mobile Social Networks (MSN)
• MSN: mobile users of similar interests cooperate to
establish network connectivity and communicate with
each other in the absence of network infrastructure
Common interest, e.g.
skiing, StarCraft, travel, music
• Properties:
– mobile users usually move around several well-visited
locations
– Regular user’s dwell time at each community
• Research challenges:
– Social-aware information sharing and dissemination
– Exploiting social science concepts (e.g. degree)
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RFID Systems; Internet of Things
Presented by Sabita
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