Smart Multisensor Systems & WSN

14/01/2015

Overview Smart multisensor sytems Introduction to WSN Smartphone as sensor node Examples of multisensor systems:

• Resima project • Secesta project • Tracking by Smartphone

Smart Multisensor Systems & Sensor Networks

Outline

From the sensor to the smart sensor

• Key features

• Standards

• Architecture

Wireless Sensor Networks

Environment

Transducer Conditioning

electronic

Sensor

Auxiliary power systems

System under

measurement Load/User

Traditional sensor schematic

From the traditional sensor...

Smart Sensors

Smart Sensors

Environment

Transducer Conditioning

electronic

Sensor

Auxiliary systems

System under

measurement A/D

Signal processing

Local user interface

Data storage

Communication

…to the smart sensor (coined in the mid-1980s).

Smart sensors are basic sensing elements with embedded intelligence (combination of a sensing element with processing capabilities provided by a microprocessor), that can perform one or more of the following function

logic functions two-way communication make decisions.

Smart Sensors

Environment

Transducer Conditioning

electronic

Sensor

Auxiliary systems

System under

measurement A/D

Signal processing

Local user interface

Data storage

Communication

…to the smart sensor (coined in the mid-1980s).

Smart sensors are basic sensing elements with embedded intelligence (combination of a sensing element with processing capabilities provided by a microprocessor), that can perform one or more of the following function

logic functions two-way communication make decisions.

IEEE 1451.2 specification defines a smart sensor as “a sensor that provides functions beyond those necessary for generating a correct representation of a sensed or controlled quantity. This function typically simplifies the integration of the transducer into applications in a networked environment”.

Smart Sensors

• increased reliability and robustness

due to reduction of number of components and system wiring, miniaturization and semplification of apparatus

Linearity: Many of the sensors show some non-linearity, by using on-chip feedback systems or look up tables

we can improve linearity.

Cross-sensitivity: Most of the sensors show an undesirable sensitivity to strain and temperature.

Incorporating relevant sensing elements and circuits on the same chip can reduce the cross-sensitivity.

Key “Smart Sensor” features:

Who Cares ?

Customers Especially end-users who care about ease of use And end-users who see the whole picture including costs

System Integrators who need to Minimize Acquisition Costs and Setup Time System Engineers with Data Acquisition, Signal Processing Responsibilities, and Maintenance Sensor Manufacturers who want to supply technology for today and tomorrow.

• self-calibration (gain/offset, parameter drift and components value)

• self-health assessment

• compensated measurements (auto zero, calibration, temperature, pressure, relative humidity correction)

• pre-processing

• self-healing (auto recovery)

•core system (microprocessor-sensor combination) adaptable to a changing environment/applications

• Network self-identification • Electronic “Data sheets” (TEDS)

•Sensor Communications for Remote Monitoring and Remote Configuration

Smart sensor are compliant with IEEE 1451 standard (Plug and Play)

Smart Sensors

IEEE 1451 family of standards

describe a set of open, common, network-independent communication interfaces for connecting transducers (sensors or actuators) to microprocessors, instrumentation systems, and control/field networks.

Goal: allow the access of transducer data through a common set of interfaces whether the transducers are connected to systems or networks via a wired or wireless means.

1451.0 – Common Functions, Communication Protocols, and Transducer Electronic Data Sheet (TEDS) Formats 1451.1 – Network Capable Application Processor Information Model (physical and logic model (data structures

and functionalities)) 1451.2 – Transducer to Microprocessor Communication Protocols & TEDS Formats 1451.3 – Digital Communication & TEDS Formats for Distributed Multidrop Systems 1451.4 – Mixed-Mode Communication Protocols & TEDS Formats 1451.5 – Wireless Communication Protocols & Transducer Electronic Data Sheet (TEDS) Formats 1451.7 – Transducers to Radio Frequency Identification (RFID) Systems Communication Protocols and Transducer

Electronic Data Sheet Formats

Smart Sensors

System-on-chip Assembled

Sensor µC/µP board + Tx

The intelligence required by such devices is available from microcontroller unit (MCU), digital signal processor (DSP), and application-specific integrated circuit (ASIC) technologies developed by several semiconductor manufacturers.

Smart Sensors

Architecture of a smart sensor node

Source: OECD based on Verdone et al., 2008

• Enhanced performances and capabilities • Customized outputs

• signal detection from sensing element • signal processing • data validation and interpretation • signal transmission and display

Smart Sensors

Architecture of a smart sensor node

Source: OECD based on Verdone et al., 2008

Multi-Sensor System: A multi-sensor system uses the information of several sensors to define the knowledge of an environment

I2C & SPI

Serial Peripheral Interface Is a synchronous serial data standard, named by Motorola, that operates in full duplex mode. SPI is often referred to as SSI (Synchronous Serial Interface). Devices communicate in master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select lines.

SCLK: serial clock (output from master); MOSI: master output, slave input (output from master); MISO: master input, slave output (output from slave); SS: slave select (active low, output from master).

Alternative naming conventions are also widely used Frequencies: 40 MHz to 100 MHz

Inter-Integrated Circuit Is a multimaster serial single-ended computer bus invented by Philips used for attaching low-speed peripherals to a motherboard, embedded system, cellphone, or other electronic device.

Frequencies: 10 kbit/s (LSm) to 5 Mbit/s (UFm)

I²C uses only two bidirectional lines: • Serial Data Line (SDA) • Serial Clock (SCL)

I²C defines basic types of messages, each of which begins with a START and ends with a STOP

Smart Sensors

Architecture of a smart sensor node

Source: OECD based on Verdone et al., 2008

Microfabrication methods make it possible to build very small and low power sensors

some mWs in continuous operative conditions some µWs in dynamic operative conditions

Two possible solutions:

Batteries (Li-ion, Li-polymer, Metal-Air rechargeable)

Energy harvesting (vibrations, PV, aeolic …)

Smart Sensors

Architecture of a smart sensor node

Source: OECD based on Verdone et al., 2008

Provide signal processing capabilities

Execution of “smart” algorithms

µController based µProcessor based

MuIN eZ430-RF2500 IRIS Beagleboard xM Beaglebone

The intelligence required by such devices is available from microcontroller unit (MCU), digital signal processor (DSP), and application-specific integrated circuit (ASIC) technologies developed by several semiconductor manufacturers.

MICA2 – 433MHz Atmel AVR 8-bit

MICAz – 802.15.4 Atmel AVR 8-bit

Telos – 802.15.4 TI MSP430

Iris – 802.15.4 Atmel AVR 8-bit Cricket – 433 MHz

Imote2 – 802.15.4 PXA271 XScale 32-bit

SunSPOT – 802.15.4

Smart Sensors

MuIN

eZ430-RF2500 IRIS XM2110CB

Producer Droids Texas Instruments Crossbow

µC Unit Microchip PIC18F2520 TI

MSP430F2274 Atmel

ATMega 1281

µC Architecture 8 bit RISC 16 bit RISC 8 bit AVR

Max Frequency 40MHz 16MHz 16MHz

Communication USB,Ethernet, ZigBee,

BlueTooth USB/2.4GHz

2.4GHz IEEE 802.15.4 (ZigBee)

Power supply 3.3V / 5V 1.83.6V 2.73.3V

Board Power Consumption (max values)

250mA

Only processor Active mode 390µA Stanby mode 1.4µA

RF Transceiver RX mode 18.8mA TX mode 21.2mA

Only processor Active mode 8mA Sleep mode 8µA

RF Transceiver RX mode 16mA TX mode 17mA

Beaglebone Beagleboard xM

Producer Beagleboard.org Beagleboard.org

µP Unit TI AM3359 ARM

Cortex-A8 TI DM3730 ARM

Cortex-A8

µP Architecture 2 x 32 bit RISC 6 x32 bit RISC

Max Frequency 720MHz 1GHz

Communication USB,Ethernet USB/2.4GHz

Power supply 5V 5V

Board Power Consumption (max values)

500mA (peak) 750 mA

Smart Sensors

Raspberry Pi

The Raspberry Pi is a credit-card-sized single-board computer developed in the UK by the Raspberry Pi Foundation with the intention of promoting the teaching of basic computer science in schools.

Operating Systems

Raspbian

Pidora

RISC OS

RaspBMC

Arch

OpenELEC

Programming languages

• Scratch • Python • HTML5 • Javascript • JQuery

• Java • C • C++ • Perl • Erlang

"Raspberry Pi" Computer Model-B Rev1 Developer : Raspberry Pi Foundation Type: Single-board computer Release date: 29 February 2012[1] Introductory price : US$ 25 (model A) and US$ 35 (model B) Operating system : Linux (Raspbian, Debian GNU/Linux, Fedora, and Arch Linux ARM) RISC OS, FreeBSD, NetBSD, Plan 9 Power: 2.5 W (model A), 3.5 W (model B) CPU: 32 bit ARM1176JZF-S (ARMv6k) 700 MHz, Raspberry Pis can dynamically increase clockspeeds, and some can temporarily reach speeds up to 1 GHz. Storage capacity: SD card slot (SD or SDHC card) Memory: 256 MB (Model A), 512 MB (Model B rev 2), 256 MB (Model B rev 1) Graphics: Broadcom VideoCore IV[3]

Raspberry Pi

Sensor Node HW Architecture

Commercial platforms typically consists of three components and can be either an individual board or embedded into a single system: • Wireless modules or motes are the key components of the sensor network as they

possess the communication capabilities and the programmable memory where the application code resides. A mode usually consists of a microcontroller, transceiver, power source, memory unit and may contains few sensors.

Mica2/Cricket/MicaZ/Iris/Telos/SunSPOT/Imote2 ecc.

• A sensor board is mounted on the mote and is embedded with multiple types of sensors. Available sensor boards include the MTS300/400 and MDA100/300 that are used in the Mica family of motes. Alternatively, the sensors can be integrated into the wireless module such as in the Telos or the SunSPOT platform.

• A programming board, also known as the gateway board, provides multiple interfaces including Ethernet, WiFi, USB, or serial ports for connecting different motes to an enterprise or industrial network or locally to a PC/laptop. These boards are used either to program the motes or gather data from them.

Smart Sensors

Architecture of a smart sensor node

Source: OECD based on Verdone et al., 2008

Various solutions: Wireless, USB, Ethernet…

Main attractives:

IEEE 802.15.4 (ZigBee)

IEEE 802.11 (Wi-Fi)

IEEE 802.15.1 (BlueTooth)

RFID

Wireless Sensor Networks (WSN)

Sensor

Communication interface

Electronic

Wireless Sensor Networks

What is a WSN?

A Wireless Sensor Network in its simplest form can be defined as a network of (possibly low-size and low-complex) devices denoted as nodes that can sense the environment and communicate the information through wireless links;

Data is forwarded, possibly via multiple hops relaying, to a sink (sometimes denoted as controller or monitor ) that can use it locally, or is connected to other networks (e.g., the Internet) through a gateway.

The nodes can be stationary or moving.

They can be aware of their location or not.

They can be homogeneous or not.

Single-sink WSN Multi-sink WSN

SINK

A wireless sensor network (WSN) in its simplest form can be defined as a network of (possibly

low-size and low-complex) devices denoted as nodes that can sense the environment and

communicate the information gathered from the monitored field through wireless links; the

data is forwarded, possibly via multiple hops relaying, to a sink that can use it locally, or is

connected to other networks (e.g., the Internet) through a gateway.

• The nodes can be stationary or moving. • They can be aware of their location or not. • They can be homogeneous or not.

Gateway

Internet

Local User

Sensor Field

Sensor nodes

Remote User

Wireless Sensor Networks

F. L. Lewis, Wireless Sensor Networks, Smart Environments: Technologies, Protocols and Applications ed. D.J. Cook and S.K. Das, JohnWiley, NewYork, 2004.

Fields of applications of WSN

Wireless Sensor Networks

WSNs Applications

WSNs may consist of many different types of sensor. As a result, a wide range of applications are possible.

Many of these applications share the same interaction pattern:

• Event detection (and classification) simple or composite

• Periodic measurements • Function approximation and edge detection • Tracking (mobile sources, e.g. an intruder in surveillance scenarios)

Environmental Applications

The autonomous coordination capabilities of WSNs are utilized in the realization of a wide variety of environmental applications.

• Tracking the movements of birds, small animals and insects • Monitoring environmental conditions that affects crops and livestock • Irrigation • Macro-instruments for large-scale Earth monitoring and planetary

exploration • Chemical/biological detection • Precision agriculture • Biological, Earth, and environmental monitoring in marine, soil and

atmosphere contexts • Forest fire detection • Meteorological or geophysical research • Flood detection • Bio-complexity mapping of the environment • Pollution studies • …

Example: ZebraNet

ZebraNet is an animal tracking system developed to investigate the long-term movement patterns of zebras, their interactions within and between species, as well as the impacts of human development. The system was deployed in Kenya to track two species of zebras.

Node architecture • GPS unit (to log the location on every 3 minutes mobility models) • Microcontroller (TI MSP430) • Short-range & Long-range RF transceivers • Li-ion battery + solar array (for recharging)

The information is collected through a base station, which is kept by the researchers and used intermittently during their trips into the field. Therefore, ZebraNet can be characterized as a highly mobile sensor network without a static sink.

Since a particular node may not be within communication range of the mobile sink for a very long time, a data sharing policy is adopted in ZebraNet so that each sensor node shares the collected information with its neighbors. This resulted in the development of particular communication protocols to address the unique challenges of this application

Health Applications

The developments in implanted biomedical devices and smart integrated sensors make the usage of

sensor networks for biomedical applications possible. • Provision of interfaces for the disabled • Integrated patient monitoring • Diagnostics • Drug administration in hospitals • Monitoring the movements and internal processes of insects or other small

animals • Telemonitoring of human physiological data • Tracking and monitoring doctors and patients inside a hospital • …

Example: Artificial Retina

GOAL: build a chronically implanted artificial retina for visually impaired people, addressing two retinal diseases: Age-related Macular Degeneration (severe vision loss

at the center of the retina in over 60) and Retinitis Pigmentosa (photoreceptor dysfunction

loss of peripheral vision)

A healthy photoreceptor stimulates the brain through electric impulses when light is illuminated from the external world. When damaged, vision is blocked at the locations of the photoreceptors.

The AR project aims to replace these damaged photoreceptors with an array of microsensors.

The ultimate goal for the prosthetic device is to create a lasting device that will enable facial recognition and the ability to read large print

The first model, Argus I, has been completely tested and implanted into six patients between 2002 and

2004. This model consists of a 16-electrode array and helps

the patients to detect whether lights are on or off, describe the motion of an object, count individual

items, and locate objects.

Home Applications

As technology advances, smart sensor nodes and actuators can be buried in appliances such as vacuum cleaners, microwave ovens, refrigerators, and DVD

players as well as water monitoring systems. These sensor nodes inside domestic devices can interact with each other and with the

external network via the Internet or satellite. They allow end-users to more easily manage home devices both locally and remotely. Accordingly, WSNs enable the

interconnection of various devices at residential places with convenient control of various applications at home.

Non-intrusive Autonomous Water Monitoring System (NAWMS)

localizes the wastage in water usage and informs tenants about more efficient usage. Since the water utility companies only provide total water usage in a house, it is not easy to determine the individual sources that contribute to that total. Using a distributed WSN, the water usage in each pipe of the house’s plumbing system can be monitored at a low cost.

Industrial Applications

• monitoring material fatigue; • managing inventory; • monitoring product quality; • constructing smart office spaces; • environmental control of office buildings; • robot control and guidance in automatic manufacturing environments; • factory process control and automation; • Smart structures with embedded sensor nodes; • machine diagnosis; • transportation; • factory instrumentation; • local control of actuators; • vehicle tracking and detection; • Instrumentation of semiconductor processing chambers, rotating machinery, wind tunnels, and

anechoic chambers; • …

Networks of wired sensors have long been used in industrial fields such as industrial sensing and control applications, building automation, and access control. However, the cost associated with the deployment of wired sensors limits the applicability of these systems.

Instead, WSNs are a promising alternative solution for these systems due to their ease of deployment, high granularity, and high accuracy provided through battery-powered wireless communication units.

Example: Preventive Manteinance

FabApp: The “health” of equipment can be monitored through vibration analysis techniques that require accelerometer sensors attached to the equipment. Based on the established science that maps a particular signature to a well-functioning device, the machines are monitored continuously.

FabApp illustrates a practical implementation of the cluster-based protocols for industrial applications

• 802.15.4 • Mica2 or Intel motes +

accelerometers • Cluster organization

• 802.11 mesh network of high-end gateway

• The root node is connected through a cable to the enterprise network

A communication network is composed of nodes, each of which has computing power and can transmit and receive messages over communication links, wireless or cabled. A single network may consist of several interconnected subnets of different topologies. Networks are further classified as Local Area Networks(LAN), e.g. inside one building, or Wide Area Networks (WAN), e.g. between buildings

Basic network topologies

WSN topologies

suffer from problems of NP-complexity; as additional nodes are added, the number of links increases exponentially. Therefore, for large networks, the routing problem is computationally intractable

are regularly distributed networks that generally allow transmission only to a node’s nearest neighbors. The nodes in these networks are generally identical, so that mesh nets are also referred to as peer-to-peer nets. Since there are generally multiple routing paths between nodes, these nets are robust to failure of individual nodes or links. ‘group leaders’ that take on additional functions. If a group leader is disabled, another node can then take over these duties.

All nodes are connected to a single hub node. The hub requires greater message handling, routing, and decision-making capabilities than the other nodes. If a communication link is cut, it only affects one node. However, if the hub is incapacitated the network is destroyed.

WSN topologies

Messages are broadcast on the bus to all nodes. Each node checks the destination address in the message header, and processes the messages addressed to it. The bus topology is passive in that each node simply listens for messages and is not responsible for retransmitting any messages.

All nodes perform the same function and there is no leader node. Messages generally travel around the ring in a single direction. However, if the ring is cut, all communication is lost. The self-healing ring network (SHR) has two rings and is more fault tolerant.

WSN topologies

ZigBee/IEEE 802.15.4 Overview New trend of wireless technology

• Most Wireless industry focuses on increasing high data throughput

• A set of applications require simple wireless connectivity, relaxed throughput, very low power, short distance and inexpensive hardware.

Industrial

Agricultural

Vehicular

Residential

Medical

Wireless Sensor Networks

WSN - ZigBee

What Is ZigBee?

• ZigBee is a standard that defines a set of communication protocols for low-data-rate short-range wireless networking.

ZigBee-based wireless devices operate in 868 MHz, 915 MHz, and 2.4 GHz frequency bands.

The maximum data rate is 250 K bits per second.

• ZigBee is targeted mainly for battery-powered applications where low data rate, low cost, and long battery life are main requirements (in many ZigBee applications the device spends most of its time in a power-saving mode, also known as sleep mode) .

The ZigBee standard is developed by the ZigBee Alliance (2002, non profit), which has hundreds of member companies, from the semiconductor industry and software developers to original equipment manufacturers (OEMs) and installers. The ZigBee standard has adopted IEEE 802.15.4 as its Physical Layer (PHY) and Medium Access Control (MAC) protocols .

WSN - ZigBee Short-Range Wireless Networking Classes

• WLAN is a replacement or extension for wired local area networks (LANs) such as Ethernet (IEEE 802.3).

• WPANs are created to provide the means for power-efficient wireless communication within the personal operating space (POS) without the need for any infrastructure. POS is the spherical region that surrounds a wireless device and has a radius of 10 meters.

ZigBee

WSN - ZigBee

ZigBee versus Bluetooth and IEEE 802.11

ZigBee

Europe

North America

Worldwide

Industrial, scientific and medical (ISM) frequency bands

WSN - ZigBee

ZigBee Wireless Networking Protocol Layers

ZigBee protocol layers are based on the Open System Interconnect (OSI) basic reference model.

The ZigBee standard defines only the networking, application, and security layers of the protocol and adopts IEEE 802.15.4 PHY and MAC layers as part of the ZigBee networking protocol. Therefore, any ZigBee-compliant device conforms to IEEE 802.15.4 as well.

The ZigBee Advantage The ZigBee protocol is designed to communicate data through hostile RF environments that are common in commercial and industrial applications. ZigBee protocol features include:

•Support for multiple network topologies such as point-to-point, point-to-multipoint and mesh networks •Low duty cycle – provides long battery life •Low latency •Direct Sequence Spread Spectrum (DSSS) •Up to 65,000 nodes per network •128-bit AES encryption for secure data connections •Collision avoidance, retries and acknowledgements

When to use the ZigBee protocol ZigBee is targeted at applications that require a low data rate, long battery life, and secure networking. ZigBee has a defined rate of 250 kbit/s, best suited for periodic or intermittent data or a single signal transmission from a sensor or input device.

WSN - ZigBee

Wireless Sensor Networks

ZigBee – Network topologies

Star Every node is connected to central node. All messages are routed via the central node.

Tree A 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level). A message is routed up the tree until it reaches a node that can route it back down the tree to the destination node.

Mesh nodes are interconnected with other nodes so that multiple pathways connect each node. Connections between nodes are dynamically updated and optimized through sophisticated, built-in mesh routing table..

ZigBee supports three network topologies:

Wireless Sensor Networks

ZigBee – Types of node

End Devices Autonomous, battery operated nodes placed in a peripheral position which just only send and receive messages.

Routers: tree and mesh topologies require at least one router node responsible for:

• Forward messages from a node to the other • Allow to “child” nodes to join the network

In a star topology the router is represented by the co-ordinator. A router can’t go in sleep mode.

Co-ordinator:

There can be just only one Co-ordinator node responsible for : • Search for a suitable Radio Channel (usually the one which has least activity) • Start the Network • allow other nodes to join the network • Messages Routing (only star topology) • Handle secutity problems

Co-ordinator End device

Router

ZigBee network applications

PERSONAL

HEALTH

CARE

ZigBee LOW DATA-RATE

RADIO DEVICES

HOME

AUTOMATION

CONSUMER

ELECTRONIC

S

TV VCR

DVD/CD

Remote

control

security

HVAC

lighting

closures

PC &

PERIPHERAL

S

consoles

portables

educational

TOYS &

GAMES

INDUSTRIAL

&

COMMERCIAL

monitors

sensors

automation

control

mouse

keyboard

joystick

monitors

diagnostics

sensors

Wireless Sensor Networks

A mobile phone as a network node, a Local Server, A Gateway……

….an example…

The phone as a terminal

Mica2 TelosB

Imote2 Mica2Dot

Iris

MicaZ

Commercially available sensor boards Open source OS with support for ad hoc networking

+

Enabling Technologies for WSN

How to interface the phone!

• Three options:

1. Direct Connection

2. WAN Connection

3. Bluetooth

Direct Connection

Serial Port

The phone is physically connected to one of the sensor nodes

Bluetooth

The phone uses a Bluetooth connection to access the WSN information

WAN Connection

GPRS WiFi

Internet

WEB TCP/IP Server

The phone uses a WAN connection to access the WSN information