Sensors and Sensor Networks
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Lesson 5 Sensors and Sensor Networks What are sensors and what are they for? Various sensors and their features What are sensor networks & their interconnections? Sensor network technologies & applications Sensor and Actuator A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. (Wikipedia) Input Signal Output Signal Sensor An actuator is a device for moving/controlling a mechanism/system, or generate some output, e.g., motor, LED, buzzer, speaker, etc. Sensors and actuators are bridges between real and digital worlds Various Sensors Phidgetsセンサー Force sensor Touch sensor Motion sensor Vib. sensor Moteセンサー Gas Sensor Gyro Accelerometer Pendulum Resistive Tilt Sensors Metal Detector Piezo Bend Sensor Gieger-Muller Radiation Sensor Pyroelectric Detector UV Detector Resistive Bend Sensors Digital Infrared Ranging CDS Cell Resistive Light Sensor Pressure Switch Limit Switch Miniature Polaroid Sensor Touch Switch Mechanical Tilt Sensors IR Pin Diode IR Sensor w/lens Thyristor Magnetic Sensor IR Reflection Sensor Magnetic Reed Switch IR Amplifier Sensor Hall Effect Magnetic Field Sensors Polaroid Sensor Board IRDA Transceiver Lite-On IR Remote Receiver Radio Shack Remote Receiver IR Modulator Receiver Solar Cell Compass Compass Piezo Ultrasonic Transducers General Ubiquitous System Model A ubiquitous/pervasive/AmI/CPS system can be regarded as a special kind of information systems which use sensors to acquire various information (of called context), process the contextual information, and then take some responses through actuators. Intelligent Processing ユビキタス 情報自動な 取得、保存、 処理、管理、 分析、判断、 使用、など Real/Physical World Sensing & Action (Sensor Network) Sensors Actuators Multimedia Information Contexts Comfortable Services Context-Aware 人 人体 物体 器具 空間 環境 Types of Sensors Acoustic, sound, vibration -- Microphone, geophone, seismometer, accelerometer, … Automotive, transportation -- Speedometer, map sensor, water sensor, parking sensor, … Chemical -- Sensing carbon, gas, hydrogen, oxygen, smoke, etc. Electric, magnetic, radio -- Hall effect, magnetometer, metal detector, telescope, … Environment, weather, moisture, humidity -- Leaf sensor, rain/snow gauge, pyranometer, … Flow, fluid velocity -- Air flow meter, flow sensor, water meter, … Ionising radiation, subatomic particles -- Cloud chamber, neutron detection, particle detector, … Types of Sensors (Cont.) Navigation instruments -- Air speed indicator, depth gauge, gyroscope, turn coordinate, … Position, angle, displacement, distance, speed, acceleration -- Accelerometer, position sensor, tilt sensor, ultrasonic sensor, … Optical, light, imaging -- Colorimeter, electro-optical sensor, infra-red sensor, photodiode, … Pressure -- Barometer, boost gauge, pressure gauge, tactile sensor, … Force, density, level -- Force gauge, level sensor, load cell, hydrometer, … Thermal, heat, temperature -- Heat sensor, radiometer, thermometer, thermistor, … Proximity, presence -- Motion detector, occupancy sensor, touch switch, ... A list of various kinds of sensors in Wikipedia Range maximum deviation from a ‘straight-line’ response Sensitivity smallest discernible change in the measured value Linearity maximum and minimum values that can be measured Resolution or discrimination Sensor Performance a measure of the change produced at the output for a given change Error – Accuracy/Precision difference betw. measured & actual values Random/System Errors System Error Temperature Sensors Resistive Thermometers - typical devices use platinum wire, linear but has poor sensitivity Thermistors - use materials with a high thermal coefficient, sensitive, highly non-linear pn junctions - a semiconductor device, linear, easy to use, limited range (-50C to 150 C) Thermometer Thermistor pn junction Force Sensors Strain gauge - stretching in one direction increases the resistance of the device, while stretching in the other direction has little effect - can be bonded to a surface to measure strain - used within load cells and pressure sensors Direction of sensitivity A strain gauge Pressure sensing principle A force sensor video Motion Sensors Motion sensors measure quantities such as Acceleration Sensor velocity and acceleration can be obtained by differentiating displacement differentiation tends to amplify high-frequency noise Alternatively can be measured directly some sensors give velocity directly e.g. measuring frequency of pulses in the counting techniques described earlier gives speed rather than position some sensors give acceleration directly e.g. accelerometers usually measure the force on a mass Accelerometer Principles of Motion Sensing Sound Sensors Microphones a number of forms are available e.g. carbon (resistive), capacitive, piezoelectric and moving-coil microphones moving-coil devices use a magnet and a coil Ultrasonic Sensor Ultrasonic sensors are used for position measurements Sound waves emitted are in the range of 213 MHz Sound Navigation And Ranging (SONAR) Radio Detection And Ranging (RADAR) – ELECTROMAGNETIC WAVES !! 15° - 20° CO2 Gas Sensor CO2 sensor measures gaseous CO2 levels in an environment Measures CO2 levels in the range of 0-5000 ppm Monitors how much infrared radiation is absorbed by CO2 molecules Infrared Source IR Detector Biosensors A biosensor is an analytical device for the detection of an analyte that combines a biological component with a physicochemical detector component. (Wikipedia) Health check, environment monitoring, food analysis, … Incorporation of a biomolecule in order to detect something Recognition Layer Species to be Filter Recognition detected (analyte) Layer Transducer Electronics Signal Electronic Tongue using Biosensors Biological taste system Taste compounds Taste cell Electric responses Brain Taste reception Nerve cell Artificial liquid system - electronic tongue Sensor array Sensor responses Computer Pattern recognition Y. Vlasov, A. Legin, A. Rudnitskaya, Anal. Bioanal. Chem. 2002, 373, 136. Nanosensors Nanosensors are any biological, chemical, or sugery sensory points used to convey information about nanoparticles to macroscopic world. Their uses mainly include various medicinal purposes and as gateways to build other nanoproducts, such as computer chips that work at nanoscale and nanorobots. (Wikipedia) Medicinal uses of nanosensors to accurately identify particular cells or places in the body. Using nanosensors to build smaller integrated circuits, as well as incorporating them in other chip/devices Nanosesnors are new, ongoing research, potential huge applications MEMS and NEMS MEMS (Micro-Electro-Mechanical System) is the technology of very small mechanical devices driven by electricity. (Wikipedia) Range from 1 to 1000 micrometres in size (i.e. 0.001 to 1 mm) Micromachines (in Japan), or Micro Systems Technology - MST (Europe) NEMS (Nano-Electro-Mechanical System), similar but smaller (<100nm) MEMS perform 2 basic types of functions: sensors or actuators. - both act as transducers converting one signal into another. MEMS actuators: electrical signal physical phenomena to move or control mechanisms. MEMS Sensors work in reverse to actuators ~ 1mm MEMS and NEMS (cont.) MEMS comprising mechanical and discrete electronic components MEMS design is different from macro devices MEMS design are based upon Silicon IC chips design Micro-actuators: micro-motor, micro-mirror, micro-fluid pump, etc. Micro-sensors: micro-accelerometer, micro-gyroscope, etc. Gyroscope Actuator Hinge Electrostatic motor MEMS Gyroscope Chip A gyroscope is a device for measuring or maintaining orientation Video for Introduction to MEMS Popular Sensors in Smart Phones Android Sensor Java Development APIs Sensors in Automotive Applications Powertrain Applications Cam/Crank Sensors Transmission Speed Sensors Throttle Position Sensors EGR Valve Position Sensors Valve Position Sensors Current Sensing Suspension Systems Position Sensing Chassis height Electronic Power Steering Position Sensing Motor Commutation Current Sensing Safety Systems Airbag Diagnostics & Control Occupant Sensing ABS/Traction - Wheel Speed Sensing Convenience Systems Door lock Position Sensing Window Position/Speed Sensing Window/Sunroof Direction Sensing for anti-pinch Seating Systems Various Contactless Switches Motor Controllers/Drivers Wiper Systems LCD screens Sensor Networks A sensor network (SN) is consisted of multiple interconnected sensors. A wireless sensor network (WSN) consists of spatially distributed autonomous sensors (called sensor nodes) to cooperatively monitor physical or environmental conditions Sensors + Wireless Networks San Fransisco’s Moscone Center equipped with sensor network Traditional Networks vs WSN An Introduction Video about Wireless Sensor Networks Sensor Nodes A sensor node, also called a mote in North America, is a WSN node that is capable of performing some processing, gathering sensory information and communicating with other connected nodes in the WSN. Examples for Wireless Sensor Nodes Dot Mote Rene Mote MICA Mote weC Mote Example: Berkeley Motes, Smart Dust Laser diode III-V process Passive CCR comm. MEMS/polysilicon • 4 KB RAM, 4 MHz CPU • 19.2 Kbps, 12m Analog I/O, DSP, Control COTS CMOS Power capacitor Multi-layer ceramic Sensor MEMS/bulk, surface, ... Solar cell CMOS or III-V Thick film battery Sol/gel V2O5 1-2 mm Sensors in a Berkeley Mote General Features of Sensor Node Small Size : few mm to a few inches Limited processing and communication MHz clock, MB flash, KB RAM, 100’s Kbps (wireless) bandwidth Limited power (MICA: 7-10 days at full blast) Failure prone nodes and links (due to deployment, fab, wireless medium, etc.) But easy to manufacture and deploy in large numbers Need to offset this with scalable and fault-tolerant OS’s and protocols Sensor-node Operating System Issues Size of code and run-time memory footprint Embedded System OS’s inapplicable: > 100KB ROM Workload characteristics Continuous ? Bursty ? Application diversity Want to reuse sensor nodes Tasks and processes Scheduling, hard and soft real-time Power consumption Communication Representative OS TinyOS, Contiki, NanoPK, LiteOS TinyOS Layers and Functions application sensing application Routing Layer routing messaging packet byte bit Messaging Layer Radio Packet Radio byte RFM photo clocks ADC Temp i2c SW HW TinyOS Language and Size • Event-driven execution (reactive mote) • Use a variant of language C called NesC 3500 3000 Bytes 2500 2000 1500 1000 500 0 Interrupts Message Dispatch Initilization C-Runtime Light Sensor Clock Scheduler Led Control Messaging Layer Packet Layer Radio Interface Routing Application Radio Byte Encoder Scheduler: 144 Bytes code Totals: 3430 Bytes code 226 Bytes data WSN Characteristics Limited power they can harvest or store Ability to withstand harsh environmental conditions Ability to cope with node failures Mobility of nodes Dynamic network topology Communication failures Heterogeneity of nodes Large scale of deployment Unattended operation Nodes are scalable, only limited by bandwidth of gateway node Typical Multiple WSN Architecture A sensor network normally constitutes a wireless ad-hoc network, and each sensor supports a multi-hop routing algorithm where nodes function as forwarders, relaying data packets to a base station. WSN Topologies Sensor Network System Antenna Server Interface electronics, radio and microcontroller Soil moisture probe Communications barrier Senor Node Sensor field Gateway Internet Sensor Network System Server Watershed Sensor field Gateway Internet Multiple Sensor Networks System Distribution field of phenomena that can be detected measured Physical Phenomena S S Sensor net S S S Storage S S S Sensor net Sensor net S S S S S Sensors that detect event User S Access Node Sensors that notify access node Internet WSN System Issues Monitoring & Managing Spaces and Things Applications data mgmt service network system architecture Comm. MEMS sensing Store Proc uRobots actuate Technologies Miniature, low-power connections to the physical world 40 Power WSN System Platforms Application Filtering Detection Transport Networking ClassificationTracking Dissemination Time Sync Interrupts Scheduler Link Layer MCU Sensors Radio OS Query Processing Routing Signal Proc. Storage Indices Timers Arbiters Hardware Heap Files Storage OTAP Queues Power Supply Sensor router Time Sync Storage ZigBee, 802.15.4, EnOcean, IETF PRL, etc Wireless Sensor Network Standards IEEE 802.15.4 & ZigBee Application Customer API – “the software” Security 32- / 64- / 128-bit encryption Network ZigBee Alliance – Brand management Star / Mesh / Cluster-Tree IEEE 802.15.4 MAC PHY 868MHz / 915MHz / 2.4GHz – Network, Security & Application layers IEEE 802.15.4 – “the hardware” – Physical & Media Access Control layers Sensor Data Management sensors observer phenomena Observer interested in phenomena with certain tolerance Accuracy, freshness, delay Sensors sample the phenomena Sensor Data Management Determining spatio-temporal sampling schedule Difficult to determine locally Data aggregation Interaction with routing Network/Resource limitations Congestion management Load balancing QoS/Realtime scheduling Sensor Data Query Fully aggregated queries Un-aggregated queries Partially aggregated queries Sink Select temp from Sensing Information Fusion One sensor is (usually) not enough - Noisy, limited accuracy, unreliable – failure, environment restriction, etc. Sensor fusion - Combine readings from several sensors into a better one Sensor 1 Obj Preprocessing (1.10, 1.06) 1.08 Sensor 2 Preprocessing (0.92, 0.96) 0.94 Sensor 3 Preprocessing (0.30, 0.36) 0.33 Sensor N Preprocessing (0.94, 0.96) 0.95 Sensing 1.08+0.94+0.95 3 0.99 Fusion Interpretation 0.33? Ignore 0.43 Perception Sensing Information Fusion Preprocessing - 'Cleanup’ the sensor readings before using them, e.g., noise reduction, re-calibration, unify the format, etc. - Data Fusion Combine data from different sources Measurements from different sensors Measurements from different positions Measurements from different times Techniques that take into account uncertainties in data sources - Discrete Bayesian methods - Neural networks - Kalman filtering Sensor Web Sensor Web - Wikipedia Semantic Sensor Web Sensor Web (Cont.) Homework Access the following websites to learn more about various sensors, sensor networks, and their features, technologies, applications, etc. Sensor - Wikipedia List of sensors - Wikipedia MEMS – Wikipedia Android Sensor Java Development APIs Wireless sensor network – Wikipedia TinyOS – Wikipedia An Introduction Video about Wireless Sensor Networks Others you like Important to get materials from Web!!
