Smart Sensors Represent the Next Evolutionary Tools for Studying the Environment

8/8/2019 Smart Sensors Represent the Next Evolutionary Tools for Studying the Environment

1/14


2/14

ABSTRACTSmart sensors represent the next evolutionary tools for studying theenvironment. Sensory data comes from smart sensors of differentmodalities in distributed locations. Smart sensor systems are capable ofprediction, interpretation, communication and intelligent interaction with theenvironment & hence will leverage new fault management of devices andcontrol for distributed resources. Tremendous advances in digital signalprocessing and laser capabilities in recent years have enabled many newsensor developments, one of these being smart sensors.Fundamental research has already been carried out to develop smartsensors to monitor and control robotics, mobile vehicles, cooperativeautonomous systems, mechatronics and bioengineering systems. It isenvisioned that concepts of smart sensors and information technology canbe transferred and applied to numerous system. The implementation of

large networks of interconnected smart sensors can monitor and controlour world. Better understanding of smart sensors performs satisfactorily inreal-world conditions and can help improve efficiency and reliability.


3/14

INTRODUCTIONSmart sensors are an extension of traditional sensors to those withadvanced learning and adaptation capabilities. The system must also bere-configurable and perform the necessary data interpretation, fusion ofdata from multiple sensors and the validation of local and remotelycollected data. These sensors therefore contain embedded processingfunctionality that provides the computational resources to perform complexsensing and actuating tasks along with high level applications. Tremendousprogress in semiconductor technology resulted in the low costmicroprocessor. Thus if it is possible to design a low cost sensor which issilicon based then the overall cost of the control system can be reduced.We can have integrated sensors which has electronics and thetransduction element together on one silicon chip. This complete systemcan be called as system-on-chip .The main aim of integrating the

electronics and the sensor is to make an intelligent sensor, which can becalled as smart sensor.


4/14

FUNCTIONS OF A SMART SENSOR SYSTEMThe functions of a smart sensor system can be described in terms ofcompensation, information processing, communications and integration.The combination of these respective elements allow for the development ofthese sensors that can operate in a multi-modal fashion as well conductingactive autonomous sensing.Compensation is the ability of the system to detect and respond tochanges in the network environment through self-diagnostic routines, self-calibration and adaptation. A smart sensor must be able to evaluate thevalidity of collected data, compare it with that obtained by other sensorsand confirm the accuracyInformation processingencompasses the data related processing thataims to enhance and interpret the collected data and maximize theefficiency of the system, through signal conditioning, data reduction, event

detection and decision making.Communicationscomponent of sensor systems incorporates thestandardized network protocol which serves to links the distributed sensorsin a coherent manner, enabling efficient communications and faulttolerance.Integrationin smart sensors involves the coupling of sensing andcomputation at the chip level. This can be implemented using micro electro-mechanical systems (MEMS), nano-technology and bio-technology.Validation of sensors is required to avoid the potential disastrous effects ofthe propagation of erroneous data. The incorporation of data validation intosmart sensors increases the overall reliability of the system.Data fusiontechniques are required in order combine information frommultiple sensors and sensor types and to ensure that only the mostrelevant information is transmitted between sensors.


5/14

SMART SENSOR NETWORKS:Wireless sensor networks are potentially one of the most importanttechnologies of this century. A sensor network is an array of sensors ofdiverse type interconnected by a communications network. Sensor data isshared between the sensors and used as input to a distributed estimationsystem which aims to extract as much relevant information from theavailable sensor data. The fundamental objectives for sensor networks arereliability, accuracy, flexibility, cost effectiveness and ease of deployment.A sensor network is made up of individual multifunctional sensor nodes.The sensor node itself may be composed of various elements such asvarious multi-mode sensing hardware (acoustic, seismic, infrared,magnetic, chemical, imagers, micro radars), embedded processor,memory, power-supply, communications device (wireless and/or wired) andlocation determination capabilities.

SIGNIFICANCE OF SENSOR NETWORK: Sensing accuracy: The utilization of a larger number and

variety of sensor nodes provides potential for greater accuracyin the information gathered as compared to that obtained from asingle sensor.

Area coverage: A distributed wireless network will enable thesensor network to span a greater geographical area withoutadverse impact on the overall network cost.

Fault tolerance: Device redundancy and consequentlyinformation redundancy can be utilized to ensure a level of faulttolerance in individual sensors.

Connectivity: Multiple sensor networks may be connectedthrough sink nodes, along with existing wired networks (e.g.Internet).

Minimal human interaction: The potential for self-organizingand self maintaining networks along with highly adaptivenetwork topology significantly reduce the need for furtherhuman interaction with a network other than the receipt of

information. Operability in harsh environments: Robust sensor design,

integrated with high levels of fault tolerance and networkreliability enable the deployment of sensor networks indangerous and hostile environments.

GENERAL ARCHITECHTURE OF SMART SENSORS:


6/14

From the definition of smart sensor it seems that it is similar to a dataacquisition system, the only difference being the presence of completesystem on a single silicon chip. In addition to this it has onchip offset andtemperature compensation. A general architecture of smart sensor consistsof following important components:Sensing element/transduction element,Amplifier,Sample and hold,Analog multiplexer,Analog to digital converter (ADC),Offset and temperature compensation,Digital to analog converter (DAC),Memory,Serial communication and Processor

The generalized architecture of smart sensor is shown below:


7/14


8/14

DESCRIPTION OF SMART SENSOR APPLICATION

Architecture of smart sensor is shown. In the architecture shown A1, A2An and S/H1, S/H2S/Hn are the amplifiers and sample and hold circuitcorresponding to different sensing element respectively. So as to get adigital form of an analog signal the analog signal is periodically sampled (itsinstantaneous value is acquired by circuit), and that constant value is heldand is converted into digital words. Any type of ADC must contain orproceeded by, a circuit that holds the voltage at the input to the ADCconverter constant during the entire conversion time. Conversion timesvary widely, from nanoseconds (for flash ADCs) tomicroseconds (successive approximation ADC) to hundreds ofmicroseconds (for dual slope integrator ADCs). ADC starts conversionwhen it receives start of conversion signal (SOC) from the processor and

after conversion is over it gives end of conversion signal to the processor.Outputs of all the sample and hold circuits are multiplexed together so thatwe can use a single ADC, which will reduce the cost of the chip. Offsetcompensation and correction comprises of an ADC for measuring areference voltage. Dedicating two channels of the multiplexer and usingonly one ADC for whole system can avoid the addition of ADC for this. Thisis helpful in offset correction and zero compensation of gain due totemperature drifts of acquisition chain. In addition to this smart sensor alsoinclude internal memory so that we can store the data and programrequired.

IMPORTANCE AND ADOPTION OF SMART SENSOR


9/14

The presence of controller/processor in smart sensor has led to correctionsfor different undesirable sensor characteristics which include input offsetand span variation, non-linearity and cross-sensitivity. As these are carriedin software, no additional hardware is required and thus calibrationbecomes an electronic process.

Cost improvementIn case of smart sensor inside hardware is more complex in the sensor onthe other hand it is simpler outside the sensor. Thus the cost of the sensoris in its setup, which can be reduced by reducing the effort of setup, and byremoving repetitive testing.

Reduced cost of bulk cables and connectorsUse of smart sensor has significantly reduced the cost of bulk cables andconnectors needed to connect different blocks (i.e. electronic circuits).

Remote DiagnosticsDue to the existence of the processor with in the package, it is possible tohave digital communication via a standard bus and a built in self-test(BIST). This is very helpful in production test of integrated circuits. Thisdiagnostic can be a set of rules based program running in the sensor.

Enhancement of applicationSmart sensor also enhances the following applications: Self calibration:

Self-calibration means adjusting some parameter of sensor during

fabrication, this can be either gain or offset or both. Self-calibration is toadjust the deviation of the output of sensor from the desired value when theinput is at minimum or it can be an initial adjustment of gain. Calibration isneeded because their adjustments usually change with time that needs thedevice to be removed and recalibrated. If it is difficult to recalibrate the unitsonce they are in service, the manufacturer over-designs, which ensure thatdevice, will operate within specification during its service life. Theseproblems are solved by smart sensor as it has built in microprocessor thathas the correction functions in its memory.

Computation:Computation also allows one to obtain the average, variance and standarddeviation for the set of measurements. This can easily be done using smartsensor. Computational ability allows to compensate for the environmental


10/14

changes such as temperature and also to correct for changes in offset andgain

Communication:

Communication is the means of exchanging or conveying information,which can be easily accomplished by smart sensor. This is very helpful assensor can broadcast information about its own status and measurementuncertainty.

Multisensing:Some smart sensor also has ability to measure more than one physical orchemical variable simultaneously. A single smart sensor can measurepressure, temperature, humidity gas flow, and infrared, chemical reactionsurface acoustic vapor etc.

System Reliability

System reliability is significantly improved due to the utilization of smartsensors. One is due to the reduction in system wiring and second is theability of the sensor to diagnose its own faults and their effect.

Better Signal to Noise RatioThe electrical output of most of the sensors is very weak and if thistransmitted through long wires at lot of noise may get coupled. But byemploying smart sensor this problem can be avoided.

Improvement in characteristics Non-linearity: Many of the sensors show some non-linearity, by

using on-chip feedback systems or look up tables we can improvelinearity.

Cross-sensitivity: Most of the sensors show an undesirablesensitivity to strain and temperature. Incorporating relevant sensingelements and circuits on the same chip can reduce the cross-sensitivity.

Offset: Offset adjustment requires expensive trimming proceduresand even this offsets tend to drift. This is very well reduced bysensitivity reduction method.

Parameter drift and component values: These are functions oftime. This can be solved by automatic calibration.


11/14

CHALLENGES: Changing network topology:

Advanced communication protocols are required to support high levelservices and real-time operation, adapting rapidly to extreme changes innetwork conditions.

Resource optimization:Optimized sensor scheduling for distributed networks, through accuratedetermination of the required density of sensor nodes in order to minimizecost, power and network traffic loads, while ensuring network reliability andadequate sensor resolution for data accuracy.

Limitations:Power, memory, processing power, life-time.

Failure prone:

Individual sensors are unreliable, particularly in harsh and unpredictableenvironments. Addressing sensor reliability can reduce the level ofredundancy required for a network to operate with the same level ofreliability.

Network congestion resulting from dense networkdeployment:

The quantity of data gathered may exceed the requirements of the networkand so evaluation of the data and transmission of only relevant and

adequate information needs to be performed.

Security is a critical factor in sensor networks, given some of the proposedapplications. An effective compromise must be obtained, between the lowbandwidth requirements of sensor network applications and securitydemands .


12/14

APPLICATIONS OF SMART SENSORS: SMART SENSOR FOR TIRE PRESSURE MONITORING:

Recent reports of accidents involving sport utility vehicles have led to tirerecalls and finger pointing at vehicle design, tire quality, tire pressure, ordriver error as the underlying cause of the problem. The information mustbe wirelessly transmitted to the driver, typically via RF, and displayed in thecabin of the vehicle. The remote sensing module consists of a pressuresensor, a signal processor, a temperature sensor that compensatespressure variations due to temperature changes, and an RF transmitter.The system is powered by a battery with embedded intelligence thatprolongs its operating life. Because battery replacement is out of thequestion, and replacing the entire module is not a cost-effective option forthe average car owner, most of the existing specifications require up to 10

years of battery life.

TPMS (Tire Pressure Monitoring Sensor):The receiver can either be dedicated to TPM use or shared with otherfunctions in the car. For instance, the receiver controller could be theexisting dashboard controller or the body controller. Or the receiver itselfcould be shared with the remote keyless entry (RKE) system since bothsystems are using the same frequency range. This functional sharingfeature helps with the system cost, reduces design cycle time, and makesthe TPMS easier to integrate into the automobile.

THE OTHER APPLICATIONS INCLUDE: Bushfire response using a low cost, typically dormant,

distributed sensor network early warning and localization ofbush fires can be achieved, hence saving life and property,whilst reducing the cost of monitoring


13/14

Intelligent transportation low cost sensors build into roadsand road signs can assist to manage traffic flow and informemergency services of traffic problems

Real-time health monitoringa nano-technology based bio-sensor network can assist in monitoring an ageing population,and inform health care professionals in a timely manner ofpotential health issues.

Unmanned aerial vehicle surveillance swarms of low costunmanned autonomous and co-operating aerial vehicles couldbe deployed to conduct surveillance and monitoring in remoteor hostile environments

Water catchment and eco-system monitoring andmanagementsensor networks that keep track of water quality,salinity, turbidity and biological contamination, soil condition,

plant stress and so on could be coordinated to assistenvironmentally sustainable management of entire watercatchment areas

Robotic landmine detection: A sensor network for thedetection and removal or deactivation of landmines. A reliablesensor network will enable the safe removal of landmines informer war zones, reducing the risk to those involved in theremoval process. The cost effectiveness of the network will aidin the its application throughout third world nations where the

after effects of war continue to take a toll on people living inareas still containing live explosives. The utilization of smartsensor technology to detect explosives, will overcomedifficulties in detection of un-encased landmines.


14/14

CONCLUSION:

Thus we conclude that the smart sensors are cost effective, highly accurateand reliable small in size and have a varied future scope beneficial tomankind. The sensor revolution is entirely practical applications that are

just coming on the market. From the experience of already existingdevices, we can expect that in the coming decade a large number ofsuccessful smart sensors will emerge.

Documents

Smart Sensors Represent the Next Evolutionary Tools for Studying the Environment