Smart Structures or Smart Materials

Smart materials and smart Smart materials and smart systemssystems

may be regarded as an 'active' material in the sense that it

is being used for more than just its structural properties

a smart structure is neither a small structure nor one made

of silicon

Term ‘smart’ really implies a form of intelligence and is

applied to civil buildings and bridges

Various possible uses of the Various possible uses of the prefix prefix 'smart''smart'Description Meaning Example

Smart material Material with a function other than passive mechanical support

Shape-memory alloy

Smart structure Civil structure that adapts to changes in its environment

Building with an active damping system

Smart sensor Micro-sensor with part, or all, of its processing unit integrated into one chip

Commercial (e.g. Motorola)automotive pressure sensor

Smart actuator Actuator with part, or all, of its processing unit integrated into one chip

Micro-motor

Smart microsystem Sensor, processor, and actuator integrated in a single chip

MEMS or MOEMS devices

Smart materials & smart Smart materials & smart systems for the futuresystems for the future• smart systems trace their origin to a field of research that

envisioned devices and materials that could mimic human muscular and nervous systems

• essential idea is to produce non-biological systems that will achieve the optimum functionality observed in biological systems through imitation of their adaptive capabilities and integrated design

• system and its related components form an entity that will act and react in a predicted manner, and ultimately behave in a pattern that emulates a biological function e.g. the human body is the ideal or ultimate smart system

• One of the first attempts to use the smart materials technology involved materials constructed to do the work of electromechanical devices for e.g. many types of sensors and actuators have been developed to measure or excite a system.

Beneficial scope of smart Beneficial scope of smart materials, structures & materials, structures & systems in the futuresystems in the futureprovides a promise of optimum responses

to highly complex problem areas like by providing early warning of the problems or adapting the response to cope with unforeseen conditions

enhances the survivability of the system and improves its life cycle

provides better control by minimizing distortion and increasing precision

enhances preventative maintenance of systems resulting in a better performance

Smart systems for Smart systems for engineering applicationsengineering applicationsGeneral Requirements and Expectations•High degree of reliability, efficiency and sustainability not only of the structure but also of the whole system.•High security of the infrastructures particularly when subjected to extreme and unconventional conditions.•Full integration of all the functions of the system.•Continuous health and integrity monitoring.•Damage detection and self-recovery.•Intelligent operational management system.

Smart systems for Smart systems for engineering applicationsengineering applicationsSmart Technologies Prospects•New sensing materials and devices.•New actuation materials and devices.•New control devices and techniques.•Self-detection, self-diagnostic, self-corrective and self-controlled functions of smart materials/systems.

SMART MATERIALS?SMART MATERIALS?• ‘Smart’ or ‘intelligent’ materials are

materials that have the intrinsic and extrinsic capabilities,

• first, to respond to stimuli and environmental changes

• second, to activate their functions according to these changes.

• To use smart materials with more acute recognition, discrimination and reaction capabilities, new materials and alloys have to satisfy a number of fundamental specifications.

Requirements for New Requirements for New Material: Material: • technical properties , including mechanical

characteristics such as plastic flow, fatigue and behavioural characteristics such as damage tolerance and electrical, heat and fire resistance;

• technological properties, encompassing manufacturing, forming, welding abilities, thermal processing, waste level and repair capacities;

• economic criteria, related to raw material and production costs, supply expenses and availability;

• environmental characteristics, including features such as toxicity and pollution;

• Note: If the functions of sensing and actuation are added to the list, then the new material/alloy is considered a smart material.

Classification of Smart Classification of Smart MaterialsMaterials• Piezoelectric: When subjected to an electric charge or a

variation in voltage, piezoelectric material will undergo some mechanical change, and vice versa. These events are called the direct and converse effects.

• Electrostrictive: This material has the same properties as piezoelectric material, but the mechanical change is proportional to the square of the electric field. This characteristic will always produce displacements in the same direction.

• Magnetostrictive: When subjected to a magnetic field, and vice versa (direct and converse effects), this material will undergo an induced mechanical strain, therefore, can be used as sensors and/or actuators.

• Shape Memory Alloys (SMA): When subjected to a thermal field, this material will undergo phase transformations which will produce shape changes. It deforms to its ‘martensitic’ condition with low temperature, and regains its original shape in its ‘austenite’ condition when heated for e.g. Nitinol TiNi

• Optical Fibres: Fibres that use intensity, phase, frequency or polarization of modulation to measure strain, temperature, electrical/magnetic fields, pressure and other measurable quantities, constitute excellent sensors.

SMART STRUCTURESSMART STRUCTURES

a smart structure is a system that incorporates particular functions of sensing and actuation to perform smart actions in an ingenious way. The basic five components of a smart structure are summarized as follows shown in (Figure1)

• Data Acquisition (tactile sensing)• Data Transmission (sensory nerves)• Command and Control Unit (brain)• Data Instructions (motor nerves)• Action Devices (muscles)

Five basic components of a Five basic components of a smart structuresmart structure

(a) (a) Data Acquisition Data Acquisition (tactile (tactile sensing)sensing) • aim: to collect the required raw data

needed for an appropriate sensing and monitoring of the structure.

• event to be sensed- radiation, magnetic, thermal, mechanical or chemical

• according to the nature of the output required, such as thermal, magnetic, electrical, optical or mechanical

• Fibre optics are an excellent example of sensors

(b) Data Transmission (b) Data Transmission (sensory (sensory nerves)nerves)• aim: to forward the raw data to the local and/or

central command and control units• fibre optics: used as sensors, duplicate the action

of conventional strain gauges and respond to a change in transmitted light which could be in intensity, phase, frequency, polarization, wavelength or mode

• They are highly sensitive, can detect minuscule variations and thus work very well

• Bragg grating sensors work very well but are expensive, while Fabry-Perot sensors are cheaper to build, which is already used in a few civil engineering applications

• For e.g., deformation and vibration are being measured in a cracked bridge in Berlin, Germany and Vibration and corrosion are being monitored in a few bridges in the US and Canada

(c) (c) Command and Control Unit Command and Control Unit (brain):(brain):• aim: to manage and control the whole

system by analyzing the data, reaching the appropriate conclusion, and determining the actions required

• the manager of day-to-day operations, responsible for monitoring the health and integrity of the system by means of a communication network which works in real time

• operates by managing optical fibre sensors and actuators, or by overseeing operational and control devices.

• It has two basic & distinct functionsa. The Processing Functionb. The Analysis Function

Command and Control Unit Command and Control Unit (brain)(brain)(contd.)(contd.)The Processing Function:• receives information; analyses it; sorts

and classifies it; and stores and/or processes it

• depending on the nature, frequency and quality of the data and its origins.

• operations are dealt with by intelligent or smart processing, with or without human intervention, and with little or no human interaction

• Lastly, expert systems can handle the retrieval, management, classification, and storage of the data

Command and Control Unit Command and Control Unit (brain)(brain)(contd.)(contd.) The Analysis Function:• deals with the detailed examining of the

raw data in an intelligent way; using the analysis, it will exploit the results to assess the condition of the structure.

• analysis consists of localizing and identifying specific variables or features as compared to threshold levels defined in codes, rules, regulations or standards

• In an adverse condition, the apt corresponding conclusion is reached, decisions are sent to the action controlling devices, which will be triggered to react

• To operate these functions, special algos are established.

(d) (d) Actuating ComponentActuating Component• they are designed according to the nature

of the required actuation-optical, magnetic, thermal, mechanical or chemical

• as well as according to the nature of the driving energy, such as thermal, magnetic, electrical or chemical

• environmental considerations too such as thermal, magnetic # electrical properties and corrosion, #as well as the size, geometry and mechanical properties of the interface have to be considered.

• lastly, the properties of the actuators such as displacement, force generation, hysteresis, response time and bandwidth are also specified aptly

(e) (e) SENSORS AND SENSORS AND ACTUATORSACTUATORS For active noise control applications• microphones are used as acoustic sensors and • loudspeakers as acoustic actuators For displacement and velocity control, two types

of transducers are convenient: • Linear Variable Differential Transformers

(LVDT) and • Linear Variable Inductance Transformers

(LVIT) two basic types of actuators• Hydraulic and pneumatic actuators :

employed when low frequency, large force and displacements are required, while

• the electromagnetic/ shaker types are utilized to react against an inertial electro-dynamic mass

Supporting with a few Supporting with a few examplesexamples• Vibration reduction in sporting goods: a new

generation of tennis rackets, golf clubs, baseball bats (Fig. 3) & ski boards etc. have been introduced to reduce the vibration in these sporting goods, increasing the user’s comfort and reducing injuries.

• Noise reduction in vehicles. Filaments of piezoelectric ceramic fibre shaped into various geometries are used in conventional fabric or material processing to counter noise in vehicles, neutralize shaking in helicopter rotor blades, or nullify or at least diminish vibrations in air conditioner fans and automobile dashboards.

• Spatial High Accuracy Position Encoding and Control System (SHAPECONS) incorporates smart components that were developed for the STEAR-9

• Program (Fig. 4).• Frangibolt, a system flown on the 1994 Clementine

mission to the moon, is used to deploy solar arrays, antennae and satellite from a launch vehicle [9].

Applications (contd.)Applications (contd.)Few applications were established

for military• Smart Skin• Smart Aircraft• Autonomous Smart systems• Stealth Applications: smart vehicles

could be constructed using stealth technologies for e.g. the B-2 stealth bomber or the F-117 stealth fighter

• Identifying space/underwater stealth targets

INTRODUCTION TO SMART INTRODUCTION TO SMART SENSORSSENSORSMain aim of Integrating the electronics and the

Sensor is to make and intelligent sensor.

Smart Sensor have the ability to take decision.

Complete system is called a system on Chip.

Smart Sensor consist of Transduction Element, Signal Conditioning Electronic and controller/processor.

DEFINITIONDEFINITION

• Sensor(producing electrical output) + interfacing electronic circuit = Smart Sensor• Combination of both sensor & actuator• Capable of – 1. Logic functions 2. Two-way Communications 3. Making decisions

MAIN FEATURESMAIN FEATURESVLSI technologiesLow power consumptionSmall sizeLow costSingle chip solutionLess space in configurationWorks with small signalsWireless RF communication

WHY SMART SENSORS?WHY SMART SENSORS?Smart Sensor enhances the following applications -1. Self-calibration: Adjust deviation of o/p of sensor from desired

value.2. Communication: Broadcast information about its own status.3. Computation: Allows one to obtain the average, variance &

standard deviation for the set of measurements.4. Multisensing: A single smart sensor can measure pressure,

temperature, humidity, gas flow & infrared, chemical reaction, surface acoustic vapour, etc.

5. Cost Effectiveness: Less hardware and reduction of repititive testing make smart sensor cost effective.

A smart sensor is made with same technology as Integrated circuits

A transduction element either includes thin metal films, Zinc Oxide and Polymeric films

GENERAL ARCHITECTURE GENERAL ARCHITECTURE

A general Architecture of smart sensor consist of following important components : 1. Sensing element/transduction element2. Amplifier 3. Sample and hold 4. Analog multiplexer5. Analog to digital converter (ADC)6. Offset and temperature compensation 7. Digital to analog converter (DAC)8. Memory9. 8Serial communication and processor

ADVANTAGESADVANTAGESThe presence of controller in smart sensor has led to corrections

for different undesirable sensor characteristics which include span variation , non –linearity, cross-sensitivity.

REDUCE COST OF BULK CABLES & CONNECTORSREMOTE DIAGNOSTICS - It is possible to have digital

communication via a standard bus & a built in self-test.SYSTEM RELIABILITY - System reliability is significantly

improved due to the utilization of smart sensor.BETTER SIGNAL TO NOISE RATIO - The electrical output

of most sensors is very weak and it is transmitted through long wires lot of noise get coupled by using smart sensor this problem is avoided .

HIGH PERFORMANCE WITH MINIMUM COSTEASY TO DESIGN, USE & MAINTAINSCALABLE – Flexible SystemSMALL RUGGED PACKAGING

APPLICATIONSAPPLICATIONS

APPLICATIONS….APPLICATIONS….ACCELEROMETER - It consists of sensing element and

electronics on Silicon.OPTICAL SENSOR - It is used for measuring exposure in

cameras, optical angle encoders INFRARED DETECTOR ARRAY – IR sensing element is

made using poly-silicon. INTEGRATED MULTI SENSOR - This chip was fabricated

using conventional Silicon planer processing, Silicon Micro machining and thin deposition technique.

SMART SENSORS IN SMART SENSORS IN BUILDINGS TODAYBUILDINGS TODAYSensicast’s Smart

Sensors automatically“introduce themselves” to thenetwork and work reliably for years. They monitor multiple data types essential for industrial, manufacturing and laboratory processes,including:• Pressure• Temperature• Current and Voltage• Motion• Light• Humidity, Moisture and many more

ReferencesReferences See Akhras, G., “Smart Structures and their Applications in Civil Engineering”, Civil

Engineering Report, CE97-2, RMC, Kingston, Ontario, Canada, 1997. See also Culshaw, B., Smart Structures and Materials, Artech House Inc, 1996 and Bank, H. T., Smith, R.C. and Wang, Y., Smart Material Structures, Modelling, Estimating and Control, John Wiley and Sons, 1996.

Ralph Smith C., “Smart Structures: Model development and Control applications ”,Centre for research in Scientific Communication, North Carolina State University, Rayleigh NC 27695-8205.

V.R. Singh ,“ Smart sensors, physics and technology”, Indian journal of pure and applied physics, vol.5, January 2005, pp7-16.

Manali Chaudhary, Prof. Srinu dharavath, “ Study of smart sensors and application”, International journal of advanced research in computer and communication engineering, vol. 3, issue 1, January 2014

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