smart structures and applications

1. SMART MATERIALS and MEMS
Course Objective:
1. This course provides a detailed overview to smart
materials, piezoelectric materials structuresand its
characteristics.
2. The study of Smart structures and modelling helps in
Vibration control using smart materials in various
applications.
3. Helps to understand the principles and concepts of
using MEMS, ER & MR Fluids for various applications.

2. 1. Introduction:
2. Closed loop and Open loop Smart Structures.
3. Applications of Smart structures,

3. Different eras of civilization are branded with their material capabilities, and these periods are referred to as: the
StoneAge, the BronzeAge, the Iron Age, and the SyntheticMaterial Age.
The StoneAge represents the earliest known period of human civilization that stretches back to one million years
BC, when tools and weapons were made out of stone
The BronzeAge (sometimes called the CopperAge) spans 3500–1000 BC. Weaponsand implements were made
of bronze(an alloyof copperand tin) during this period
The Iron Age followed the BronzeAge around 1000 BC and was characterized by the introductionof iron
metallurgy.
The SyntheticMaterial Age started in the early part of the twentieth centurywith the development of a wide range of
man-made synthetic materials.
The twenty-first centurymay be visualized as the Multifunctional MaterialsAge. The inspiration for multifunctional
materials comes from nature; hence, these are often referred to as bio-inspired materials.
This category encompasses smart materials and structures, multifunctionalmaterials, and nano-structuredmaterials.
These are also referred to as intelligent, adaptive, active, sensory, and metamorphic structuresand materials and/or
systems

4. The ultimate goal is to develop biologically inspired multifunctional materials with the
capability to adapt their structural characteristics (stiffness,damping, viscosity, etc.) as
required, monitor their health condition, perform self-diagnosis and self-repair, morph their
shape, and undergo significant controlled motion over a wide range of operating conditions.
• The standard of living has been impacted by the emergence of high performance materials.
• The field of smart materials and structures is the knowledge of physics, mathematics,
chemistry, computer sciences, with material, electrical and mechanical engineering
• These are also referred to as intelligent, adaptive, active, sensory, and metamorphic
structures and materials and/or systems.
.

5. Two types of smartness in structures can be distinguished: closed-loop and open-loop.Aclosed-
loop smart structure senses the changes to diagnose the nature of the problem, takes action to
mitigate the problem, and also stores the data of the episode for future reference
closed-loopand open-loop.
A closed-loop smart structure senses the changes to diagnose the nature of the problem, takes action to
mitigatethe problem, and also stores the data of the episode for future reference.
Open-loop smartness means that the design is such that structural integrity is enhanced only when needed, and
the structure relapses to its normal state when there is no need for enhanced integrity.
• An open-loopcontrolsystem takes input underthe considerationand doesn’t react on the feedback to obtain
the output. This is why it is also called a non-feedbackcontrolsystem.
• There are no disturbancesor variations in this system and works on fix conditions.
• A closed loop system is also referred as a feedback controlsystem. These systems record the outputinstead
of input and modify it according to the need. It generates preferred condition of the outputas compared to the
original one. It doesn’t encounterany external or internal disturbances.

8. These two types of control system have contrast with each other. They have dissimilarities some of which are
discussed below:
1.Effect of output
– An open loop control system acts completely on the basis of input and the output has no effect on the
control action.
– A closed loop control system considers the current output and alters it to the desired condition. The control
action in these systems is based on the output.
2. Reaction to Internal and External Disturbances
– An open loop control system works on fixed operation conditions and there are no disturbances.
– A closed loop control system doesn’t encounter and react on external disturbances or internal variations.
3. Stability
– Open loop control systems are mostly stable.
– In closed loop control systems stabilityis a major issue.

9. 4. Effect on gain
– There is no effect on gain.
– There is no-linear change in system gain.
5. Implementation
– The structure of open loop control system is rather easy to construct. These systems can be easily
implemented.
– The working principle and structures of closed loop control systems are rather complex and they are often
difficult to implement.
6. Cost
– As an open loop control system is easy to implement, it needs lesser number of components to be constructed.
Such systems need good calibration and lesser power rating. The overall cost of these systems is low.
– As the principle is complex, a closed loop control system needs larger number of components than an open
loop control systems. These systems comparatively need less calibration and higher power rating. The overall
cost of these systemsis higher.

10. A smart material is defined as a material that transforms its characteristics, such as mechanical
states (strain, position or velocity) or material characteristics, (stiffness, damping, or viscosity)
under external field (electric, magnetic, or thermal).
a smart material is one whose electrical, mechanical or acoustic properties or their structure,
composition or functions change in a specified manner in response to some stimulus from the
environment.

11. Development of smart materials and structures is possible through one of three approaches.
1. In the first approach, the new materials with smart functionality can be synthesized at the atomic and
molecular level.
2. In the second approach, actuators and sensors are attached to a conventional structure, which adaptively
responds to external disturbances.
3. In the third approach, active plies representing actuators and sensors are synthesized with non-
active plies to form a laminated structure.
The key elements of smart structures are: actuators, sensors, power conditioning, control logics, and computers
Conventional Smart material
Conventionaldisplacementactuatorsare: electromagnetic
(includingvoice coils), hydraulic,and servo- or stepper
motors
Typicalsmart material
actuatorsare: piezoelectric, electrostrictive,
magnetostrictive, shape memory alloys,
and Electrorheological/Magnetorheological (ER/MR)fluids.
Conventionalsensors are strain gauges, accelerometers,
and potentiometers
smart materialssensors
can be fiber optics, piezoelectrics (ceramics and polymers),
and magnetostrictives.

12. A smart structure involves distributed actuators and sensors, and one or more
microprocessors that analyze the responses from the sensors and use integrated
control theory to command the actuators to apply localized strains or displacements to
alter system response.
a smart structure involves five key elements: actuators, sensors, control strategies,
power and signal conditioning electronics, and a computer.
Many types of actuators and sensors, such as piezoelectric materials, shape memory
alloys, electrostrictive materials, magnetostrictive materials, electro- and magneto-
rheological fluids, and fiber optics, are being considered for various applications.
Smart Structures
Smart structures are usually systems containing multifunctional components that can
perform sensing, control and actuation. Key materials used to construct these
structures are called smart materials.

14. Transducer A device that is actuated by power from one system and supplies power, usually
in another form, to a second system.
Sensor A device that responds to a physical stimulus (as heat, light, sound, pressure,
magnetism or a particular motion) and transmits a resulting impulse (as for measurement or
operating a control).
Actuator One that actuates, e.g. a mechanical device for moving or controlling something.

20. 1. Numerous applications of smart structures technology to various physical systems are
evolving to actively control vibration, noise, aeroelastic stability, damping, shape change,
and stress distribution.
2. Piezoelectric materials These are ceramics or polymers which can produce a linear change
of shape in response to an applied electric field. The application of the field causes the
material to expand or contract almost instantly. These materials have already found several
uses in actuators.
3. Electrostrictive materials These materials can also change their dimensions significantly on
the application of an electric field; the effect is reciprocal as well. these materials have also
found widespread application in medical and engineering fields
4. Magnetostrictive materials These are quite similar to electrostrictive materials, except for
the fact that they respond to magnetic fields. These materials are also used in similar
applications to those of electrostrictive materials.

21. 1. Rheological materials are in the liquid phase. These can change state instantly through the
application of an electric or magnetic charge. These fluids may find applications in brakes,
shock absorbers and dampers for vehicle seats.
2. Thermoresponsive materials Shape memory alloys (SMAs) are another widely used type of
smart materials, which change shape in response to changes in temperature.
3. Electrochromic materials Electrochromism is the ability of a material to change its optical
properties (e.g. color) when a voltage is applied across it. These are used as antistatic layers,
electrochrome layers in liquid crystal displays (LCDs) and cathodes in lithium batteries.
4. Biomimetic materials Most physical materials available contrast sharply with those in the
natural world where animals and plants have the clear ability to adapt to their environment in
real time.
5. Smart gels These are gels that can shrink or swell by several orders of magnitude (even by a
factor of 1000). Some of these can also be programed to absorb or release fluids in response
to a chemical or physical stimulus. These gels are used in areas such as food, drug delivery
and chemical processing.

22. APPLICATION AREAS FOR SMART SYSTEMS
Reduction of vibrations in sporting goods. To increase the users’ comfort, several new smart
sporting goods (e.g. tennis rackets, golf clubs, baseball bats, skis, etc.) are available on the market.
Noise control in vehicles. Composites of piezoelectric ceramic fibers are used reduce noise in
vehicles, shaking in helicopter rotor blades or vibrations in air conditioner fans and automobile
dashboards.
Aerospace applications. Demonstrated aerospace applications of smart structures include the
spatial high accuracy position encoding and control system (SHAPECONS) and Frangibolt (used to
deploy solar arrays, antennas and satellites from a launch vehicle) in the Clementine mission.
In the battlefield, soldiers may wear clothing made of special tactile material that can detect signals
from the human body to determine bullet wounds.
There are several potential locations for the use of smart materials and structures in aircraft.
Ground, marine or space smart vehicles will be a feature of future military operations. These
manned or unmanned carriage systems, equipped with sensors, actuators and sophisticated
controls, can improve surveillance and target identification and improve battlefield awareness.

23. Adaptive Structures (A): have distributed actuators to alter characteristics in a
prescribed manner. They may not have sensors. Examples are conventional aircraft
wings with flaps and ailerons, and rotor blades with servo-flaps.
Sensory Structures (B): have distributed sensors to monitor the characteristics of the
structure (health monitoring). Sensors may detect strain, displacement, acceleration,
temperature, electromagnetic properties, and extent of damage.
Controlled Structures (C): overlap both adaptive and sensory structures. These
constitute actuators, sensors, and a feedback control system to actively control
the characteristics of the structure.
Active Structures (D): are a subset of controlled structures. Integrated actuators
and sensors have load carrying capability (structural functionality).
Intelligent or Smart Structures (E): are a subset of active structures. Additionally,
they have highly integrated control logic and power electronics.
Classification of smart structures.

24. END