APPLICATION OF SMART MATERIALS IN MODERN
ENGINEERING FIELDS
Structural
Applications of Smart Materials in Construction Engineering Using Robotics
Abstract -Sensors and Actuators designs have mimicked nature to a
large extent. Similar to our five senses - sight, sound, smell, taste and touch
-correspondingly visual/optical, acoustic/ultrasonic, electrical, chemical and
thermal/magnetic sensors have been developed. The response from these primary
sensors is converted to electrical signals, which are transmitted to the brain
(central processing unit) for further processing. In addition to the
processing, the role of the processor is to make decision based on these
inputs. This is currently done manually by an experienced operator who has an
understanding of the sensing and processing technology. To aid the operator in
making a more judicious decision, the conditioned signal has to be presented
with as much pertinent information displayed in an arresting way. A further
development would be to provide the virtual machine itself to make the judgment
- smart sensor. The next stage in this would be for the processor to decide on
the course of action and the actuation mechanism to respond accordingly. Virtual
human robots can be equipped with sensors, memory, perception, and behavioural motor.
This eventually makes these virtual human
robots to act or react to events. The design of a behavioural
animation system raises questions about creating autonomous actors, endowing
them with perception, selecting their actions, their motor control and making
their behaviour believable and the behaviour should be spontaneous and
unpredictable.
Keywords- smart materials, structures, smart sensors, actuators.
INTRODUCTION
There is an increasing awareness of the benefits to be derived from
the development and exploitation of smart materials and structures in
applications ranging from hydrospace to aerospace. With the ability to respond
autonomously to changes in their environment, smart systems can offer a
simplified approach to the control of various material and system
characteristics such as light transmission, viscosity, strain, noise and
vibration etc. depending on the smart materials used [1]. There are a number of
materials that act as both sensors and actuators that can monitor and respond
to their environment. However, with the ability to also modify their properties
in response to an environmental change, they can be 'very smart' and, in effect,
learn. While the scope of sensors and actuators is quite broad, three main
sub-programs have been identified – Smart Structures and Materials, Miniature
Sensor and Actuators and Automated Testing, Inspection Monitoring and
Evaluation. These are exciting times for Sensors and Actuators with the
maturing of the enabling technologies of Photonics and Electronics paving the
way for inventive and innovative system designs. For the modelling of sensor
behaviours, the ultimate objective is to build intelligent autonomous virtual
humans with adaptation, perception and memory. These virtual humans should be
able to act freely and emotionally. They should be conscious and unpredictable.
The virtual humans are expected in the near future to represent computer the
concepts of behaviour, intelligence, autonomy, adaptation, perception, memory,
freedom, emotion, consciousness, and unpredictability. Behaviour for virtual
humans may be defined as a manner of conducting themselves. It is also the
response of an individual, group, or species to its environment.
Intelligence may be defined as the ability to learn or understand or
to deal with new or trying situations[1].
A. Mechatronic devices
The essential ingredients of any robotic system are sensors,
computation and actuators. Appropriate choices of sensors and actuators can
simplify a robotic system or may even be the difference between its success and
failure. Mechatronic devices are the novel actuators including those based on
shape memory alloy, electrorheological fluids, magnetic fluids and the
piezoelectic effect as well as a wide range of sensors for measuring quantities
of importance for robotic systems [1].
B. Robotic mechanisms
All of the sensors, actuators [1]-[2] and algorithms that are
developed should be tested by incorporating them into a mobile robot platform,
humanoid robot or fixed manipulator/ gripper system. An extensive experience of
building legged, wheeled and tracked land vehicles, submersibles and flying
robots as well as robotic grippers and complete humanoid robots are required.
II. VIRTUAL REALITY APPLICATION
Virtual human robots (Fig. 1) can be equipped with sensors, memory,
perception, and behavioral motor. This eventually makes this to act or react to
events. The design of a behavioral animation system raises questions about
creating autonomous actors, endowing them with perception, selecting their actions,
their motor control and making their behaviour believable and the behavior
should be spontaneous and unpredictable. They should give an illusion of life,
making the people believe that that they are really alive. A virtual human can
be developed which include the basic components of a smart system embedded sensor(s),
an information processing (software) system for data analysis, logic and
decision making and system hardware (e.g., multiplexers, actuators
etc) interfaced to a computer for control, actuation and feedback
[4].
III. SENSORS AND ACTUATORS
Development of the research and technology base in Sensors and
Actuators (Fig. 2) requires a basic understanding of the principles and
mechanics of the components. Programs identified within the Sensors and
Actuators SRP, include
* Optical Sensors and Digital Imaging
* Smart Materials and Structures
* Non-Destructive Testing and Evaluation
* Bio-chemical Sensors
* Other related programmes
Being a fairly broad discipline, the Sensors and Actuators SRP has
common ground and overlap with most of the other SRP's. For example, with the MEMS
programme, there is the development of optical sensors for characterization and
reliability of MEMS devices. Similarly a suite of techniques is developed for
NDT and stress management of electronic packaging systems. With the biomedical group,
there is work on development of fiber optic biosensors for bacterial sensing
and detection. While the research focus is on development of novel sensors and
actuators, industrial support requires integrated system development as well.
The Smart Structures and Materials program is a particular case in point of an
integrated system incorporating sensors, processing and decision making
capabilities and actuation. It can be defined as "a system or material which
has built-in or intrinsic sensor(s), actuator(s), and control mechanism(s)
whereby it is capable of sensing a stimulus, responding to it in a predetermined
manner and extent, in a shortlappropriate time, and reverting to its original state
as soon as the stimulus is removed". The term stimulus may include stress,
strain, incident light, electric field, gas molecules, temperature, hydrostatic
pressure etc. whereas, the response could be any of a number of possibilities,
such as motion or change in optical properties, conductivity, surface tension,
dielectric, piezoelectric or pyroelectric properties, mechanical
modulus or permeability [5]. Although Japanese and American scientists have rather
different views of smart/intelligent materials, they are generally regarded to
be a group of materials that have varying degrees of sensing and actuating functions
that can be incorporated into systems having feedback loops to constantly vary
or "tune" one or more material property such as size, shape, color,
structure or composition. Using sophisticated hardware (control devices e.g.,
actuators) and software these materials can be incorporated into what is
described as a smart/intelligent system, that possesses a higher level of
intelligence such as selfdiagnosis, self-repair, learning ability, ability to discriminate
shapes and forms, ability to judge etc.
A. Optical Sensors and Digital Imaging
Optical components such as optical fibers, lasers and detectors are
only recently being
developed fueled by the applications in the communications industry.
Electronics and Optics have been competing technologies in sensor and actuator
system over the years. Indeed, the evolution of electronics and optics has
taken similar routes. Optical Sensors offer some advantages over electrical
sensors, such as use of passive, dielectric and insulating components. No electrical
power at the measurement point is required, thus no heat generation, electrical
shorting and fire hazard problems. Remote non-contact sensing and whole-field
visual display of the measure and rounds of the positive aspects of optical
sensors. However, electrical sensors have a longer industrial history and thus
components and devices for these sensors are readily available. Thus electrical
sensors are more prevalent. The cost of these components is competitive and
various off-the-shelf systems are becoming available. Optoelectronics has
merged these two competing technologies, taking the best of each. Optics has
the advantage in the primary sensing capabilities, while electronics is
currently leading in the processing and actuating technologies. Thus this has a
lot to offer in development of novel sensor processor- actuator systems [6].
B. Environmental Requirements
The sensor implanted humanoid has to survey the construction and, if
possible, the whole life span of the structure. During the construction phases,
the sensor is exposed to a hostile environment and has therefore to be rugged
enough to protect the fibers from external agent. Chemical aggression has to be
taken into account since concrete can be particularly aggressive because of its
high alkalinity. These requirements are often contrasting with the ones of the
previous point. To protect the fiber one tends to isolate if from the
environment by using thicker or multiple layers of coating. This has the side
effect to impede the strain transmission from the structure to the fiber.
Finally, the sensor must be easy to use by humanoid and has to be installed
rapidly without major disturbance to the building yard schedule respond to all
these requirements. Humanoids may be embedded with all these requirements so
that the sensors can either be embedded into concrete, installed on the surface
of an existing structure or secured inside a borehole by grouting.
The current investigations on the fiber optics are
* Studying the feasibility of using a fiber optic sensor (Fig.3) for
measuring strain.
* Experimentally determining the sensibility of fiber optic soil
strains sensors.
* Developing a fiber optic sensor, this can measure the visco
elastic strain and permanent deformation of soil.
* Studying the effect of soil moisture content on the ability of the
fiber optic sensor to measure soil strains.
The Disadvantages that counts includes,
* Sensors should be handled with care and Fibre optic sensors are
still more expensive.
* Special skills are needed while installing the sensors.
With the advent of smart/intelligent materials and their
applications on structures which are known as smart/intelligent structures
result in value addition of structures in terms of operational, functional serviceability
during their use as a structural member of a building or any other equipment,
vehicle etc. This technique also helps in monitoring of structures during their
service and indicates the defects, damages occur in their use in the form of
cracks, delaminations, deformations etc. which is very useful in assessing the
suitability and fitness of a structure in rendering further service for their
remaining life. Though this technique is quite evidently gaining momentum in
their applications in the field manufacturing, robotics, evidently gaining momentum
in their applications in the fIeld manufacturing, robotics, materials but its
use in civil engineering structures is yet to gain attention of the designers
and constructors. As the construction cost of the civil engineering structures
is escalating and also subjected to natural calamities like earthquakes, forces
of wind, weathering etc. its structural fitness has to be established from time
to time for its sustainable serviceability and structural adequacy by applying
smart materials concepts [2]-[3].
C. Ceramic-based Actuator Materials
It has been tacitly assumed to this point that all actuator
materials behave similarly. In broad terms, some actuators are developed using
piezoelectric materials whereas others exploit electrostrictive materials based
on relaxor ferroelectrics. In addition, within the piezoelectric materials
there is considerable variation in how each material responds to an applied
voltage which is a reflection of both their composition and microstructure.
Smart Materials represent an enabling technology that has applications across a
wide range of sectors including construction, transportation, agriculture, food
and packaging, healthcare, sport and leisure, white goods, energy and environment,
space, and defence. Smart Materials are materials that sense their environment
and respond. Research and Development projects to incorporate Humanoids in the
following application areas include
* Modern Built-Environment
* Environmentally Friendly Transport
* Sustainable Production and Consumption
IV. BACKGROUND
Smart Materials are materials that respond to environmental stimuli,
such as temperature, moisture, pH, or electric and magnetic fields. For
example, photochromic materials that change colour in response to light; shape
memory alloys and polymers which change/recover their shape in response to heat
and electro- and magnetorheological fluids that change viscosity in response to
electric or magnetic stimuli. Smart Materials can be used directly to make smart
systems or structures or embedded in structures whose inherent properties can
be changed to meet high value-added performance needs. Smart Materials technology
is relatively new to the economy and has a strong innovative content. According
to work by the Materials Foresight Panel, the use of smart materials could make
a significant impact in many market sectors. In the food industry, smart labels
and tags could be used in the implementation of traceability protocols to
improve food quality and safety e.g. using thermo chromic ink to monitor
temperature history. In construction, smart materials and systems could be used
in 'smart' buildings, for environmental control, security and structural health
monitoring e.g. strain measurement in bridges using embedded fibre optic
sensors (Fig. 4). Magneto-rheological fluids have been used to damp
cable-stayed bridges and reduce the effects of earthquakes. In aerospace, smart
materials could find applications in 'smart wings', health and usage monitoring
systems (HUMS), and active vibration control in helicopter blades. In marine
and rail transport, possibilities include strain monitoring using embedded
fibre optic sensors. Smart textiles are also finding applications in sportswear
that could be developed for everyday wear and for health and safety purposes
[8]-[12].
A. Structural Health Monitoring
Virtual human robots can be equipped with sensors, memory,
perception, and behavioral motor. This eventually makes these virtual human
robots to act or react to events.
* Also called Damage Detection
* Using response signals to determine if there has been a change in
the system's parameters.
* Mathematically very much like parameter identification in many
respects
* Numerous methods have been proposed.
* Impact is high for SMH systems that work without taking the base
system out of operation.
B. Smart Structures
Key areas of focus for the development of smart structures to
include: Miniaturisation and integration of components, e.g. application of
sensors or smart materials in components Robustness of the smart system, e.g.interfacial
issues relating to external connections to smart structures Device fabrication and
manufacturability, e.g. Electrorheological fluids in active suspension systems,
applications in telematics and traffic management Structural health monitoring,
control and lifetime extension (including self-repair) of structures operating
in hostile environments, e.g. vibration control in Aerospace and Construction
applications. Thermal management of high temperature turbines for power
generation. Selfmonitoring, self-repairing, low maintenance structures, e.g.
bridges and rail track Smart structures that can self-monitor internal
stresses, strains, creep, corrosion and wear would deliver significant
benefits.
Projects can be based on any material format (e.g. speciality
polymers, fibres and textiles, coatings, adhesives, composites, metals, and
inorganic materials), which incorporate sensors or active functional materials
such as: piezoelectrics, photochromics, thermochromics, electro and magneto rheological
fluids, shape memory alloys, aeroelastictailored and other auxetic materials.
For the modelling of actor behaviors, the ultimate objective is to build intelligent
autonomous virtual humans with
adaptation, perception and memory. These virtual humans should be able
to act freely and emotionally. They should be conscious and unpredictable. But
can we expect in the near future to represent in the computer the concepts of
behavior, intelligence, autonomy, adaptation, perception, memory, freedom, emotion,
consciousness, and unpredictability [9]-[10].
C. Key Points
* This is the first successful trial in the worldto remotely control
a man emulating robot soas to drive an industrial vehicle (backhoe) outdoors in
lieu of a human operator.
* Furthermore, the robot's operation was controlled while having it
wear protective clothing to protect it against the rain and dust outside. This
too marks a world-first success demonstrating the robot's capability of performing
outdoor work even in the rain.
* This has been achieved with an HRP- IS robot whose Honda R&D
made hardware was provided with control software developed by the AIST.
* The robot has a promising application potential for restoration
work in environments struck by catastrophes and in civil engineering and
construction project sites where it can "work" safely and smoothly.
D. Outline
This robot was remotely controlled to perform outdoor work (Fig.5)
tasks normally carried out by human operators involving the operation (driving
and excavation) of a vibrating industrial vehicle (backhoe) in the seated
position. Furthermore, operation was
achieved with the robot wearing protective clothing to protect
against rain and dust. This also marks a world first success indicating the
robot's ability to carry out outdoor work tasks even in the rain. These results
were achieved thanks to the development of the following three technologies:
* The "remote control technology" for instructing the
humanoid robot to perform total body movements under remote control and the
"remote control system" for executing the remote control tasks (KHI).
* The "protection technology" for protecting the humanoid
robot against shock and vibrations of its operating seat and against the
influences of the natural environment such as rain and dust (Tokyo Construction).
* The "full-body operation control technology" for controlling
the humanoid robot's total body work movements with autonomous control
capability to prevent the robot from falling. There have been many attempts
until the present to robotize the industrial vehicles (including backhoes) themselves
for work on sites requiring their operation
in dangerous work areas or in adverse environments. In contrast, the
use of a humanoid robot to operate the industrial vehicle instead of a human
operator has two distinct advantages:
* This means that robot does not only drive the vehicle but is also
capable of executing the attendant work tasks (alighting from the vehicle to
check the work site, carrying out simple repairs, etc.) and
* It permits the robotizing of all industrial vehicles without
needing to modify them. Once humanoid robots (Fig. 5) now engaged in other types
of work can be used, when necessary, for operational duties normally performed
by human operators there will be a definite chance for a greater expansion of
the humanoid robot market which in
turn holds promise of further reductions in their production and
operating costs. The major insight gained from this success that has
demonstrated the humanoid robot's ability to replace the human operator in
operating (driving and excavation duties) commercially used industrial vehicles
(backhoe) under remote control is the realization that humanoid robots are
capable of moving in the same manner as humans. The humanoid robot's ability to
carry out outdoor work tasks even in the rain by "wearing" protective
clothing has widened the scope of the environmental conditions in which it is
capable of executing work. From these two aspects there is every reason to
expect that these results will make a substantial contribution toward the
realization of practical work-performing humanoid robots. The development tasks
ahead will include work to create wireless remote control and achieve a robot
capable of boarding the industrial vehicle independently.
V. SMART MATERIALS AND
STRUCTURE
SYSTEM
The use of smart materials (Fig-6) could make a significant impact
in many market sectors. In the food industry, smart labels and tags could be
used in the implementation of traceability protocols to improve food quality
and safety e.g. using thermochromic ink to monitor temperature history. In
construction, smart materials and systems could be used in 'smart' buildings,
for environmental control, security and structural health monitoring e.g.
strain measurement in bridges using embedded fibre optic sensors. Magneto-rheological
fluids have been used to damp cable-stayed bridges and reduce the effects of
earthquakes. In aerospace, smart materials could find applications
in 'smart wings', health and usage monitoring systems (HUMS), and active
vibration control in helicopter blades. In marine and rail transport,
possibilities include strain monitoring using embedded fibre optic sensors.
Smart Structures, e.g. structures, with integrated sensors and actuator materials,
which might eliminate the need for heavy mechanical actuation systems or
damping systems through their functionality for shape change or vibration
control. Self-monitoring, Control and Selfrepair, e.g. applications of
functionally graded layers capable of a response tailored to their environment.
This will involve use of sensor and actuator technologies for automatic control
of conditions within buildings for comfort and energy savings, tagging for food
packaging and for crime prevention application of sensors or smart materials in
components Robustness of the smart system, e.g. interfacial issues relating to
external connections to smart structures Device fabrication and manufacturability,
e.g. electro-rheological fluids in active suspension systems, applications in
telematics and traffic management Structural health monitoring, control and
lifetime extension (including self-repair) of structures operating in hostile
environments, e.g. vibration control in Aerospace and Construction applications.
Projects can be based on any material format (e.g. speciality polymers, fibres
and textiles, coatings, adhesives, composites, metals, and inorganic
materials), which incorporate sensors or active functional materials such as:
piezoelectrics, photochromics, thermochromics, electro and magneto rheological
fluids, shape memory alloys, aeroelastictailored and other auxetic materials
[10]-[1 1]. The potential application areas of smart materials and structures
are very widespread and include energy - conservation, expensive systems with
high potential for operational savings, e.g. transportation systems
such as aircraft or automobiles, aerospace structures, civil
infrastructure, structural health monitoring, intelligent highways, high-speed
railways, active noise suppression, robotics. In order to increase the speed of
the railway vehicle and reduce the energy consumption, the vehicle body needs
to be designed as light as possible, for heavy bodies result in limitations in
the operating speed and requires actuators of increased size and power, so the flexibility
of the structure becomes an important issue. Besides railway vehicles, flexible
structures are also considered important in many other areas such as road
vehicles, robotics and especially aerospace structures. the use of smart
materials to minimize vibrations via robust control. Thus the aim of the proposed
research is to contribute to the improvement of the performance of a flexible
body of railway vehicles through the use of humanoid enabled smart materials to
minimize vibrations via robust control. In order to achieve the aim, the tasks
of research may include the following
* Rigorous study of flexible-bodies and smart materials (feasibility
study)
* Modeling of the flexible body controlled via smart materials.
Model reduction will be considered to reduce the complexity of the model.
* Development of appropriate control strategies
* Demonstration, evaluation and validation The idea of incorporating
humanoid enabled smart materials into flexible structures to achieve improved performance
of the flexible structure with application to railway flexible bodies. The
motivation for the proposed research is introduced and tasks that may be involved
in this research.
A. Characteristics of Sensor for Strain measurement
Optical fibre sensing systems (Fig.4) will be significantly less
expensive than the conventional counterparts than the future, particularly
those that are commercialized and produced in large quantities. Since a light
signal rather than the electric current is carried, optical fibre sensors have
very little loss and are immune to lighting damages. Mostly these sensors are
based on the principle of white light interferometry. Some of the Fibre Optic
Sensors are
SOFO displacement sensor
Bragg grating strain sensor
Micro bending displacement sensor
Fabry perot strain sensor
Raman distributed temperature sensor
B. Determination of Displacement by using SOFO Sensors
It is a fiber optic displacement sensor with a resolution in the
micrometer range and has an excellent long-term stability. The measurement
setup uses low-coherence interferometry to measure the length difference
between two optical fibers installed on the structure to be monitored. The
measurement fiber is pre tensioned and mechanically coupled to the structure at
two anchorage points in order to follow its deformations, while the reference
fiber is free and acts as temperature reference. Both fibers are installed inside
the same pipe and the measurement basis can be chosen between 200mm and 10m.The
resolution of the system is 2 micrometer independently from the measurement
basis and its measurement basis and its precision is of 0.2% of 12 the measured
deformation even over years of operation .The SOFO system (Fig.7) has been successfully
used to monitor more than 50 structures including bridges, tunnels, piles, dam,
nuclear power plant etc. [9]
VI. CONCLUSION
Sensors are playing a vital role in all sorts of sciences. Hence,
instead of placing various sensors at variable places in various application
areas, it may be better to embed these sensors in humanoids and it could be effectively
used in detecting, monitoring, message
conveying, repairing etc., Thus the mobility of humanoids may be
used effectively. A smart intelligent structure includes distributed actuators,
sensors and microprocessors that analyze the response from the sensors and use
distributed parameter control theory to command actuators, to apply localized strains.
A smart structure has the capacity to respond to a changing external
environment such as loads, temperatures and shape change, as well as to varying
internal environment i.e., failure of a structure. This technology has numerous
applications much as vibration and buckling control, ape control, damage assessment
and active noise control. Smart structure techniques are being increasingly
applied to civil engineering structures for health monitoring of buildings with
strain and corrosion sensors.
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