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The authors have developed a tiny, low-cost accelerometer that utilizesa semiconductor fabrication technology called MEMS (Micro Electro-mechanical System), for building a sensor network which would have a large quantity of such sensors deployed all over the host structure to be monitored. Due to the small dimension and extremely low power consumption, the sensor device is well-suited for such networks, where the supply of external power is very constrained. The authors have designed both a sensor device, and a sensor module having wireless communication capability built around it, and tested them in real-world tunnels, as well as in test labs. The test results showed that our prototype performed adequately for its intended use.
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KSCE Journal of Civil Engineering (0000) 00(0):1-10
DOI 10.1007/s12205-013-0108-4
Information Technology
A MEMS-based Commutation Module with Vibration Sensor for
Wireless Sensor Network-based Tunnel-blasting Monitoring
Jungyeol Kim*, Soonwook Kwon**, Seunghee Park***, and Youngsuk Kim****
Received Feburary 27, 2012/Accepted January 21, 2013
The authors have developed a tiny, low-cost accelerometer that utilizesa semiconductor fabrication technology called MEMS (Micro
Electro-mechanical System), for building a sensor network which would have a large quantity of such sensors deployed all over the
host structure to be monitored. Due to the small dimension and extremely low power consumption, the sensor device is well-suited
for such networks, where the supply of external power is very constrained. The authors have designed both a sensor device, and a
sensor module having wireless communication capability built around it, and tested them in real-world tunnels, as well as in test labs.
The test results showed that our prototype performed adequately for its intended use.
Keywords: vibration sensor, tunnel, structural health monitoring, MEMS, sensor network
1. Introduction
Blasting work using explosives produces extensive noise and
vibration that can negatively affect nearby residents and facilities.
For that reason, many jurisdictional authorities require monitoring
of such works. To monitor the effects of the explosion, the
vibration of bedrocks and artificial structures in the nearby area
is measured, and the measurement value is analyzed for assessment
of possible effects from the explosion. Currently such measurement
job relies on very expensive sensors, making it uneconomical
when considered for building a sensor network.
Our research that is described in this paper has two goals:
first, to develop an inexpensiveyetaccurate accelerometer based
on MEMS (Micro Electro-Mechanical Systems) technology for
small dimension and cost reduction; second, to develop a
wireless communication module for easier deployment of the
sensor network based on our MEMS sensors.However, the
communication module can also be configured for other
sensor types.
This paper is structured as follows: first, it briefly reviews the
measuring process of tunnels, and the available technology for
tunnel measurement-specifically for wireless sensor networks,
and the current state-of-the-art regarding sensor technology
suited toa network approach, featuring low power consumption,
small physical dimension, etc. Second, the authors describe a
technological overview, with test result of our wireless com-
munication node designed for the sensor network monitoring
vibration of a tunnel. Third, the authors present a sensor device
designed by the authors using Micro Electromechanical System
(MEMS) technology, together with test results of our prototype.
Finally, alternative power supply methodology, which has been
the subject of active research, is discussed, together with
preliminary testing of available technologies.
2. Analysis of (Tunnel) Measuring Process
To provide a technical review of current practices in measuring
tunnels, the authors collected various manuals and guides for
measuring tunnels from published sources, such as the national
standard specification of civil engineering projects, Korean
Standard for testing and measurement, tunneling manuals from
several private firms, etc.
The authors also tested existing technological elements for
measuring (Fig. 1). The elements were evaluated using the following
criteria: application area, sensor type (conventional versus MEMS),
communication method (by-wire vs. wireless), and measuring
method (dynamic vs. static).
Although reliable and precise, existing sensor technologies
revealed shortcomings when it came to the communication criterion,
as they demonstrated inconvenience, due to cable connection
*Senior Researcher, Korea Institute of Construction Technology, Koyang, Korea (E-mail:
**Member, Associate Professor, Dept. of Civil, Architectural and Environmental System Engineering, Sungkyunkwan University, Suwon 440-746, Korea
(Corresponding Author, E-mail:
***Member, Assistant Professor, Dept. of Civil, Architectural and Environmental System Engineering, Sungkyunkwan University, Suwon 440-746, Korea
****Member, Professor, Dept. of Architectural Engineering, Inha University, Incheon, Korea (E-mail:
우편번호 보내 주세요 ..
Jungyeol Kim, Soonwook Kwon, Seunghee Park, and Youngsuk Kim
2 KSCE Journal of Civil Engineering
problems. The test led us to decide that all sensors used in our
system must utilize wireless communication (Zigbee) for
transmitting sensor readings; also, for the sensors, existing
sensors were not to be replaced with MEMS counterparts, if
they offered better results than the newer, less matured
MEMS breed.
3. Review of State-of-the-art Researches
Even for MEMS, there are many technologies that can be
used for making vibration sensors. Available MEMS sensors
for measuring acceleration, force and deformation include
piezoelectric, piezo-resistive, capacitive, resonance, optical
and magnetic.The authors surveyed research papers published
in international journals and conference proceedings from
2005 onwards that cover various MEMS sensors, and the
wireless sensor networks that employ them. The authors also
reviewed some non-MEMS sensor technologies applied to
health monitoring of construction structures, including
tunnels (Table 1).
For the sensor technologies, the authors used performance
criteria (e.g. accuracy, measurable range, etc.) for making a
comparison between them.
Many of the currently available MEMS sensors are based on
the electro-mechanical type, which measures the varying capacitance
of a moving mass; to increase sensitivity, the mass is shaped like
a comb. Such sensors can have various application areas other
than accelerometers, such as inclination sensors (Yu et al., 2009),
etc. As their comb-like shape is very vulnerable to external
Table 1. Review of Sensor Technologies for the Tunnel Measurement System
Source Tech highlights What is sensed Sensor type
Sensor performance
Measurable range Accuracy
Alfado, Weiss
et al. (2009)
multi-axis CMOS-MEMS
stress sensor
Piezo-resistive ~ 250 kPa
100 Pa, w/ 1Hz
interval, 15.2dB SNR
775 uW /
Azevedo et al.
Silicon carbide (SiC)
MEMS resonant strain
sensor-silicon comb-driven
double-ended tuning fork
(CDDETF) type
(deformation) -
measuring resonant
frequency, which
varies over applied
Survivable up
to 10000 g
Sensitivity: 66 Hz/ue,
Resolution: 0.11ue
over 10-20k Hz,
-109 dBc/Hz noise
Kon and
High-res MEMS
piezoelectric strain sensor
using Zinc Oxide (ZnO)
Piezoresistive N/A
40.3 ne at 2140 Hz,
28.7 ne at 10 KHz
Yu et al.
Wireless inclination
sensor system, which
uses VTI’s SCA100T
MEMS inclinometer
tive, using over-
damped elements
to avoid vibration
±30 deg
D01), ±90 deg
Survivable up to
Resolution: 0.0025
deg at 10 Hz
Sensitivity: 70 mV/deg
(D01), 35 mV/deg
Ötügen et al.
(2008, 2009)
Micro-optical wall shear
stress sensor using whis-
pering gallery mode
(WGM) resonator - optical
Shear stress
Optical - using non
moving deformation
of light-transmitting
material, sensing its
optical resonance
Up to 1 kHz 0.01Pa N/A
Kang, Schulz
et al. (2006)
carbon nano-tube (CNT)
strain sensor - a resistive
type electrical strain sensor
Strain Resistive
N/A 20v
Leng et al.
Fiber optic sensors using
extrinsic Fabry-Perot
interferometric sensors
and fiber Bragg grating
sensors (as a part of a
fiber-optic sensor network)
strain optical
when up to 14
MPa force is
Fig. 1. Test of Existing Sensor Technology
A MEMS-based Commutation Module with Vibration Sensor for Wireless Sensor Network-based Tunnel-blasting Monitoring
Vol. 00, No. 0 / 000 0000 3
shock, the capacitive-type sensors have inherent drawback in
terms of durability, which have been addressed in (Azevedo et
al., 2007).
Another type of MEMS sensor uses the piezo-resistive property
of a metal oxide layer. For such sensors, Kon et al. (2008)
demonstrated a simply shaped (compared to the comb-shaped)
piezo-resistive sensor that was sensitive to higher frequency
vibration. Alfado et al. (2009) took a similar approach, which
implemented multi-axis sensors on a single device. In general,
those sensors are able to measure physical deformation (i.e. not
accompanying movement) that should be limited to a microscopic
An optical method is seen in two series of studies (Ioppolo et
al., 2008; Ioppolo et al., 2009), which measure the varying optical
resonance of a light-transmitting mass caused by its deformation,
thus sensing strain. The varying intensity of a laser beam
transmitted through an optical fiber is also used for a strain
sensor (Leng et al., 2006), though optical fiber is vulnerable to
damage caused by external force, so a protection mechanism is
Though not classified as MEMS, Kang et al. (2006) showed
that Carbon Nano-Tube (CNT) can be used for sensing external
force, which can be embedded into the building structure.
Although there are numerous methods known for MEMS
sensors, sensing movement (and thus acceleration) is best
implemented with a varying-capacitance type sensor; however,
there are several drawbacks if we consider such sensors for
sensing vibration: first, the sensor is vulnerable to excessive
shock, which can be caused from blast, so it must be designed
for durability. Second, a durable design may decrease the
sensitivity of the sensor when measuring smaller movement;
to address this issue, the authors designed a cantilever-type
opto-mechanical sensor that provides both durability and
4. Development of MEMS-based Vibration Sensor
The authors developed two different MEMS sensor types-a
conventional, comb-type, electro-mechanical sensor, and a
cantilever-type opto-mechanical one. The latter was designed
after two iterations of the former studies (Kim et al., 2005; Kwon
et al., 2006), because our electro-mechanical design didn’t achieve
sufficient performance for measuring micro-acceleration. The
developmental details of those sensor types are described in the
following sections.
4.1 Design and Fabrication
The authorsfirst designed a single axis MEMS accelerometer
capable of sensing planar acceleration. It is a differential type,
using comb-shaped electrodes for applying the area-variation
method. The mass is suspended with a folded-beam spring,
which is illustrated in Fig. 2. Our design was evaluated with
ANSYS software for stresses applied to the spring and the
pendulum mass, and the resonance mode of the sensor as well
(Fig. 3). The result was used for determination of the size of the
micro-components and operational frequency range of the sensor,
The authors fabricated our sensors several times, as we revised
the design. Later revisions have addressed performance issues in
earlier ones, such as linearity, sensitivity, noise. For the last
(fourth) revision, three-axis vibration sensors utilizing three discrete
single-axis sensors were developed, accompanied by improved
circuitry and communication performance; as a result, the authors
had a mass of 120 µg, with springs whose dimensionsare 450 µm ×
4 µm, with maximum detectable frequency of 1 kHz. Fig. 4
shows a picture of our sensor sample taken with a Scanning
Electron Microscope (SEM).
Fig. 2. Design Sketch of Our Single-axis MEMS Accelerometer
Fig. 3. ANSYS Simulation of the MEMS Sensor Design: (Left)
Stress Analysis for the Mass and the Spring; (Right) Analy-
sis of Its First-order Mode of Resonance (999 Hz)
Fig. 4. Scan Electron Microscope (SEM) Image of our MEMS Device
Jungyeol Kim, Soonwook Kwon, Seunghee Park, and Youngsuk Kim
4 KSCE Journal of Civil Engineering
4.2 Making a 3-axis Vibration Sensor and a Communica-
tion Module
Using the single axis MEMS accelerometer we developed, the
authors built a 3-axis vibration sensor, by combining three sensor
modules with newly-developed circuitry (Fig. 5). One of the
issues in combining the sensors was accommodating the three
sensor channels into the limited bandwidth of the communication
A communication module consists of multiple transmitters
embedded in MEMS vibration sensors, and a receiver that
collects data from the transmitters. Both transmitters and the
receiver use Zigbee communication protocol (based on IEEE
802.15.4), which enables error-free data transfer from multiple
transmitters over the 2.4 GHz radio band.
Performance of a wireless communication module is a
constraining factor for sampling rate of an individual sensor,
number of available transmitters, power consumption, etc. To
extract maximum performance from the communication module,
each transmitter node was set to send data in a 200 ms interval,
with the help of internal memory for buffering sensor readings
during the interval. Also, the sensor was set to measure at least
300 Hz of vibration frequency (i.e. sampling rate), as the burst-mode
data transmission used in our system enabled us to squeeze out more
bandwidth by reducing overheads in the data packet-which, at a
300 Hz sampling rate, allowed simultaneoustransmission of ten
single-axis sensor readings, or three triple-axis sensor readings.
For operation of overall sensor network (dubbed as USN,
ubiquitous sensor network), the authors developed internal
measuring software and network software on TinyOS 2.0, which
also contributed to low-power performance.
Our wireless data transmitter consists of a sensor module
(which itself consists of a MEMS sensor and a driver circuitry), a
signal processing circuitry, a Zigbee communication module and
a power supply. Fig. 6 shows an actual transmitter module.
Input voltage from the MEMS sensor (i.e. sensor output signal) is
amplified first, then is fed to an embedded low-pass filter for
removing noise, An embedded analog-to-digital converter generates
a stream of 16-bit word data from the amplified, noise-free
analog signal. The data stream is then to be transmitted via a
Zigbee communication module (which is built around a CC2420
chip from Texas Instruments). The module is configured to
buffer the data in its embedded memory for allowing burst-mode
transmission, which allows the achieving of a 300 Hz sampling
rate over the rathernarrow bandwidth of Zigbee.
A receiver module communicates with multiple sensor modules
over 2.4 GHz Zigbee protocol. When it receives data from the
sensor modules, it passes the collected data to a host computer
via USB. A data receiver can be connected up to three transmitters,
each of which has three data channels assigned for X, Y, and Z
4.3 Laboratory and Field Tests of the Sensor Module
The authors analyzed performance of our prototype sensor by
comparing its performance with existing sensors. For the
comparison, a commercial ICP accelerometer (capable of measuring
-0.5G to +0.5G) and a MEMS accelerometer manufactured by
Analog Devices (capable of measuring -1.7G to +1.7G) were
Fig. 5. 3-axis Vibration Sensor Module Built with Three MEMS
Fig. 6. A Wireless Communication Module, with Open Protective
Fig. 7. Test Result: Triangular Dots Show Readings from Our Pro-
totype, Square Dots Show Readings from a Commercial
MEMS Sensor (for Comparison), Small Diamond Dots Show
Readings from the ICP Sensor (as a Reference)
A MEMS-based Commutation Module with Vibration Sensor for Wireless Sensor Network-based Tunnel-blasting Monitoring
Vol. 00, No. 0 / 000 0000 5
used. The ICP sensor was selected as a reference, because it has a
very low noise level, and is very sensitive. For the test, the
authors installed these sensors on the same elastomeric test bed;
then, the authors produced artificial waves, having variable
magnitudes ranging from 0.5 mm up to 48 mm, for measurement.
Fig. 7 illustrates the test result. Since ICP sensors cannot measure
accelerations greater than ±0.5 g, only two MEMS sensors were
used for measurements over that value.
From the test result, it is shown that the measurement value
from our prototype is closer to the reference value (from the ICP
sensor) than the commercial MEMS sensor. The average error
ratio of our prototype was 8.2%, while that of the commercial
MEMS sensor was 10.1%. Both MEMS sensors behaved worse
as the acceleration increased, yet the commercial sensor had
more error than ours. On the other hand, those MEMS sensors
showed difficulty in measuring acceleration less than 0.1 g, due
to their inherent noise level.The full comparison of commercial
MEMS sensor and our prototype in Fig. 8 shows similar trends
among them.
The authors conducted a test of our prototype sensor module at
an actual blasting site located in Daesan, South Korea (see Fig. 9
for pictures of the actual test scene). Sensor device and its
communication module showed their performance and robustness
in the actual site.
5. Opto-mechanical Vibration Sensor Design
In order to improve our MEMS sensor, the authors iterated our
design and fabrication effortsfive times. For the first three iterations,
the authors tried to improve various performance aspects, such as
linearity, sensitivity, and noise rejection.For the fourth iteration,
the authors developed a 3-axis accelerometer, utilizing our
single-axis sensor devices. For the fifth and final iteration, the
authors designed a new sensor type for measuring micro
acceleration less than 100 mg, which was not possible with our
varying capacitance type design, due to higher noise floor. Such
a limit was considered unbeatable for that type of MEMS
accelerometers, including commercial devices.
5.1 Designing the Optic-MEMS Accelerometer
For measuring the micro acceleration (< 100 mg), the authors
developed an opto-MEMS type sensor design. This sensor
design is coupled with a laser displacement-measurement module
that allows measurementof the actual vibration. The laser
measurement module has a simple construction, is less prone to
noise issues, and is very precise, which has been proven in
various applications. Cost reduction is also viable, by using LED
light sources.
For our prototype, the module consisted of a laser, a photo
diode, signal processing circuitry and power supply. The authors
used a P15 laser module from 3 Laser Tech Inc., of output power
35 mW at 635 nm single wavelength. The diameter of the beam
output was adjusted to 200 µm, using an optical lens. The light-
sensing photodiode was a Hamamatsu Model S3979, a photo
diode for single-axis displacement measurement; its nominal
resolution of displacement is 0.1 µm, and maximum sensitivity is
obtained at 920 µm wavelength. At 635 nm, its performance
degradation is negligible, and even shows better resistance to
temperature changes, according to the datasheet. The power
supply and signal processing circuitry were connected to the
laser and the photo diode respectively. Fig. 10 shows a simple
diagram of the signal processing module.
In our optical sensor module, the laser beam is projected to a
MEMS-fabricated cantilever, which will create movement of the
reflected beam due to the vibrating cantilever, which is captured
by the photo diode, and is converted to electronic signals to be
Fig. 8. The Full Comparison of Commercial MEMS Sensor and
MEMS Prototype
Fig. 9. Snapshots of the Testing of the Sensor Module at an Actual
Blasting Site
Jungyeol Kim, Soonwook Kwon, Seunghee Park, and Youngsuk Kim
6 KSCE Journal of Civil Engineering
processed by downstream modules. Fig. 11 is a diagram of the
entire optical measurement module, and Fig. 12 shows the cross-
section diagram of the module.
5.2 Design Variables of the Accelerometer
Three variables significantly affect the resolution of the MEMS
accelerometer: these are resonant frequency, vertical displacement,
and linearity.
5.2.1 Resonant Frequency
Resonant frequency of a vibrating object is determined by its
shape and material. It was necessary to analyze the shape of our
accelerometer mass, in order to decide the measurable frequency
range. Since our accelerometer is cantilever-shaped, the authors
used a simple beam-like shape for modeling our accelerometer to
simplify the analysis. Using the simple beam model, its shape is
determined with three parameters of length(L), width(W), and
thickness (T). For such a beam-shaped elastic structure, Eq. (1)
shows how the resonant frequency is related to other variables.
= Resonant frequency
K = Elasticity coefficient
M =Mass
From Eq. (1), it is revealed that a higher elasticity coefficient
and lower mass is necessary for achieving a higher resonant
frequency. For the elasticity coefficient (K) and mass (M), the
following Equations are known:
E = Young’s Modulus
W =Width
L = Length
t = Thickness
r = Density
From Eqs. (2) and (3), the following Equation regarding the
resonant frequency can be derived:
From Eq. (4), it can be seen that the resonant frequency of a
beam-shaped elastic object is determined by its thickness (t)
and length(L). Therefore, such an object should have a high
elastic coefficient with low mass, if it needs a high resonant
5.2.2 Vertical Displacement
Vertical displacement of an accelerometer is caused by elastic
movement; therefore, the following Equation can also be applied:
M ρ LWt⋅⋅ =
Fig. 10. Circuit Diagram of the Signal Processing Module
Fig. 11. Concept of the Optical Vibration Measurement Module
Fig. 12. Cut-away View of the MEMS-based Opto-mechanical Vibra-
tion Sensor
A MEMS-based Commutation Module with Vibration Sensor for Wireless Sensor Network-based Tunnel-blasting Monitoring
Vol. 00, No. 0 / 000 0000 7
K = Elasticity coefficient
x = Vertical displacement
F = Driving force
This implies that lower elasticity coefficient and higher driving
force are necessary for achieving more vertical movement, and
that the shape of the sensor should be designed to lower its own
elasticity coefficient for sufficient displacement.
5.2.3 Linearity
Although an elastic mass deforms in a linear manner, the
frequency of the driving force adversely affects damping of the
movement. This issue is discussed in a later chapter.
5.2.4 OtheR Design Factors
Minimum area
Since the displacement of the accelerometer is measured
optically using a laser, it should have a reflective surface whose
area is sufficient for such measurement. Since we used a circular
laser beam whose diameter is 200 µm, the reflective surface
should be larger than that.
Q-factor represents the response of a resonant mass inside a
fluid. To increase the factor, the area must be small.
5.3 Shape of High-resolution Accelerometer
Our MEMS accelerometer is made of Silicon with 50 µm
thickness due to the fabrication process. It is designed to satisfy
two conflicting goals: to have a large reflective area, while
having minimal overall size for faster response and better
sensitivity. Figs. 13 and 14 show two shapes we have designed.
The DT type cantilever (which has dual spring beams) is
designed to have a high Q-factor, by reducing the area of the
springs while maintaining its width; the ST type, which has a
large single spring beam, tries to minimize the loss of Q-factor,
by reducing the sensor area while keeping its displacement
5.4 Optimization of the Sensor Design
As demonstrated in Eqs. (1) and (5), the accelerometer mass
must have both a higher resonant frequency and a larger vertical
displacement; the latter property requires lower elasticity,
whereas the former requires a higher one. To choose the optimal
design parameter, the authors conducted numerical analysis on
the sensor shape against its Length(L), Width(W), resonant
frequency and vertical displacement (design variables). Fig. 15
illustrates the relationship between design variables and their
result (resonance/deformation). The authors used pre-determined
design variables, such as minimum width, target resonant frequency,
Fig. 13. Shape of the Accelerometer Mass - cantilever ST Type
Fig. 14. Shape of the Accelerometer Mass - cantilever DT Type
Fig. 15. Numerical Analysis of Bending Mode with Respect to Shape
Jungyeol Kim, Soonwook Kwon, Seunghee Park, and Youngsuk Kim
8 KSCE Journal of Civil Engineering
target displacement, etc., then ran the analysis program, using
5.5 Iteration of the Initial Sensor Design
The authors chose the ST type cantilever over the DT type,
because the former allowed a higher measurable frequency.
Based on it, the authors designed five different shapes that were
subject to finite element analysis for their dynamic behavior (see
Table 2 for detailed shape parameters of those sensors). The
analysis result shows that they generate displacements of 26 µm
~122 µm when 0.1 mg vibration is applied; for the secondary
resonant mode, all of them are above 250 Hz, which is our
design goal for maximum measurable frequency (see Fig. 16).
5.6 Fabrication of the Sensor
Our accelerometer is fabricated on a 4 inch SOI (Silicon on
Insulator) wafer. There are several issues to consider when designing
the sensor layout on wafer: we want to harvest as many sensors
as possible from a single wafer, yet spacing between individual
sensors must be arranged so that the completed sensors can be
detached easily from the wafer. Also, the fabrication process
needs to be carefully planned, so that they can be produced
The layout design also features supporting structures, which
prevent the fabricated sensors from damage when various forces
are applied to the wafer during the fabrication process. To
remove the remaining area, a deep silicon etching process is
used. Fig. 17 shows the photomask layout of the wafer.
5.7 Evaluation
To evaluate our MEMS-based optical sensor, the authors
measured the same vibration using two sensors - a reference
sensor (Wilcoxon Research 731A, Fig. 18), and our prototype.
The readings from both sensors were fed to a Dacron Photon 24-
bit dynamic signal analyzer (Fig. 19) for further analysis. To
reduce difference in attenuation of the input vibration, both
sensors were located as close to each other as possible, and their
readings were time-synchronized. The g-value of the reference
sensor was calculated using a linear conversion equation provided
by the sensor manufacturer, whereas our module didn’t apply
any conversion for linearity compensation.
From the test result, among five design alternatives, the STF3
model was closest to the reference sensor with respect to its
Table 1. Five Design Candidates for Our Opto-mechanical Sensor Mass (Unit: µm)
Type Lspr Wspr Lsei Wsei
STF1 3000 1000 500 1000
STF2 3000 1000 1000 1000
STF3 5000 1500 1000 1000
STF4 5000 1500 1000 1500
STF5 5000 1500 1500 1500
Fig. 16. FEM Analysis of Five Design Candidates (Example, STF2) - 0.1 mg is Applied. From Left to Right: (a) Vertical Displacement, (b)
Resonant Mode 1, (c) Resonant Mode 2
Fig. 17. Photo Mask Layout of Our Accelerometer
Fig. 18. Wincoxon Resarch 731A Vibration Sensor and Its Specifi-
A MEMS-based Commutation Module with Vibration Sensor for Wireless Sensor Network-based Tunnel-blasting Monitoring
Vol. 00, No. 0 / 000 0000 9
dynamic characteristics. STF1 and STF2 fell short of sensitivity,
whereas STF4 and STF5 didn’t behave well in terms of signal
attenuation. Fig. 20 was taken from the test scene.
After calibrating our sensor module, the authors acquired the
final measurement values from our module, which is shown in
Fig. 21. The graph shows variable magnitude of the test vibration,
up to 500 mg.
For the 0~100 mg range, the standard deviation of the difference
with respect to the reference sensor was 2.77, showing that our
sensor was able to measure reliably in that range; for 100 mg~
500 mg, it was 4.52%.
6. Conclusions
For development of a new breed of sensors, the authors
investigated two different sensor types, both of which were
based on MEMS technology. The first type uses a comb-shaped
suspended mass that causes varying capacitance while the mass
is moving, due to external vibration; the second type, our latest
iteration, combined optical measurement using reflectors mounted
on a MEMS-fabricated cantilever, which enhanced sensitivity in
small-acceleration, e.g. less than 100 mg.
Basically, the result of this research can be applied to the
ground vibration monitoring due to blasting for tunnel construction.
It can measure vibration and acceleration of the blasting, and its
data can be utilized for the analysis of nearby ground condition.
Also, the sensor module can be used for the impact analysis of
buildings and civil infrastructures close to the blasting point.
Furthermore, with the ease and speed of its deployment, the
sensor module can be employed for the emergency vibration or
acceleration measurement of any artificial structure.
However, the sensor module has several limitations. The first
limitation is its power consumption. Although the prototype
sensor module requires lower power than conventional sensors
and it can be operated several days with commercial batteries, its
power consumption still needs to be optimized for the long-term
battery operation. Solar cell or fuel cell can be an alternative
power source of this module at this point. The second limitation
is its size. The size and the arrangement of sensor jig, circuit, and
case are not optimized as other commercialized sensors. These
limitations should be overcome for the actual use of this module
during the commercialized process in the future.
This study was conducted as a base project of Korea Institute
of Construction Technology under the support of Ministry of
Knowledge Economy (Project Code: KICT 2009-061).
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10 KSCE Journal of Civil Engineering
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Kim, J. Y., Kwon, S. W., Yoo, H. S., and Cho, M. Y. (2005),
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Construction (ISARC), 11-14 September 2005, Ferrara, Italy.
Kwon, S. W., Kim, J. Y., Yoo, H. S., and Cho, M. Y. (2006). Wireless
vibration sensor for tunnel construction, 23
ISARC, 3-5 October
2006, Tokyo, Japan, pp. 614-620.
... The advantage of the drilling and blasting method is that the construction period is short and the efficiency is high, but the disturbance to the surrounding rock is also great, especially when the tunnel passes through certain special geological areas, such as weak fracture zones, karst areas, and layered geological areas. In these cases, when constructing the tunnel using the drilling and blasting method, special attention should be paid to the deformation of surrounding rock under the action of blasting disturbance to avoid causing engineering accidents [5][6][7][8]. ...
... In Formula (5), ω n is the natural frequency; ξ n is the damping ratio; and τ is the generalized force. ...
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To study the influence of drilling and blasting on the deformation of the tunnel lining in a multimedium surrounding rock section, this paper constructs the deformation calculation theory of the explosion stress wave of the tunnel lining. We select single-medium surrounding rock, multimedium surrounding rock, different explosion accelerations, and different surrounding rock grades as research variables and analyse in depth the causes of the deformation response of the tunnel lining. It is found that the stress wave causes more damage to the surrounding rock closer to the explosion point, and the disturbance to the surrounding rock increases with the increase of the acceleration of the explosion stress wave. And the better the surrounding rock grade, the more obvious the creep effect formed by the explosion stress wave, and the more damaging the stress wave propagation is to the tunnel lining. After the stress wave propagation medium changes from soft to hard, the energy will produce a “nest effect” at the interface between the two media, and the energy will accumulate briefly at the interface. When a certain amount of energy has accumulated, it propagates into the hard medium in an excited state, which causes large vibration of the tunnel lining in the soft medium area. The stress wave propagation medium changes from hard to soft, and the excessive energy in the hard medium produces huge vibration only at the junction of the hard–soft media, and there is no “nest effect.”
... The test was conducted during blasting operation by installing 15 sensor modules at a 20 m distance with a data interval of 10 s. Success of wireless data and capability of MEMS sensor resulted in development of a sensor network module on TinyOS 2.0 operating system for ground vibration monitoring [131]. TinyOS is robust, power efficient, flexible, and widely use operating system for sensor nodes that developed in University of California, Berkeley in 2001 [132]. ...
... TinyOS is robust, power efficient, flexible, and widely use operating system for sensor nodes that developed in University of California, Berkeley in 2001 [132]. Kim et al [131] developed two different types of MEMS sensor for ground vibration monitoring including comb-type sensor, and an optic-cantilever type sensor. Recent development and practical studies have proved MEMS accelerometers' superior capacity to monitor blastinduced ground vibration [133][134][135]. ...
In-situ monitoring is an important aspect of geotechnical projects to ensure safety and optimise design measures. However, existing conventional monitoring instruments are limited in their accuracy, durability, complex and high cost of installation and requirement for ongoing real time measurement. Advancements in sensing technology in recent years have created a unique prospect for geotechnical monitoring to overcome some of those limitations. For this reason, micro-electro-mechanical system (MEMS) technology has gained popularity for geotechnical monitoring. MEMS devices combine both mechanical and electrical components to convert environment system stimuli to electrical signals. MEMS-based sensors provide advantages to traditional sensors in that they are millimetre to micron sized and sufficiently inexpensive to be ubiquitously distributed within an environment or structure. This ensures that the monitoring of the in-situ system goes beyond discrete point data but provides an accurate assessment of the entire structures response. The capability to operate with wireless technology makes MEMS microsensors even more desirable in geotechnical monitoring where dynamic changes in heterogeneous materials at great depth and over large areas are expected. Many of these locations are remote or hazardous to access directly and are thus a target for MEMS development. This paper provides a review of current applications of existing MEMS technology to the field/s of geotechnical engineering and provides a path forward for the expansion of this research and commercialisation of products.
... In continuation to the previous results, Jung Yeol et al. (2013) have been implemented a tiny, low-cost, accurate sensor board based on TinyOS 2.0 platform embedding MCU, on 16-bit ADC, a low pass filter and a Chip Con 2420 chip for RF communication module to monitor the ground vibration due to blasting for tunnel construction. In this, every transmitter node was set up to send the data in a two-hundred-millisecond interval at 300 Hz sampling rate [15]. ...
... The prototype was installed along with minimate plus seismograph at ACC Dungri limestone mine, India [20]. The authors [13][14][15][16][17][18][19][20] implemented a WSN system using RF modules such as ZigBee and ChipCon 2420 chip only. Moreover, the coverage range of these RF modules are low and did not discuss the IoT wireless connectivity. ...
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The recent proliferation of wireless sensor networks (WSNs) evolution into the Internet of Things (IoT) vision enables a variety of low-cost monitoring applications which allows a seamless transfer of information via embedded computing and network devices. Ambiguous ground vibration can be induced by blasting demolition is a severe concern which grievously damages the nearby dwellings and plants. It is an indispensable prerequisite for measuring the blast-induced ground vibration (BIGV), accomplishing a topical and most active research area. Thus, proposed and developed an architecture which emphasizes the IoT realm and implements a low-power wide-area networks (LPWANs) based system. Especially, using the available Long-Range (LoRa) Correct as Radio Frequency (RF) module, construct a WSN configuration for acquisition and streaming of required data from and to an IoT gateway. The system can wirelessly deliver the information to mine management and surrounding rural peoples to aware of the intensity of BIGV level. In this article, an endeavor has been made to introduce a LoRa WAN connectivity and proved the potentiality of the integrated WSN paradigm by testing of data transmission-reception in a non-line of sight (NLOS) condition. The path loss metrics and other required parameters have been measured using the LoRa WAN technology at 2.4 GHz frequency.
... The effect of Sun, and battery capacity have been measured and estimated by Ashraf A.A. Beshr, and Islam M. Abo Elnaga [2]. The authors concluded that the leveling process has been enhanced by (10)(11)(12)(13)(14)(15) %. Moreover, Reda el al [3] studied the effects of angle incidence and targets with different colors on distance measurement about the total station refrectorless, and The accuracy of reflectorless distance measurement is also investigated, In addition to that, comparison was made for manual and automatic target recognition measurement. ...
... Evaluating and measuring the vibration has a lot of variations and possible technologies. Piezoelectric, resonance, and magnetic can be used to measure the vibration values [14]. It is now easy to measure these vibrations through a remarkable development in technology that produces, digital devices, including vibration sensors. ...
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A digital surveying instrument has a crucial and effective role in civil engineering. These digital surveying instruments have contributed to providing quick and simplified solutions to solve many surveying problems: particularly accuracy, saving time, and effort .Therefore, the main objective of this research is the study of the vibrations effect on digital devices efficiency during the observation process, which occur frequently especially when the devices occupy the bridges during observation or when the occupation of the device is set nearby the railways, as well as in construction sites with heavy equipment movement. Although most digital surveying instruments contain a compensator device, this research find out through the experimental test that the effect of vibration on the accuracy of observation results and the noticed errors may extend to many centimeters. In case of using the digital level devices (SOKKIA SDL-30) under exposure to vibration (up to 20 KHZ/Sec), the average error of elevation was 36.9 mm in 80 m distance and the maximum standard deviation elevation error was 18.26 mm. But in the case of using the reflector-less total station (SOKKIA SET330RK) under exposure to vibration (from 7.5 to 15 KHZ/Sec), the average error of positioning was 79.95 mm in 85 m distance and the maximum standard deviation positioning error was 43.41 mm.
... In continuation to the previous results, Jung Yeol et al. in 2010 developed a tiny, low-cost, accurate sensor board based on TinyOS 2.0 platform embedding MCU, on a 16-bit ADC, a low pass filter and a ChipCon 2420 chip for a RF communication module to monitor the ground vibration due to blasting for tunnel construction. In this, every transmitter node was set up to send the data in a 200 ms interval at a 300 Hz sampling rate [35]. In 2014, Ooi et al. used an ADXL 203CE accelerometer manufactured by Analog Devices [38] having a resolution of 0.005×10 −3 m s −2 to measure ground surface vibration during underground blasting. ...
... Proposed MEMS-based accelerometer wireless sensor prototypes for BIGV monitoring (a) Jung Yeol et al.[35], (b) Jung Yeol et al.[36], (c)Kwon et al. [37] ...
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Ubiquitous wireless sensor network (WSN) enables low-cost monitoring applications such as blast-induced ground vibration (BIGV) and structural health monitoring (SHM). In particular, monitoring and analyzing the blast-induced ambiguous ground vibration is an essential requisite to control and protect surrounding grievous damage structures. Similarly, improving health and longevity of structures using WSN is a new facet that owes to diminish the low-cost installation. Recent advances in WSNs are forging new prospects for sensors. Variety of intelligent sensors are integrated into the wireless system to monitor environmental, and health of civil infrastructures. Considering the current trends in the area of development of wireless monitoring prototypes, Micro-Electro-Mechanical-Systems(MEMS) accelerometer sensors are widely prevalent owing to the small physical size and inexpensive. In general, BIGV waves are less intensity and low-frequency signals. Hence, it is essential to select an appropriate accelerometer to detect micro-vibration waves. The study exemplifies a summarized review of recently made MEMS-based accelerometer wireless systems for intelligent and reliable monitoring of BIGV and SHM since the last decade. Especially, this research effort focuses on the numerous adopted accelerometers and their characteristics such as sensitivity, noise density, measurement range, bandwidth, resolution, network topologies, and performance of designed systems to analyze the micro-vibration levels comprehensively.
... Among the many different ways to measure the vibration (Kim, Kwon & Kim, 2013), we used a vibration sensor (SW-420); this sensor can be connected to Arduino hardware (Yadesh & Venkatachalam, 2016;Nasution, Muchtar & Siregar, 2017). Arduino is an easy program, from which we can use a microcontroller board called Arduino Uno. ...
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The digital level (SOKKIA SDL-30) and total station (SOKKIA CX-105) are highlighted as examples of digital surveying instruments. In this study, it is clarified how some surrounding factors can affect their efficiency such as vibration, sunlight, and its direction, temperature, and battery capacity. Through vibration testing as one of these factors ,both the digital level and the total station using the reflector-less were exposed to vibration up to 25 KHZ/Sec, the average and the standard deviations elevation error for the digital level increased by 2 times at 80 m distance , and the average and the standard deviations positioning error increased 3 times for the total station using the reflector-less total at 80 m distance between the instrument and bar code. 64.3% and 51.25% are the increasing ratios in average error for digital level and total station with reflector-less prism by testing the effect of sunlight and its position. The increase in temperature leads to an increase in the average error with 150 % and 66.6% for digital level and reflectorless total station. Finally, the lack of battery efficiency led to a shortage of accuracy of the Surveying Instruments.
... Few researchers (Kim 2013) already remarked the advantages of WSN technology over conventional monitoring systems. It covers a wide range of objects from various embedded operating systems and micro-controller units to wireless protocols. ...
Conference Paper
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In recent decades, the ground vibration induced by blasting is an inevitable outcome and severely damages surrounding structures. Hence, it is essential to monitor the ground vibration to evaluate and control the adverse consequences of blasting. Several conventional instruments were widely adopted to measure vibration in terms of Peak Particle Velocity (PPV). The major limitation of the conventional system is wire-based, expensive, and cannot transfer real-time seamless information. To mitigate, proposed a novel real-time, low-cost wireless vibration system. In this context, design and implement an economical wireless system to monitor PPV effectively. Further, discuss the overall architecture, integrating of hardware, and implementation of software protocols in the process of making the wireless system. Developed prototype having an accelerometer, Radio Frequency (RF) module, and microcontroller unit. The system was installed at different locations in Mine-A, India and obtained results ensure that PPV values are varied from 0.191 to 8.60 mm/sec.
... Though many works have been done by all the world scholars, the most attempts were based on the monitoring data to summarize the empirical equation [8][9][10][11][12][13][14][15][16][17][18], which is restricted for the real engineering blasting vibration. At the same time, some new methods are used to analyze the blasting problem, such as the soft computing method [19], artificial neural networks method [20], MEMS-based commutation module, [21] and RES-based model [22]. But it should be based on large number of in situ monitoring data, not considering the effect of vibration frequency and duration. ...
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In the tunnel and underground space engineering, the blasting wave will attenuate from shock wave to stress wave to elastic seismic wave in the host rock. Also, the host rock will form crushed zone, fractured zone, and elastic seismic zone under the blasting loading and waves. In this paper, an accurate mathematical dynamic loading model was built. And the crushed zone as well as fractured zone was considered as the blasting vibration source thus deducting the partial energy for cutting host rock. So this complicated dynamic problem of segmented differential blasting was regarded as an equivalent elastic boundary problem by taking advantage of Saint-Venant’s Theorem. At last, a 3D model in finite element software FLAC3D accepted the constitutive parameters, uniformly distributed mutative loading, and the cylindrical attenuation law to predict the velocity curves and effective tensile curves for calculating safety criterion formulas of surrounding rock and tunnel liner after verifying well with the in situ monitoring data.
This paper presents a low-power second-order sigma-delta modulator (SDM) for micro-electromechanical systems (MEMS) digital geophones (DGPs). The proposed SDM optimizes the performance of the first stage integrator and uses an adaptive class-AB current recycling operational transconductance amplifier (OTA) to improve the current efficiency. In addition, gain-enhancing circuits are applied in the OTA to increase the DC gain, and the chopper technique is used in the first stage integrator to reduce the flicker noise. The proposed SDM was implemented in the SMIC 0.18 μm CMOS technology and occupies an area of 0.82 mm². The simulation results reveal the signal-to-noise ratio (SNR) was 76.46 dB and the effective number of bit (ENOB) was 12.4 bits. Measurements show that the SNR was 57.5 dB and the ENOB was 9.26 bits with a sampling rate of 256 KHz, an oversampling ratio 128, and a signal bandwidth of 1 KHz. The proposed SDM has a supply voltage of 1.8 V and a power consumption of 193.5 μW, which is suitable for the low-power MEMS DGPs applications.
Purpose Vibration monitoring is important task for any system to ensure safe operations. Improvement of control strategies is crucial for the vibration monitoring. Design/methodology/approach Since predictive control is one of the options for the vibration monitoring in this article the predictive model for vibration monitoring was created. Findings Although the achieved prediction results were acceptable, there is need for more work to apply and test these results in real environment. Originality/value Artificial neural network (ANN) was implemented as the predictive model while extreme learning machine (ELM) and back propagation (BP) learning schemes were used as training algorithms for the ANN. BP learning algorithm minimizes the error function by using the gradient descent method. ELM training algorithm is based on selecting of the input weights randomly of the ANN network and the output weight of the network are determined analytically.
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During and after tunnel construction, many problems including civil petitions and construction delay result from tunnel deformation, ground settlement, ground vibration, and tunnel lining crack. In relation to tunnel construction and maintenance, this study explains a development background of small wireless vibration sensors and their applications based on RF(Radio Frequency)-MEMS (Micro Electro Mechanical System) technology. The advantages and usefulness of the wireless automatic monitoring system is addressed compared with the conventional wired or survey measurement systems. Thus, the study provides a framework of the process for monitoring, manipulating, and transferring data from MEMS sensor and explains the application of the new developed automatic monitoring system for tunnel construction and maintenance.
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Recently, the demand for sensor technology has increased remarkably in all industrial fields. Sensor technology is closely related to cutting-edge technologies such as semiconductor technology and minute structure building technology, and thus, the high demand for small and light devices with high performance provides the impetus for conducting studies in order to develop sensors with much better performance. In this study, we developed a MEMS-based vibration sensor for tunnel construction and maintenance monitoring system. For this, we investigated the definition and summary of MEMS technology and also analyzed the types and characteristics of MEMS processing technology and the strong points of MEMS technology. We also analyzed current research results on sensor applications based on MEMS for construction. The types of work, characteristic and frequency of tunnel measurement, and investigated the characteristics of measuring instruments for doing the pertinent works are analyzed. We manufactured the MEMS vibration sensor for tunnel construction in order to measure blast vibration and we also measured the vibration through experiments.
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In this paper, we discuss the dynamic performance of a novel wall shear stress sensor concept based on whispering gallery mode (WGM) shifts of a dielectric microsphere resonator. In the shear stress sensor model, the wall shear stress acting on a sensing element, typically 125 m in diameter, is transmitted mechanically to the microsphere and the transmitted force leads to shifts in the WGMs of the microsphere. By monitoring these WGM shifts, the magnitude as well as the direction of the wall shear stress can be measured. The measurement principle was demonstrated in a previous paper which presented static shear stress results. The sensor used in the present study is a dielectric microsphere made of Polydimethylsyloxane (PDMS), and is tested for loading for dynamic measurements, An electronic circuit is developed to track the fast moving optical resonances (WGM) under dynamic loading.
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A carbon nanotube polymer material was used to form a piezoresistive strain sensor for structural health monitoring applications. The polymer improves the interfacial bonding between the nanotubes. Previous single walled carbon nanotube buckypaper sensors produced distorted strain measurements because the van der Waals attraction force allowed axial slipping of the smooth surfaces of the nanotubes. The polymer sensor uses larger multi-walled carbon nanotubes which improve the strain transfer, repeatability and linearity of the sensor. An electrical model of the nanotube strain sensor was derived based on electrochemical impedance spectroscopy and strain testing. The model is useful for designing nanotube sensor systems. A biomimetic artificial neuron was developed by extending the length of the sensor. The neuron is a long continuous strain sensor that has a low cost, is simple to install and is lightweight. The neuron has a low bandwidth and adequate strain sensitivity. The neuron sensor is particularly useful for detecting large strains and cracking, and can reduce the number of channels of data acquisition needed for the health monitoring of large structures.
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A modular wireless microelectromechanical system (MEMS) inclination sensor system (WMISS) is developed and tested for providing structural health monitoring of large-scale hook structures. The operating principle of a 3-D-MEMS-based dual-axis inclinometer is analyzed. A wireless MEMS sensor is integrated using sensing disposal, wireless communication, and power units. The WMISS is calibrated by using a laser displacement sensor in a pendular structure. The maximal error of the wireless MEMS inclination sensor is about 1%. The resolution is plusmn0.0025<sup>deg</sup>. With the new-type tuned mass damper control module, an experiment on a WMISS for the swing monitoring of a Lanjiang hook model is developed. Experimental results indicate that the developed WMISS is highly precise, convenient, stable, and low cost and has long range, and thus, a WMISS can accurately and conveniently monitor the swing of a Lanjiang hook model.
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This paper presents the modeling, fabrication, and testing of a high-performance dynamic strain sensor. Using microelectromechanical systems (MEMS) technology, ZnO piezoelectric microsensors are directly fabricated on silicon and steel substrates. The sensors are intended to be used as point sensors for vibration sensing without putting an extra burden on the host structures. A model that incorporates piezoelectric effects into an RC circuit, representing the sensor architecture, is developed to describe the voltage output characteristics of the piezoelectric microsensors. It is shown that the sensitivity of microplanar piezoelectric sensors that utilize the e <sub>31</sub> effect is linearly proportional to sensor thickness but unrelated to sensor area. Sensor characterization was performed on a cantilever beam cut from a fabricated silicon wafer. The experimental data indicate that the overall sensor and circuit system is capable of resolving better than 40.3 nanostrain time domain signal at frequencies above 2 kHz. The corresponding noise floor is lower than 200 femto-strain per root hertz and the sensitivity, defined as the sensor voltage output over strain input, is calculated to be 340 V/epsiv . Micro ZnO piezoelectric sensors fabricated on steel hard disk drive suspensions also show excellent results. The sensor not only has a better signal-to-noise ratio but also detects more vibration information than the combination of two laser-Doppler-vibrometer measurements in different directions.
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In this paper, we present a silicon carbide MEMS resonant strain sensor for harsh environment applications. The sensor is a balanced-mass double-ended tuning fork (BDETF) fabricated from 3C-SiC deposited on a silicon substrate. The SiC was etched in a plasma etch chamber using a silicon oxide mask, achieving a selectivity of 5:1 and etch rate of 2500 Aring/min. The device resonates at atmospheric pressure and operates from room temperature to above 300degC. The device was also subjected to 10 000 g shock (out-of-plane) without damage or shift in resonant frequency. The BDETF exhibits a strain sensitivity of 66 Hz/muepsiv and achieves a strain resolution of 0.11 muepsiv in a bandwidth from 10 to 20 kHz, comparable to state-of-the-art silicon sensors
The capability to assess the biomechanical properties of living bone is important for basic research as well as the clinical management of skeletal trauma and disease. Even though radiodensitometric imaging is commonly used to infer bone quality, bone strength does not necessarily correlate well with these non-invasive measurements. This paper reports on the design, fabrication and initial testing of an implantable ultra-miniature multi-axis sensor for directly measuring bone stresses at a micro-scale. The device, which is fabricated with CMOS-MEMS processes, is intended to be permanently implanted within open fractures, or embedded in bone grafts, or placed on implants at the interfaces between bone and prosthetics. The stress sensor comprises an array of piezoresistive pixels to detect a stress tensor at the interfacial area between the MEMS chip and bone, with a resolution to 100 Pa, in 1 s averaging. The sensor system design and manufacture is also compatible with the integration of wireless RF telemetry, for power and data retrieval, all within a 3 mm × 3 mm × 0.3 mm footprint. The piezoresistive elements are integrated within a textured surface to enhance sensor integration with bone. Finite element analysis led to a sensor design for normal and shear stress detection. A wired sensor was fabricated in the Jazz 0.35 µm BiCMOS process and then embedded in mock bone material to characterize its response to tensile and bending loads up to 250 kPa.
This paper is concerned with the design concepts, modelling and implementation of various fibre optic sensor protection systems for development in concrete structures. The design concepts of fibre optic sensor protection system and on-site requirements for surface-mounted and embedded optical fibre sensor in concrete structures have been addressed. The aspects of finite element (FE) modelling of selected sensor protection systems in terms of strain transfer efficiency from the structure to the sensing region have also been focused in this paper. Finally, the experimental validations of specified sensor protection system in concrete structures have been performed successfully. Protected extrinsic Fabry–Perot interferometric (EFPI) and fibre Bragg grating (FBG) sensors have been used to monitor the structural health status of plain and composite wrapped concrete cylinders. Results obtained indicate that the protection system for the sensors performs adequately in concrete environment and there is very good correlation between results obtained by the protected fibre optic sensors and conventional electrical resistance strain gauges.