The current schemes of detecting the status of passengers in airplanes cannot satisfy the more strict regulations recently
released by the United States Transportation Security Administration. In basis of investigation on the current seat
occupancy sensors for vehicles, in this paper we present a novel scheme of seat occupancy sensors based on Fiber Bragg
Grating technology to improve the in-flight security of airplanes. This seat occupancy sensor system can be used to
detect the status of passengers and to trigger the airbags to control the inflation of air bags, which have been installed in
the airplanes of some major airlines under the new law. This scheme utilizes our previous research results of Weight-In-
Motion sensor system based on optical fiber Bragg grating. In contrast to the current seat occupancy sensors for vehicles,
this new seat occupancy sensor has so many merits that it is very suitable to be applied in aerospace industry or high
speed railway system. Moreover, combined with existing Fiber Bragg Grating strain or temperature sensor systems built
in airplanes, this proposed method can construct a complete airline passenger management system.
KEYWORDS: Demodulation, Fiber Bragg gratings, Sensors, Analog electronics, Data acquisition, Signal processing, Resistors, Signal detection, Software development, Optical fibers
A National Instruments (NI) DAQ card PCI 5105 is installed in a high-speed demodulation system based on Fiber
Fabry-Pérot Tunable Filter. The instability of the spectra of Fiber Bragg Grating sensors caused by intrinsic drifts of
FFP-TF needs an appropriate, flexible trigger. However, the driver of the DAQ card in the current development
environment does not provide the functions of analog trigger but digital trigger type. Moreover, the high level of the
trigger signal from the tuning voltage of FFP-TF is larger than the maximum input overload voltage of PCI 5105 card.
To resolve this incompatibility, a novel converter to change an analog trigger signal into a digital trigger signal has been
reported previously. However, the obvious delay time between input and output signals limits the function of
demodulation system. Accordingly, we report an improved low-cost, small-size converter with an adjustable delay time.
This new scheme can decline the delay time to or close to zero when the frequency of trigger signal is less than 3,000
Hz. This method might be employed to resolve similar problems or to be applied in semiconductor integrated circuits.
The wavelength demodulation based on a Fiber Fabry-Pérot Tunable Filter (FFP-TF) is a common method for
multiplexing Fiber Bragg Grating (FBG) sensors. But this method cannot be used to detect high frequency signals due to
the limitation by the highest scanning rate that the FFP-TF can achieve. To overcome this disadvantage, in this paper we
present a scheme of cognitive sensors network based on FFP-TF technology. By perceiving the sensing environment,
system can automatically switch into monitoring signals in two modes to obtain better measurement results: multi
measurement points, low frequency (<1 KHz) signal, and few measurement points but high frequency (~50 KHz) signals.
This cognitive sensors network can be realized in current technology and satisfy current most industrial requirements.
In this paper, we present a study of detecting the hysteresis effect in strain-stress curve of carbon fiber reinforced
materials by Fiber Bragg Grating technology. By calculating the dissipative energy density contoured by hysteresis
loops, this method can be further applied in detecting the cracks and fatigue of carbon fiber reinforced laminates. In
contrast to the traditional sensors, such FBG sensors have numerous merits, such as small size, immunity to
Electromagnetic Interference and easy installation into the carbon fiber reinforced laminates. This method can also be
extended into monitoring other materials which also exhibit hysteresis effects in their strain-stress curves.
Recently, many accidents were reported that some passengers were unfortunately restrained and killed at the gaps
between the Platform Screen Doors (PSDs) and the doors of the subway trains. In this paper, one proposal of real time
monitoring system based on optical time domain reflectrometer (OTDR) to detect the intrusions at these gaps is
presented. In this method the locations and weight of intrusions can be obtained by detecting the abrupt power loss of
backscattering light caused by the weight of intrusions upon the microbending sensor heads. This method can be easily
multiplexed and extended into a multi-function sensing system, such as monitoring the temperature, smoking and the
strains in the tracks, or applied in other fields, such as escalators, board gates for ferries or planes.
Safety flight of aircrafts requires that the aircraft center of gravity (CG) must fall within specified limits established
by the manufacturer. However, the aircraft CG depends not only on the structure of planes, but also on the
passengers and their luggage. The current method of estimating the weight of passengers and luggage by the average
weight may result in a violation of this requirement. To reduce the discrepancy between the actual weight and
estimated weight, we propose a method of improving the accuracy of calculating the CG of the plane by weighing
the passengers and their personal luggage. This method is realized by a Weigh-In-Motion (WIM) system installed at
boarding gates based on optical fiber Bragg grating (FBG) technology. One prototype of WIM is fabricated and
tested at lab. The resolution of this system is 2 kg and can be further improved by advanced manufacture technology.
With the accurate weight of passengers and luggage coming from the WIM system and the locations of passengers
and luggage obtained from boarding cards, the aircraft CG can be calculated correctly. This method can be applied
into other fields, such as escalators, boarding gates for ferries.
In this paper we report a scheme of low-cost, small-size differential electrical converter to change analog trigger
signals into digital trigger signals. This converter successfully resolves the incompatibility between the digital trigger
mode of NI (National Instruments) data acquisition card PCI 5105 in Measurement Studio development environment
for a demodulator and the requirement from instability of spectra of fiber Bragg grating (FBG) sensors. The
instability is caused by intrinsic drifts of FFP-TF inside this high speed demodulator. The obtained results of
frequency response about the converter have clearly demonstrated that this method is effective when the frequency
of trigger signal is less than 3,000 Hz. This converter can satisfy the current requirements of demodulator based on
FFP-TF, since mostly actual working scanning frequency of FFP-TF is less than 1,000 Hz. This method may be recommended to resolve similar problems for other NI customers who have developed their data acquisition system based on Measurement Studio.
A high speed, portable, multi-function WIM sensing system based on Fiber Bragg Grating (FBG) technology is reported
in this paper. This system is developed to measure the total weight, the distribution of weight of vehicle in motion, the
distance of wheel axles and the distance between left and right wheels. In this system, a temperature control system and a
real-time compensation system are employed to eliminate the drifts of optical fiber Fabry-Pérot tunable filter. Carbon
Fiber Laminated Composites are used in the sensor heads to obtain high reliability and sensitivity. The speed of tested
vehicles is up to 20 mph, the full scope of measurement is 4000 lbs, and the static resolution of sensor head is 20 lbs. The
demodulator has high speed (500 Hz) data collection, and high stability. The demodulator and the light source are packed
into a 17'' rack style enclosure. The prototype has been tested respectively at Stevens' campus and Army base. Some
experiences of avoiding the pitfalls in developing this system are also presented in this paper.
A high speed, high performance, portable, dual-channel, optical Fiber Bragg Grating demodulator based on fiber Fabry-
Pérot tunable filter (FFP-FT) is reported in this paper. The high speed demodulation can be achieved to detect the
dynamical loads of vehicles with speed of 15 mph. However, the drifts of piezoelectric transducer (PZT) in the cavity of
FFP-FT dramatically degrade the stability of system. Two schemes are implemented to improve the stability of system.
Firstly, a temperature control system is installed to effectively remove the thermal drifts of PZT. Secondly, a scheme of
changing the bias voltage of FFP-FT to restrain non-thermal drifts has been realized at lab and will be further developed
to an automatic control system based on microcontroller. Although this demodulator is originally used in Weight-In-
Motion (WIM) sensing system, it can be extended into other aspects and the schemes presented in this paper will be
useful in many applications.
A portable, multi-function WIM sensing system based on Fiber Bragg Grating (FBG) technology is developed to
measure the total weight, the distribution of weight of vehicle in motion (the weights of left front, right front, left rear
and right rear wheels respectively), the distance of wheels axles and distance between left and right wheels. Currently the
speed of vehicle to be tested can be up to 15 mph, the full scope of measurement for this system is 4000 lbs, and the
static sensitivity of sensor head is 20 lbs. This system has been tested respectively at Stevens' campus and Army base.
Compared to other schemes, our method has a number of advantages such as immune to electromagnetic interference,
high repeatability, lightweight, low power consumption, high sensitivity to dynamic strain caused by load of vehicles in
high-speed. The accuracy of whole system can be improved by simulating the mathematical model of sensor heads and
improving the quality of manufacture as well as the calibration condition in the future.
A novel fiber Bragg grating (FBG)-based weigh-in-motion (WIM) system is introduced in order to achieve a better performance compared with the existing WIM systems. This novel WIM system uses the fiber-reinforced composite (FRC) as the load-supporting material in combination with the FBG technology. The sensor is designed as a multiply FRC laminate with the FBG embedded inside it. A theoretical model is developed to analyze the mechanism of this WIM system. Both static and dynamic tests are conducted to verify the system performance. With the extraordinary mechanical properties of the FRC, this novel WIM system has achieved larger dynamic range and higher sensitivity than prior works. The simple design of the system also reduces the engineering difficulties and overall costs.
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